Debugging Envoy and Istiod

Istio provides two very valuable commands to help diagnose traffic management configuration problems, the proxy-status and proxy-config commands. The proxy-status command allows you to get an overview of your mesh and identify the proxy causing the problem. Then proxy-config can be used to inspect Envoy configuration and diagnose the issue.

If you want to try the commands described below, you can either:


  • Use similar commands against your own application running in a Kubernetes cluster.

Get an overview of your mesh

The proxy-status command allows you to get an overview of your mesh. If you suspect one of your sidecars isn’t receiving configuration or is out of sync then proxy-status will tell you this.

$ istioctl proxy-status
NAME                                                   CDS        LDS        EDS        RDS          PILOT                       VERSION
details-v1-6fc55d65c9-x6qz8.default                    SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
istio-ingressgateway-74f5cf489f-xqcnh.istio-system     SYNCED     SYNCED     SYNCED     NOT SENT     istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
productpage-v1-7f44c4d57c-5f99x.default                SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
prometheus-68b46fc8bb-dc965.istio-system               SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
ratings-v1-6f855c5fff-mlqmv.default                    SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
reviews-v1-54b8794ddf-tc8hd.default                    SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
reviews-v2-c4d6568f9-4flql.default                     SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2
reviews-v3-7f66977689-hwknn.default                    SYNCED     SYNCED     SYNCED     SYNCED       istiod-56b6dd58dd-fx5tx     1.6.0-rc.2

If a proxy is missing from this list it means that it is not currently connected to a Istiod instance so will not be receiving any configuration.

  • SYNCED means that Envoy has acknowledged the last configuration Istiod has sent to it.
  • NOT SENT means that Istiod hasn’t sent anything to Envoy. This usually is because Istiod has nothing to send.
  • STALE means that Istiod has sent an update to Envoy but has not received an acknowledgement. This usually indicates a networking issue between Envoy and Istiod or a bug with Istio itself.

Retrieve diffs between Envoy and Istiod

The proxy-status command can also be used to retrieve a diff between the configuration Envoy has loaded and the configuration Istiod would send, by providing a proxy ID. This can help you determine exactly what is out of sync and where the issue may lie.

$ istioctl proxy-status details-v1-6dcc6fbb9d-wsjz4.default
--- Istiod Clusters
+++ Envoy Clusters
@@ -374,36 +374,14 @@
             "edsClusterConfig": {
                "edsConfig": {
                   "ads": {

                "serviceName": "outbound|443||public-cr0bdc785ce3f14722918080a97e1f26be-alb1.kube-system.svc.cluster.local"
-            },
-            "connectTimeout": "1.000s",
-            "circuitBreakers": {
-               "thresholds": [
-                  {
-                  }
-               ]
-            }
-         }
-      },
-      {
-         "cluster": {
-            "name": "outbound|53||kube-dns.kube-system.svc.cluster.local",
-            "type": "EDS",
-            "edsClusterConfig": {
-               "edsConfig": {
-                  "ads": {
-                  }
-               },
-               "serviceName": "outbound|53||kube-dns.kube-system.svc.cluster.local"
             "connectTimeout": "1.000s",
             "circuitBreakers": {
                "thresholds": [


Listeners Match
Routes Match

Here you can see that the listeners and routes match but the clusters are out of sync.

Deep dive into Envoy configuration

The proxy-config command can be used to see how a given Envoy instance is configured. This can then be used to pinpoint any issues you are unable to detect by just looking through your Istio configuration and custom resources. To get a basic summary of clusters, listeners or routes for a given pod use the command as follows (changing clusters for listeners or routes when required):

