Circuit Breaking

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

Circuit breaking is an important pattern for creating resilient microserviceapplications. 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 theconfiguration by intentionally “tripping” the circuit breaker.

Before you begin

如果您启用了 sidecar 自动注入，通过以下命令部署 httpbin 服务：

Zip

  1. $ kubectl apply -f @samples/httpbin/httpbin.yaml@

否则，您必须在部署 httpbin 应用程序前进行手动注入，部署命令如下：

Zip

  1. $ kubectl apply -f <(istioctl kube-inject -f @samples/httpbin/httpbin.yaml@)

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

Configuring the circuit breaker

  • Create a destination rule to apply circuit breaking settingswhen calling the httpbin service:

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.

  1. $ kubectl apply -f - <<EOF
  2. apiVersion: networking.istio.io/v1alpha3
  3. kind: DestinationRule
  4. metadata:
  5.   name: httpbin
  6. spec:
  7.   host: httpbin
  8.   trafficPolicy:
  9.     connectionPool:
  10.       tcp:
  11.         maxConnections: 1
  12.       http:
  13.         http1MaxPendingRequests: 1
  14.         maxRequestsPerConnection: 1
  15.     outlierDetection:
  16.       consecutiveErrors: 1
  17.       interval: 1s
  18.       baseEjectionTime: 3m
  19.       maxEjectionPercent: 100
  20. EOF
  • Verify the destination rule was created correctly:
  1. $ kubectl get destinationrule httpbin -o yaml
  2. apiVersion: networking.istio.io/v1alpha3
  3. kind: DestinationRule
  4. metadata:
  5.   name: httpbin
  6.   ...
  7. spec:
  8.   host: httpbin
  9.   trafficPolicy:
  10.     connectionPool:
  11.       http:
  12.         http1MaxPendingRequests: 1
  13.         maxRequestsPerConnection: 1
  14.       tcp:
  15.         maxConnections: 1
  16.     outlierDetection:
  17.       baseEjectionTime: 180.000s
  18.       consecutiveErrors: 1
  19.       interval: 1.000s
  20.       maxEjectionPercent: 100

Adding a client

Create a client to send traffic to the httpbin service. The client isa simple load-testing client called fortio.Fortio lets you control the number of connections, concurrency, anddelays for outgoing HTTP calls. You will use this client to “trip” the circuit breakerpolicies you set in the DestinationRule.

  • Inject the client with the Istio sidecar proxy so network interactions aregoverned by Istio:

Zip

  1. $ kubectl apply -f <(istioctl kube-inject -f @samples/httpbin/sample-client/fortio-deploy.yaml@)
  • 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:
  1. $ FORTIO_POD=$(kubectl get pod | grep fortio | awk '{ print $1 }')
  2. $ kubectl exec -it $FORTIO_POD  -c fortio /usr/bin/fortio -- load -curl  http://httpbin:8000/get
  3. HTTP/1.1 200 OK
  4. server: envoy
  5. date: Tue, 16 Jan 2018 23:47:00 GMT
  6. content-type: application/json
  7. access-control-allow-origin: *
  8. access-control-allow-credentials: true
  9. content-length: 445
  10. x-envoy-upstream-service-time: 36
  12. {
  13.   "args": {},
  14.   "headers": {
  15.     "Content-Length": "0",
  16.     "Host": "httpbin:8000",
  17.     "User-Agent": "istio/fortio-0.6.2",
  18.     "X-B3-Sampled": "1",
  19.     "X-B3-Spanid": "824fbd828d809bf4",
  20.     "X-B3-Traceid": "824fbd828d809bf4",
  21.     "X-Ot-Span-Context": "824fbd828d809bf4;824fbd828d809bf4;0000000000000000",
  22.     "X-Request-Id": "1ad2de20-806e-9622-949a-bd1d9735a3f4"
  23.   },
  24.   "origin": "127.0.0.1",
  25.   "url": "http://httpbin:8000/get"
  26. }

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 andhttp1MaxPendingRequests: 1. These rules indicate that if you exceed more thanone connection and request concurrently, you should see some failures when theistio-proxy opens the circuit for further requests and connections.

