package daemon import ( "bytes" "fmt" "runtime" "strings" "time" "golang.org/x/net/context" "github.com/Sirupsen/logrus" "github.com/docker/docker/container" "github.com/docker/docker/daemon/exec" "github.com/docker/engine-api/types" "github.com/docker/engine-api/types/strslice" ) const ( // Longest healthcheck probe output message to store. Longer messages will be truncated. maxOutputLen = 4096 // Default interval between probe runs (from the end of the first to the start of the second). // Also the time before the first probe. defaultProbeInterval = 30 * time.Second // The maximum length of time a single probe run should take. If the probe takes longer // than this, the check is considered to have failed. defaultProbeTimeout = 30 * time.Second // Default number of consecutive failures of the health check // for the container to be considered unhealthy. defaultProbeRetries = 3 // Maximum number of entries to record maxLogEntries = 5 ) const ( // Exit status codes that can be returned by the probe command. exitStatusHealthy = 0 // Container is healthy exitStatusUnhealthy = 1 // Container is unhealthy ) // probe implementations know how to run a particular type of probe. type probe interface { // Perform one run of the check. Returns the exit code and an optional // short diagnostic string. run(context.Context, *Daemon, *container.Container) (*types.HealthcheckResult, error) } // cmdProbe implements the "CMD" probe type. type cmdProbe struct { // Run the command with the system's default shell instead of execing it directly. shell bool } // exec the healthcheck command in the container. // Returns the exit code and probe output (if any) func (p *cmdProbe) run(ctx context.Context, d *Daemon, container *container.Container) (*types.HealthcheckResult, error) { cmdSlice := strslice.StrSlice(container.Config.Healthcheck.Test)[1:] if p.shell { if runtime.GOOS != "windows" { cmdSlice = append([]string{"/bin/sh", "-c"}, cmdSlice...) } else { cmdSlice = append([]string{"cmd", "/S", "/C"}, cmdSlice...) } } entrypoint, args := d.getEntrypointAndArgs(strslice.StrSlice{}, cmdSlice) execConfig := exec.NewConfig() execConfig.OpenStdin = false execConfig.OpenStdout = true execConfig.OpenStderr = true execConfig.ContainerID = container.ID execConfig.DetachKeys = []byte{} execConfig.Entrypoint = entrypoint execConfig.Args = args execConfig.Tty = false execConfig.Privileged = false execConfig.User = container.Config.User d.registerExecCommand(container, execConfig) d.LogContainerEvent(container, "exec_create: "+execConfig.Entrypoint+" "+strings.Join(execConfig.Args, " ")) output := &limitedBuffer{} err := d.ContainerExecStart(ctx, execConfig.ID, nil, output, output) if err != nil { return nil, err } info, err := d.getExecConfig(execConfig.ID) if err != nil { return nil, err } if info.ExitCode == nil { return nil, fmt.Errorf("Healthcheck has no exit code!") } // Note: Go's json package will handle invalid UTF-8 for us out := output.String() return &types.HealthcheckResult{ End: time.Now(), ExitCode: *info.ExitCode, Output: out, }, nil } // Update the container's Status.Health struct based on the latest probe's result. func handleProbeResult(d *Daemon, c *container.Container, result *types.HealthcheckResult) { c.Lock() defer c.Unlock() retries := c.Config.Healthcheck.Retries if retries <= 0 { retries = defaultProbeRetries } h := c.State.Health oldStatus := h.Status if len(h.Log) >= maxLogEntries { h.Log = append(h.Log[len(h.Log)+1-maxLogEntries:], result) } else { h.Log = append(h.Log, result) } if result.ExitCode == exitStatusHealthy { h.FailingStreak = 0 h.Status = types.Healthy } else { // Failure (including invalid exit code) h.FailingStreak++ if h.FailingStreak >= retries { h.Status = types.Unhealthy } // Else we're starting or healthy. Stay in that state. } if oldStatus != h.Status { d.LogContainerEvent(c, "health_status: "+h.Status) } } // Run the container's monitoring thread until notified via "stop". // There is never more than one monitor thread running per container at a time. func monitor(d *Daemon, c *container.Container, stop chan struct{}, probe probe) { probeTimeout := timeoutWithDefault(c.Config.Healthcheck.Timeout, defaultProbeTimeout) probeInterval := timeoutWithDefault(c.Config.Healthcheck.Interval, defaultProbeInterval) for { select { case <-stop: logrus.Debug("Stop healthcheck monitoring (received while idle)") return case <-time.After(probeInterval): logrus.Debug("Running health check...") startTime := time.Now() ctx, cancelProbe := context.WithTimeout(context.Background(), probeTimeout) results := make(chan *types.HealthcheckResult) go func() { result, err := probe.run(ctx, d, c) if err != nil { logrus.Warnf("Health check error: %v", err) results <- &types.HealthcheckResult{ ExitCode: -1, Output: err.Error(), Start: startTime, End: time.Now(), } } else { result.Start = startTime logrus.Debugf("Health check done (exitCode=%d)", result.ExitCode) results <- result } close(results) }() select { case <-stop: logrus.Debug("Stop healthcheck monitoring (received while probing)") // Stop timeout and kill probe, but don't wait for probe to exit. cancelProbe() return case result := <-results: handleProbeResult(d, c, result) // Stop timeout cancelProbe() case <-ctx.Done(): logrus.Debug("Health check taking too long") handleProbeResult(d, c, &types.HealthcheckResult{ ExitCode: -1, Output: fmt.Sprintf("Health check exceeded timeout (%v)", probeTimeout), Start: startTime, End: time.Now(), }) cancelProbe() // Wait for probe to exit (it might take a while to respond to the TERM // signal and we don't want dying probes to pile up). <-results } } } } // Get a suitable probe implementation for the container's healthcheck configuration. // Nil will be returned if no healthcheck was configured or NONE was set. func getProbe(c *container.Container) probe { config := c.Config.Healthcheck if config == nil || len(config.Test) == 0 { return nil } switch config.Test[0] { case "CMD": return &cmdProbe{shell: false} case "CMD-SHELL": return &cmdProbe{shell: true} default: logrus.Warnf("Unknown healthcheck type '%s' (expected 'CMD')", config.Test[0]) return nil } } // Ensure the health-check monitor is running or not, depending on the current // state of the container. // Called from monitor.go, with c locked. func (d *Daemon) updateHealthMonitor(c *container.Container) { h := c.State.Health if h == nil { return // No healthcheck configured } probe := getProbe(c) wantRunning := c.Running && !c.Paused && probe != nil if wantRunning { if stop := h.OpenMonitorChannel(); stop != nil { go monitor(d, c, stop, probe) } } else { h.CloseMonitorChannel() } } // Reset the health state for a newly-started, restarted or restored container. // initHealthMonitor is called from monitor.go and we should never be running // two instances at once. // Called with c locked. func (d *Daemon) initHealthMonitor(c *container.Container) { // If no healthcheck is setup then don't init the monitor if getProbe(c) == nil { return } // This is needed in case we're auto-restarting d.stopHealthchecks(c) if c.State.Health == nil { h := &container.Health{} h.Status = types.Starting c.State.Health = h } d.updateHealthMonitor(c) } // Called when the container is being stopped (whether because the health check is // failing or for any other reason). func (d *Daemon) stopHealthchecks(c *container.Container) { h := c.State.Health if h != nil { h.CloseMonitorChannel() } } // Buffer up to maxOutputLen bytes. Further data is discarded. type limitedBuffer struct { buf bytes.Buffer truncated bool // indicates that data has been lost } // Append to limitedBuffer while there is room. func (b *limitedBuffer) Write(data []byte) (int, error) { bufLen := b.buf.Len() dataLen := len(data) keep := min(maxOutputLen-bufLen, dataLen) if keep > 0 { b.buf.Write(data[:keep]) } if keep < dataLen { b.truncated = true } return dataLen, nil } // The contents of the buffer, with "..." appended if it overflowed. func (b *limitedBuffer) String() string { out := b.buf.String() if b.truncated { out = out + "..." } return out } // If configuredValue is zero, use defaultValue instead. func timeoutWithDefault(configuredValue time.Duration, defaultValue time.Duration) time.Duration { if configuredValue == 0 { return defaultValue } return configuredValue } func min(x, y int) int { if x < y { return x } return y }