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。
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小编使用的Istio源码是 release 1.5。
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 -efww UID PID PPID C STIME TTY TIME CMD istio-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=false istio-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；
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：
用于设置默认配置文件的默认配置相关参数；
启动 status server进行健康检测；
构造Proxy实例,包括配置，启动参数，并构造构造agent实例；
构造watcher实例，并启动；
开启线程监听信号，进行优雅退出；
启动 agent；
kubectl exec -it details-v1-6c9f8bcbcb-shltm -c istio-proxy -- /usr/local/bin/pilot-agent proxy --help
Envoy proxy agent
Usage:
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
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：
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}
}
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
}
...
}
}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，欢迎关注创新互联行业资讯频道。
