Traffic Routing

Configuration affecting traffic routing. Here are a few terms useful to define in the context of traffic routing.

Service a unit of application behavior bound to a unique name in a service registry. Services consist of multiple network endpoints implemented by workload instances running on pods, containers, VMs etc.

Service versions (a.k.a. subsets) - In a continuous deployment scenario, for a given service, there can be distinct subsets of instances running different variants of the application binary. These variants are not necessarily different API versions. They could be iterative changes to the same service, deployed in different environments (prod, staging, dev, etc.). Common scenarios where this occurs include A/B testing, canary rollouts, etc. The choice of a particular version can be decided based on various criterion (headers, url, etc.) and/or by weights assigned to each version. Each service has a default version consisting of all its instances.

Source - A downstream client calling a service.

Host - The address used by a client when attempting to connect to a service.

Access model - Applications address only the destination service (Host) without knowledge of individual service versions (subsets). The actual choice of the version is determined by the proxy/sidecar, enabling the application code to decouple itself from the evolution of dependent services.

ConnectionPoolSettings

Connection pool settings for an upstream host. The settings apply to each individual host in the upstream service. See Envoy’s circuit breaker for more details. Connection pool settings can be applied at the TCP level as well as at HTTP level.

For example, the following rule sets a limit of 100 connections to redis service called myredissrv with a connect timeout of 30ms

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: bookinfo-redis
spec:
  host: myredissrv.prod.svc.cluster.local
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 100
        connectTimeout: 30ms
FieldTypeDescription
tcpConnectionPoolSettings.TCPSettings

Settings common to both HTTP and TCP upstream connections.

httpConnectionPoolSettings.HTTPSettings

HTTP connection pool settings.

ConnectionPoolSettings.HTTPSettings

Settings applicable to HTTP1.1/HTTP2/GRPC connections.

FieldTypeDescription
http1MaxPendingRequestsint32

Maximum number of pending HTTP requests to a destination. Default 1024.

http2MaxRequestsint32

Maximum number of requests to a backend. Default 1024.

maxRequestsPerConnectionint32

Maximum number of requests per connection to a backend. Setting this parameter to 1 disables keep alive.

maxRetriesint32

Maximum number of retries that can be outstanding to all hosts in a cluster at a given time. Defaults to 3.

ConnectionPoolSettings.TCPSettings

Settings common to both HTTP and TCP upstream connections.

FieldTypeDescription
maxConnectionsint32

Maximum number of HTTP1 /TCP connections to a destination host.

connectTimeoutgoogle.protobuf.Duration

TCP connection timeout.

CorsPolicy

Describes the Cross-Origin Resource Sharing (CORS) policy, for a given service. Refer to https://developer.mozilla.org/en-US/docs/Web/HTTP/AccesscontrolCORS for further details about cross origin resource sharing. For example, the following rule restricts cross origin requests to those originating from example.com domain using HTTP POST/GET, and sets the Access-Control-Allow-Credentials header to false. In addition, it only exposes X-Foo-bar header and sets an expiry period of 1 day.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
    corsPolicy:
      allowOrigin:
      - example.com
      allowMethods:
      - POST
      - GET
      allowCredentials: false
      allowHeaders:
      - X-Foo-Bar
      maxAge: "1d"
FieldTypeDescription
allowOriginstring[]

The list of origins that are allowed to perform CORS requests. The content will be serialized into the Access-Control-Allow-Origin header. Wildcard * will allow all origins.

allowMethodsstring[]

List of HTTP methods allowed to access the resource. The content will be serialized into the Access-Control-Allow-Methods header.

allowHeadersstring[]

List of HTTP headers that can be used when requesting the resource. Serialized to Access-Control-Allow-Methods header.

exposeHeadersstring[]

A white list of HTTP headers that the browsers are allowed to access. Serialized into Access-Control-Expose-Headers header.

maxAgegoogle.protobuf.Duration

Specifies how long the the results of a preflight request can be cached. Translates to the Access-Control-Max-Age header.

allowCredentialsgoogle.protobuf.BoolValue

Indicates whether the caller is allowed to send the actual request (not the preflight) using credentials. Translates to Access-Control-Allow-Credentials header.

Destination

Destination indicates the network addressable service to which the request/connection will be sent after processing a routing rule. The destination.host should unambiguously refer to a service in the service registry. Istio’s service registry is composed of all the services found in the platform’s service registry (e.g., Kubernetes services, Consul services), as well as services declared through the ServiceEntry resource.

Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.

The following Kubernetes example routes all traffic by default to pods of the reviews service with label “version: v1” (i.e., subset v1), and some to subset v2, in a kubernetes environment.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
  namespace: foo
spec:
  hosts:
  - reviews # interpreted as reviews.foo.svc.cluster.local
  http:
  - match:
    - uri:
        prefix: "/wpcatalog"
    - uri:
        prefix: "/consumercatalog"
    rewrite:
      uri: "/newcatalog"
    route:
    - destination:
        host: reviews # interpreted as reviews.foo.svc.cluster.local
        subset: v2
  - route:
    - destination:
        host: reviews # interpreted as reviews.foo.svc.cluster.local
        subset: v1

And the associated DestinationRule

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews-destination
  namespace: foo
spec:
  host: reviews # interpreted as reviews.foo.svc.cluster.local
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

The following VirtualService sets a timeout of 5s for all calls to productpage.prod.svc.cluster.local service in Kubernetes. Notice that there are no subsets defined in this rule. Istio will fetch all instances of productpage.prod.svc.cluster.local service from the service registry and populate the sidecar’s load balancing pool. Also, notice that this rule is set in the istio-system namespace but uses the fully qualified domain name of the productpage service, productpage.prod.svc.cluster.local. Therefore the rule’s namespace does not have an impact in resolving the name of the productpage service.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: my-productpage-rule
  namespace: istio-system
spec:
  hosts:
  - productpage.prod.svc.cluster.local # ignores rule namespace
  http:
  - timeout: 5s
    route:
    - destination:
        host: productpage.prod.svc.cluster.local

To control routing for traffic bound to services outside the mesh, external services must first be added to Istio’s internal service registry using the ServiceEntry resource. VirtualServices can then be defined to control traffic bound to these external services. For example, the following rules define a Service for wikipedia.org and set a timeout of 5s for http requests.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-wikipedia
spec:
  hosts:
  - wikipedia.org
  location: MESH_EXTERNAL
  ports:
  - number: 80
    name: example-http
    protocol: HTTP
  resolution: DNS

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: my-wiki-rule
spec:
  hosts:
  - wikipedia.org
  http:
  - timeout: 5s
    route:
    - destination:
        host: wikipedia.org
FieldTypeDescription
hoststring

REQUIRED. The name of a service from the service registry. Service names are looked up from the platform’s service registry (e.g., Kubernetes services, Consul services, etc.) and from the hosts declared by ServiceEntry. Traffic forwarded to destinations that are not found in either of the two, will be dropped.

Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.

subsetstring

The name of a subset within the service. Applicable only to services within the mesh. The subset must be defined in a corresponding DestinationRule.

portPortSelector

Specifies the port on the host that is being addressed. If a service exposes only a single port it is not required to explicitly select the port.

DestinationRule

DestinationRule defines policies that apply to traffic intended for a service after routing has occurred. These rules specify configuration for load balancing, connection pool size from the sidecar, and outlier detection settings to detect and evict unhealthy hosts from the load balancing pool. For example, a simple load balancing policy for the ratings service would look as follows:

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: bookinfo-ratings
spec:
  host: ratings.prod.svc.cluster.local
  trafficPolicy:
    loadBalancer:
      simple: LEAST_CONN

Version specific policies can be specified by defining a named subset and overriding the settings specified at the service level. The following rule uses a round robin load balancing policy for all traffic going to a subset named testversion that is composed of endpoints (e.g., pods) with labels (version:v3).

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: bookinfo-ratings
spec:
  host: ratings.prod.svc.cluster.local
  trafficPolicy:
    loadBalancer:
      simple: LEAST_CONN
  subsets:
  - name: testversion
    labels:
      version: v3
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN

Note: Policies specified for subsets will not take effect until a route rule explicitly sends traffic to this subset.

Traffic policies can be customized to specific ports as well. The following rule uses the least connection load balancing policy for all traffic to port 80, while uses a round robin load balancing setting for traffic to the port 9080.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: bookinfo-ratings-port
spec:
  host: ratings.prod.svc.cluster.local
  trafficPolicy: # Apply to all ports
    portLevelSettings:
    - port:
        number: 80
      loadBalancer:
        simple: LEAST_CONN
    - port:
        number: 9080
      loadBalancer:
        simple: ROUND_ROBIN
FieldTypeDescription
hoststring

REQUIRED. The name of a service from the service registry. Service names are looked up from the platform’s service registry (e.g., Kubernetes services, Consul services, etc.) and from the hosts declared by ServiceEntries. Rules defined for services that do not exist in the service registry will be ignored.

Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.

Note that the host field applies to both HTTP and TCP services.

trafficPolicyTrafficPolicy

Traffic policies to apply (load balancing policy, connection pool sizes, outlier detection).

subsetsSubset[]

One or more named sets that represent individual versions of a service. Traffic policies can be overridden at subset level.

DestinationWeight

Each routing rule is associated with one or more service versions (see glossary in beginning of document). Weights associated with the version determine the proportion of traffic it receives. For example, the following rule will route 25% of traffic for the “reviews” service to instances with the “v2” tag and the remaining traffic (i.e., 75%) to “v1”.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v2
      weight: 25
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v1
      weight: 75

And the associated DestinationRule

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews-destination
spec:
  host: reviews.prod.svc.cluster.local
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

Traffic can also be split across two entirely different services without having to define new subsets. For example, the following rule forwards 25% of traffic to reviews.com to dev.reviews.com

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route-two-domains
spec:
  hosts:
  - reviews.com
  http:
  - route:
    - destination:
        host: dev.reviews.com
      weight: 25
    - destination:
        host: reviews.com
      weight: 75
FieldTypeDescription
destinationDestination

REQUIRED. Destination uniquely identifies the instances of a service to which the request/connection should be forwarded to.

weightint32

REQUIRED. The proportion of traffic to be forwarded to the service version. (0-100). Sum of weights across destinations SHOULD BE == 100. If there is only destination in a rule, the weight value is assumed to be 100.

EnvoyFilter

EnvoyFilter describes Envoy proxy-specific filters that can be used to customize the Envoy proxy configuration generated by Istio networking subsystem (Pilot). This feature must be used with care, as incorrect configurations could potentially destabilize the entire mesh.

NOTE 1: Since this is break glass configuration, there will not be any backward compatibility across different Istio releases. In other words, this configuration is subject to change based on internal implementation of Istio networking subsystem.

NOTE 2: When multiple EnvoyFilters are bound to the same workload, all filter configurations will be processed sequentially in order of creation time. The behavior is undefined if multiple EnvoyFilter configurations conflict with each other.

The following example for Kubernetes enables Envoy’s Lua filter for all inbound calls arriving at service port 8080 of the reviews service pod with labels “app: reviews”.

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: reviews-lua
spec:
  workloadLabels:
    app: reviews
  filters:
  - listenerMatch:
      portNumber: 8080
      listenerType: SIDECAR_INBOUND #will match with the inbound listener for reviews:8080
    filterName: envoy.lua
    filterType: HTTP
    filterConfig:
      inlineCode: |
        ... lua code ...
FieldTypeDescription
workloadLabelsmap<string, string>

One or more labels that indicate a specific set of pods/VMs whose proxies should be configured to use these additional filters. The scope of label search is platform dependent. On Kubernetes, for example, the scope includes pods running in all reachable namespaces. Omitting the selector applies the filter to all proxies in the mesh. NOTE: There can be only one EnvoyFilter bound to a specific workload. The behavior is undefined if multiple EnvoyFilter configurations are specified for the same workload.

filtersEnvoyFilter.Filter[]

REQUIRED: Envoy network filters/http filters to be added to matching listeners. When adding network filters to http connections, care should be taken to ensure that the filter is added before envoy.httpconnectionmanager.

EnvoyFilter.Filter

Envoy filters to be added to a network or http filter chain.

FieldTypeDescription
listenerMatchEnvoyFilter.ListenerMatch

Filter will be added to the listener only if the match conditions are true. If not specified, the filters will be applied to all listeners.

insertPositionEnvoyFilter.InsertPosition

Insert position in the filter chain. Defaults to FIRST

filterTypeEnvoyFilter.Filter.FilterType

REQUIRED: The type of filter to instantiate.

filterNamestring

REQUIRED: The name of the filter to instantiate. The name must match a supported filter compiled into Envoy.

filterConfiggoogle.protobuf.Struct

REQUIRED: Filter specific configuration which depends on the filter being instantiated.

EnvoyFilter.Filter.FilterType

NameDescription
INVALID

placeholder

HTTP

Http filter

NETWORK

Network filter

EnvoyFilter.InsertPosition

Indicates the relative index in the filter chain where the filter should be inserted.

FieldTypeDescription
indexEnvoyFilter.InsertPosition.Index

Position of this filter in the filter chain.

relativeTostring

If BEFORE or AFTER position is specified, specify the name of the filter relative to which this filter should be inserted.

EnvoyFilter.InsertPosition.Index

Index/position in the filter chain.

NameDescription
FIRST

Insert first

LAST

Insert last

BEFORE

Insert before the named filter.

AFTER

Insert after the named filter.

EnvoyFilter.ListenerMatch

Select a listener to add the filter to based on the match conditions. All conditions specified in the ListenerMatch must be met for the filter to be applied to a listener.

