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// Copyright 2015 The Bazel Authors. All rights reserved.
//
// 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 com.google.devtools.build.lib.worker;
import com.google.common.hash.HashCode;
import com.google.devtools.build.lib.vfs.Path;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ProcessBuilder.Redirect;
/**
* Interface to a worker process running as a child process.
*
* <p>A worker process must follow this protocol to be usable via this class: The worker process is
* spawned on demand. The worker process is free to exit whenever necessary, as new instances will
* be relaunched automatically. Communication happens via the WorkerProtocol protobuf, sent to and
* received from the worker process via stdin / stdout.
*
* <p>Other code in Blaze can talk to the worker process via input / output streams provided by this
* class.
*/
class Worker {
private final WorkerKey workerKey;
private final int workerId;
private final Path workDir;
private final Path logFile;
private Process process;
private Thread shutdownHook;
Worker(WorkerKey workerKey, int workerId, final Path workDir, Path logFile) {
this.workerKey = workerKey;
this.workerId = workerId;
this.workDir = workDir;
this.logFile = logFile;
final Worker self = this;
this.shutdownHook =
new Thread() {
@Override
public void run() {
try {
self.shutdownHook = null;
self.destroy();
} catch (IOException e) {
// We can't do anything here.
}
}
};
Runtime.getRuntime().addShutdownHook(shutdownHook);
}
void createProcess() throws IOException {
String[] command = workerKey.getArgs().toArray(new String[0]);
// Follows the logic of {@link com.google.devtools.build.lib.shell.Command}.
File executable = new File(command[0]);
if (!executable.isAbsolute() && executable.getParent() != null) {
command[0] = new File(workDir.getPathFile(), command[0]).getAbsolutePath();
}
ProcessBuilder processBuilder =
new ProcessBuilder(command)
.directory(workDir.getPathFile())
.redirectError(Redirect.appendTo(logFile.getPathFile()));
processBuilder.environment().clear();
processBuilder.environment().putAll(workerKey.getEnv());
this.process = processBuilder.start();
}
void destroy() throws IOException {
if (shutdownHook != null) {
Runtime.getRuntime().removeShutdownHook(shutdownHook);
}
if (process != null) {
destroyProcess(process);
}
}
/**
* Destroys a process and waits for it to exit. This is necessary for the child to not become a
* zombie.
*
* @param process the process to destroy.
*/
private static void destroyProcess(Process process) {
boolean wasInterrupted = false;
try {
process.destroy();
while (true) {
try {
process.waitFor();
return;
} catch (InterruptedException ie) {
wasInterrupted = true;
}
}
} finally {
// Read this for detailed explanation: http://www.ibm.com/developerworks/library/j-jtp05236/
if (wasInterrupted) {
Thread.currentThread().interrupt(); // preserve interrupted status
}
}
}
/**
* Returns a unique id for this worker. This is used to distinguish different worker processes in
* logs and messages.
*/
int getWorkerId() {
return this.workerId;
}
HashCode getWorkerFilesHash() {
return workerKey.getWorkerFilesHash();
}
boolean isAlive() {
// This is horrible, but Process.isAlive() is only available from Java 8 on and this is the
// best we can do prior to that.
try {
process.exitValue();
return false;
} catch (IllegalThreadStateException e) {
return true;
}
}
InputStream getInputStream() {
return process.getInputStream();
}
OutputStream getOutputStream() {
return process.getOutputStream();
}
public void prepareExecution(WorkerKey key) throws IOException {}
public void finishExecution(WorkerKey key) throws IOException {}
}
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