mirror of https://github.com/gohugoio/hugo
74 lines
1.8 KiB
Go
74 lines
1.8 KiB
Go
// Copyright 2019 The Hugo Authors. All rights reserved.
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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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// 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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// Package para implements parallel execution helpers.
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package para
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import (
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"context"
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"golang.org/x/sync/errgroup"
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)
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// Workers configures a task executor with the most number of tasks to be executed in parallel.
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type Workers struct {
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sem chan struct{}
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}
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// Runner wraps the lifecycle methods of a new task set.
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//
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// Run will block until a worker is available or the context is cancelled,
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// and then run the given func in a new goroutine.
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// Wait will wait for all the running goroutines to finish.
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type Runner interface {
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Run(func() error)
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Wait() error
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}
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type errGroupRunner struct {
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*errgroup.Group
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w *Workers
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ctx context.Context
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}
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func (g *errGroupRunner) Run(fn func() error) {
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select {
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case g.w.sem <- struct{}{}:
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case <-g.ctx.Done():
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return
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}
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g.Go(func() error {
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err := fn()
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<-g.w.sem
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return err
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})
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}
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// New creates a new Workers with the given number of workers.
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func New(numWorkers int) *Workers {
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return &Workers{
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sem: make(chan struct{}, numWorkers),
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}
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}
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// Start starts a new Runner.
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func (w *Workers) Start(ctx context.Context) (Runner, context.Context) {
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g, ctx := errgroup.WithContext(ctx)
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return &errGroupRunner{
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Group: g,
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ctx: ctx,
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w: w,
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}, ctx
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}
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