FieldTypeDescription
portNumberuint32

The service port/gateway port to which traffic is being sent/received. If not specified, matches all listeners. Even though inbound listeners are generated for the instance/pod ports, only service ports should be used to match listeners.

portNamePrefixstring

Instead of using specific port numbers, a set of ports matching a given port name prefix can be selected. E.g., “mongo” selects ports named mongo-port, mongo, mongoDB, MONGO, etc. Matching is case insensitive.

listenerTypeEnvoyFilter.ListenerMatch.ListenerType

Inbound vs outbound sidecar listener or gateway listener. If not specified, matches all listeners.

listenerProtocolEnvoyFilter.ListenerMatch.ListenerProtocol

Selects a class of listeners for the same protocol. If not specified, applies to listeners on all protocols. Use the protocol selection to select all HTTP listeners (includes HTTP2/gRPC/HTTPS where Envoy terminates TLS) or all TCP listeners (includes HTTPS passthrough using SNI).

addressstring[]

One or more IP addresses to which the listener is bound. If specified, should match at least one address in the list.

EnvoyFilter.ListenerMatch.ListenerProtocol

NameDescription
ALL

All protocols

HTTP

HTTP or HTTPS (with termination) / HTTP2/gRPC

TCP

Any non-HTTP listener

EnvoyFilter.ListenerMatch.ListenerType

NameDescription
ANY

All listeners

SIDECAR_INBOUND

Inbound listener in sidecar

SIDECAR_OUTBOUND

Outbound listener in sidecar

GATEWAY

Gateway listener

Gateway

Gateway describes a load balancer operating at the edge of the mesh receiving incoming or outgoing HTTP/TCP connections. The specification describes a set of ports that should be exposed, the type of protocol to use, SNI configuration for the load balancer, etc.

For example, the following Gateway configuration sets up a proxy to act as a load balancer exposing port 80 and 9080 (http), 443 (https), and port 2379 (TCP) for ingress. The gateway will be applied to the proxy running on a pod with labels app: my-gateway-controller. While Istio will configure the proxy to listen on these ports, it is the responsibility of the user to ensure that external traffic to these ports are allowed into the mesh.

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-gateway
spec:
  selector:
    app: my-gatweway-controller
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - uk.bookinfo.com
    - eu.bookinfo.com
    tls:
      httpsRedirect: true # sends 301 redirect for http requests
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - uk.bookinfo.com
    - eu.bookinfo.com
    tls:
      mode: SIMPLE #enables HTTPS on this port
      serverCertificate: /etc/certs/servercert.pem
      privateKey: /etc/certs/privatekey.pem
  - port:
      number: 9080
      name: http-wildcard
      protocol: HTTP
    hosts:
    - "*"
  - port:
      number: 2379 # to expose internal service via external port 2379
      name: mongo
      protocol: MONGO
    hosts:
    - "*"

The Gateway specification above describes the L4-L6 properties of a load balancer. A VirtualService can then be bound to a gateway to control the forwarding of traffic arriving at a particular host or gateway port.

For example, the following VirtualService splits traffic for “https://uk.bookinfo.com/reviews”, “https://eu.bookinfo.com/reviews”, “http://uk.bookinfo.com:9080/reviews”, “http://eu.bookinfo.com:9080/reviews” into two versions (prod and qa) of an internal reviews service on port 9080. In addition, requests containing the cookie “user: dev-123” will be sent to special port 7777 in the qa version. The same rule is also applicable inside the mesh for requests to the “reviews.prod.svc.cluster.local” service. This rule is applicable across ports 443, 9080. Note that “http://uk.bookinfo.com” gets redirected to “https://uk.bookinfo.com” (i.e. 80 redirects to 443).

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-rule
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  - uk.bookinfo.com
  - eu.bookinfo.com
  gateways:
  - my-gateway
  - mesh # applies to all the sidecars in the mesh
  http:
  - match:
    - headers:
        cookie:
          user: dev-123
    route:
    - destination:
        port:
          number: 7777
        host: reviews.qa.svc.cluster.local
  - match:
      uri:
        prefix: /reviews/
    route:
    - destination:
        port:
          number: 9080 # can be omitted if its the only port for reviews
        host: reviews.prod.svc.cluster.local
      weight: 80
    - destination:
        host: reviews.qa.svc.cluster.local
      weight: 20

The following VirtualService forwards traffic arriving at (external) port 27017 to internal Mongo server on port 5555. This rule is not applicable internally in the mesh as the gateway list omits the reserved name mesh.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-Mongo
spec:
  hosts:
  - mongosvr.prod.svc.cluster.local #name of internal Mongo service
  gateways:
  - my-gateway
  tcp:
  - match:
    - port: 27017
    route:
    - destination:
        host: mongo.prod.svc.cluster.local
        port:
          number: 5555
FieldTypeDescription
serversServer[]

REQUIRED: A list of server specifications.

selectormap<string, string>

REQUIRED: One or more labels that indicate a specific set of pods/VMs on which this gateway configuration should be applied. The scope of label search is platform dependent. On Kubernetes, for example, the scope includes pods running in all reachable namespaces.

HTTPFaultInjection

HTTPFaultInjection can be used to specify one or more faults to inject while forwarding http requests to the destination specified in a route. Fault specification is part of a VirtualService rule. Faults include aborting the Http request from downstream service, and/or delaying proxying of requests. A fault rule MUST HAVE delay or abort or both.

Note: Delay and abort faults are independent of one another, even if both are specified simultaneously.

FieldTypeDescription
delayHTTPFaultInjection.Delay

Delay requests before forwarding, emulating various failures such as network issues, overloaded upstream service, etc.

abortHTTPFaultInjection.Abort

Abort Http request attempts and return error codes back to downstream service, giving the impression that the upstream service is faulty.

HTTPFaultInjection.Abort

Abort specification is used to prematurely abort a request with a pre-specified error code. The following example will return an HTTP 400 error code for 10% of the requests to the “ratings” service “v1”.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
    fault:
      abort:
        percent: 10
        httpStatus: 400

The httpStatus field is used to indicate the HTTP status code to return to the caller. The optional percent field, a value between 0 and 100, is used to only abort a certain percentage of requests. If not specified, all requests are aborted.

FieldTypeDescription
percentint32

Percentage of requests to be aborted with the error code provided (0-100).

httpStatusint32 (oneof)

REQUIRED. HTTP status code to use to abort the Http request.

HTTPFaultInjection.Delay

Delay specification is used to inject latency into the request forwarding path. The following example will introduce a 5 second delay in 10% of the requests to the “v1” version of the “reviews” service from all pods with label env: prod

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  http:
  - match:
    - sourceLabels:
        env: prod
    route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v1
    fault:
      delay:
        percent: 10
        fixedDelay: 5s

The fixedDelay field is used to indicate the amount of delay in seconds. An optional percent field, a value between 0 and 100, can be used to only delay a certain percentage of requests. If left unspecified, all request will be delayed.

FieldTypeDescription
percentint32

Percentage of requests on which the delay will be injected (0-100).

fixedDelaygoogle.protobuf.Duration (oneof)

REQUIRED. Add a fixed delay before forwarding the request. Format: 1h/1m/1s/1ms. MUST be >=1ms.

