forked from juju/juju
/
logforwarder.go
262 lines (228 loc) · 6.47 KB
/
logforwarder.go
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// Copyright 2016 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.
package logforwarder
import (
"io"
"sync"
"github.com/juju/errors"
"github.com/juju/worker/v3/catacomb"
"gopkg.in/tomb.v2"
"github.com/DavinZhang/juju/api/base"
"github.com/DavinZhang/juju/apiserver/params"
"github.com/DavinZhang/juju/logfwd"
)
// logger is here to stop the desire of creating a package level logger.
// Don't do this, instead use the one passed as manifold config.
type logger interface{}
var _ logger = struct{}{}
// LogStream streams log entries from a log source (e.g. the Juju controller).
type LogStream interface {
// Next returns the next batch of log records from the stream.
Next() ([]logfwd.Record, error)
}
// LogStreamFn is a function that opens a log stream.
type LogStreamFn func(_ base.APICaller, _ params.LogStreamConfig, controllerUUID string) (LogStream, error)
// SendCloser is responsible for sending log records to a log sink.
type SendCloser interface {
sender
io.Closer
}
type sender interface {
// Send sends the records to its log sink. It is also responsible
// for notifying the controller that record was forwarded.
Send([]logfwd.Record) error
}
// TODO(ericsnow) It is likely that eventually we will want to support
// multiplexing to multiple senders, each in its own goroutine (or worker).
// LogForwarder is a worker that forwards log records from a source
// to a sender.
type LogForwarder struct {
catacomb catacomb.Catacomb
args OpenLogForwarderArgs
enabledCh chan bool
mu sync.Mutex
enabled bool
}
// OpenLogForwarderArgs holds the info needed to open a LogForwarder.
type OpenLogForwarderArgs struct {
// ControllerUUID identifies the controller.
ControllerUUID string
// LogForwardConfig is the API used to access log forwarding config.
LogForwardConfig LogForwardConfig
// Caller is the API caller that will be used.
Caller base.APICaller
// Name is the name given to the log sink.
Name string
// OpenSink is the function that opens the underlying log sink that
// will be wrapped.
OpenSink LogSinkFn
// OpenLogStream is the function that will be used to for the
// log stream.
OpenLogStream LogStreamFn
Logger Logger
}
// processNewConfig acts on a new syslog forward config change.
func (lf *LogForwarder) processNewConfig(currentSender SendCloser) (SendCloser, error) {
lf.mu.Lock()
defer lf.mu.Unlock()
closeExisting := func() error {
lf.enabled = false
// If we are already sending, close the current sender.
if currentSender != nil {
return currentSender.Close()
}
return nil
}
// Get the new config and set up log forwarding if enabled.
cfg, ok, err := lf.args.LogForwardConfig.LogForwardConfig()
if err != nil {
_ = closeExisting()
return nil, errors.Trace(err)
}
if !ok || !cfg.Enabled {
lf.args.Logger.Infof("config change - log forwarding not enabled")
return nil, closeExisting()
}
// If the config is not valid, we don't want to exit with an error
// and bounce the worker; we'll just log the issue and wait for another
// config change to come through.
// We'll continue sending using the current sink.
if err := cfg.Validate(); err != nil {
lf.args.Logger.Errorf("invalid log forward config change: %v", err)
return currentSender, nil
}
// Shutdown the existing sink since we need to now create a new one.
if err := closeExisting(); err != nil {
return nil, errors.Trace(err)
}
sink, err := OpenTrackingSink(TrackingSinkArgs{
Name: lf.args.Name,
Config: cfg,
Caller: lf.args.Caller,
OpenSink: lf.args.OpenSink,
})
if err != nil {
return nil, errors.Trace(err)
}
lf.enabledCh <- true
return sink, nil
}
// waitForEnabled returns true if streaming is enabled.
// Otherwise if blocks and waits for enabled to be true.
func (lf *LogForwarder) waitForEnabled() (bool, error) {
lf.mu.Lock()
enabled := lf.enabled
lf.mu.Unlock()
if enabled {
return true, nil
}
select {
case <-lf.catacomb.Dying():
return false, tomb.ErrDying
case enabled = <-lf.enabledCh:
}
lf.mu.Lock()
defer lf.mu.Unlock()
if !lf.enabled && enabled {
lf.args.Logger.Infof("log forward enabled, starting to stream logs to syslog sink")
}
lf.enabled = enabled
return enabled, nil
}
// NewLogForwarder returns a worker that forwards logs received from
// the stream to the sender.
func NewLogForwarder(args OpenLogForwarderArgs) (*LogForwarder, error) {
lf := &LogForwarder{
args: args,
enabledCh: make(chan bool, 1),
}
err := catacomb.Invoke(catacomb.Plan{
Site: &lf.catacomb,
Work: func() error {
return errors.Trace(lf.loop())
},
})
if err != nil {
return nil, errors.Trace(err)
}
return lf, nil
}
func (lf *LogForwarder) loop() error {
configWatcher, err := lf.args.LogForwardConfig.WatchForLogForwardConfigChanges()
if err != nil {
return errors.Trace(err)
}
if err := lf.catacomb.Add(configWatcher); err != nil {
return errors.Trace(err)
}
records := make(chan []logfwd.Record)
var stream LogStream
go func() {
for {
enabled, err := lf.waitForEnabled()
if err == tomb.ErrDying {
return
}
if !enabled {
continue
}
// Lazily create log streamer if needed.
if stream == nil {
streamCfg := params.LogStreamConfig{
Sink: lf.args.Name,
// TODO(wallyworld) - this should be configurable via lf.args.LogForwardConfig
MaxLookbackRecords: 100,
}
stream, err = lf.args.OpenLogStream(lf.args.Caller, streamCfg, lf.args.ControllerUUID)
if err != nil {
lf.catacomb.Kill(errors.Annotate(err, "creating log stream"))
break
}
}
rec, err := stream.Next()
if err != nil {
lf.catacomb.Kill(errors.Annotate(err, "getting next log record"))
break
}
select {
case <-lf.catacomb.Dying():
return
case records <- rec: // Wait until the last one is sent.
}
}
}()
var sender SendCloser
defer func() {
if sender != nil {
sender.Close()
}
}()
for {
select {
case <-lf.catacomb.Dying():
return lf.catacomb.ErrDying()
case _, ok := <-configWatcher.Changes():
if !ok {
return errors.New("syslog configuration watcher closed")
}
if sender, err = lf.processNewConfig(sender); err != nil {
return errors.Trace(err)
}
case rec := <-records:
if sender == nil {
continue
}
if err := sender.Send(rec); err != nil {
return errors.Trace(err)
}
}
}
}
// Kill implements Worker.Kill()
func (lf *LogForwarder) Kill() {
lf.catacomb.Kill(nil)
}
// Wait implements Worker.Wait()
func (lf *LogForwarder) Wait() error {
return lf.catacomb.Wait()
}