164 lines
3.7 KiB
Go
164 lines
3.7 KiB
Go
package notifications
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import (
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"container/list"
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"fmt"
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"sync"
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events "github.com/docker/go-events"
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"github.com/sirupsen/logrus"
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)
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// eventQueue accepts all messages into a queue for asynchronous consumption
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// by a sink. It is unbounded and thread safe but the sink must be reliable or
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// events will be dropped.
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type eventQueue struct {
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sink events.Sink
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events *list.List
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listeners []eventQueueListener
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cond *sync.Cond
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mu sync.Mutex
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closed bool
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}
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// eventQueueListener is called when various events happen on the queue.
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type eventQueueListener interface {
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ingress(event events.Event)
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egress(event events.Event)
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}
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// newEventQueue returns a queue to the provided sink. If the updater is non-
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// nil, it will be called to update pending metrics on ingress and egress.
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func newEventQueue(sink events.Sink, listeners ...eventQueueListener) *eventQueue {
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eq := eventQueue{
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sink: sink,
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events: list.New(),
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listeners: listeners,
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}
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eq.cond = sync.NewCond(&eq.mu)
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go eq.run()
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return &eq
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}
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// Write accepts the events into the queue, only failing if the queue has
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// beend closed.
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func (eq *eventQueue) Write(event events.Event) error {
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eq.mu.Lock()
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defer eq.mu.Unlock()
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if eq.closed {
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return ErrSinkClosed
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}
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for _, listener := range eq.listeners {
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listener.ingress(event)
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}
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eq.events.PushBack(event)
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eq.cond.Signal() // signal waiters
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return nil
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}
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// Close shuts down the event queue, flushing
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func (eq *eventQueue) Close() error {
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eq.mu.Lock()
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defer eq.mu.Unlock()
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if eq.closed {
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return fmt.Errorf("eventqueue: already closed")
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}
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// set closed flag
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eq.closed = true
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eq.cond.Signal() // signal flushes queue
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eq.cond.Wait() // wait for signal from last flush
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return eq.sink.Close()
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}
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// run is the main goroutine to flush events to the target sink.
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func (eq *eventQueue) run() {
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for {
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event := eq.next()
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if event == nil {
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return // nil block means event queue is closed.
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}
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if err := eq.sink.Write(event); err != nil {
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logrus.Warnf("eventqueue: error writing events to %v, these events will be lost: %v", eq.sink, err)
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}
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for _, listener := range eq.listeners {
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listener.egress(event)
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}
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}
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}
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// next encompasses the critical section of the run loop. When the queue is
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// empty, it will block on the condition. If new data arrives, it will wake
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// and return a block. When closed, a nil slice will be returned.
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func (eq *eventQueue) next() events.Event {
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eq.mu.Lock()
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defer eq.mu.Unlock()
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for eq.events.Len() < 1 {
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if eq.closed {
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eq.cond.Broadcast()
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return nil
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}
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eq.cond.Wait()
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}
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front := eq.events.Front()
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block := front.Value.(events.Event)
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eq.events.Remove(front)
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return block
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}
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// ignoredSink discards events with ignored target media types and actions.
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// passes the rest along.
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type ignoredSink struct {
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events.Sink
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ignoreMediaTypes map[string]bool
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ignoreActions map[string]bool
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}
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func newIgnoredSink(sink events.Sink, ignored []string, ignoreActions []string) events.Sink {
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if len(ignored) == 0 {
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return sink
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}
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ignoredMap := make(map[string]bool)
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for _, mediaType := range ignored {
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ignoredMap[mediaType] = true
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}
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ignoredActionsMap := make(map[string]bool)
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for _, action := range ignoreActions {
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ignoredActionsMap[action] = true
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}
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return &ignoredSink{
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Sink: sink,
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ignoreMediaTypes: ignoredMap,
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ignoreActions: ignoredActionsMap,
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}
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}
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// Write discards events with ignored target media types and passes the rest
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// along.
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func (imts *ignoredSink) Write(event events.Event) error {
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if imts.ignoreMediaTypes[event.(Event).Target.MediaType] || imts.ignoreActions[event.(Event).Action] {
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return nil
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}
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return imts.Sink.Write(event)
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}
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func (imts *ignoredSink) Close() error {
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return nil
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}
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