HTTPMatchRequest

HttpMatchRequest specifies a set of criterion to be met in order for the rule to be applied to the HTTP request. For example, the following restricts the rule to match only requests where the URL path starts with /ratings/v2/ and the request contains a custom end-user header with value jason.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - match:
    - headers:
        end-user:
          exact: jason
      uri:
        prefix: "/ratings/v2/"
    route:
    - destination:
        host: ratings.prod.svc.cluster.local

HTTPMatchRequest CANNOT be empty.

FieldTypeDescription
uriStringMatch

URI to match values are case-sensitive and formatted as follows:

  • exact: "value" for exact string match

  • prefix: "value" for prefix-based match

  • regex: "value" for ECMAscript style regex-based match

schemeStringMatch

URI Scheme values are case-sensitive and formatted as follows:

  • exact: "value" for exact string match

  • prefix: "value" for prefix-based match

  • regex: "value" for ECMAscript style regex-based match

methodStringMatch

HTTP Method values are case-sensitive and formatted as follows:

  • exact: "value" for exact string match

  • prefix: "value" for prefix-based match

  • regex: "value" for ECMAscript style regex-based match

authorityStringMatch

HTTP Authority values are case-sensitive and formatted as follows:

  • exact: "value" for exact string match

  • prefix: "value" for prefix-based match

  • regex: "value" for ECMAscript style regex-based match

headersmap<string, StringMatch>

The header keys must be lowercase and use hyphen as the separator, e.g. x-request-id.

Header values are case-sensitive and formatted as follows:

  • exact: "value" for exact string match

  • prefix: "value" for prefix-based match

  • regex: "value" for ECMAscript style regex-based match

Note: The keys uri, scheme, method, and authority will be ignored.

portuint32

Specifies the ports on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.

sourceLabelsmap<string, string>

One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified at the top, it should include the reserved gateway mesh in order for this field to be applicable.

gatewaysstring[]

Names of gateways where the rule should be applied to. Gateway names at the top of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

HTTPRedirect

HTTPRedirect can be used to send a 301 redirect response to the caller, where the Authority/Host and the URI in the response can be swapped with the specified values. For example, the following rule redirects requests for /v1/getProductRatings API on the ratings service to /v1/bookRatings provided by the bookratings service.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - match:
    - uri:
        exact: /v1/getProductRatings
  redirect:
    uri: /v1/bookRatings
    authority: newratings.default.svc.cluster.local
  ...
FieldTypeDescription
uristring

On a redirect, overwrite the Path portion of the URL with this value. Note that the entire path will be replaced, irrespective of the request URI being matched as an exact path or prefix.

authoritystring

On a redirect, overwrite the Authority/Host portion of the URL with this value.

HTTPRetry

Describes the retry policy to use when a HTTP request fails. For example, the following rule sets the maximum number of retries to 3 when calling ratings:v1 service, with a 2s timeout per retry attempt.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
    retries:
      attempts: 3
      perTryTimeout: 2s
FieldTypeDescription
attemptsint32

REQUIRED. Number of retries for a given request. The interval between retries will be determined automatically (25ms+). Actual number of retries attempted depends on the httpReqTimeout.

perTryTimeoutgoogle.protobuf.Duration

Timeout per retry attempt for a given request. format: 1h/1m/1s/1ms. MUST BE >=1ms.

HTTPRewrite

HTTPRewrite can be used to rewrite specific parts of a HTTP request before forwarding the request to the destination. Rewrite primitive can be used only with the DestinationWeights. The following example demonstrates how to rewrite the URL prefix for api call (/ratings) to ratings service before making the actual API call.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings-route
spec:
  hosts:
  - ratings.prod.svc.cluster.local
  http:
  - match:
    - uri:
        prefix: /ratings
    rewrite:
      uri: /v1/bookRatings
    route:
    - destination:
        host: ratings.prod.svc.cluster.local
        subset: v1
FieldTypeDescription
uristring

rewrite the path (or the prefix) portion of the URI with this value. If the original URI was matched based on prefix, the value provided in this field will replace the corresponding matched prefix.

authoritystring

rewrite the Authority/Host header with this value.

HTTPRoute

Describes match conditions and actions for routing HTTP/1.1, HTTP2, and gRPC traffic. See VirtualService for usage examples.

FieldTypeDescription
matchHTTPMatchRequest[]

Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.

routeDestinationWeight[]

A http rule can either redirect or forward (default) traffic. The forwarding target can be one of several versions of a service (see glossary in beginning of document). Weights associated with the service version determine the proportion of traffic it receives.

redirectHTTPRedirect

A http rule can either redirect or forward (default) traffic. If traffic passthrough option is specified in the rule, route/redirect will be ignored. The redirect primitive can be used to send a HTTP 301 redirect to a different URI or Authority.

rewriteHTTPRewrite

Rewrite HTTP URIs and Authority headers. Rewrite cannot be used with Redirect primitive. Rewrite will be performed before forwarding.

timeoutgoogle.protobuf.Duration

Timeout for HTTP requests.

retriesHTTPRetry

Retry policy for HTTP requests.

faultHTTPFaultInjection

Fault injection policy to apply on HTTP traffic at the client side. Note that timeouts or retries will not be enabled when faults are enabled on the client side.

mirrorDestination

Mirror HTTP traffic to a another destination in addition to forwarding the requests to the intended destination. Mirrored traffic is on a best effort basis where the sidecar/gateway will not wait for the mirrored cluster to respond before returning the response from the original destination. Statistics will be generated for the mirrored destination.

corsPolicyCorsPolicy

Cross-Origin Resource Sharing policy (CORS). Refer to https://developer.mozilla.org/en-US/docs/Web/HTTP/AccesscontrolCORS for further details about cross origin resource sharing.

appendHeadersmap<string, string>

Additional HTTP headers to add before forwarding a request to the destination service.

L4MatchAttributes

L4 connection match attributes. Note that L4 connection matching support is incomplete.

FieldTypeDescription
destinationSubnetsstring[]

IPv4 or IPv6 ip addresses of destination with optional subnet. E.g., a.b.c.d/xx form or just a.b.c.d.

portuint32

Specifies the port on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.

sourceLabelsmap<string, string>

One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified at the top, it should include the reserved gateway mesh in order for this field to be applicable.

gatewaysstring[]

Names of gateways where the rule should be applied to. Gateway names at the top of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

LoadBalancerSettings

Load balancing policies to apply for a specific destination. See Envoy’s load balancing documentation for more details.

