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Date: 七月 29, 2016

Swarmkit笔记(5)——Node.Run()函数

Swarmd程序的精髓就是Node.Run()函数。刨除前面一大堆CA验证的相关代码,下面是实际执行manageragent的部分。

......
managerReady := make(chan struct{})
agentReady := make(chan struct{})
var managerErr error
var agentErr error
var wg sync.WaitGroup
wg.Add(2)
go func() {
    managerErr = n.runManager(ctx, securityConfig, managerReady) // store err and loop
    wg.Done()
    cancel()
}()
go func() {
    agentErr = n.runAgent(ctx, db, securityConfig.ClientTLSCreds, agentReady)
    wg.Done()
    cancel()
}()
......

如果node的角色是agent,则runManager goroutine就会阻塞在Node.waitRole()这里:

func (n *Node) runManager(ctx context.Context, securityConfig *ca.SecurityConfig, ready chan struct{}) error {
    for {
        n.waitRole(ctx, ca.ManagerRole)
        ......
    }
}

因此只有Node.runAgent()这个goroutine可以顺畅执行。

如果node的角色是manager,则runManagerrunAgent这两个goroutine都会运行,即manager本身也是一个agent

Swarmkit笔记(4)——swarmd命令选项

Swarmd程序支持的命令选项:

func init() {
    mainCmd.Flags().BoolP("version", "v", false, "Display the version and exit")
    mainCmd.Flags().StringP("log-level", "l", "info", "Log level (options \"debug\", \"info\", \"warn\", \"error\", \"fatal\", \"panic\")")
    mainCmd.Flags().StringP("state-dir", "d", "./swarmkitstate", "State directory")
    mainCmd.Flags().StringP("join-token", "", "", "Specifies the secret token required to join the cluster")
    mainCmd.Flags().String("engine-addr", "unix:///var/run/docker.sock", "Address of engine instance of agent.")
    mainCmd.Flags().String("hostname", "", "Override reported agent hostname")
    mainCmd.Flags().String("listen-remote-api", "0.0.0.0:4242", "Listen address for remote API")
    mainCmd.Flags().String("listen-control-api", "./swarmkitstate/swarmd.sock", "Listen socket for control API")
    mainCmd.Flags().String("listen-debug", "", "Bind the Go debug server on the provided address")
    mainCmd.Flags().String("join-addr", "", "Join cluster with a node at this address")
    mainCmd.Flags().Bool("force-new-cluster", false, "Force the creation of a new cluster from data directory")
    mainCmd.Flags().Uint32("heartbeat-tick", 1, "Defines the heartbeat interval (in seconds) for raft member health-check")
    mainCmd.Flags().Uint32("election-tick", 3, "Defines the amount of ticks (in seconds) needed without a Leader to trigger a new election")
    mainCmd.Flags().Var(&externalCAOpt, "external-ca", "Specifications of one or more certificate signing endpoints")
}

(1)versionlog-levelhostname最简单,不必细说。
(2)state-dir目录存储远端manager以及CA认证等相关信息:

# ls -alt
total 24
drwx------ 5 root root 4096 Jul 29 02:40 .
drwx------ 4 root root 4096 Jul 29 02:40 raft
-rw------- 1 root root   63 Jul 29 02:40 state.json
drwxr-xr-x 2 root root 4096 Jul 29 02:40 worker
drwxr-xr-x 2 root root 4096 Jul 29 02:40 certificates
drwxr-xr-x 3 root root 4096 Jul 29 02:40 ..

(3)join-tokennode用来加入某个clustertoken,在第一次认证请求时会被用到。
(4)engine-addr指定实际用来执行executorengine位置,默认是使用本机Docker
(5)listen-remote-api指定监听一个tcp port,用来接收和处理其它node的访问请求。
(6)listen-control-api指定一个Unix socket,用来接收和处理swarmctl程序的访问请求。
(7)listen-debug指定监听一个用来debug程序的端口。
(8)join-addr指定要加入的cluster的一个node地址,通过连接这个node来加入这个cluster
(9)其余force-new-clusterheartbeat-tickelection-tickexternal-ca解释的都很清楚,不必赘述。

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