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moby--moby/daemon/logger/logger.go

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// Package logger defines interfaces that logger drivers implement to
// log messages.
//
// The other half of a logger driver is the implementation of the
// factory, which holds the contextual instance information that
// allows multiple loggers of the same type to perform different
// actions, such as logging to different locations.
package logger
import (
"errors"
"time"
"github.com/docker/docker/pkg/jsonlog"
)
// ErrReadLogsNotSupported is returned when the logger does not support reading logs.
var ErrReadLogsNotSupported = errors.New("configured logging reader does not support reading")
const (
// TimeFormat is the time format used for timestamps sent to log readers.
TimeFormat = jsonlog.RFC3339NanoFixed
logWatcherBufferSize = 4096
)
// Message is datastructure that represents record from some container.
type Message struct {
ContainerID string
Line []byte
Source string
Timestamp time.Time
}
// Logger is the interface for docker logging drivers.
type Logger interface {
Log(*Message) error
Name() string
Close() error
}
// ReadConfig is the configuration passed into ReadLogs.
type ReadConfig struct {
Since time.Time
Tail int
Follow bool
}
// LogReader is the interface for reading log messages for loggers that support reading.
type LogReader interface {
// Read logs from underlying logging backend
ReadLogs(ReadConfig) *LogWatcher
}
// LogWatcher is used when consuming logs read from the LogReader interface.
type LogWatcher struct {
// For sending log messages to a reader.
Msg chan *Message
// For sending error messages that occur while while reading logs.
Err chan error
closeNotifier chan struct{}
}
// NewLogWatcher returns a new LogWatcher.
func NewLogWatcher() *LogWatcher {
return &LogWatcher{
Msg: make(chan *Message, logWatcherBufferSize),
Err: make(chan error, 1),
closeNotifier: make(chan struct{}),
}
}
// Close notifies the underlying log reader to stop.
func (w *LogWatcher) Close() {
// only close if not already closed
select {
case <-w.closeNotifier:
default:
close(w.closeNotifier)
}
}
// WatchClose returns a channel receiver that receives notification
// when the watcher has been closed. This should only be called from
// one goroutine.
func (w *LogWatcher) WatchClose() <-chan struct{} {
return w.closeNotifier
}