istio.io/content/en/docs/tasks/traffic-management/circuit-breaking/index.md

title	description	weight	keywords	owner	test
Circuit Breaking	This task shows you how to configure circuit breaking for connections, requests, and outlier detection.	50	traffic-management circuit-breaking	istio/wg-networking-maintainers	yes

This task shows you how to configure circuit breaking for connections, requests, and outlier detection.

Circuit breaking is an important pattern for creating resilient microservice applications. Circuit breaking allows you to write applications that limit the impact of failures, latency spikes, and other undesirable effects of network peculiarities.

In this task, you will configure circuit breaking rules and then test the configuration by intentionally "tripping" the circuit breaker.

Before you begin

• Setup Istio by following the instructions in the Installation guide.

{{< boilerplate start-httpbin-service >}}

The httpbin application serves as the backend service for this task.

Configuring the circuit breaker

1. Create a destination rule to apply circuit breaking settings when calling the httpbin service:

   {{< warning >}} If you installed/configured Istio with mutual TLS authentication enabled, you must add a TLS traffic policy mode: ISTIO_MUTUAL to the DestinationRule before applying it. Otherwise requests will generate 503 errors as described here. {{< /warning >}}

   {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1 kind: DestinationRule metadata: name: httpbin spec: host: httpbin trafficPolicy: connectionPool: tcp: maxConnections: 1 http: http1MaxPendingRequests: 1 maxRequestsPerConnection: 1 outlierDetection: consecutive5xxErrors: 1 interval: 1s baseEjectionTime: 3m maxEjectionPercent: 100 EOF {{< /text >}}

2. Verify the destination rule was created correctly:

   {{< text bash yaml >}} $ kubectl get destinationrule httpbin -o yaml apiVersion: networking.istio.io/v1 kind: DestinationRule ... spec: host: httpbin trafficPolicy: connectionPool: http: http1MaxPendingRequests: 1 maxRequestsPerConnection: 1 tcp: maxConnections: 1 outlierDetection: baseEjectionTime: 3m consecutive5xxErrors: 1 interval: 1s maxEjectionPercent: 100 {{< /text >}}

Adding a client

Create a client to send traffic to the httpbin service. The client is a simple load-testing client called fortio. Fortio lets you control the number of connections, concurrency, and delays for outgoing HTTP calls. You will use this client to "trip" the circuit breaker policies you set in the DestinationRule. 

1. Inject the client with the Istio sidecar proxy so network interactions are governed by Istio.

   If you have enabled automatic sidecar injection, deploy the fortio service:

   {{< text bash >}} $ kubectl apply -f @samples/httpbin/sample-client/fortio-deploy.yaml@ {{< /text >}}

   Otherwise, you have to manually inject the sidecar before deploying the fortio application:

   {{< text bash >}} $ kubectl apply -f <(istioctl kube-inject -f @samples/httpbin/sample-client/fortio-deploy.yaml@) {{< /text >}}

2. Log in to the client pod and use the fortio tool to call httpbin. Pass in curl to indicate that you just want to make one call:

   {{< text bash >}} export FORTIO_POD=(kubectl get pods -l app=fortio -o 'jsonpath={.items[0].metadata.name}') $ kubectl exec "$FORTIO_POD" -c fortio -- /usr/bin/fortio curl -quiet http://httpbin:8000/get HTTP/1.1 200 OK server: envoy date: Tue, 25 Feb 2020 20:25:52 GMT content-type: application/json content-length: 586 access-control-allow-origin: * access-control-allow-credentials: true x-envoy-upstream-service-time: 36

   { "args": {}, "headers": { "Content-Length": "0", "Host": "httpbin:8000", "User-Agent": "fortio.org/fortio-1.3.1", "X-B3-Parentspanid": "8fc453fb1dec2c22", "X-B3-Sampled": "1", "X-B3-Spanid": "071d7f06bc94943c", "X-B3-Traceid": "86a929a0e76cda378fc453fb1dec2c22", "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/default/sa/httpbin;Hash=68bbaedefe01ef4cb99e17358ff63e92d04a4ce831a35ab9a31d3c8e06adb038;Subject="";URI=spiffe://cluster.local/ns/default/sa/default" }, "origin": "127.0.0.1", "url": "http://httpbin:8000/get" } {{< /text >}}

You can see the request succeeded! Now, it's time to break something.

Tripping the circuit breaker

In the DestinationRule settings, you specified maxConnections: 1 and http1MaxPendingRequests: 1. These rules indicate that if you exceed more than one connection and request concurrently, you should see some failures when the istio-proxy opens the circuit for further requests and connections.

1. Call the service with two concurrent connections (-c 2) and send 20 requests (-n 20):

   {{< text bash >}} $ kubectl exec "$FORTIO_POD" -c fortio -- /usr/bin/fortio load -c 2 -qps 0 -n 20 -loglevel Warning http://httpbin:8000/get 20:33:46 I logger.go:97> Log level is now 3 Warning (was 2 Info) Fortio 1.3.1 running at 0 queries per second, 6->6 procs, for 20 calls: http://httpbin:8000/get Starting at max qps with 2 thread(s) [gomax 6] for exactly 20 calls (10 per thread + 0) 20:33:46 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:33:47 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:33:47 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) Ended after 59.8524ms : 20 calls. qps=334.16 Aggregated Function Time : count 20 avg 0.0056869 +/- 0.003869 min 0.000499 max 0.0144329 sum 0.113738

