package daemon import ( "io" "os/exec" "sync" "time" log "github.com/Sirupsen/logrus" "github.com/docker/docker/daemon/execdriver" "github.com/docker/docker/pkg/common" "github.com/docker/docker/runconfig" ) const defaultTimeIncrement = 100 // containerMonitor monitors the execution of a container's main process. // If a restart policy is specified for the container the monitor will ensure that the // process is restarted based on the rules of the policy. When the container is finally stopped // the monitor will reset and cleanup any of the container resources such as networking allocations // and the rootfs type containerMonitor struct { mux sync.Mutex // container is the container being monitored container *Container // restartPolicy is the current policy being applied to the container monitor restartPolicy runconfig.RestartPolicy // failureCount is the number of times the container has failed to // start in a row failureCount int // shouldStop signals the monitor that the next time the container exits it is // either because docker or the user asked for the container to be stopped shouldStop bool // startSignal is a channel that is closes after the container initially starts startSignal chan struct{} // stopChan is used to signal to the monitor whenever there is a wait for the // next restart so that the timeIncrement is not honored and the user is not // left waiting for nothing to happen during this time stopChan chan struct{} // timeIncrement is the amount of time to wait between restarts // this is in milliseconds timeIncrement int // lastStartTime is the time which the monitor last exec'd the container's process lastStartTime time.Time } // newContainerMonitor returns an initialized containerMonitor for the provided container // honoring the provided restart policy func newContainerMonitor(container *Container, policy runconfig.RestartPolicy) *containerMonitor { return &containerMonitor{ container: container, restartPolicy: policy, timeIncrement: defaultTimeIncrement, stopChan: make(chan struct{}), startSignal: make(chan struct{}), } } // Stop signals to the container monitor that it should stop monitoring the container // for exits the next time the process dies func (m *containerMonitor) ExitOnNext() { m.mux.Lock() // we need to protect having a double close of the channel when stop is called // twice or else we will get a panic if !m.shouldStop { m.shouldStop = true close(m.stopChan) } m.mux.Unlock() } // Close closes the container's resources such as networking allocations and // unmounts the contatiner's root filesystem func (m *containerMonitor) Close() error { // Cleanup networking and mounts m.container.cleanup() // FIXME: here is race condition between two RUN instructions in Dockerfile // because they share same runconfig and change image. Must be fixed // in builder/builder.go if err := m.container.toDisk(); err != nil { log.Errorf("Error dumping container %s state to disk: %s", m.container.ID, err) return err } return nil } // Start starts the containers process and monitors it according to the restart policy func (m *containerMonitor) Start() error { var ( err error exitStatus execdriver.ExitStatus // this variable indicates where we in execution flow: // before Run or after afterRun bool ) // ensure that when the monitor finally exits we release the networking and unmount the rootfs defer func() { if afterRun { m.container.Lock() m.container.setStopped(&exitStatus) defer m.container.Unlock() } m.Close() }() // reset the restart count m.container.RestartCount = -1 for { m.container.RestartCount++ if err := m.container.startLogging(); err != nil { m.resetContainer(false) return err } pipes := execdriver.NewPipes(m.container.stdin, m.container.stdout, m.container.stderr, m.container.Config.OpenStdin) m.container.LogEvent("start") m.lastStartTime = time.Now() if exitStatus, err = m.container.daemon.Run(m.container, pipes, m.callback); err != nil { // if we receive an internal error from the initial start of a container then lets // return it instead of entering the restart loop if m.container.RestartCount == 0 { m.container.ExitCode = -1 m.resetContainer(false) return err } log.Errorf("Error running container: %s", err) } // here container.Lock is already lost afterRun = true m.resetMonitor(err == nil && exitStatus.ExitCode == 0) if m.shouldRestart(exitStatus.ExitCode) { m.container.SetRestarting(&exitStatus) if exitStatus.OOMKilled { m.container.LogEvent("oom") } m.container.LogEvent("die") m.resetContainer(true) // sleep with a small time increment between each restart to help avoid issues cased by quickly // restarting the container because of some types of errors ( networking cut out, etc... ) m.waitForNextRestart() // we need to check this before reentering the loop because the waitForNextRestart could have // been terminated by a request from a user if m.shouldStop { return err } continue } if exitStatus.OOMKilled { m.container.LogEvent("oom") } m.container.LogEvent("die") m.resetContainer(true) return err } } // resetMonitor resets the stateful fields on the containerMonitor based on the // previous runs success or failure. Regardless of success, if the container had // an execution time of more than 10s then reset the timer back to the default func (m *containerMonitor) resetMonitor(successful bool) { executionTime := time.Now().Sub(m.lastStartTime).Seconds() if executionTime > 10 { m.timeIncrement = defaultTimeIncrement } else { // otherwise we need to increment the amount of time we wait before restarting // the process. We will build up by multiplying the increment by 2 m.timeIncrement *= 2 } // the container exited successfully so we need to reset the failure counter if successful { m.failureCount = 0 } else { m.failureCount++ } } // waitForNextRestart waits with the default time increment to restart the container unless // a user or docker asks for the container to be stopped func (m *containerMonitor) waitForNextRestart() { select { case <-time.After(time.Duration(m.timeIncrement) * time.Millisecond): case <-m.stopChan: } } // shouldRestart checks the restart policy and applies the rules to determine if // the container's process should be restarted func (m *containerMonitor) shouldRestart(exitCode int) bool { m.mux.Lock() defer m.mux.Unlock() // do not restart if the user or docker has requested that this container be stopped if m.shouldStop { return false } switch m.restartPolicy.Name { case "always": return true case "on-failure": // the default value of 0 for MaximumRetryCount means that we will not enforce a maximum count if max := m.restartPolicy.MaximumRetryCount; max != 0 && m.failureCount > max { log.Debugf("stopping restart of container %s because maximum failure could of %d has been reached", common.TruncateID(m.container.ID), max) return false } return exitCode != 0 } return false } // callback ensures that the container's state is properly updated after we // received ack from the execution drivers func (m *containerMonitor) callback(processConfig *execdriver.ProcessConfig, pid int) { if processConfig.Tty { // The callback is called after the process Start() // so we are in the parent process. In TTY mode, stdin/out/err is the PtySlave // which we close here. if c, ok := processConfig.Stdout.(io.Closer); ok { c.Close() } } m.container.setRunning(pid) // signal that the process has started // close channel only if not closed select { case <-m.startSignal: default: close(m.startSignal) } if err := m.container.ToDisk(); err != nil { log.Debugf("%s", err) } } // resetContainer resets the container's IO and ensures that the command is able to be executed again // by copying the data into a new struct // if lock is true, then container locked during reset func (m *containerMonitor) resetContainer(lock bool) { container := m.container if lock { container.Lock() defer container.Unlock() } if container.Config.OpenStdin { if err := container.stdin.Close(); err != nil { log.Errorf("%s: Error close stdin: %s", container.ID, err) } } if err := container.stdout.Clean(); err != nil { log.Errorf("%s: Error close stdout: %s", container.ID, err) } if err := container.stderr.Clean(); err != nil { log.Errorf("%s: Error close stderr: %s", container.ID, err) } if container.command != nil && container.command.ProcessConfig.Terminal != nil { if err := container.command.ProcessConfig.Terminal.Close(); err != nil { log.Errorf("%s: Error closing terminal: %s", container.ID, err) } } // Re-create a brand new stdin pipe once the container exited if container.Config.OpenStdin { container.stdin, container.stdinPipe = io.Pipe() } if container.logDriver != nil { container.logDriver.Close() container.logDriver = nil } c := container.command.ProcessConfig.Cmd container.command.ProcessConfig.Cmd = exec.Cmd{ Stdin: c.Stdin, Stdout: c.Stdout, Stderr: c.Stderr, Path: c.Path, Env: c.Env, ExtraFiles: c.ExtraFiles, Args: c.Args, Dir: c.Dir, SysProcAttr: c.SysProcAttr, } }