熔断

本任务展示如何为连接、请求以及异常检测配置熔断。

熔断，是创建弹性微服务应用程序的重要模式。熔断能够使您的应用程序具备应对来自故障、潜在峰值和其他未知网络因素影响的能力。

这个任务中，你将配置熔断规则，然后通过有意的使熔断器“跳闸”来测试配置。

开始之前

  • 跟随安装指南安装 Istio。

  • 启动 Httpbin 样例程序。

    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@)

应用程序 httpbin 作为此任务的后端服务。

配置熔断器

  1. 创建一个目标规则，在调用 httpbin 服务时应用熔断设置：

    如果您的 Istio 启用了双向 TLS 身份验证，则必须在应用目标规则之前将 TLS 流量策略 mode：ISTIO_MUTUAL 添加到 DestinationRule。否则请求将产生 503 错误，如这里所述。

    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.       consecutive5xxErrors: 1
    17.       interval: 1s
    18.       baseEjectionTime: 3m
    19.       maxEjectionPercent: 100
    20. EOF

  2. 验证目标规则是否已正确创建：

    1. $ kubectl get destinationrule httpbin -o yaml
    2. apiVersion: networking.istio.io/v1beta1
    3. kind: DestinationRule
    4. ...
    5. spec:
    6.   host: httpbin
    7.   trafficPolicy:
    8.     connectionPool:
    9.       http:
    10.         http1MaxPendingRequests: 1
    11.         maxRequestsPerConnection: 1
    12.       tcp:
    13.         maxConnections: 1
    14.     outlierDetection:
    15.       baseEjectionTime: 3m
    16.       consecutive5xxErrors: 1
    17.       interval: 1s
    18.       maxEjectionPercent: 100

增加一个客户端

创建客户端程序以发送流量到 httpbin 服务。这是一个名为 Fortio 的负载测试客户端，它可以控制连接数、并发数及发送 HTTP 请求的延迟。通过 Fortio 能够有效的触发前面在 DestinationRule 中设置的熔断策略。

  1. 向客户端注入 Istio Sidecar 代理，以便 Istio 对其网络交互进行管理：

    如果你启用了自动注入 Sidecar，可以直接部署 fortio 应用：

    Zip

    1. $ kubectl apply -f @samples/httpbin/sample-client/fortio-deploy.yaml@

    否则，你需要在部署 fortio 应用前手动注入 Sidecar：

    Zip

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

  2. 登入客户端 Pod 并使用 Fortio 工具调用 httpbin 服务。-curl 参数表明发送一次调用：

    1. $ export FORTIO_POD=$(kubectl get pods -l app=fortio -o 'jsonpath={.items[0].metadata.name}')
    2. $ kubectl exec "$FORTIO_POD" -c fortio -- /usr/bin/fortio curl -quiet http://httpbin:8000/get
    3. HTTP/1.1 200 OK
    4. server: envoy
    5. date: Tue, 25 Feb 2020 20:25:52 GMT
    6. content-type: application/json
    7. content-length: 586
    8. access-control-allow-origin: *
    9. access-control-allow-credentials: true
    10. x-envoy-upstream-service-time: 36
    12. {
    13.   "args": {},
    14.   "headers": {
    15.     "Content-Length": "0",
    16.     "Host": "httpbin:8000",
    17.     "User-Agent": "fortio.org/fortio-1.3.1",
    18.     "X-B3-Parentspanid": "8fc453fb1dec2c22",
    19.     "X-B3-Sampled": "1",
    20.     "X-B3-Spanid": "071d7f06bc94943c",
    21.     "X-B3-Traceid": "86a929a0e76cda378fc453fb1dec2c22",
    22.     "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/default/sa/httpbin;Hash=68bbaedefe01ef4cb99e17358ff63e92d04a4ce831a35ab9a31d3c8e06adb038;Subject=\"\";URI=spiffe://cluster.local/ns/default/sa/default"
    23.   },
    24.   "origin": "127.0.0.1",
    25.   "url": "http://httpbin:8000/get"
    26. }

可以看到调用后端服务的请求已经成功！接下来，可以测试熔断。

触发熔断器

在 DestinationRule 配置中，您定义了 maxConnections: 1 和 http1MaxPendingRequests: 1。这些规则意味着，如果并发的连接和请求数超过一个，在 istio-proxy 进行进一步的请求和连接时，后续请求或连接将被阻止。

  1. 发送并发数为 2 的连接（-c 2），请求 20 次（-n 20）：

    1. $ kubectl exec "$FORTIO_POD" -c fortio -- /usr/bin/fortio load -c 2 -qps 0 -n 20 -loglevel Warning http://httpbin:8000/get
    2. 20:33:46 I logger.go:97> Log level is now 3 Warning (was 2 Info)
    3. Fortio 1.3.1 running at 0 queries per second, 6->6 procs, for 20 calls: http://httpbin:8000/get
    4. Starting at max qps with 2 thread(s) [gomax 6] for exactly 20 calls (10 per thread + 0)
    5. 20:33:46 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    6. 20:33:47 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    7. 20:33:47 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    8. Ended after 59.8524ms : 20 calls. qps=334.16
    9. Aggregated Function Time : count 20 avg 0.0056869 +/- 0.003869 min 0.000499 max 0.0144329 sum 0.113738
    10. # range, mid point, percentile, count
    11. >= 0.000499 <= 0.001 , 0.0007495 , 10.00, 2
    12. > 0.001 <= 0.002 , 0.0015 , 15.00, 1
    13. > 0.003 <= 0.004 , 0.0035 , 45.00, 6
    14. > 0.004 <= 0.005 , 0.0045 , 55.00, 2
    15. > 0.005 <= 0.006 , 0.0055 , 60.00, 1
    16. > 0.006 <= 0.007 , 0.0065 , 70.00, 2
    17. > 0.007 <= 0.008 , 0.0075 , 80.00, 2
    18. > 0.008 <= 0.009 , 0.0085 , 85.00, 1
    19. > 0.011 <= 0.012 , 0.0115 , 90.00, 1
    20. > 0.012 <= 0.014 , 0.013 , 95.00, 1
    21. > 0.014 <= 0.0144329 , 0.0142165 , 100.00, 1
    22. # target 50% 0.0045
    23. # target 75% 0.0075
    24. # target 90% 0.012
    25. # target 99% 0.0143463
    26. # target 99.9% 0.0144242
    27. Sockets used: 4 (for perfect keepalive, would be 2)
    28. Code 200 : 17 (85.0 %)
    29. Code 503 : 3 (15.0 %)
    30. Response Header Sizes : count 20 avg 195.65 +/- 82.19 min 0 max 231 sum 3913
    31. Response Body/Total Sizes : count 20 avg 729.9 +/- 205.4 min 241 max 817 sum 14598
    32. All done 20 calls (plus 0 warmup) 5.687 ms avg, 334.2 qps

