如何进行Pilot-agent作用及其源码的分析

本篇文章为大家展示了如何进行Pilot-agent作用及其源码的分析，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

小编使用的Istio源码是 release 1.5。

介绍

Sidecar在注入的时候会注入istio-init和istio-proxy两个容器。Pilot-agent就是启动istio-proxy的入口。通过kubectl命令我们可以看到启动命令：

[root@localhost ~]# kubectl exec -it details-v1-6c9f8bcbcb-shltm -c istio-proxy -- ps -efwwUID         PID   PPID  C STIME TTY          TIME CMDistio-p+      1      0  0 08:52 ?        00:00:13 /usr/local/bin/pilot-agent proxy sidecar --domain default.svc.cluster.local --configPath /etc/istio/proxy --binaryPath /usr/local/bin/envoy --serviceCluster details.default --drainDuration 45s --parentShutdownDuration 1m0s --discoveryAddress istiod.istio-system.svc:15012 --zipkinAddress zipkin.istio-system:9411 --proxyLogLevel=warning --proxyComponentLogLevel=misc:error --connectTimeout 10s --proxyAdminPort 15000 --concurrency 2 --controlPlaneAuthPolicy NONE --dnsRefreshRate 300s --statusPort 15020 --trust-domain=cluster.local --controlPlaneBootstrap=falseistio-p+     18      1  0 08:52 ?        00:01:11 /usr/local/bin/envoy -c /etc/istio/proxy/envoy-rev0.json --restart-epoch 0 --drain-time-s 45 --parent-shutdown-time-s 60 --service-cluster details.default --service-node sidecar~172.20.0.14~details-v1-6c9f8bcbcb-shltm.default~default.svc.cluster.local --max-obj-name-len 189 --local-address-ip-version v4 --log-format [Envoy (Epoch 0)] [%Y-%m-%d %T.%e][%t][%l][%n] %v -l warning --component-log-level misc:error --concurrency 2

Pilot-agent除了启动istio-proxy以外还有以下能力：

• 生成Envoy的Bootstrap配置文件；

• 健康检查；

• 监视证书的变化，通知Envoy进程热重启，实现证书的热加载；

• 提供Envoy守护功能，当Envoy异常退出的时候重启Envoy；

• 通知Envoy优雅退出；

代码执行流程分析

 proxyCmd = &cobra.Command{                Use:   "proxy",                Short: "Envoy proxy agent",                FParseErrWhitelist: cobra.FParseErrWhitelist{                         UnknownFlags: true,                },                RunE: func(c *cobra.Command, args []string) error {                        ...                        // 用于设置默认配置文件的默认配置相关参数                        proxyConfig := mesh.DefaultProxyConfig()                        // set all flags                        proxyConfig.CustomConfigFile = customConfigFile                        proxyConfig.ProxyBootstrapTemplatePath = templateFile                        proxyConfig.ConfigPath = configPath                        proxyConfig.BinaryPath = binaryPath                        proxyConfig.ServiceCluster = serviceCluster                        proxyConfig.DrainDuration = types.DurationProto(drainDuration)                        proxyConfig.ParentShutdownDuration = types.DurationProto(parentShutdownDuration)                        proxyConfig.DiscoveryAddress = discoveryAddress                        proxyConfig.ConnectTimeout = types.DurationProto(connectTimeout)                        proxyConfig.StatsdUdpAddress = statsdUDPAddress                        ...                        ctx, cancel := context.WithCancel(context.Background())                         // 启动 status server                        if statusPort > 0 {                                localHostAddr := localHostIPv4                                if proxyIPv6 {                                        localHostAddr = localHostIPv6                                }                                prober := kubeAppProberNameVar.Get()                                //健康探测                                statusServer, err := status.NewServer(status.Config{                                        LocalHostAddr:  localHostAddr,                                        AdminPort:      proxyAdminPort,                    //通过参数--statusPort 15020设置                                        StatusPort:     statusPort,                                        KubeAppProbers: prober,                                        NodeType:       role.Type,                                })                                if err != nil {                                        cancel()                                        return err                                }                                go waitForCompletion(ctx, statusServer.Run)                        }                         ...                         //构造Proxy实例,包括配置，启动参数等                        envoyProxy := envoy.NewProxy(envoy.ProxyConfig{                                Config:              proxyConfig,                                Node:                role.ServiceNode(),                                LogLevel:            proxyLogLevel,                                ComponentLogLevel:   proxyComponentLogLevel,                                PilotSubjectAltName: pilotSAN,                                MixerSubjectAltName: mixerSAN,                                NodeIPs:             role.IPAddresses,                                DNSRefreshRate:      dnsRefreshRate,                                PodName:             podName,                                PodNamespace:        podNamespace,                                PodIP:               podIP,                                SDSUDSPath:          sdsUDSPath,                                SDSTokenPath:        sdsTokenPath,                                STSPort:             stsPort,                                ControlPlaneAuth:    controlPlaneAuthEnabled,                                DisableReportCalls:  disableInternalTelemetry,                                OutlierLogPath:      outlierLogPath,                                PilotCertProvider:   pilotCertProvider,                        })                        //构造agent实例，实现了Agent接口                        agent := envoy.NewAgent(envoyProxy, features.TerminationDrainDuration())                        if nodeAgentSDSEnabled {                                tlsCertsToWatch = []string{}                        }                        //构造watcher实例                        watcher := envoy.NewWatcher(tlsCertsToWatch, agent.Restart)                        //启动 watcher                        go watcher.Run(ctx)                        // 优雅退出                        go cmd.WaitSignalFunc(cancel)                        //启动 agent                        return agent.Run(ctx)                },        }

