mirror of https://github.com/docker/cli.git
120 lines
3.1 KiB
Go
120 lines
3.1 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package watch
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import (
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"io"
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"sync"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/util/net"
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utilruntime "k8s.io/apimachinery/pkg/util/runtime"
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"k8s.io/klog"
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)
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// Decoder allows StreamWatcher to watch any stream for which a Decoder can be written.
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type Decoder interface {
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// Decode should return the type of event, the decoded object, or an error.
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// An error will cause StreamWatcher to call Close(). Decode should block until
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// it has data or an error occurs.
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Decode() (action EventType, object runtime.Object, err error)
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// Close should close the underlying io.Reader, signalling to the source of
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// the stream that it is no longer being watched. Close() must cause any
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// outstanding call to Decode() to return with an error of some sort.
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Close()
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}
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// StreamWatcher turns any stream for which you can write a Decoder interface
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// into a watch.Interface.
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type StreamWatcher struct {
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sync.Mutex
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source Decoder
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result chan Event
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stopped bool
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}
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// NewStreamWatcher creates a StreamWatcher from the given decoder.
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func NewStreamWatcher(d Decoder) *StreamWatcher {
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sw := &StreamWatcher{
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source: d,
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// It's easy for a consumer to add buffering via an extra
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// goroutine/channel, but impossible for them to remove it,
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// so nonbuffered is better.
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result: make(chan Event),
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}
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go sw.receive()
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return sw
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}
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// ResultChan implements Interface.
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func (sw *StreamWatcher) ResultChan() <-chan Event {
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return sw.result
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}
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// Stop implements Interface.
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func (sw *StreamWatcher) Stop() {
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// Call Close() exactly once by locking and setting a flag.
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sw.Lock()
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defer sw.Unlock()
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if !sw.stopped {
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sw.stopped = true
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sw.source.Close()
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}
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}
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// stopping returns true if Stop() was called previously.
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func (sw *StreamWatcher) stopping() bool {
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sw.Lock()
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defer sw.Unlock()
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return sw.stopped
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}
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// receive reads result from the decoder in a loop and sends down the result channel.
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func (sw *StreamWatcher) receive() {
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defer close(sw.result)
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defer sw.Stop()
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defer utilruntime.HandleCrash()
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for {
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action, obj, err := sw.source.Decode()
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if err != nil {
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// Ignore expected error.
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if sw.stopping() {
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return
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}
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switch err {
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case io.EOF:
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// watch closed normally
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case io.ErrUnexpectedEOF:
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klog.V(1).Infof("Unexpected EOF during watch stream event decoding: %v", err)
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default:
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msg := "Unable to decode an event from the watch stream: %v"
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if net.IsProbableEOF(err) {
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klog.V(5).Infof(msg, err)
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} else {
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klog.Errorf(msg, err)
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}
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}
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return
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}
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sw.result <- Event{
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Type: action,
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Object: obj,
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}
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}
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}
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