    有趣的是，几乎所有的请求都完成了！istio-proxy 确实允许存在一些误差。

    1. Code 200 : 17 (85.0 %)
    2. Code 503 : 3 (15.0 %)

  2. 将并发连接数提高到 3 个：

    1. $ kubectl exec "$FORTIO_POD" -c fortio -- /usr/bin/fortio load -c 3 -qps 0 -n 30 -loglevel Warning http://httpbin:8000/get
    2. 20:32:30 I logger.go:97> Log level is now 3 Warning (was 2 Info)
    3. Fortio 1.3.1 running at 0 queries per second, 6->6 procs, for 30 calls: http://httpbin:8000/get
    4. Starting at max qps with 3 thread(s) [gomax 6] for exactly 30 calls (10 per thread + 0)
    5. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    6. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    7. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    8. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    9. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    10. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    11. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    12. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    13. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    14. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    15. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    16. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    17. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    18. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    19. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    20. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    21. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    22. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    23. 20:32:30 W http_client.go:679> Parsed non ok code 503 (HTTP/1.1 503)
    24. Ended after 51.9946ms : 30 calls. qps=576.98
    25. Aggregated Function Time : count 30 avg 0.0040001633 +/- 0.003447 min 0.0004298 max 0.015943 sum 0.1200049
    26. # range, mid point, percentile, count
    27. >= 0.0004298 <= 0.001 , 0.0007149 , 16.67, 5
    28. > 0.001 <= 0.002 , 0.0015 , 36.67, 6
    29. > 0.002 <= 0.003 , 0.0025 , 50.00, 4
    30. > 0.003 <= 0.004 , 0.0035 , 60.00, 3
    31. > 0.004 <= 0.005 , 0.0045 , 66.67, 2
    32. > 0.005 <= 0.006 , 0.0055 , 76.67, 3
    33. > 0.006 <= 0.007 , 0.0065 , 83.33, 2
    34. > 0.007 <= 0.008 , 0.0075 , 86.67, 1
    35. > 0.008 <= 0.009 , 0.0085 , 90.00, 1
    36. > 0.009 <= 0.01 , 0.0095 , 96.67, 2
    37. > 0.014 <= 0.015943 , 0.0149715 , 100.00, 1
    38. # target 50% 0.003
    39. # target 75% 0.00583333
    40. # target 90% 0.009
    41. # target 99% 0.0153601
    42. # target 99.9% 0.0158847
    43. Sockets used: 20 (for perfect keepalive, would be 3)
    44. Code 200 : 11 (36.7 %)
    45. Code 503 : 19 (63.3 %)
    46. Response Header Sizes : count 30 avg 84.366667 +/- 110.9 min 0 max 231 sum 2531
    47. Response Body/Total Sizes : count 30 avg 451.86667 +/- 277.1 min 241 max 817 sum 13556
    48. All done 30 calls (plus 0 warmup) 4.000 ms avg, 577.0 qps

    现在，您将开始看到预期的熔断行为，只有 36.7% 的请求成功，其余的均被熔断器拦截：

    1. Code 200 : 11 (36.7 %)
    2. Code 503 : 19 (63.3 %)

  3. 查询 istio-proxy 状态以了解更多熔断详情:

    1. $ kubectl exec "$FORTIO_POD" -c istio-proxy -- pilot-agent request GET stats | grep httpbin | grep pending
    2. cluster.outbound|8000||httpbin.default.svc.cluster.local.circuit_breakers.default.remaining_pending: 1
    3. cluster.outbound|8000||httpbin.default.svc.cluster.local.circuit_breakers.default.rq_pending_open: 0
    4. cluster.outbound|8000||httpbin.default.svc.cluster.local.circuit_breakers.high.rq_pending_open: 0
    5. cluster.outbound|8000||httpbin.default.svc.cluster.local.upstream_rq_pending_active: 0
    6. cluster.outbound|8000||httpbin.default.svc.cluster.local.upstream_rq_pending_failure_eject: 0
    7. cluster.outbound|8000||httpbin.default.svc.cluster.local.upstream_rq_pending_overflow: 21
    8. cluster.outbound|8000||httpbin.default.svc.cluster.local.upstream_rq_pending_total: 29

    可以看到 upstream_rq_pending_overflow 值 21，这意味着，目前为止已有 21 个调用被标记为熔断。

清理

  1. 清理规则:

    1. $ kubectl delete destinationrule httpbin

  2. 下线 httpbin 服务和客户端：

    1. $ kubectl delete deploy httpbin fortio-deploy
    2. $ kubectl delete svc httpbin