Routing Rules

RouteRule

Glossary & concepts

Service is a unit of an application with a unique name that other services use to refer to the functionality being called. Service instances are pods/VMs/containers that implement the service.

Service versions - In a continuous deployment scenario, for a given service, there can be multiple sets of instances running potentially 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 - downstream client (browser or another service) calling the Envoy proxy/sidecar (typically to reach another service).

Destination - The remote upstream service to which the Envoy proxy/sidecar is talking to, on behalf of the source service. There can be one or more service versions for a given service (see the discussion on versions above). Envoy would choose the version based on various routing rules.

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

Route rule provides a custom routing policy based on the source and destination service versions and connection/request metadata. The rule must provide a set of conditions for each protocol (TCP, UDP, HTTP) that the destination service exposes on its ports.

The rule applies only to the ports on the destination service for which it provides protocol-specific match condition, e.g. if the rule does not specify TCP condition, the rule does not apply to TCP traffic towards the destination service.

For example, a simple rule to send 100% of incoming traffic for a “reviews” service to version “v1” can be specified as follows:

apiVersion: config.istio.io/v1alpha2
kind: RouteRule
metadata:
  name: my-rule
  namespace: default # optional (default is "default")
spec:
  destination:
    name: reviews
    namespace: my-namespace # optional (default is metadata namespace field)
  route:
  - labels:
      version: v1
    weight: 100
Field Type Description
destination IstioService

REQUIRED: Destination uniquely identifies the destination associated with this routing rule. This field is applicable for hostname-based resolution for HTTP traffic as well as IP-based resolution for TCP/UDP traffic.

Note: The route rule destination specification represents all version of the service and therefore the IstioService's labels field MUST be empty.

precedence int32 RECOMMENDED. Precedence is used to disambiguate the order of application of rules for the same destination service. A higher number takes priority. If not specified, the value is assumed to be 0. The order of application for rules with the same precedence is unspecified.
match MatchCondition Match condtions to be satisfied for the route rule to be activated. If match is omitted, the route rule applies only to HTTP traffic.
route[] repeated DestinationWeight REQUIRED (route|redirect). A routing rule can either redirect traffic or forward 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.
redirect HTTPRedirect REQUIRED (route|redirect). A routing rule can either redirect traffic or forward traffic. The redirect primitive can be used to send a HTTP 302 redirect to a different URI or Authority.
rewrite HTTPRewrite Rewrite HTTP URIs and Authority headers. Rewrite cannot be used with Redirect primitive. Rewrite will be performed before forwarding.
websocketUpgrade bool Indicates that a HTTP/1.1 client connection to this particular route should be allowed (and expected) to upgrade to a WebSocket connection. The default is false. Envoy expects the first request to this route to contain the WebSocket upgrade headers. Otherwise, the request will be rejected.
httpReqTimeout HTTPTimeout Timeout policy for HTTP requests.
httpReqRetries HTTPRetry Retry policy for HTTP requests.
httpFault HTTPFaultInjection Fault injection policy to apply on HTTP traffic

IstioService

IstioService identifies a service and optionally service version. The FQDN of the service is composed from the name, namespace, and implementation-specific domain suffix (e.g. on Kubernetes, “reviews” + “default” + “svc.cluster.local” -> “reviews.default.svc.cluster.local”).

Field Type Description
name string The short name of the service such as "foo".
namespace string Optional namespace of the service. Defaults to value of metadata namespace field.
domain string Domain suffix used to construct the service FQDN in implementations that support such specification.
service string The service FQDN.
labels repeated map<string, string>

Optional one or more labels that uniquely identify the service version.

Note: When used for a RouteRule destination, labels MUST be empty.

MatchCondition

Match condition specifies a set of criterion to be met in order for the route rule to be applied to the connection or HTTP request. The condition provides distinct set of conditions for each protocol with the intention that conditions apply only to the service ports that match the protocol. For example, the following route rule restricts the rule to match only requests originating from “reviews:v2”, accessing ratings service where the URL path starts with /ratings/v2/ and the request contains a “cookie” with value “user=jason”,

metadata:
  name: my-rule
  namespace: default
spec:
  destination:
    name: ratings
  match:
    source:
      name: reviews
      labels:
        version: v2
    request:
      headers:
        cookie:
          regex: "^(.*?;)?(user=jason)(;.*)?"
        uri:
          prefix: "/ratings/v2/"

MatchCondition CANNOT be empty. At least one source or request header must be specified.

Field Type Description
source IstioService Identifies the service initiating a connection or a request.
request MatchRequest Attributes of an HTTP request to match.