  • Call the service with two concurrent connections (-c 2) and send 20 requests(-n 20):
  1. $ kubectl exec -it $FORTIO_POD  -c fortio /usr/bin/fortio -- load -c 2 -qps 0 -n 20 -loglevel Warning http://httpbin:8000/get
  2. Fortio 0.6.2 running at 0 queries per second, 2->2 procs, for 5s: http://httpbin:8000/get
  3. Starting at max qps with 2 thread(s) [gomax 2] for exactly 20 calls (10 per thread + 0)
  4. 23:51:10 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  5. Ended after 106.474079ms : 20 calls. qps=187.84
  6. Aggregated Function Time : count 20 avg 0.010215375 +/- 0.003604 min 0.005172024 max 0.019434859 sum 0.204307492
  7. # range, mid point, percentile, count
  8. >= 0.00517202 <= 0.006 , 0.00558601 , 5.00, 1
  9. > 0.006 <= 0.007 , 0.0065 , 20.00, 3
  10. > 0.007 <= 0.008 , 0.0075 , 30.00, 2
  11. > 0.008 <= 0.009 , 0.0085 , 40.00, 2
  12. > 0.009 <= 0.01 , 0.0095 , 60.00, 4
  13. > 0.01 <= 0.011 , 0.0105 , 70.00, 2
  14. > 0.011 <= 0.012 , 0.0115 , 75.00, 1
  15. > 0.012 <= 0.014 , 0.013 , 90.00, 3
  16. > 0.016 <= 0.018 , 0.017 , 95.00, 1
  17. > 0.018 <= 0.0194349 , 0.0187174 , 100.00, 1
  18. # target 50% 0.0095
  19. # target 75% 0.012
  20. # target 99% 0.0191479
  21. # target 99.9% 0.0194062
  22. Code 200 : 19 (95.0 %)
  23. Code 503 : 1 (5.0 %)
  24. Response Header Sizes : count 20 avg 218.85 +/- 50.21 min 0 max 231 sum 4377
  25. Response Body/Total Sizes : count 20 avg 652.45 +/- 99.9 min 217 max 676 sum 13049
  26. All done 20 calls (plus 0 warmup) 10.215 ms avg, 187.8 qps

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

  1. Code 200 : 19 (95.0 %)
  2. Code 503 : 1 (5.0 %)
  • Bring the number of concurrent connections up to 3:
  1. $ kubectl exec -it $FORTIO_POD  -c fortio /usr/bin/fortio -- load -c 3 -qps 0 -n 30 -loglevel Warning http://httpbin:8000/get
  2. Fortio 0.6.2 running at 0 queries per second, 2->2 procs, for 5s: http://httpbin:8000/get
  3. Starting at max qps with 3 thread(s) [gomax 2] for exactly 30 calls (10 per thread + 0)
  4. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  5. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  6. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  7. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  8. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  9. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  10. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  11. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  12. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  13. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  14. 23:51:51 W http.go:617> Parsed non ok code 503 (HTTP/1.1 503)
  15. Ended after 71.05365ms : 30 calls. qps=422.22
  16. Aggregated Function Time : count 30 avg 0.0053360199 +/- 0.004219 min 0.000487853 max 0.018906468 sum 0.160080597
  17. # range, mid point, percentile, count
  18. >= 0.000487853 <= 0.001 , 0.000743926 , 10.00, 3
  19. > 0.001 <= 0.002 , 0.0015 , 30.00, 6
  20. > 0.002 <= 0.003 , 0.0025 , 33.33, 1
  21. > 0.003 <= 0.004 , 0.0035 , 40.00, 2
  22. > 0.004 <= 0.005 , 0.0045 , 46.67, 2
  23. > 0.005 <= 0.006 , 0.0055 , 60.00, 4
  24. > 0.006 <= 0.007 , 0.0065 , 73.33, 4
  25. > 0.007 <= 0.008 , 0.0075 , 80.00, 2
  26. > 0.008 <= 0.009 , 0.0085 , 86.67, 2
  27. > 0.009 <= 0.01 , 0.0095 , 93.33, 2
  28. > 0.014 <= 0.016 , 0.015 , 96.67, 1
  29. > 0.018 <= 0.0189065 , 0.0184532 , 100.00, 1
  30. # target 50% 0.00525
  31. # target 75% 0.00725
  32. # target 99% 0.0186345
  33. # target 99.9% 0.0188793
  34. Code 200 : 19 (63.3 %)
  35. Code 503 : 11 (36.7 %)
  36. Response Header Sizes : count 30 avg 145.73333 +/- 110.9 min 0 max 231 sum 4372
  37. Response Body/Total Sizes : count 30 avg 507.13333 +/- 220.8 min 217 max 676 sum 15214
  38. All done 30 calls (plus 0 warmup) 5.336 ms avg, 422.2 qps

Now you start to see the expected circuit breaking behavior. Only 63.3% of therequests succeeded and the rest were trapped by circuit breaking:

  1. Code 200 : 19 (63.3 %)
  2. Code 503 : 11 (36.7 %)
  • Query the istio-proxy stats to see more:
  1. $ kubectl exec $FORTIO_POD -c istio-proxy -- pilot-agent request GET stats | grep httpbin | grep pending
  2. cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_active: 0
  3. cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_failure_eject: 0
  4. cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_overflow: 12
  5. cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_total: 39

You can see 12 for the upstream_rq_pending_overflow value which means 12calls so far have been flagged for circuit breaking.

Cleaning up

  • Remove the rules:
  1. $ kubectl delete destinationrule httpbin
  • Shutdown the httpbin service and client:
  1. $ kubectl delete deploy httpbin fortio-deploy
  2. $ kubectl delete svc httpbin

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