执行流程大概分成这么几步：

1. 用于设置默认配置文件的默认配置相关参数；

2. 启动 status server进行健康检测；

3. 构造Proxy实例,包括配置，启动参数，并构造构造agent实例；

4. 构造watcher实例，并启动；

5. 开启线程监听信号，进行优雅退出；

6. 启动 agent；

默认配置相关参数

kubectl exec -it details-v1-6c9f8bcbcb-shltm -c istio-proxy -- /usr/local/bin/pilot-agent proxy --helpEnvoy proxy agentUsage:        pilot-agent proxy [flags]Flags:                --binaryPath string                 Path to the proxy binary (default "/usr/local/bin/envoy")                --concurrency int                   number of worker threads to run                --configPath string                 Path to the generated configuration file directory (default "/etc/istio/proxy")                --connectTimeout duration           Connection timeout used by Envoy for supporting services (default 1s)                --controlPlaneAuthPolicy string     Control Plane Authentication Policy (default "NONE")                --controlPlaneBootstrap             Process bootstrap provided via templateFile to be used by control plane components. (default true)                --customConfigFile string           Path to the custom configuration file                --datadogAgentAddress string        Address of the Datadog Agent                --disableInternalTelemetry          Disable internal telemetry                --discoveryAddress string           Address of the discovery service exposing xDS (e.g. istio-pilot:8080) (default "istio-pilot:15010")                --dnsRefreshRate string             The dns_refresh_rate for bootstrap STRICT_DNS clusters (default "300s")                --domain string                     DNS domain suffix. If not provided uses ${POD_NAMESPACE}.svc.cluster.local                --drainDuration duration            The time in seconds that Envoy will drain connections during a hot restart (default 45s)                --envoyAccessLogService string      Settings of an Envoy gRPC Access Log Service API implementation                --envoyMetricsService string        Settings of an Envoy gRPC Metrics Service API implementation        -h, --help                              help for proxy                --id string                         Proxy unique ID. If not provided uses ${POD_NAME}.${POD_NAMESPACE} from environment variables                --ip string                         Proxy IP address. If not provided uses ${INSTANCE_IP} environment variable.                --lightstepAccessToken string       Access Token for LightStep Satellite pool                --lightstepAddress string           Address of the LightStep Satellite pool                --lightstepCacertPath string        Path to the trusted cacert used to authenticate the pool                --lightstepSecure                   Should connection to the LightStep Satellite pool be secure                --mixerIdentity string              The identity used as the suffix for mixer's spiffe SAN. This would only be used by pilot all other proxy would get this value from pilot                --outlierLogPath string             The log path for outlier detection                --parentShutdownDuration duration   The time in seconds that Envoy will wait before shutting down the parent process during a hot restart (default 1m0s)                --pilotIdentity string              The identity used as the suffix for pilot's spiffe SAN                --proxyAdminPort uint16             Port on which Envoy should listen for administrative commands (default 15000)                --proxyComponentLogLevel string     The component log level used to start the Envoy proxy (default "misc:error")                --proxyLogLevel string              The log level used to start the Envoy proxy (choose from {trace, debug, info, warning, error, critical, off}) (default "warning")                --serviceCluster string             Service cluster (default "istio-proxy")                --serviceregistry string            Select the platform for service registry, options are {Kubernetes, Consul, Mock} (default "Kubernetes")                --statsdUdpAddress string           IP Address and Port of a statsd UDP listener (e.g. 10.75.241.127:9125)                --statusPort uint16                 HTTP Port on which to serve pilot agent status. If zero, agent status will not be provided.                --stsPort int                       HTTP Port on which to serve Security Token Service (STS). If zero, STS service will not be provided.                --templateFile string               Go template bootstrap config                --tokenManagerPlugin string         Token provider specific plugin name. (default "GoogleTokenExchange")                --trust-domain string               The domain to use for identities                --zipkinAddress string              Address of the Zipkin service (e.g. zipkin:9411)

