139 lines
3.8 KiB
Go
139 lines
3.8 KiB
Go
// +build !windows
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package main
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import (
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"fmt"
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"net"
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"os"
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"os/signal"
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"strings"
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"golang.org/x/sys/unix"
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"google.golang.org/grpc"
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"github.com/Sirupsen/logrus"
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"github.com/containerd/containerd"
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shimapi "github.com/containerd/containerd/api/services/shim"
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"github.com/containerd/containerd/linux/shim"
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"github.com/containerd/containerd/reaper"
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"github.com/containerd/containerd/sys"
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runc "github.com/crosbymichael/go-runc"
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"github.com/urfave/cli"
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)
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const usage = `
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__ _ __ __ _
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_________ ____ / /_____ _(_)___ ___ _________/ / _____/ /_ (_)___ ___
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/ ___/ __ \/ __ \/ __/ __ ` + "`" + `/ / __ \/ _ \/ ___/ __ /_____/ ___/ __ \/ / __ ` + "`" + `__ \
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/ /__/ /_/ / / / / /_/ /_/ / / / / / __/ / / /_/ /_____(__ ) / / / / / / / / /
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\___/\____/_/ /_/\__/\__,_/_/_/ /_/\___/_/ \__,_/ /____/_/ /_/_/_/ /_/ /_/
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shim for container lifecycle and reconnection
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`
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func main() {
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app := cli.NewApp()
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app.Name = "containerd-shim"
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app.Version = containerd.Version
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app.Usage = usage
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app.Flags = []cli.Flag{
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cli.BoolFlag{
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Name: "debug",
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Usage: "enable debug output in logs",
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},
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}
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app.Before = func(context *cli.Context) error {
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if context.GlobalBool("debug") {
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logrus.SetLevel(logrus.DebugLevel)
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}
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return nil
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}
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app.Action = func(context *cli.Context) error {
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// start handling signals as soon as possible so that things are properly reaped
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// or if runtime exits before we hit the handler
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signals, err := setupSignals()
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if err != nil {
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return err
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}
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if err := setupRoot(); err != nil {
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return err
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}
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path, err := os.Getwd()
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if err != nil {
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return err
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}
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var (
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server = grpc.NewServer()
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sv = shim.New(path)
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)
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logrus.Debug("registering grpc server")
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shimapi.RegisterShimServer(server, sv)
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if err := serve(server, "shim.sock"); err != nil {
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return err
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}
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return handleSignals(signals, server)
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}
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if err := app.Run(os.Args); err != nil {
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fmt.Fprintf(os.Stderr, "containerd-shim: %s\n", err)
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os.Exit(1)
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}
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}
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// setupSignals creates a new signal handler for all signals and sets the shim as a
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// sub-reaper so that the container processes are reparented
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func setupSignals() (chan os.Signal, error) {
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signals := make(chan os.Signal, 2048)
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signal.Notify(signals)
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// make sure runc is setup to use the monitor
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// for waiting on processes
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runc.Monitor = reaper.Default
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// set the shim as the subreaper for all orphaned processes created by the container
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if err := sys.SetSubreaper(1); err != nil {
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return nil, err
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}
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return signals, nil
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}
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// serve serves the grpc API over a unix socket at the provided path
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// this function does not block
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func serve(server *grpc.Server, path string) error {
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l, err := net.FileListener(os.NewFile(3, "socket"))
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if err != nil {
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return err
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}
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logrus.WithField("socket", path).Debug("serving api on unix socket")
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go func() {
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defer l.Close()
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if err := server.Serve(l); err != nil &&
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!strings.Contains(err.Error(), "use of closed network connection") {
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logrus.WithError(err).Fatal("containerd-shim: GRPC server failure")
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}
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}()
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return nil
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}
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func handleSignals(signals chan os.Signal, server *grpc.Server) error {
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for s := range signals {
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logrus.WithField("signal", s).Debug("received signal")
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switch s {
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case unix.SIGCHLD:
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if err := reaper.Reap(); err != nil {
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logrus.WithError(err).Error("reap exit status")
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}
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case unix.SIGTERM, unix.SIGINT:
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// TODO: should we forward signals to the processes if they are still running?
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// i.e. machine reboot
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server.Stop()
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return nil
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}
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}
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return nil
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}
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// setupRoot sets up the root as the shim is started in its own mount namespace
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func setupRoot() error {
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return unix.Mount("", "/", "", unix.MS_SLAVE|unix.MS_REC, "")
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}
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