在Istio中，到底怎么获取 Envoy 访问日志？

Envoy 访问日志记录了通过 Envoy 进行请求 / 响应交互的相关记录，可以方便地了解具体通信过程和调试定位问题。

环境准备

部署 httpbin 服务：

kubectl apply -f samples/httpbin/httpbin.yaml

部署 sleep 服务：

kubectl apply -f samples/sleep/sleep.yaml 

httpbin 服务作为接收请求的服务端， sleep 服务作为发送请求的客户端。

还需要开启 Envoy 访问日志，执行以下命令修改 istio 配置：

kubectl -n istio-system edit configmap istio

编辑yaml文件的对应配置：

data:
  mesh: |-
    accessLogEncoding: JSON
    accessLogFile: /dev/stdout

其中，accessLogEncoding表示 accesslog 输出格式，Istio 预定义了 TEXT 和 JSON 两种日志输出格式。默认使用 TEXT，通常改成 JSON 以提升可读性；accessLogFile:表示 accesslog 输出位置，通常指定到 /dev/stdout (标准输出)，以便使用 kubectl logs 来查看日志。

保证yaml文件后，配置随即生效。

测试访问日志

在 sleep 服务中向 httpbin 服务发出请求：

export SLEEP_POD=$(kubectl get pods -l app=sleep -o 'jsonpath={.items[0].metadata.name}')
kubectl exec "$SLEEP_POD" -c sleep -- curl -sS http://httpbin:8000/headers

返回结果如下：

{
  "headers": {
    "Accept": "*/*", 
    "Host": "httpbin:8000", 
    "User-Agent": "curl/7.81.0-DEV", 
    "X-B3-Parentspanid": "ed0178f3e1f48dd1", 
    "X-B3-Sampled": "0", 
    "X-B3-Spanid": "6c38b689ee5ab0c8", 
    "X-B3-Traceid": "f17ce19c174cae85ed0178f3e1f48dd1", 
    "X-Envoy-Attempt-Count": "1", 
    "X-Forwarded-Client-Cert": "......"
  }
}

执行以下命令，查看sleep 服务的Envoy日志：

kubectl logs -l app=sleep -c istio-proxy

可以看到sleep服务对httpbin服务的调用的日志：

{
     "authority": "httpbin:8000",
     "bytes_received": 0,
     "bytes_sent": 533,
     "connection_termination_details": null,
     "downstream_local_address": "172.24.146.239:8000",
     "downstream_remote_address": "172.24.158.25:49350",
     "duration": 3,
     "method": "GET",
     "path": "/headers",
     "protocol": "HTTP/1.1",
     "request_id": "ea40d320-348f-4f58-86d4-da157b0e0cca",
     "requested_server_name": null,
     "response_code": 200,
     "response_code_details": "via_upstream",
     "response_flags": "-",
     "route_name": "default",
     "start_time": "2022-07-04T10:00:09.401Z",
     "upstream_cluster": "outbound|8000||httpbin.istio-demo.svc.cluster.local",
     "upstream_host": "172.24.158.96:80",
     "upstream_local_address": "172.24.158.25:41812",
     "upstream_service_time": "2",
     "upstream_transport_failure_reason": null,
     "user_agent": "curl/7.81.0-DEV",
     "x_forwarded_for": null
}

执行以下命令，查看httpbin 服务的Envoy日志：

kubectl logs -l app=httpbin -c istio-proxy

可以看到httpbin服务被sleep服务调用的Envoy日志：

{
     "authority": "httpbin:8000",
     "bytes_received": 0,
     "bytes_sent": 533,
     "connection_termination_details": null,
     "downstream_local_address": "172.24.158.96:80",
     "downstream_remote_address": "172.24.158.25:41812",
     "duration": 2,
     "method": "GET",
     "path": "/headers",
     "protocol": "HTTP/1.1",
     "request_id": "ea40d320-348f-4f58-86d4-da157b0e0cca",
     "requested_server_name": "outbound_.8000_._.httpbin.istio-demo.svc.cluster.local",
     "response_code": 200,
     "response_code_details": "via_upstream",
     "response_flags": "-",
     "route_name": "default",
     "start_time": "2022-07-04T10:00:09.401Z",
     "upstream_cluster": "inbound|80||",
     "upstream_host": "172.24.158.96:80",
     "upstream_local_address": "127.0.0.6:33665",
     "upstream_service_time": "1",
     "upstream_transport_failure_reason": null,
     "user_agent": "curl/7.81.0-DEV",
     "x_forwarded_for": null
}

看到这么多参数，是不是有点懵逼？没关系接下来，我们详细看看！

刨析Envoy日志

清理

删除 httpbin 和 sleep 服务:

kubectl delete -f samples/httpbin/httpbin.yaml
kubectl delete -f samples/sleep/sleep.yaml