For example, the following rule uses a round robin load balancing policy for all traffic going to the ratings service.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: bookinfo-ratings
spec:
  host: ratings.prod.svc.cluster.local
  trafficPolicy:
    loadBalancer:
      simple: ROUND_ROBIN

The following example sets up sticky sessions for the ratings service hashing-based load balancer for the same ratings service using the the User cookie as the hash key.

 apiVersion: networking.istio.io/v1alpha3
 kind: DestinationRule
 metadata:
   name: bookinfo-ratings
 spec:
   host: ratings.prod.svc.cluster.local
   trafficPolicy:
     loadBalancer:
       consistentHash:
         httpCookie:
           name: user
           ttl: 0s
FieldTypeDescription
simpleLoadBalancerSettings.SimpleLB (oneof)
consistentHashLoadBalancerSettings.ConsistentHashLB (oneof)

LoadBalancerSettings.ConsistentHashLB

Consistent Hash-based load balancing can be used to provide soft session affinity based on HTTP headers, cookies or other properties. This load balancing policy is applicable only for HTTP connections. The affinity to a particular destination host will be lost when one or more hosts are added/removed from the destination service.

FieldTypeDescription
httpHeaderNamestring (oneof)

Hash based on a specific HTTP header.

useSourceIpbool (oneof)

Hash based on the source IP address.

minimumRingSizeuint64

The minimum number of virtual nodes to use for the hash ring. Defaults to 1024. Larger ring sizes result in more granular load distributions. If the number of hosts in the load balancing pool is larger than the ring size, each host will be assigned a single virtual node.

LoadBalancerSettings.ConsistentHashLB.HTTPCookie

Describes a HTTP cookie that will be used as the hash key for the Consistent Hash load balancer. If the cookie is not present, it will be generated.

FieldTypeDescription
namestring

REQUIRED. Name of the cookie.

pathstring

Path to set for the cookie.

ttlgoogle.protobuf.Duration

REQUIRED. Lifetime of the cookie.

LoadBalancerSettings.SimpleLB

Standard load balancing algorithms that require no tuning.

NameDescription
ROUND_ROBIN

Round Robin policy. Default

LEAST_CONN

The least request load balancer uses an O(1) algorithm which selects two random healthy hosts and picks the host which has fewer active requests.

RANDOM

The random load balancer selects a random healthy host. The random load balancer generally performs better than round robin if no health checking policy is configured.

PASSTHROUGH

This option will forward the connection to the original IP address requested by the caller without doing any form of load balancing. This option must be used with care. It is meant for advanced use cases. Refer to Original Destination load balancer in Envoy for further details.

OutlierDetection

A Circuit breaker implementation that tracks the status of each individual host in the upstream service. Applicable to both HTTP and TCP services. For HTTP services, hosts that continually return 5xx errors for API calls are ejected from the pool for a pre-defined period of time. For TCP services, connection timeouts or connection failures to a given host counts as an error when measuring the consecutive errors metric. See Envoy’s outlier detection for more details.

The following rule sets a connection pool size of 100 connections and 1000 concurrent HTTP2 requests, with no more than 10 req/connection to “reviews” service. In addition, it configures upstream hosts to be scanned every 5 mins, such that any host that fails 7 consecutive times with 5XX error code will be ejected for 15 minutes.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews-cb-policy
spec:
  host: reviews.prod.svc.cluster.local
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 100
      http:
        http2MaxRequests: 1000
        maxRequestsPerConnection: 10
    outlierDetection:
      consecutiveErrors: 7
      interval: 5m
      baseEjectionTime: 15m
FieldTypeDescription
consecutiveErrorsint32

Number of errors before a host is ejected from the connection pool. Defaults to 5. When the upstream host is accessed over HTTP, a 5xx return code qualifies as an error. When the upstream host is accessed over an opaque TCP connection, connect timeouts and connection error/failure events qualify as an error.

intervalgoogle.protobuf.Duration

Time interval between ejection sweep analysis. format: 1h/1m/1s/1ms. MUST BE >=1ms. Default is 10s.

baseEjectionTimegoogle.protobuf.Duration

Minimum ejection duration. A host will remain ejected for a period equal to the product of minimum ejection duration and the number of times the host has been ejected. This technique allows the system to automatically increase the ejection period for unhealthy upstream servers. format: 1h/1m/1s/1ms. MUST BE >=1ms. Default is 30s.

maxEjectionPercentint32

Maximum % of hosts in the load balancing pool for the upstream service that can be ejected. Defaults to 10%.

Port

Port describes the properties of a specific port of a service.

FieldTypeDescription
numberuint32

REQUIRED: A valid non-negative integer port number.

protocolstring

REQUIRED: The protocol exposed on the port. MUST BE one of HTTP|HTTPS|GRPC|HTTP2|MONGO|TCP|TLS. TLS is used to indicate secure connections to non HTTP services.

namestring

Label assigned to the port.

PortSelector

PortSelector specifies the number of a port to be used for matching or selection for final routing.

FieldTypeDescription
numberuint32 (oneof)

Valid port number

Server

Server describes the properties of the proxy on a given load balancer port. For example,

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-ingress
spec:
  selector:
    app: my-ingress-gateway
  servers:
  - port:
      number: 80
      name: http2
      protocol: HTTP2
    hosts:
    - "*"

Another example

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-tcp-ingress
spec:
  selector:
    app: my-tcp-ingress-gateway
  servers:
  - port:
      number: 27018
      name: mongo
      protocol: MONGO
    hosts:
    - "*"

The following is an example of TLS configuration for port 443

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-tls-ingress
spec:
  selector:
    app: my-tls-ingress-gateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - "*"
    tls:
      mode: SIMPLE
      serverCertificate: /etc/certs/server.pem
      privateKey: /etc/certs/privatekey.pem
FieldTypeDescription
portPort

REQUIRED: The Port on which the proxy should listen for incoming connections

hostsstring[]

REQUIRED. A list of hosts exposed by this gateway. At least one host is required. While typically applicable to HTTP services, it can also be used for TCP services using TLS with SNI. May contain a wildcard prefix for the bottom-level component of a domain name. For example *.foo.com matches bar.foo.com and *.com matches bar.foo.com, example.com, and so on.

Note: A VirtualService that is bound to a gateway must have one or more hosts that match the hosts specified in a server. The match could be an exact match or a suffix match with the server’s hosts. For example, if the server’s hosts specifies “*.example.com”, VirtualServices with hosts dev.example.com, prod.example.com will match. However, VirtualServices with hosts example.com or newexample.com will not match.

tlsServer.TLSOptions

Set of TLS related options that govern the server’s behavior. Use these options to control if all http requests should be redirected to https, and the TLS modes to use.

Server.TLSOptions

FieldTypeDescription
httpsRedirectbool

If set to true, the load balancer will send a 301 redirect for all http connections, asking the clients to use HTTPS.

modeServer.TLSOptions.TLSmode

Optional: Indicates whether connections to this port should be secured using TLS. The value of this field determines how TLS is enforced.

serverCertificatestring

REQUIRED if mode is SIMPLE or MUTUAL. The path to the file holding the server-side TLS certificate to use.

privateKeystring

REQUIRED if mode is SIMPLE or MUTUAL. The path to the file holding the server’s private key.

caCertificatesstring

REQUIRED if mode is MUTUAL. The path to a file containing certificate authority certificates to use in verifying a presented client side certificate.

subjectAltNamesstring[]

A list of alternate names to verify the subject identity in the certificate presented by the client.