从上面输出我们也可以看到proxy参数的含义以及对应的默认值。

func DefaultProxyConfig() meshconfig.ProxyConfig {        return meshconfig.ProxyConfig{                ConfigPath:             constants.ConfigPathDir,                BinaryPath:             constants.BinaryPathFilename,                ServiceCluster:         constants.ServiceClusterName,                DrainDuration:          types.DurationProto(45 * time.Second),                ParentShutdownDuration: types.DurationProto(60 * time.Second),                DiscoveryAddress:       constants.DiscoveryPlainAddress,                ConnectTimeout:         types.DurationProto(1 * time.Second),                StatsdUdpAddress:       "",                EnvoyMetricsService:    &meshconfig.RemoteService{Address: ""},                EnvoyAccessLogService:  &meshconfig.RemoteService{Address: ""},                ProxyAdminPort:         15000,                ControlPlaneAuthPolicy: meshconfig.AuthenticationPolicy_NONE,                CustomConfigFile:       "",                Concurrency:            0,                StatNameLength:         189,                Tracing:                nil,        }}

默认的启动参数都在DefaultProxyConfig方法中设置，默认的启动配置如下所示：

• ConfigPath：/etc/istio/proxy

• BinaryPath：/usr/local/bin/envoy

• ServiceCluster：istio-proxy

• DrainDuration：45s

• ParentShutdownDuration：60s

• DiscoveryAddress：istio-pilot:15010

• ConnectTimeout：1s

• StatsdUdpAddress：""

• EnvoyMetricsService：meshconfig.RemoteService

• EnvoyAccessLogService：meshconfig.RemoteService

• ProxyAdminPort：15000

• ControlPlaneAuthPolicy：0

• CustomConfigFile：""

• Concurrency：0

• StatNameLength：189

• Tracing：nil

status server健康检查

初始化status server：

func NewServer(config Config) (*Server, error) {        s := &Server{                statusPort: config.StatusPort,                ready: &ready.Probe{                        LocalHostAddr: config.LocalHostAddr,                        AdminPort:     config.AdminPort,                        NodeType:      config.NodeType,                },        }        ...        return s, nil}

初始化完成之后会开启一个线程调用statusServer的 Run方法：

go waitForCompletion(ctx, statusServer.Run)func (s *Server) Run(ctx context.Context) {        log.Infof("Opening status port %d\n", s.statusPort)        mux := http.NewServeMux()        // Add the handler for ready probes.        // 初始化探针的回调处理器        // /healthz/ready        mux.HandleFunc(readyPath, s.handleReadyProbe)        mux.HandleFunc(quitPath, s.handleQuit)        //应用端口检查        mux.HandleFunc("/app-health/", s.handleAppProbe)        //端口通过参数--statusPort 15020设置        l, err := net.Listen("tcp", fmt.Sprintf(":%d", s.statusPort))        if err != nil {                log.Errorf("Error listening on status port: %v", err.Error())                return        }        ...        defer l.Close()        //开启监听        go func() {                if err := http.Serve(l, mux); err != nil {                        log.Errora(err)                         notifyExit()                }        }()         <-ctx.Done()        log.Info("Status server has successfully terminated")}

Run方法会开启一个线程并监听15020端口，调用路径为 /healthz/ready，并通过调用handleReadyProbe处理器来调用Envoy的15000端口判断Envoy是否已经 ready 接受相对应的流量。调用过程如下：

watcher监控管理

在进行watcher监控之前会通过NewAgent生成agent实例：

func NewAgent(proxy Proxy, terminationDrainDuration time.Duration) Agent {        return &agent{                proxy:                    proxy,                //用于管理启动 Envoy 后的状态通道，用于监视 Envoy 进程的状态                statusCh:                 make(chan exitStatus),                //活跃的Epoch 集合                activeEpochs:             map[int]chan error{},                //默认5s                terminationDrainDuration: terminationDrainDuration,                //当前的Epoch                currentEpoch:             -1,        }}

然后构建watcher实例：

//构造watcher实例watcher := envoy.NewWatcher(tlsCertsToWatch, agent.Restart)type watcher struct {        //证书列表        certs   []string        //envoy 重启函数        updates func(interface{})} func NewWatcher(certs []string, updates func(interface{})) Watcher {        return &watcher{                certs:   certs,                updates: updates,        }}

watcher里面总共就两个参数certs是监听的证书列表，updates是envoy 重启函数，如果证书文件发生变化则调用updates来reload envoy。

