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

  • 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
    $ 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
    $ 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:

    $ kubectl apply -f - <<EOF
    apiVersion: networking.istio.io/v1alpha3
    kind: DestinationRule
    metadata:
      name: httpbin
    spec:
      host: httpbin
      trafficPolicy:
        connectionPool:
          tcp:
            maxConnections: 1
          http:
            http1MaxPendingRequests: 1
            maxRequestsPerConnection: 1
        outlierDetection:
          consecutiveErrors: 1
          interval: 1s
          baseEjectionTime: 3m
          maxEjectionPercent: 100
    EOF
    
  2. 验证目标规则是否已正确创建:

    $ kubectl get destinationrule httpbin -o yaml
    apiVersion: networking.istio.io/v1alpha3
    kind: DestinationRule
    metadata:
      name: httpbin
      ...
    spec:
      host: httpbin
      trafficPolicy:
        connectionPool:
          http:
            http1MaxPendingRequests: 1
            maxRequestsPerConnection: 1
          tcp:
            maxConnections: 1
        outlierDetection:
          baseEjectionTime: 180.000s
          consecutiveErrors: 1
          interval: 1.000s
          maxEjectionPercent: 100
    

增加一个客户

创建客户端程序以发送流量到 httpbin 服务。这是一个名为 Fortio 的负载测试客户的,其可以控制连接数、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:

    Zip
    $ 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:

    $ FORTIO_POD=$(kubectl get pod | grep fortio | awk '{ print $1 }')
    $ kubectl exec -it $FORTIO_POD  -c fortio /usr/bin/fortio -- load -curl  http://httpbin:8000/get
    HTTP/1.1 200 OK
    server: envoy
    date: Tue, 16 Jan 2018 23:47:00 GMT
    content-type: application/json
    access-control-allow-origin: *
    access-control-allow-credentials: true
    content-length: 445
    x-envoy-upstream-service-time: 36
    
    {
      "args": {},
      "headers": {
        "Content-Length": "0",
        "Host": "httpbin:8000",
        "User-Agent": "istio/fortio-0.6.2",
        "X-B3-Sampled": "1",
        "X-B3-Spanid": "824fbd828d809bf4",
        "X-B3-Traceid": "824fbd828d809bf4",
        "X-Ot-Span-Context": "824fbd828d809bf4;824fbd828d809bf4;0000000000000000",
        "X-Request-Id": "1ad2de20-806e-9622-949a-bd1d9735a3f4"
      },
      "origin": "127.0.0.1",
      "url": "http://httpbin:8000/get"
    }
    

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

DestinationRule 配置中,您定义了 maxConnections: 1http1MaxPendingRequests: 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):

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

    Code 200 : 19 (95.0 %)
    Code 503 : 1 (5.0 %)
    
  2. 将并发连接数提高到 3 个:

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

    现在,您将开始看到预期的熔断行为,只有 63.3% 的请求成功,其余的均被熔断器拦截:

    Code 200 : 19 (63.3 %)
    Code 503 : 11 (36.7 %)
    
  3. 查询 istio-proxy 状态以了解更多熔断详情:

    $ kubectl exec $FORTIO_POD -c istio-proxy -- pilot-agent request GET stats | grep httpbin | grep pending
    cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_active: 0
    cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_failure_eject: 0
    cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_overflow: 12
    cluster.outbound|80||httpbin.springistio.svc.cluster.local.upstream_rq_pending_total: 39
    

    可以看到 upstream_rq_pending_overflow12,这意味着,目前为止已有 12 个调用被标记为熔断。

清理

  1. 清理规则:

    $ kubectl delete destinationrule httpbin
    
  2. 下线 httpbin 服务和客户端:

    $ kubectl delete deploy httpbin fortio-deploy
    $ kubectl delete svc httpbin
    
这些信息有用吗?
Do you have any suggestions for improvement?

Thanks for your feedback!