$ istioctl proxy-config cluster -n istio-system istio-ingressgateway-7d6874b48f-qxhn5
SERVICE FQDN                                                               PORT      SUBSET     DIRECTION     TYPE
BlackHoleCluster                                                           -         -          -             STATIC
agent                                                                      -         -          -             STATIC
details.default.svc.cluster.local                                          9080      -          outbound      EDS
istio-ingressgateway.istio-system.svc.cluster.local                        80        -          outbound      EDS
istio-ingressgateway.istio-system.svc.cluster.local                        443       -          outbound      EDS
istio-ingressgateway.istio-system.svc.cluster.local                        15021     -          outbound      EDS
istio-ingressgateway.istio-system.svc.cluster.local                        15443     -          outbound      EDS
istiod.istio-system.svc.cluster.local                                      443       -          outbound      EDS
istiod.istio-system.svc.cluster.local                                      853       -          outbound      EDS
istiod.istio-system.svc.cluster.local                                      15010     -          outbound      EDS
istiod.istio-system.svc.cluster.local                                      15012     -          outbound      EDS
istiod.istio-system.svc.cluster.local                                      15014     -          outbound      EDS
kube-dns.kube-system.svc.cluster.local                                     53        -          outbound      EDS
kube-dns.kube-system.svc.cluster.local                                     9153      -          outbound      EDS
kubernetes.default.svc.cluster.local                                       443       -          outbound      EDS
productpage.default.svc.cluster.local                                      9080      -          outbound      EDS
prometheus.istio-system.svc.cluster.local                                  9090      -          outbound      EDS
prometheus_stats                                                           -         -          -             STATIC
ratings.default.svc.cluster.local                                          9080      -          outbound      EDS
reviews.default.svc.cluster.local                                          9080      -          outbound      EDS
sds-grpc                                                                   -         -          -             STATIC
xds-grpc                                                                   -         -          -             STRICT_DNS
zipkin                                                                     -         -          -             STRICT_DNS

In order to debug Envoy you need to understand Envoy clusters/listeners/routes/endpoints and how they all interact. We will use the proxy-config command with the -o json and filtering flags to follow Envoy as it determines where to send a request from the productpage pod to the reviews pod at reviews:9080.

  1. If you query the listener summary on a pod you will notice Istio generates the following listeners:

    • A listener on that receives all inbound traffic to the pod and a listener on that receives all outbound traffic to the pod, then hands the request over to a virtual listener.
    • A virtual listener per service IP, per each non-HTTP for outbound TCP/HTTPS traffic.
    • A virtual listener on the pod IP for each exposed port for inbound traffic.
    • A virtual listener on per each HTTP port for outbound HTTP traffic.
    $ istioctl proxy-config listeners productpage-v1-6c886ff494-7vxhs
    ADDRESS            PORT      TYPE         53        TCP        <--+     15012     TCP           |      15443     TCP           | Receives outbound non-HTTP traffic for relevant IP:PORT pair from listener ``          443       TCP           |     443       TCP           |      443       TCP        <--+            9090      HTTP+TCP   <--+         9153      HTTP+TCP      |            15010     HTTP+TCP      |            80        HTTP+TCP      | Receives outbound HTTP+TCP traffic for relevant port from listener ``            15014     HTTP+TCP      |     853       HTTP+TCP      |      15021     HTTP+TCP   <--+            9080      HTTP+TCP   // Receives all inbound traffic on 9080 from listener ``            15001     TCP        // Receives all outbound traffic to the pod from IP tables and hands over to virtual listener            15006     HTTP+TCP            15090     HTTP            15021     HTTP
  2. From the above summary you can see that every sidecar has a listener bound to which is where IP tables routes all inbound pod traffic to and a listener bound to which is where IP tables routes all outbound pod traffic to. This listener has useOriginalDst set to true which means it hands the request over to the listener that best matches the original destination of the request. If it can’t find any matching virtual listeners it sends the request to the PassthroughCluster which connects to the destination directly.

    $ istioctl proxy-config listeners productpage-v1-6c886ff494-7vxhs --port 15001 -o json
            "name": "virtualOutbound",
            "address": {
                "socketAddress": {
                    "address": "",
                    "portValue": 15001
            "filterChains": [
                    "filters": [
                            "name": "istio.stats",
                            "typedConfig": {
                                "@type": "",
                                "typeUrl": "",
                                "value": {
                                    "config": {
                                        "configuration": "{\n  \"debug\": \"false\",\n  \"stat_prefix\": \"istio\"\n}\n",
                                        "root_id": "stats_outbound",
                                        "vm_config": {
                                            "code": {
                                                "local": {
                                                    "inline_string": "envoy.wasm.stats"
                                            "runtime": "envoy.wasm.runtime.null",
                                            "vm_id": "tcp_stats_outbound"
                            "name": "envoy.tcp_proxy",
                            "typedConfig": {
                                "@type": "",
                                "statPrefix": "PassthroughCluster",
                                "cluster": "PassthroughCluster"
                    "name": "virtualOutbound-catchall-tcp"
            "useOriginalDst": true,
            "trafficDirection": "OUTBOUND"
  3. Our request is an outbound HTTP request to port 9080 this means it gets handed off to the virtual listener. This listener then looks up the route configuration in its configured RDS. In this case it will be looking up route 9080 in RDS configured by Istiod (via ADS).

