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thread.go
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thread.go
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// Copyright 2020 Buf Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package thread
import (
"runtime"
"sync"
"go.uber.org/multierr"
)
var (
globalParallelism = runtime.NumCPU()
globalLock sync.RWMutex
)
// Parallelism returns the current parellism.
//
// This defaults to the number of CPUs.
func Parallelism() int {
globalLock.RLock()
parallelism := globalParallelism
globalLock.RUnlock()
return parallelism
}
// SetParallelism sets the parallelism.
//
// If parallelism < 1, this sets the parallelism to 1.
func SetParallelism(parallelism int) {
if parallelism < 1 {
parallelism = 1
}
globalLock.Lock()
globalParallelism = parallelism
globalLock.Unlock()
}
// Parallelize runs the jobs in parallel.
//
// A max of Parallelism jobs will be run at once.
// Returns the combined error from the jobs.
func Parallelize(jobs ...func() error) error {
if len(jobs) == 1 {
return jobs[0]()
}
semaphoreC := make(chan struct{}, Parallelism())
var retErr error
var wg sync.WaitGroup
var lock sync.Mutex
for _, job := range jobs {
job := job
wg.Add(1)
semaphoreC <- struct{}{}
go func() {
if err := job(); err != nil {
lock.Lock()
retErr = multierr.Append(retErr, err)
lock.Unlock()
}
<-semaphoreC
wg.Done()
}()
}
wg.Wait()
return retErr
}