package daemon import ( "errors" "strconv" "time" "golang.org/x/net/context" "github.com/Sirupsen/logrus" "github.com/docker/docker/api/types" "github.com/docker/docker/api/types/backend" containertypes "github.com/docker/docker/api/types/container" timetypes "github.com/docker/docker/api/types/time" "github.com/docker/docker/container" "github.com/docker/docker/daemon/logger" ) // ContainerLogs copies the container's log channel to the channel provided in // the config. If ContainerLogs returns an error, no messages have been copied. // and the channel will be closed without data. // // if it returns nil, the config channel will be active and return log // messages until it runs out or the context is canceled. func (daemon *Daemon) ContainerLogs(ctx context.Context, containerName string, config *types.ContainerLogsOptions) (<-chan *backend.LogMessage, error) { lg := logrus.WithFields(logrus.Fields{ "module": "daemon", "method": "(*Daemon).ContainerLogs", "container": containerName, }) if !(config.ShowStdout || config.ShowStderr) { return nil, errors.New("You must choose at least one stream") } container, err := daemon.GetContainer(containerName) if err != nil { return nil, err } if container.RemovalInProgress || container.Dead { return nil, errors.New("can not get logs from container which is dead or marked for removal") } if container.HostConfig.LogConfig.Type == "none" { return nil, logger.ErrReadLogsNotSupported } cLog, err := daemon.getLogger(container) if err != nil { return nil, err } logReader, ok := cLog.(logger.LogReader) if !ok { return nil, logger.ErrReadLogsNotSupported } follow := config.Follow && container.IsRunning() tailLines, err := strconv.Atoi(config.Tail) if err != nil { tailLines = -1 } var since time.Time if config.Since != "" { s, n, err := timetypes.ParseTimestamps(config.Since, 0) if err != nil { return nil, err } since = time.Unix(s, n) } readConfig := logger.ReadConfig{ Since: since, Tail: tailLines, Follow: follow, } logs := logReader.ReadLogs(readConfig) // past this point, we can't possibly return any errors, so we can just // start a goroutine and return to tell the caller not to expect errors // (if the caller wants to give up on logs, they have to cancel the context) // this goroutine functions as a shim between the logger and the caller. messageChan := make(chan *backend.LogMessage, 1) go func() { // set up some defers defer func() { // ok so this function, originally, was placed right after that // logger.ReadLogs call above. I THINK that means it sets off the // chain of events that results in the logger needing to be closed. // i do not know if an error in time parsing above causing an early // return will result in leaking the logger. if that is the case, // it would also have been a bug in the original code logs.Close() if cLog != container.LogDriver { // Since the logger isn't cached in the container, which // occurs if it is running, it must get explicitly closed // here to avoid leaking it and any file handles it has. if err := cLog.Close(); err != nil { logrus.Errorf("Error closing logger: %v", err) } } }() // close the messages channel. closing is the only way to signal above // that we're doing with logs (other than context cancel i guess). defer close(messageChan) lg.Debug("begin logs") for { select { // i do not believe as the system is currently designed any error // is possible, but we should be prepared to handle it anyway. if // we do get an error, copy only the error field to a new object so // we don't end up with partial data in the other fields case err := <-logs.Err: lg.Errorf("Error streaming logs: %v", err) select { case <-ctx.Done(): case messageChan <- &backend.LogMessage{Err: err}: } return case <-ctx.Done(): lg.Debug("logs: end stream, ctx is done: %v", ctx.Err()) return case msg, ok := <-logs.Msg: // there is some kind of pool or ring buffer in the logger that // produces these messages, and a possible future optimization // might be to use that pool and reuse message objects if !ok { lg.Debug("end logs") return } m := msg.AsLogMessage() // just a pointer conversion, does not copy data // there could be a case where the reader stops accepting // messages and the context is canceled. we need to check that // here, or otherwise we risk blocking forever on the message // send. select { case <-ctx.Done(): return case messageChan <- m: } } } }() return messageChan, nil } func (daemon *Daemon) getLogger(container *container.Container) (logger.Logger, error) { if container.LogDriver != nil && container.IsRunning() { return container.LogDriver, nil } return container.StartLogger() } // mergeLogConfig merges the daemon log config to the container's log config if the container's log driver is not specified. func (daemon *Daemon) mergeAndVerifyLogConfig(cfg *containertypes.LogConfig) error { if cfg.Type == "" { cfg.Type = daemon.defaultLogConfig.Type } if cfg.Config == nil { cfg.Config = make(map[string]string) } if cfg.Type == daemon.defaultLogConfig.Type { for k, v := range daemon.defaultLogConfig.Config { if _, ok := cfg.Config[k]; !ok { cfg.Config[k] = v } } } return logger.ValidateLogOpts(cfg.Type, cfg.Config) }