    $ istioctl proxy-config listeners productpage-v1-6c886ff494-7vxhs -o json --address --port 9080
    "rds": {
        "configSource": {
            "ads": {}
        "routeConfigName": "9080"
  4. The 9080 route configuration only has a virtual host for each service. Our request is heading to the reviews service so Envoy will select the virtual host to which our request matches a domain. Once matched on domain Envoy looks for the first route that matches the request. In this case we don’t have any advanced routing so there is only one route that matches on everything. This route tells Envoy to send the request to the outbound|9080||reviews.default.svc.cluster.local cluster.

    $ istioctl proxy-config routes productpage-v1-6c886ff494-7vxhs --name 9080 -o json
            "name": "9080",
            "virtualHosts": [
                    "name": "reviews.default.svc.cluster.local:9080",
                    "domains": [
                    "routes": [
                            "name": "default",
                            "match": {
                                "prefix": "/"
                            "route": {
                                "cluster": "outbound|9080||reviews.default.svc.cluster.local",
                                "timeout": "0s",
  5. This cluster is configured to retrieve the associated endpoints from Istiod (via ADS). So Envoy will then use the serviceName field as a key to look up the list of Endpoints and proxy the request to one of them.

    $ istioctl proxy-config cluster productpage-v1-6c886ff494-7vxhs --fqdn reviews.default.svc.cluster.local -o json
            "name": "outbound|9080||reviews.default.svc.cluster.local",
            "type": "EDS",
            "edsClusterConfig": {
                "edsConfig": {
                    "ads": {}
                "serviceName": "outbound|9080||reviews.default.svc.cluster.local"
            "connectTimeout": "10s",
            "circuitBreakers": {
                "thresholds": [
                        "maxConnections": 4294967295,
                        "maxPendingRequests": 4294967295,
                        "maxRequests": 4294967295,
                        "maxRetries": 4294967295
  6. To see the endpoints currently available for this cluster use the proxy-config endpoints command.

    $ istioctl proxy-config endpoints productpage-v1-6c886ff494-7vxhs --cluster "outbound|9080||reviews.default.svc.cluster.local"
    ENDPOINT            STATUS      OUTLIER CHECK     CLUSTER     HEALTHY     OK                outbound|9080||reviews.default.svc.cluster.local     HEALTHY     OK                outbound|9080||reviews.default.svc.cluster.local     HEALTHY     OK                outbound|9080||reviews.default.svc.cluster.local

Inspecting bootstrap configuration

So far we have looked at configuration retrieved (mostly) from Istiod, however Envoy requires some bootstrap configuration that includes information like where Istiod can be found. To view this use the following command:

$ istioctl proxy-config bootstrap -n istio-system istio-ingressgateway-7d6874b48f-qxhn5
    "bootstrap": {
        "node": {
            "id": "router~",
            "cluster": "istio-ingressgateway",
            "metadata": {
                    "POD_NAME": "istio-ingressgateway-7d6874b48f-qxhn5",
                    "istio": "sidecar"
            "buildVersion": "0/1.8.0-dev//RELEASE"

Verifying connectivity to Istiod

Verifying connectivity to Istiod is a useful troubleshooting step. Every proxy container in the service mesh should be able to communicate with Istiod. This can be accomplished in a few simple steps:

  1. Create a sleep pod:

    $ kubectl create namespace foo
    $ kubectl apply -f <(istioctl kube-inject -f samples/sleep/sleep.yaml) -n foo
  2. Test connectivity to Istiod using curl. The following example invokes the v1 registration API using default Istiod configuration parameters and mutual TLS enabled:

    $ kubectl exec $(kubectl get pod -l app=sleep -n foo -o jsonpath={}) -c sleep -n foo -- curl -sS istiod.istio-system:15014/debug/endpointz

You should receive a response listing the “service” and “endpoint” for each service in the mesh.

What Envoy version is Istio using?

To find out the Envoy version used in deployment, you can exec into the container and query the server_info endpoint:

$ kubectl exec -it prometheus-68b46fc8bb-dc965 -c istio-proxy -n istio-system pilot-agent request GET server_info
 "version": "12cfbda324320f99e0e39d7c393109fcd824591f/1.14.1/Clean/RELEASE/BoringSSL"
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