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logger.go
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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"
"sort"
"strings"
"sync"
"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 {
Line []byte
Source string
Timestamp time.Time
Attrs LogAttributes
}
// LogAttributes is used to hold the extra attributes available in the log message
// Primarily used for converting the map type to string and sorting.
type LogAttributes map[string]string
type byKey []string
func (s byKey) Len() int { return len(s) }
func (s byKey) Less(i, j int) bool {
keyI := strings.Split(s[i], "=")
keyJ := strings.Split(s[j], "=")
return keyI[0] < keyJ[0]
}
func (s byKey) Swap(i, j int) {
s[i], s[j] = s[j], s[i]
}
func (a LogAttributes) String() string {
var ss byKey
for k, v := range a {
ss = append(ss, k+"="+v)
}
sort.Sort(ss)
return strings.Join(ss, ",")
}
// 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
closeOnce sync.Once
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
w.closeOnce.Do(func() {
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
}