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moby--moby/daemon/logs.go
Nalin Dahyabhai e611a189cb Add log reading to the journald log driver
If a logdriver doesn't register a callback function to validate log
options, it won't be usable.  Fix the journald driver by adding a dummy
validator.

Teach the client and the daemon's "logs" logic that the server can also
supply "logs" data via the "journald" driver.  Update documentation and
tests that depend on error messages.

Add support for reading log data from the systemd journal to the
journald log driver.  The internal logic uses a goroutine to scan the
journal for matching entries after any specified cutoff time, formats
the messages from those entries as JSONLog messages, and stuffs the
results down a pipe whose reading end we hand back to the caller.

If we are missing any of the 'linux', 'cgo', or 'journald' build tags,
however, we don't implement a reader, so the 'logs' endpoint will still
return an error.

Make the necessary changes to the build setup to ensure that support for
reading container logs from the systemd journal is built.

Rename the Jmap member of the journald logdriver's struct to "vars" to
make it non-public, and to make it easier to tell that it's just there
to hold additional variable values that we want journald to record along
with log data that we're sending to it.

In the client, don't assume that we know which logdrivers the server
implements, and remove the check that looks at the server.  It's
redundant because the server already knows, and the check also makes
using older clients with newer servers (which may have new logdrivers in
them) unnecessarily hard.

When we try to "logs" and have to report that the container's logdriver
doesn't support reading, send the error message through the
might-be-a-multiplexer so that clients which are expecting multiplexed
data will be able to properly display the error, instead of tripping
over the data and printing a less helpful "Unrecognized input header"
error.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com> (github: nalind)
2015-09-11 16:50:03 -04:00

94 lines
2.3 KiB
Go

package daemon
import (
"fmt"
"io"
"strconv"
"time"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/daemon/logger"
"github.com/docker/docker/pkg/stdcopy"
)
// ContainerLogsConfig holds configs for logging operations. Exists
// for users of the daemon to to pass it a logging configuration.
type ContainerLogsConfig struct {
// if true stream log output
Follow bool
// if true include timestamps for each line of log output
Timestamps bool
// return that many lines of log output from the end
Tail string
// filter logs by returning on those entries after this time
Since time.Time
// whether or not to show stdout and stderr as well as log entries.
UseStdout, UseStderr bool
OutStream io.Writer
Stop <-chan bool
}
// ContainerLogs hooks up a container's stdout and stderr streams
// configured with the given struct.
func (daemon *Daemon) ContainerLogs(container *Container, config *ContainerLogsConfig) error {
if !(config.UseStdout || config.UseStderr) {
return fmt.Errorf("You must choose at least one stream")
}
outStream := config.OutStream
errStream := outStream
if !container.Config.Tty {
errStream = stdcopy.NewStdWriter(outStream, stdcopy.Stderr)
outStream = stdcopy.NewStdWriter(outStream, stdcopy.Stdout)
}
config.OutStream = outStream
cLog, err := container.getLogger()
if err != nil {
return err
}
logReader, ok := cLog.(logger.LogReader)
if !ok {
return logger.ErrReadLogsNotSupported
}
follow := config.Follow && container.IsRunning()
tailLines, err := strconv.Atoi(config.Tail)
if err != nil {
tailLines = -1
}
logrus.Debug("logs: begin stream")
readConfig := logger.ReadConfig{
Since: config.Since,
Tail: tailLines,
Follow: follow,
}
logs := logReader.ReadLogs(readConfig)
for {
select {
case err := <-logs.Err:
logrus.Errorf("Error streaming logs: %v", err)
return nil
case <-config.Stop:
logs.Close()
return nil
case msg, ok := <-logs.Msg:
if !ok {
logrus.Debugf("logs: end stream")
return nil
}
logLine := msg.Line
if config.Timestamps {
logLine = append([]byte(msg.Timestamp.Format(logger.TimeFormat)+" "), logLine...)
}
if msg.Source == "stdout" && config.UseStdout {
outStream.Write(logLine)
}
if msg.Source == "stderr" && config.UseStderr {
errStream.Write(logLine)
}
}
}
}