2018-05-22 21:43:36 +02:00
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// Copyright 2016-2018, Pulumi Corporation.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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2018-04-20 03:59:14 +02:00
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package cancel
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import (
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"context"
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"github.com/pulumi/pulumi/pkg/util/contract"
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)
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// Context provides the ability to observe cancellation and termination requests from a Source. A termination request
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// automatically triggers a corresponding cancellation request. This can be used to implement cancellation with two
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// priority levels.
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type Context struct {
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terminate context.Context
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cancel context.Context
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}
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// Source provides the ability to deliver cancellation and termination requests to a Context. A termination request
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// automatically triggers a corresponding cancellation request. This can be used to implement cancellation with two
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// priority levels.
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type Source struct {
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context *Context
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terminate context.CancelFunc
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cancel context.CancelFunc
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}
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// NewContext creates a new cancellation context and source parented to the given context. The returned cancellation
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// context will be terminated when the supplied root context is canceled.
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func NewContext(ctx context.Context) (*Context, *Source) {
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contract.Require(ctx != nil, "ctx")
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// Set up two new cancellable contexts: one for termination and one for cancellation. The cancellation context is a
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// child context of the termination context and will therefore be automatically cancelled when termination is
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// requested. Both are children of the supplied context--cancelling the supplied context will cause termination.
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terminationContext, terminate := context.WithCancel(ctx)
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cancellationContext, cancel := context.WithCancel(terminationContext)
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c := &Context{
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terminate: terminationContext,
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cancel: cancellationContext,
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}
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s := &Source{
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context: c,
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terminate: terminate,
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cancel: cancel,
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}
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return c, s
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}
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// Canceled returns a channel that will be closed when the context is canceled or terminated.
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func (c *Context) Canceled() <-chan struct{} {
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return c.cancel.Done()
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}
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// CancelErr returns a non-nil error iff the context has been canceled or terminated.
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func (c *Context) CancelErr() error {
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return c.cancel.Err()
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}
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// Terminated returns a channel that will be closed when the context is terminated.
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func (c *Context) Terminated() <-chan struct{} {
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return c.terminate.Done()
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}
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// TerminateErr returns a non-nil error iff the context has been terminated.
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func (c *Context) TerminateErr() error {
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return c.terminate.Err()
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}
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// Context returns the Context to which this source will deliver cancellation and termination requests.
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func (s *Source) Context() *Context {
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return s.context
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}
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// Cancel cancels this source's context.
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func (s *Source) Cancel() {
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s.cancel()
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}
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// Terminate terminates this source's context (which also cancels this context).
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func (s *Source) Terminate() {
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s.terminate()
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}
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