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process.go
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process.go
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// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You 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 command
import (
"context"
"errors"
"os/exec"
)
import (
"go.uber.org/multierr"
)
var errWaitAlreadyCalled = errors.New("wait already called on process")
type process struct {
cmd *exec.Cmd
done func()
waitC chan error
}
// newProcess wraps an *exec.Cmd and monitors it for exiting.
// When the process exits, done will be called.
//
// This implements the Process interface.
//
// The process is expected to have been started by the caller.
func newProcess(cmd *exec.Cmd, done func()) *process {
return &process{
cmd: cmd,
done: done,
waitC: make(chan error, 1),
}
}
// Monitor starts monitoring of the *exec.Cmd.
func (p *process) Monitor() {
go func() {
p.waitC <- p.cmd.Wait()
close(p.waitC)
p.done()
}()
}
// Wait waits for the process to exit.
func (p *process) Wait(ctx context.Context) error {
select {
case err, ok := <-p.waitC:
// Process exited
if ok {
return err
}
return errWaitAlreadyCalled
case <-ctx.Done():
// Timed out. Send a kill signal and release our handle to it.
return multierr.Combine(ctx.Err(), p.cmd.Process.Kill())
}
}