istio 的日志收集方法
istio 为每个 pod 注入 envoy 容器后，envoy 能够记录每个 pod 的请求。
原始访问日志
是否记录访问日志以及访问日志的存放位置，通过 accessLogFile 设置：
# $ kubectl -n istio-system get configmap istio -o yaml |grep accessLogFile
# Set accessLogFile to empty string to disable access log.
accessLogFile: "/dev/stdout"
默认显示到标准输出，可以用下面的方式查看：
$ kubectl logs -f productpage-v1-667bc85676-sgbqp -c istio-proxy
[2019-11-27T06:45:55.152Z] "GET /reviews/0 HTTP/1.1" 200 - "-" "-" 0 379 74 74 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.97 Safari/537.36" "105f2059-fbc8-9446-8bbb-b9c1a37019bd" "reviews:9080" "172.17.0.32:9080" outbound|9080|v2|reviews.default.svc.cluster.local - 10.100.249.106:9080 172.17.0.27:40612 - -
[2019-11-27T06:45:55.121Z] "GET /productpage HTTP/1.1" 200 - "-" "-" 0 5286 110 103 "172.17.0.1" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.97 Safari/537.36" "105f2059-fbc8-9446-8bbb-b9c1a37019bd" "192.168.99.100:31380" "127.0.0.1:9080" inbound|9080|http|productpage.default.svc.cluster.local - 172.17.0.27:9080 172.17.0.1:0 - default
...
生成并收集日志
istio 支持自定义日志格式，并将统一收集到指定位置。这一步操作和 指标采集 类似，通过 instance、handler 和 route 三个 CRD 设置。
log-entry.yaml 定义了日志 newlog，并收集到 mixer 的标准输出：
$ kubectl apply -f samples/bookinfo/telemetry/log-entry.yaml
instance 定义的日志格式，名称为 newlog，在 params 中设置了级别、时间戳以及属性组成：
# Configuration for logentry instances
apiVersion: config.istio.io/v1alpha2
kind: instance
metadata:
name: newlog
namespace: istio-system
spec:
compiledTemplate: logentry
params:
severity: '"warning"'
timestamp: request.time
variables:
source: source.labels["app"] | source.workload.name | "unknown"
user: source.user | "unknown"
destination: destination.labels["app"] | destination.workload.name | "unknown"
responseCode: response.code | 0
responseSize: response.size | 0
latency: response.duration | "0ms"
monitored_resource_type: '"UNSPECIFIED"'
handler 定义了采集器，名称为 newloghandler，直接打印到 stdio，输出格式为 json：
# Configuration for a stdio handler
apiVersion: config.istio.io/v1alpha2
kind: handler
metadata:
name: newloghandler
namespace: istio-system
spec:
compiledAdapter: stdio
params:
severity_levels:
warning: 1 # Params.Level.WARNING
outputAsJson: true
rule 定义了采集动作，将 newlog 日志收集到 newloghandler：
# Rule to send logentry instances to a stdio handler
apiVersion: config.istio.io/v1alpha2
kind: rule
metadata:
name: newlogstdio
namespace: istio-system
spec:
match: "true" # match for all requests
actions:
- handler: newloghandler
instances:
- newlog
采集效果
上面定义的 newlog 采集规则，将日志输出到标准输出，这里的标准输出是 telemetry 的标准输出：
$ kubectl logs -f -n istio-system -l istio-mixer-type=telemetry -c mixer
{"level":"warn","time":"2019-11-27T08:24:05.706343Z","instance":"newlog.instance.istio-system","destination":"productpage","latency":"1.072931146s","responseCode":200,"responseSize":4183,"source":"istio-ingressgateway","user":"unknown"}
{"level":"warn","time":"2019-11-27T08:24:05.188835Z","instance":"newlog.instance.istio-system","destination":"productpage","latency":"1.654626443s","responseCode":200,"responseSize":4183,"source":"istio-ingressgateway","user":"unknown"}
将日志收集到 es
handler 可以指向多种日志收集系统，例如 通过flutentd收集：
# Configuration for a Fluentd handler
apiVersion: config.istio.io/v1alpha2
kind: handler
metadata:
name: handler
namespace: istio-system
spec:
compiledAdapter: fluentd
params:
address: "fluentd-es.logging:24224"