Server.TLSOptions.TLSmode

TLS modes enforced by the proxy

NameDescription
PASSTHROUGH

Forward the connection to the upstream server selected based on the SNI string presented by the client.

SIMPLE

Secure connections with standard TLS semantics.

MUTUAL

Secure connections to the upstream using mutual TLS by presenting client certificates for authentication.

ServiceEntry

ServiceEntry enables adding additional entries into Istio’s internal service registry, so that auto-discovered services in the mesh can access/route to these manually specified services. A service entry describes the properties of a service (DNS name, VIPs ,ports, protocols, endpoints). These services could be external to the mesh (e.g., web APIs) or mesh-internal services that are not part of the platform’s service registry (e.g., a set of VMs talking to services in Kubernetes).

The following configuration adds a set of MongoDB instances running on unmanaged VMs to Istio’s registry, so that these services can be treated as any other service in the mesh. The associated DestinationRule is used to initiate mTLS connections to the database instances.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-mongocluster
spec:
  hosts:
  - mymongodb.somedomain # not used
  addresses:
  - 192.192.192.192/24 # VIPs
  ports:
  - number: 27018
    name: mongodb
    protocol: MONGO
  location: MESH_INTERNAL
  resolution: STATIC
  endpoints:
  - address: 2.2.2.2
  - address: 3.3.3.3

and the associated DestinationRule

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: mtls-mongocluster
spec:
  host: mymongodb.somedomain
  trafficPolicy:
    tls:
      mode: MUTUAL
      clientCertificate: /etc/certs/myclientcert.pem
      privateKey: /etc/certs/client_private_key.pem
      caCertificates: /etc/certs/rootcacerts.pem

The following example uses a combination of service entry and TLS routing in virtual service to demonstrate the use of SNI routing to forward unterminated TLS traffic from the application to external services via the sidecar. The sidecar inspects the SNI value in the ClientHello message to route to the appropriate external service.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-https
spec:
  hosts:
  - api.dropboxapi.com
  - www.googleapis.com
  - api.facebook.com
  location: MESH_EXTERNAL
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  resolution: DNS

And the associated VirtualService to route based on the SNI value.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: tls-routing
spec:
  hosts:
  - api.dropboxapi.com
  - www.googleapis.com
  - api.facebook.com
  tls:
  - match:
    - port: 443
      sniHosts:
      - api.dropboxapi.com
    route:
    - destination:
        host: api.dropboxapi.com
  - match:
    - port: 443
      sniHosts:
      - www.googleapis.com
    route:
    - destination:
        host: www.googleapis.com
  - match:
    - port: 443
      sniHosts:
      - api.facebook.com
    route:
    - destination:
        host: api.facebook.com

The following example demonstrates the use of a dedicated egress gateway through which all external service traffic is forwarded.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-httpbin
spec:
  hosts:
  - httpbin.com
  location: MESH_EXTERNAL
  ports:
  - number: 80
    name: http
    protocol: HTTP
  resolution: DNS

Define a gateway to handle all egress traffic.

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
 name: istio-egressgateway
spec:
 selector:
   istio: egressgateway
 servers:
 - port:
     number: 80
     name: http
     protocol: HTTP
   hosts:
   - "*"

And the associated VirtualService to route from the sidecar to the gateway service (istio-egressgateway.istio-system.svc.cluster.local), as well as route from the gateway to the external service.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: gateway-routing
spec:
  hosts:
  - httpbin.com
  gateways:
  - mesh
  - istio-egressgateway
  http:
  - match:
    - port: 80
      gateways:
      - mesh
    route:
    - destination:
        host: istio-egressgateway.istio-system.svc.cluster.local
  - match:
    - port: 80
      gateway:
      - istio-egressgateway
    route:
    - destination:
        host: httpbin.com

The following example demonstrates the use of wildcards in the hosts for external services. If the connection has to be routed to the IP address requested by the application (i.e. application resolves DNS and attempts to connect to a specific IP), the discovery mode must be set to NONE.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-wildcard-example
spec:
  hosts:
  - "*.bar.com"
  location: MESH_EXTERNAL
  ports:
  - number: 80
    name: http
    protocol: HTTP
  resolution: NONE

The following example demonstrates a service that is available via a Unix Domain Socket on the host of the client. The resolution must be set to STATIC to use unix address endpoints.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: unix-domain-socket-example
spec:
  hosts:
  - "example.unix.local"
  location: MESH_EXTERNAL
  ports:
  - number: 80
    name: http
    protocol: HTTP
  resolution: STATIC
  endpoints:
  - address: unix:///var/run/example/socket

For HTTP based services, it is possible to create a VirtualService backed by multiple DNS addressable endpoints. In such a scenario, the application can use the HTTP_PROXY environment variable to transparently reroute API calls for the VirtualService to a chosen backend. For example, the following configuration creates a non-existent external service called foo.bar.com backed by three domains: us.foo.bar.com:8080, uk.foo.bar.com:9080, and in.foo.bar.com:7080

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-dns
spec:
  hosts:
  - foo.bar.com
  location: MESH_EXTERNAL
  ports:
  - number: 80
    name: https
    protocol: HTTP
  resolution: DNS
  endpoints:
  - address: us.foo.bar.com
    ports:
      https: 8080
  - address: uk.foo.bar.com
    ports:
      https: 9080
  - address: in.foo.bar.com
    ports:
      https: 7080

With HTTP_PROXY=http://localhost/, calls from the application to http://foo.bar.com will be load balanced across the three domains specified above. In other words, a call to http://foo.bar.com/baz would be translated to http://uk.foo.bar.com/baz.

FieldTypeDescription
hostsstring[]

REQUIRED. The hosts associated with the ServiceEntry. Could be a DNS name with wildcard prefix (external services only). DNS names in hosts will be ignored if the application accesses the service over non-HTTP protocols such as mongo/opaque TCP/even HTTPS. In such scenarios, the IP addresses specified in the Addresses field or the port will be used to uniquely identify the destination.

addressesstring[]

The virtual IP addresses associated with the service. Could be CIDR prefix. For HTTP services, the addresses field will be ignored and the destination will be identified based on the HTTP Host/Authority header. For non-HTTP protocols such as mongo/opaque TCP/even HTTPS, the hosts will be ignored. If one or more IP addresses are specified, the incoming traffic will be identified as belonging to this service if the destination IP matches the IP/CIDRs specified in the addresses field. If the Addresses field is empty, traffic will be identified solely based on the destination port. In such scenarios, the port on which the service is being accessed must not be shared by any other service in the mesh. In other words, the sidecar will behave as a simple TCP proxy, forwarding incoming traffic on a specified port to the specified destination endpoint IP/host. Unix domain socket addresses are not supported in this field.

portsPort[]

REQUIRED. The ports associated with the external service. If the Endpoints are unix domain socket addresses, there must be exactly one port.

locationServiceEntry.Location

Specify whether the service should be considered external to the mesh or part of the mesh.

resolutionServiceEntry.Resolution

REQUIRED: Service discovery mode for the hosts. Care must be taken when setting the resolution mode to NONE for a TCP port without accompanying IP addresses. In such cases, traffic to any IP on said port will be allowed (i.e. 0.0.0.0:).

endpointsServiceEntry.Endpoint[]

One or more endpoints associated with the service.

