internal/cli/agent.go
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package cli import ( "flag" "fmt" "log" "os" "os/signal" "strings" "syscall" "time" "git.j3s.sh/cascade/internal/agent" ) type agentCommand struct { // gracefulTimeout controls how long we wait before forcefully terminating // note that this value interacts with serf's LeavePropagateDelay config gracefulTimeout time.Duration flagBindDNS string flagBindHTTP string flagBindSerf string flagJoin string flagNode string } func (c *agentCommand) Usage() { fmt.Print( `usage: cascade agent [flags] this command starts the cascade agent, which is responsible for basically everything, including service registration, health checking, cluster membership, and hosting the API. flags: -bind-dns=<addr> address the DNS server binds to (default = 127.0.0.1:8600) -bind-http=<addr> address the http api/interace binds to (default = 127.0.0.1:8500) -bind-serf=<addr> address the serf agent binds to (default = 0.0.0.0:8301) -join=<addrs> comma-separated address of agents to join at start time (default = nil) -node=<name> name of this node, must be globally unique (default = hostname) `) } func (c *agentCommand) Init(args []string) agentCommand { c.gracefulTimeout = 10 * time.Second flags := flag.NewFlagSet("", flag.ContinueOnError) flags.Usage = c.Usage flags.StringVar(&c.flagBindDNS, "bind-dns", "", "") flags.StringVar(&c.flagBindHTTP, "bind-http", "", "") flags.StringVar(&c.flagBindSerf, "bind-serf", "", "") flags.StringVar(&c.flagJoin, "join", "", "") flags.StringVar(&c.flagNode, "node", "", "") if err := flags.Parse(args); err != nil { fmt.Println(err) os.Exit(1) } return *c } func RunAgent(args []string) { c := agentCommand{} c.Init(args) config, err := c.getAgentConfig() if err != nil { fmt.Println(err) os.Exit(1) } agent := agent.New(config) fmt.Printf("-> starting cascade agent\n") fmt.Printf(" node '%s'\n", config.NodeName) if len(config.StartJoin) > 0 { fmt.Printf(" join '%s'\n", config.StartJoin) } fmt.Printf(" bind addrs:\n") fmt.Printf(" dns '%s'\n", config.DNSBindAddr) fmt.Printf(" http '%s'\n", config.HTTPBindAddr) fmt.Printf(" serf '%s'\n", config.SerfBindAddr) fmt.Printf("\n-> logs\n") if err := agent.Start(); err != nil { fmt.Println(err) os.Exit(1) } defer agent.Shutdown() if err := c.startupJoin(agent); err != nil { fmt.Println(err) os.Exit(1) } if err := c.handleSignals(agent); err != nil { fmt.Println(err) os.Exit(1) } } // handleSignals blocks until we get an exit-causing signal func (c agentCommand) handleSignals(agent *agent.Agent) error { signalCh := make(chan os.Signal, 4) signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM) // Wait for a signal var sig os.Signal select { case s := <-signalCh: sig = s case <-agent.ShutdownCh(): // Agent is already shutdown! return nil } fmt.Fprintf(os.Stderr, "caught signal %s", sig) // Check if we should do a graceful leave graceful := false if sig == os.Interrupt || sig == syscall.SIGTERM { graceful = true } // Bail fast if not doing a graceful leave if !graceful { fmt.Fprintf(os.Stderr, "leave cluster with zero grace") return nil } // Attempt a graceful leave gracefulCh := make(chan struct{}) fmt.Printf("shutting down gracefully") go func() { if err := agent.Leave(); err != nil { fmt.Println("Error: ", err) return } close(gracefulCh) }() // Wait for leave or another signal select { case <-signalCh: return fmt.Errorf("idfk") case <-time.After(c.gracefulTimeout): return fmt.Errorf("leave timed out") case <-gracefulCh: return nil } } func (c agentCommand) startupJoin(a *agent.Agent) error { if len(a.Config.StartJoin) == 0 { return nil } n, err := a.Join(a.Config.StartJoin) if err != nil { return err } if n > 0 { log.Printf("issue join request nodes=%d\n", n) } return nil } // getAgentConfig takes a default agent config and modifies it based // on user specified flags. It also does some a little input validation. func (c agentCommand) getAgentConfig() (*agent.Config, error) { config := agent.DefaultConfig() if c.flagBindDNS != "" { if err := parseFlagAddress(c.flagBindDNS, config.DNSBindAddr); err != nil { return nil, err } } if c.flagBindHTTP != "" { if err := parseFlagAddress(c.flagBindHTTP, config.HTTPBindAddr); err != nil { return nil, err } } if c.flagBindSerf != "" { if err := parseFlagAddress(c.flagBindSerf, config.SerfBindAddr); err != nil { return nil, err } } if c.flagJoin != "" { // TODO: moar validation config.StartJoin = strings.Split(c.flagJoin, ",") } if c.flagNode != "" { config.NodeName = c.flagNode } return config, nil }