启动watcher：

go watcher.Run(ctx)func (w *watcher) Run(ctx context.Context) {         //启动envoy        w.SendConfig()         //监听证书变化        go watchCerts(ctx, w.certs, watchFileEvents, defaultMinDelay, w.SendConfig)        <-ctx.Done()        log.Info("Watcher has successfully terminated")}

watcher的Run方法首先会调用SendConfig启动Envoy，然后启动一个线程监听证书的变化。

func (w *watcher) SendConfig() {        h := sha256.New()        generateCertHash(h, w.certs)        w.updates(h.Sum(nil))}

SendConfig方法会获取当前的证书集合hash之后传入到updates方法中，updates方法就是在初始化NewWatcher的时候传入的，这里是会调用到agent的Restart方法的：

func (a *agent) Restart(config interface{}) {         a.restartMutex.Lock()        defer a.restartMutex.Unlock()         a.mutex.Lock()        //校验传入的参数是否产生了变化        if reflect.DeepEqual(a.currentConfig, config) {                // Same configuration - nothing to do.                a.mutex.Unlock()                return        }        //活跃的Epoch        hasActiveEpoch := len(a.activeEpochs) > 0        //获取当前的Epoch        activeEpoch := a.currentEpoch         //因为配置变了,所以Epoch加1        epoch := a.currentEpoch + 1        log.Infof("Received new config, creating new Envoy epoch %d", epoch)        //更新当前的配置以及Epoch        a.currentEpoch = epoch        a.currentConfig = config         // 用来做做主动退出        abortCh := make(chan error, 1)    // 设置当前活跃Epoch的abortCh管道，用于优雅关闭        a.activeEpochs[a.currentEpoch] = abortCh         a.mutex.Unlock()         if hasActiveEpoch {                a.waitUntilLive(activeEpoch)        }        //启动envoy,会将结果放入到statusCh管道中        go a.runWait(config, epoch, abortCh)}

Restart方法会判断传入的配置是否和当前的配置一致，如果不一致，那么设置好当前的配置后调用runWait方法启动Envoy，并将启动结果放入到statusCh管道中：

func (a *agent) runWait(config interface{}, epoch int, abortCh <-chan error) {        log.Infof("Epoch %d starting", epoch)        //启动envoy        err := a.proxy.Run(config, epoch, abortCh)        //删除当前 epoch 对应的配置文件        a.proxy.Cleanup(epoch)        a.statusCh <- exitStatus{epoch: epoch, err: err}}

envoy启动流程

在上面讲了，envoy的启动会在runWait方法中进行，通过调用proxy的Run方法会通过模板文件创建/etc/istio/proxy/envoy-rev0.json配置文件，然会直接使用exec包调用envoy启动命令启动envoy。

func (e *envoy) Run(config interface{}, epoch int, abort <-chan error) error {        var fname string        //如果指定了模板文件，则使用用户指定的，否则则使用默认的        if len(e.Config.CustomConfigFile) > 0 {                 fname = e.Config.CustomConfigFile        } else {                out, err := bootstrap.New(bootstrap.Config{                        Node:                e.Node,                        DNSRefreshRate:      e.DNSRefreshRate,                        Proxy:               &e.Config,                        PilotSubjectAltName: e.PilotSubjectAltName,                        MixerSubjectAltName: e.MixerSubjectAltName,                        LocalEnv:            os.Environ(),                        NodeIPs:             e.NodeIPs,                        PodName:             e.PodName,                        PodNamespace:        e.PodNamespace,                        PodIP:               e.PodIP,                        SDSUDSPath:          e.SDSUDSPath,                        SDSTokenPath:        e.SDSTokenPath,                        STSPort:             e.STSPort,                        ControlPlaneAuth:    e.ControlPlaneAuth,                        DisableReportCalls:  e.DisableReportCalls,                        OutlierLogPath:      e.OutlierLogPath,                        PilotCertProvider:   e.PilotCertProvider,                }).CreateFileForEpoch(epoch)                if err != nil {                        log.Errora("Failed to generate bootstrap config: ", err)                        os.Exit(1) // Prevent infinite loop attempting to write the file, let k8s/systemd report                }                fname = out        }         //设置启动参数        args := e.args(fname, epoch, istioBootstrapOverrideVar.Get())        log.Infof("Envoy command: %v", args)        //直接使用exec包调用envoy启动命令        cmd := exec.Command(e.Config.BinaryPath, args...)        cmd.Stdout = os.Stdout        cmd.Stderr = os.Stderr        if err := cmd.Start(); err != nil {                return err        }        done := make(chan error, 1)        go func() {                done <- cmd.Wait()        }()        //等待 abort channel 和 done，用于结束 Envoy 和正确返回当前的启动状态        select {    //用于优雅关闭，后面会讲到        case err := <-abort:                log.Warnf("Aborting epoch %d", epoch)                if errKill := cmd.Process.Kill(); errKill != nil {                        log.Warnf("killing epoch %d caused an error %v", epoch, errKill)                }                return err        case err := <-done:                return err        }}

