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