ServiceEntry.Endpoint

Endpoint defines a network address (IP or hostname) associated with the mesh service.

FieldTypeDescription
addressstring

REQUIRED: Address associated with the network endpoint without the port. Domain names can be used if and only if the resolution is set to DNS, and must be fully-qualified without wildcards. Use the form unix:///absolute/path/to/socket for unix domain socket endpoints.

portsmap<string, uint32>

Set of ports associated with the endpoint. The ports must be associated with a port name that was declared as part of the service. Do not use for unix:// addresses.

labelsmap<string, string>

One or more labels associated with the endpoint.

ServiceEntry.Location

Location specifies whether the service is part of Istio mesh or outside the mesh. Location determines the behavior of several features, such as service-to-service mTLS authentication, policy enforcement, etc. When communicating with services outside the mesh, Istio’s mTLS authentication is disabled, and policy enforcement is performed on the client-side as opposed to server-side.

NameDescription
MESH_EXTERNAL

Signifies that the service is external to the mesh. Typically used to indicate external services consumed through APIs.

MESH_INTERNAL

Signifies that the service is part of the mesh. Typically used to indicate services added explicitly as part of expanding the service mesh to include unmanaged infrastructure (e.g., VMs added to a Kubernetes based service mesh).

ServiceEntry.Resolution

Resolution determines how the proxy will resolve the IP addresses of the network endpoints associated with the service, so that it can route to one of them. The resolution mode specified here has no impact on how the application resolves the IP address associated with the service. The application may still have to use DNS to resolve the service to an IP so that the outbound traffic can be captured by the Proxy. Alternatively, for HTTP services, the application could directly communicate with the proxy (e.g., by setting HTTP_PROXY) to talk to these services.

NameDescription
NONE

Assume that incoming connections have already been resolved (to a specific destination IP address). Such connections are typically routed via the proxy using mechanisms such as IP table REDIRECT/ eBPF. After performing any routing related transformations, the proxy will forward the connection to the IP address to which the connection was bound.

STATIC

Use the static IP addresses specified in endpoints (see below) as the backing instances associated with the service.

DNS

Attempt to resolve the IP address by querying the ambient DNS, during request processing. If no endpoints are specified, the proxy will resolve the DNS address specified in the hosts field, if wildcards are not used. If endpoints are specified, the DNS addresses specified in the endpoints will be resolved to determine the destination IP address. DNS resolution cannot be used with unix domain socket endpoints.

StringMatch

Describes how to match a given string in HTTP headers. Match is case-sensitive.

FieldTypeDescription
exactstring (oneof)

exact string match

prefixstring (oneof)

prefix-based match

regexstring (oneof)

ECMAscript style regex-based match

Subset

A subset of endpoints of a service. Subsets can be used for scenarios like A/B testing, or routing to a specific version of a service. Refer to VirtualService documentation for examples of using subsets in these scenarios. In addition, traffic policies defined at the service-level can be overridden at a subset-level. The following rule uses a round robin load balancing policy for all traffic going to a subset named testversion that is composed of endpoints (e.g., pods) with labels (version:v3).

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: bookinfo-ratings
spec:
  host: ratings.prod.svc.cluster.local
  trafficPolicy:
    loadBalancer:
      simple: LEAST_CONN
  subsets:
  - name: testversion
    labels:
      version: v3
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN

Note: Policies specified for subsets will not take effect until a route rule explicitly sends traffic to this subset.

FieldTypeDescription
namestring

REQUIRED. Name of the subset. The service name and the subset name can be used for traffic splitting in a route rule.

labelsmap<string, string>

REQUIRED. Labels apply a filter over the endpoints of a service in the service registry. See route rules for examples of usage.

trafficPolicyTrafficPolicy

Traffic policies that apply to this subset. Subsets inherit the traffic policies specified at the DestinationRule level. Settings specified at the subset level will override the corresponding settings specified at the DestinationRule level.

TCPRoute

Describes match conditions and actions for routing TCP traffic. The following routing rule forwards traffic arriving at port 27017 for mongo.prod.svc.cluster.local to another Mongo server on port 5555.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-Mongo
spec:
  hosts:
  - mongo.prod.svc.cluster.local
  tcp:
  - match:
    - port: 27017
    route:
    - destination:
        host: mongo.backup.svc.cluster.local
        port:
          number: 5555
FieldTypeDescription
matchL4MatchAttributes[]

Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.

routeDestinationWeight[]

The destination to which the connection should be forwarded to. Currently, only one destination is allowed for TCP services. When TCP weighted routing support is introduced in Envoy, multiple destinations with weights can be specified.

TLSMatchAttributes

TLS connection match attributes.

FieldTypeDescription
sniHostsstring[]

REQUIRED. SNI (server name indicator) to match on. Wildcard prefixes can be used in the SNI value. E.g., *.com will match foo.example.com as well as example.com.

destinationSubnetsstring[]

IPv4 or IPv6 ip addresses of destination with optional subnet. E.g., a.b.c.d/xx form or just a.b.c.d.

portuint32

Specifies the port on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.

sourceLabelsmap<string, string>

One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified at the top, it should include the reserved gateway mesh in order for this field to be applicable.

gatewaysstring[]

Names of gateways where the rule should be applied to. Gateway names at the top of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

TLSRoute

Describes match conditions and actions for routing unterminated TLS traffic (TLS/HTTPS) The following routing rule forwards unterminated TLS traffic arriving at port 443 of gateway called “mygateway” to internal services in the mesh based on the SNI value.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-sni
spec:
  hosts:
  - "*.bookinfo.com"
  gateways:
  - mygateway
  tls:
  - match:
    - port: 443
      sniHosts:
      - login.bookinfo.com
    route:
    - destination:
        host: login.prod.svc.cluster.local
  - match:
    - port: 443
      sniHosts:
      - reviews.bookinfo.com
    route:
    - destination:
        host: reviews.prod.svc.cluster.local
FieldTypeDescription
matchTLSMatchAttributes[]

REQUIRED. Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.

routeDestinationWeight[]

The destination to which the connection should be forwarded to. Currently, only one destination is allowed for TLS services. When TCP weighted routing support is introduced in Envoy, multiple destinations with weights can be specified.

TLSSettings

SSL/TLS related settings for upstream connections. See Envoy’s TLS context for more details. These settings are common to both HTTP and TCP upstreams.