Run方法会通过调用CreateFileForEpoch方法获取到模板文件：/var/lib/istio/envoy/envoy_bootstrap_tmpl.json，然后生成/etc/istio/proxy/envoy-rev0.json文件并返回路径；通过调用args方法来配置envoy的启动参数，然后调用exec.Command启动envoy，BinaryPath为/usr/local/bin/envoy。

最后异步获取cmd的返回结果，存入到done管道中作为方法的参数返回。返回的参数在runWait方法中会被接受到，存入到statusCh管道中。

在调用agent的run方法的时候会监听statusCh管道中的数据：

agent.Run(ctx)func (a *agent) Run(ctx context.Context) error {        log.Info("Starting proxy agent")        for {                select {                //如果 proxy-Envoy 的状态发生了变化                case status := <-a.statusCh:                        a.mutex.Lock()                        if status.err != nil {                                if status.err.Error() == errOutOfMemory {                                        log.Warnf("Envoy may have been out of memory killed. Check memory usage and limits.")                                }                                log.Errorf("Epoch %d exited with error: %v", status.epoch, status.err)                        } else {                                //正常退出                                log.Infof("Epoch %d exited normally", status.epoch)                        }                        //删除当前 epoch 对应的配置文件                        delete(a.activeEpochs, status.epoch)                        active := len(a.activeEpochs)                        a.mutex.Unlock()                        if active == 0 {                                log.Infof("No more active epochs, terminating")                                return nil                        }                 ...        }}

优雅退出

pilot-agent会开启一个线程调用WaitSignalFunc方法监听syscall.SIGINT、syscall.SIGTERM信号，然后调用context的cancel来实现优化关闭的效果：

func WaitSignalFunc(cancel func()) {        sigs := make(chan os.Signal, 1)        signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)        <-sigs        cancel()        _ = log.Sync()}

当context的cancel方法被调用的时候，agent的Run方法里面select监听的ctx.Done()方法也会立即返回，调用terminate方法：

func (a *agent) Run(ctx context.Context) error {         for {                select {                //如果 proxy-Envoy 的状态发生了变化                case status := <-a.statusCh:                        ...                 case <-ctx.Done():                        a.terminate()                        log.Info("Agent has successfully terminated")                        return nil                }        }}func (a *agent) terminate() {        log.Infof("Agent draining Proxy")        e := a.proxy.Drain()        if e != nil {                log.Warnf("Error in invoking drain listeners endpoint %v", e)        }        log.Infof("Graceful termination period is %v, starting...", a.terminationDrainDuration)        //睡眠5s        time.Sleep(a.terminationDrainDuration)        log.Infof("Graceful termination period complete, terminating remaining proxies.")        a.abortAll()}

terminate方法会调用sleep休眠5s，然后调用abortAll通知所有活跃Epoch进行优雅关闭。

var errAbort = errors.New("epoch aborted")func (a *agent) abortAll() {        a.mutex.Lock()        defer a.mutex.Unlock()        for epoch, abortCh := range a.activeEpochs {                log.Warnf("Aborting epoch %d...", epoch)                abortCh <- errAbort        }        log.Warnf("Aborted all epochs")}

abortAll会获取到所有活跃的Epoch对应的abortCh管道，并插入一条数据。如果这个时候有活跃的Epoch正在等待cmd返回结果，那么会直接调用kill方法将进程杀死：

func (e *envoy) Run(config interface{}, epoch int, abort <-chan error) error {        ...        //等待 abort channel 和 done，用于结束 Envoy 和正确返回当前的启动状态        select {    //用于优雅关闭，后面会讲到        case err := <-abort:                log.Warnf("Aborting epoch %d", epoch)                if errKill := cmd.Process.Kill(); errKill != nil {                        log.Warnf("killing epoch %d caused an error %v", epoch, errKill)                }                return err        case err := <-done:                return err        }}

上述内容就是如何进行Pilot-agent作用及其源码的分析，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注行业资讯频道。