MatchRequest

MatchRequest specifies the attributes of an HTTP request to be used for matching a request.

Field Type Description
headers repeated map<string, StringMatch>

Set of HTTP match conditions based on HTTP/1.1, HTTP/2, GRPC request metadata, such as uri, scheme, authority. 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" or just "value" for exact string match

prefix: "value" for prefix-based match

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

Note 1: The keys uri, scheme, method, and authority correspond to URI, protocol scheme (e.g., HTTP, HTTPS), HTTP method (e.g., GET, POST), and the HTTP Host header respectively.

Note 2: uri can be used to perform URL matches. For all HTTP headers including uri, exact, prefix and ECMA style regular expression matches are supported.

StringMatch

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

Field Type Description
exact string (oneof ) exact string match
prefix string (oneof ) prefix-based match
regex string (oneof ) ECMAscript style regex-based match

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”.

metadata:
  name: my-rule
  namespace: default
spec:
  destination:
    name: reviews
  route:
  - labels:
      version: v2
    weight: 25
  - labels:
      version: v1
    weight: 75
Field Type Description
destination IstioService Sometimes required. Optional destination uniquely identifies the destination service. If not specified, the value is inherited from the parent route rule.
labels repeated map<string, string> Sometimes required. Service version identifier for the destination service.
weight int32 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. When using multiple weights, either destination or labels must be specified.

HTTPRedirect

HTTPRedirect can be used to send a 302 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 route rule redirects requests for /v1/getProductRatings API on the ratings service to /v1/bookRatings provided by the bookratings service.

metadata:
  name: my-rule
  namespace: default
spec:
  destination:
    name: ratings
  match:
    request:
      headers:
        uri: /v1/getProductRatings
  redirect:
    uri: /v1/bookRatings
    authority: bookratings.default.svc.cluster.local
Field Type Description
uri string 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.
authority string On a redirect, overwrite the Authority/Host portion of the URL with this value

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.

metadata:
  name: my-rule
  namespace: default
spec:
  destination:
    name: ratings
  match:
    request:
      headers:
        uri:
          prefix: /ratings
  rewrite:
    uri: /v1/bookRatings
  route:
  - labels:
      version: v1
Field Type Description
uri string 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.
authority string rewrite the Authority/Host header with this value.

HTTPTimeout

Describes HTTP request timeout. For example, the following rule sets a 10 second timeout for calls to the ratings:v1 service

metadata:
  name: my-rule
  namespace: default
spec:
  destination:
    name: ratings
  route:
  - labels:
      version: v1
  httpReqTimeout:
    simpleTimeout:
      timeout: 10s
Field Type Description
simpleTimeout SimpleTimeoutPolicy

SimpleTimeoutPolicy

Field Type Description
timeout Duration REQUIRED. Timeout for a HTTP request. Includes retries as well. Default 15s. format: 1h/1m/1s/1ms. MUST BE >=1ms. It is possible to control timeout per request by supplying the timeout value via x-envoy-upstream-rq-timeout-ms HTTP header.

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.

metadata:
  name: my-rule
  namespace: default
spec:
  destination:
    name: ratings
  route:
  - labels:
      version: v1
  httpReqRetries:
    simpleRetry:
      attempts: 3
      perTryTimeout: 2s
Field Type Description
simpleRetry SimpleRetryPolicy

SimpleRetryPolicy

Field Type Description
attempts int32 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.
perTryTimeout Duration Timeout per retry attempt for a given request. format: 1h/1m/1s/1ms. MUST BE >=1ms.

HTTPFaultInjection

HTTPFaultInjection can be used to specify one or more faults to inject while forwarding http requests to the destination specified in the route rule. Fault specification is part of a route 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.

Field Type Description
delay Delay Delay requests before forwarding, emulating various failures such as network issues, overloaded upstream service, etc.
abort Abort Abort Http request attempts and return error codes back to downstream service, giving the impression that the upstream service is faulty.

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”.

metadata:
  name: my-rule
spec:
  destination:
    name: reviews
  route:
  - labels:
      version: v1
  httpFault:
    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.

Field Type Description
percent float percentage of requests to be aborted with the error code provided (0-100).
httpStatus int32 REQUIRED. HTTP status code to use to abort the Http request.

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.

metadata:
  name: my-rule
spec:
  destination:
    name: reviews
  route:
  - labels:
      version: v1
  httpFault:
    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.

Field Type Description
percent float percentage of requests on which the delay will be injected (0-100)
fixedDelay Duration REQUIRED. Add a fixed delay before forwarding the request. Format: 1h/1m/1s/1ms. MUST be >=1ms.