• 熔断
    • 开始之前
    • 断路器
      • 设置客户端
    • 触发熔断机制
    • 清理

    熔断

    本任务展示了用连接、请求以及外部检测来进行熔断配置的过程。

    断路器是创建弹性微服务应用程序的重要模式。断路器允许您编写限制故障、延迟峰值以及其他不良网络特性影响的应用程序。

    在此任务中,您将配置断路器规则,然后通过故意“跳闸”断路器来测试配置。

    开始之前

    • 跟随安装指南 设置 Istio。

    • 启动 httpbin 示例应用,这个应用将会作为本任务的后端服务。

    如果启用了 Sidecar 的自动注入,只需运行:

    Zip

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

    否则就需要在部署 httpbin 应用之前手工注入 Sidecar 了:

    Zip

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

    httpbin 应用程序用作为此任务的后端服务。

    断路器

    • 创建一个 目标规则,针对 httpbin 服务设置断路器:

    如果您的 Istio 启用了双向 TLS 身份验证,则必须在应用之前将 TLS 流量策略 mode:ISTIO_MUTUAL 添加到 DestinationRule。否则请求将产生 503 错误,如设置目标规则后出现 503 错误所述。

    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. consecutiveErrors: 1
    17. interval: 1s
    18. baseEjectionTime: 3m
    19. maxEjectionPercent: 100
    20. EOF
    • 检查我们的目标规则,确定已经正确建立:
    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

    设置客户端

    现在我们已经设置了调用 httpbin 服务的规则,接下来创建一个客户端,用来向后端服务发送请求,观察是否会触发熔断策略。这里要使用一个简单的负载测试客户端,名字叫 fortio。这个客户端可以控制连接数量、并发数以及发送 HTTP 请求的延迟。使用这一客户端,能够有效的触发前面在目标规则中设置的熔断策略。

    • 这里我们会把给客户端也进行 Sidecar 的注入,以此保证 Istio 对网络交互的控制:

    Zip

    1. $ kubectl apply -f <(istioctl kube-inject -f @samples/httpbin/sample-client/fortio-deploy.yaml@)
    • 接下来就可以登入客户端 Pod 并使用 Fortio 工具来调用 httpbin-curl 参数表明只调用一次:
    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
    11. {
    12. "args": {},
    13. "headers": {
    14. "Content-Length": "0",
    15. "Host": "httpbin:8000",
    16. "User-Agent": "istio/fortio-0.6.2",
    17. "X-B3-Sampled": "1",
    18. "X-B3-Spanid": "824fbd828d809bf4",
    19. "X-B3-Traceid": "824fbd828d809bf4",
    20. "X-Ot-Span-Context": "824fbd828d809bf4;824fbd828d809bf4;0000000000000000",
    21. "X-Request-Id": "1ad2de20-806e-9622-949a-bd1d9735a3f4"
    22. },
    23. "origin": "127.0.0.1",
    24. "url": "http://httpbin:8000/get"
    25. }

    不难看出,调用已经成功。接下来做些变化。

    触发熔断机制

    在上面的熔断设置中指定了 maxConnections: 1 以及 http1MaxPendingRequests: 1。这意味着如果超过了一个连接同时发起请求,Istio 就会熔断,阻止后续的请求或连接。

    • 接下来尝试一下两个并发连接(-c 2),发送 20 请求(-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

    这里可以看到,几乎所有请求都通过了。Istio-proxy 允许存在一些误差。

    1. Code 200 : 19 (95.0 %)
    2. Code 503 : 1 (5.0 %)
    • 接下来把并发连接数量提高到 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

    这时候会观察到,熔断行为按照之前的设计生效了,只有 63.3% 的请求获得通过,剩余请求被断路器拦截了:

    1. Code 200 : 19 (63.3 %)
    2. Code 503 : 11 (36.7 %)
    • 我们可以查询 istio-proxy 的状态,获取更多相关信息:
    1. $ kubectl exec -it $FORTIO_POD -c istio-proxy -- sh -c 'curl localhost:15000/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

    upstream_rq_pending_overflow 的值是 12,说明有 12 次调用被标志为熔断。

    清理

    • 清理规则:
    1. $ kubectl delete destinationrule httpbin
    • 关闭 httpbin 服务和客户端:
    1. $ kubectl delete deploy httpbin fortio-deploy
    2. $ kubectl delete svc httpbin