   range, mid point, percentile, count

   = 0.000499 <= 0.001 , 0.0007495 , 10.00, 2 0.001 <= 0.002 , 0.0015 , 15.00, 1 0.003 <= 0.004 , 0.0035 , 45.00, 6 0.004 <= 0.005 , 0.0045 , 55.00, 2 0.005 <= 0.006 , 0.0055 , 60.00, 1 0.006 <= 0.007 , 0.0065 , 70.00, 2 0.007 <= 0.008 , 0.0075 , 80.00, 2 0.008 <= 0.009 , 0.0085 , 85.00, 1 0.011 <= 0.012 , 0.0115 , 90.00, 1 0.012 <= 0.014 , 0.013 , 95.00, 1 0.014 <= 0.0144329 , 0.0142165 , 100.00, 1

   target 50% 0.0045

   target 75% 0.0075

   target 90% 0.012

   target 99% 0.0143463

   target 99.9% 0.0144242

   Sockets used: 4 (for perfect keepalive, would be 2) Code 200 : 17 (85.0 %) Code 503 : 3 (15.0 %) Response Header Sizes : count 20 avg 195.65 +/- 82.19 min 0 max 231 sum 3913 Response Body/Total Sizes : count 20 avg 729.9 +/- 205.4 min 241 max 817 sum 14598 All done 20 calls (plus 0 warmup) 5.687 ms avg, 334.2 qps {{< /text >}}

   It's interesting to see that almost all requests made it through! The istio-proxy does allow for some leeway.

   {{< text plain >}} Code 200 : 17 (85.0 %) Code 503 : 3 (15.0 %) {{< /text >}}

2. Bring the number of concurrent connections up to 3:

   {{< text bash >}} $ kubectl exec "$FORTIO_POD" -c fortio -- /usr/bin/fortio load -c 3 -qps 0 -n 30 -loglevel Warning http://httpbin:8000/get 20:32:30 I logger.go:97> Log level is now 3 Warning (was 2 Info) Fortio 1.3.1 running at 0 queries per second, 6->6 procs, for 30 calls: http://httpbin:8000/get Starting at max qps with 3 thread(s) [gomax 6] for exactly 30 calls (10 per thread + 0) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503) Ended after 51.9946ms : 30 calls. qps=576.98 Aggregated Function Time : count 30 avg 0.0040001633 +/- 0.003447 min 0.0004298 max 0.015943 sum 0.1200049

   range, mid point, percentile, count

   = 0.0004298 <= 0.001 , 0.0007149 , 16.67, 5 0.001 <= 0.002 , 0.0015 , 36.67, 6 0.002 <= 0.003 , 0.0025 , 50.00, 4 0.003 <= 0.004 , 0.0035 , 60.00, 3 0.004 <= 0.005 , 0.0045 , 66.67, 2 0.005 <= 0.006 , 0.0055 , 76.67, 3 0.006 <= 0.007 , 0.0065 , 83.33, 2 0.007 <= 0.008 , 0.0075 , 86.67, 1 0.008 <= 0.009 , 0.0085 , 90.00, 1 0.009 <= 0.01 , 0.0095 , 96.67, 2 0.014 <= 0.015943 , 0.0149715 , 100.00, 1

   target 50% 0.003

   target 75% 0.00583333

   target 90% 0.009

   target 99% 0.0153601

   target 99.9% 0.0158847

   Sockets used: 20 (for perfect keepalive, would be 3) Code 200 : 11 (36.7 %) Code 503 : 19 (63.3 %) Response Header Sizes : count 30 avg 84.366667 +/- 110.9 min 0 max 231 sum 2531 Response Body/Total Sizes : count 30 avg 451.86667 +/- 277.1 min 241 max 817 sum 13556 All done 30 calls (plus 0 warmup) 4.000 ms avg, 577.0 qps {{< /text >}}

   Now you start to see the expected circuit breaking behavior. Only 36.7% of the requests succeeded and the rest were trapped by circuit breaking:

   {{< text plain >}} Code 200 : 11 (36.7 %) Code 503 : 19 (63.3 %) {{< /text >}}

3. Query the istio-proxy stats to see more:

   {{< text bash >}} $ kubectl exec "$FORTIO_POD" -c istio-proxy -- pilot-agent request GET stats | grep httpbin | grep pending cluster.outbound|8000||httpbin.default.svc.cluster.local;.circuit_breakers.default.remaining_pending: 1 cluster.outbound|8000||httpbin.default.svc.cluster.local;.circuit_breakers.default.rq_pending_open: 0 cluster.outbound|8000||httpbin.default.svc.cluster.local;.circuit_breakers.high.rq_pending_open: 0 cluster.outbound|8000||httpbin.default.svc.cluster.local;.upstream_rq_pending_active: 0 cluster.outbound|8000||httpbin.default.svc.cluster.local;.upstream_rq_pending_failure_eject: 0 cluster.outbound|8000||httpbin.default.svc.cluster.local;.upstream_rq_pending_overflow: 21 cluster.outbound|8000||httpbin.default.svc.cluster.local;.upstream_rq_pending_total: 29 {{< /text >}}

   You can see 21 for the upstream_rq_pending_overflow value which means 21 calls so far have been flagged for circuit breaking.

Cleaning up

1. Remove the rules:

   {{< text bash >}} $ kubectl delete destinationrule httpbin {{< /text >}}

2. Shutdown the [httpbin]({{< github_tree >}}/samples/httpbin) service and client:

   {{< text bash >}} $ kubectl delete -f @samples/httpbin/sample-client/fortio-deploy.yaml@ $ kubectl delete -f @samples/httpbin/httpbin.yaml@ {{< /text >}}