For example, the following rule configures a client to use mutual TLS for connections to upstream database cluster.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: db-mtls
spec:
  host: mydbserver.prod.svc.cluster.local
  trafficPolicy:
    tls:
      mode: MUTUAL
      clientCertificate: /etc/certs/myclientcert.pem
      privateKey: /etc/certs/client_private_key.pem
      caCertificates: /etc/certs/rootcacerts.pem

The following rule configures a client to use TLS when talking to a foreign service whose domain matches *.foo.com.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: tls-foo
spec:
  host: "*.foo.com"
  trafficPolicy:
    tls:
      mode: SIMPLE

The following rule configures a client to use Istio mutual TLS when talking to rating services.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: ratings-istio-mtls
spec:
  host: ratings.prod.svc.cluster.local
  trafficPolicy:
    tls:
      mode: ISTIO_MUTUAL
FieldTypeDescription
modeTLSSettings.TLSmode

REQUIRED: Indicates whether connections to this port should be secured using TLS. The value of this field determines how TLS is enforced.

clientCertificatestring

REQUIRED if mode is MUTUAL. The path to the file holding the client-side TLS certificate to use. Should be empty if mode is ISTIO_MUTUAL.

privateKeystring

REQUIRED if mode is MUTUAL. The path to the file holding the client’s private key. Should be empty if mode is ISTIO_MUTUAL.

caCertificatesstring

OPTIONAL: The path to the file containing certificate authority certificates to use in verifying a presented server certificate. If omitted, the proxy will not verify the server’s certificate. Should be empty if mode is ISTIO_MUTUAL.

subjectAltNamesstring[]

A list of alternate names to verify the subject identity in the certificate. If specified, the proxy will verify that the server certificate’s subject alt name matches one of the specified values. Should be empty if mode is ISTIO_MUTUAL.

snistring

SNI string to present to the server during TLS handshake. Should be empty if mode is ISTIO_MUTUAL.

TLSSettings.TLSmode

TLS connection mode

NameDescription
DISABLE

Do not setup a TLS connection to the upstream endpoint.

SIMPLE

Originate a TLS connection to the upstream endpoint.

MUTUAL

Secure connections to the upstream using mutual TLS by presenting client certificates for authentication.

ISTIO_MUTUAL

Secure connections to the upstream using mutual TLS by presenting client certificates for authentication. Compared to Mutual mode, this mode uses certificates generated automatically by Istio for mTLS authentication. When this mode is used, all other fields in TLSSettings should be empty.

TrafficPolicy

Traffic policies to apply for a specific destination, across all destination ports. See DestinationRule for examples.

FieldTypeDescription
loadBalancerLoadBalancerSettings

Settings controlling the load balancer algorithms.

connectionPoolConnectionPoolSettings

Settings controlling the volume of connections to an upstream service

outlierDetectionOutlierDetection

Settings controlling eviction of unhealthy hosts from the load balancing pool

tlsTLSSettings

TLS related settings for connections to the upstream service.

portLevelSettingsTrafficPolicy.PortTrafficPolicy[]

Traffic policies specific to individual ports. Note that port level settings will override the destination-level settings. Traffic settings specified at the destination-level will not be inherited when overridden by port-level settings, i.e. default values will be applied to fields omitted in port-level traffic policies.

TrafficPolicy.PortTrafficPolicy

Traffic policies that apply to specific ports of the service

FieldTypeDescription
portPortSelector

Specifies the port name or number of a port on the destination service on which this policy is being applied.

Names must comply with DNS label syntax (rfc1035) and therefore cannot collide with numbers. If there are multiple ports on a service with the same protocol the names should be of the form-.

loadBalancerLoadBalancerSettings

Settings controlling the load balancer algorithms.

connectionPoolConnectionPoolSettings

Settings controlling the volume of connections to an upstream service

outlierDetectionOutlierDetection

Settings controlling eviction of unhealthy hosts from the load balancing pool

tlsTLSSettings

TLS related settings for connections to the upstream service.

VirtualService

A VirtualService defines a set of traffic routing rules to apply when a host is addressed. Each routing rule defines matching criteria for traffic of a specific protocol. If the traffic is matched, then it is sent to a named destination service (or subset/version of it) defined in the registry.

The source of traffic can also be matched in a routing rule. This allows routing to be customized for specific client contexts.

The following example on Kubernetes, routes all HTTP traffic by default to pods of the reviews service with label “version: v1”. In addition, HTTP requests containing /wpcatalog/, /consumercatalog/ url prefixes will be rewritten to /newcatalog and sent to pods with label “version: v2”.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews-route
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  http:
  - match:
    - uri:
        prefix: "/wpcatalog"
    - uri:
        prefix: "/consumercatalog"
    rewrite:
      uri: "/newcatalog"
    route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v2
  - route:
    - destination:
        host: reviews.prod.svc.cluster.local
        subset: v1

A subset/version of a route destination is identified with a reference to a named service subset which must be declared in a corresponding DestinationRule.

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews-destination
spec:
  host: reviews.prod.svc.cluster.local
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
FieldTypeDescription
hostsstring[]

REQUIRED. The destination hosts to which traffic is being sent. Could be a DNS name with wildcard prefix or an IP address. Depending on the platform, short-names can also be used instead of a FQDN (i.e. has no dots in the name). In such a scenario, the FQDN of the host would be derived based on the underlying platform.

A host name can be defined by only one VirtualService. A single VirtualService can be used to describe traffic properties for multiple HTTP and TCP ports.

Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.

The hosts field applies to both HTTP and TCP services. Service inside the mesh, i.e., those found in the service registry, must always be referred to using their alphanumeric names. IP addresses are allowed only for services defined via the Gateway.

gatewaysstring[]

The names of gateways and sidecars that should apply these routes. A single VirtualService is used for sidecars inside the mesh as well as for one or more gateways. The selection condition imposed by this field can be overridden using the source field in the match conditions of protocol-specific routes. The reserved word mesh is used to imply all the sidecars in the mesh. When this field is omitted, the default gateway (mesh) will be used, which would apply the rule to all sidecars in the mesh. If a list of gateway names is provided, the rules will apply only to the gateways. To apply the rules to both gateways and sidecars, specify mesh as one of the gateway names.

httpHTTPRoute[]

An ordered list of route rules for HTTP traffic. HTTP routes will be applied to platform service ports named ‘http-’/‘http2-’/‘grpc-*’, gateway ports with protocol HTTP/HTTP2/GRPC/ TLS-terminated-HTTPS and service entry ports using HTTP/HTTP2/GRPC protocols. The first rule matching an incoming request is used.

tlsTLSRoute[]

An ordered list of route rule for non-terminated TLS & HTTPS traffic. Routing is typically performed using the SNI value presented by the ClientHello message. TLS routes will be applied to platform service ports named ‘https-’, ‘tls-’, unterminated gateway ports using HTTPS/TLS protocols (i.e. with “passthrough” TLS mode) and service entry ports using HTTPS/TLS protocols. The first rule matching an incoming request is used. NOTE: Traffic ‘https-’ or ‘tls-’ ports without associated virtual service will be treated as opaque TCP traffic.

tcpTCPRoute[]

An ordered list of route rules for opaque TCP traffic. TCP routes will be applied to any port that is not a HTTP or TLS port. The first rule matching an incoming request is used.