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Merge pull request #101 from Marcono1234/process-handling
Move process output handling to separate class & add tests
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,160 @@ | ||
| /* | ||
| * This file is part of git-commit-id-plugin-core by Konrad 'ktoso' Malawski <[email protected]> | ||
| * | ||
| * git-commit-id-plugin-core is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU Lesser General Public License as published by | ||
| * the Free Software Foundation, either version 3 of the License, or | ||
| * (at your option) any later version. | ||
| * | ||
| * git-commit-id-plugin-core is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU Lesser General Public License | ||
| * along with git-commit-id-plugin-core. If not, see <http://www.gnu.org/licenses/>. | ||
| */ | ||
|
|
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| package pl.project13.core; | ||
|
|
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| import java.io.BufferedReader; | ||
| import java.io.InputStream; | ||
| import java.io.InputStreamReader; | ||
| import java.nio.charset.StandardCharsets; | ||
| import java.util.Objects; | ||
| import java.util.concurrent.Callable; | ||
| import java.util.concurrent.ExecutionException; | ||
| import java.util.concurrent.ExecutorService; | ||
| import java.util.concurrent.Executors; | ||
| import java.util.concurrent.Future; | ||
| import java.util.concurrent.ThreadFactory; | ||
| import java.util.concurrent.TimeUnit; | ||
| import java.util.concurrent.TimeoutException; | ||
| import java.util.function.Consumer; | ||
| import java.util.function.Supplier; | ||
|
|
||
| /** | ||
| * Handles waiting for a {@link Process} and reading its stdout and stderr output. | ||
| */ | ||
| class ProcessHandler implements AutoCloseable { | ||
| private final Process process; | ||
|
|
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| private final ExecutorService outputReaderExecutor; | ||
| private final Future<Void> stdoutFuture; | ||
| private final Future<String> stderrFuture; | ||
|
|
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| private String stderrOutput = null; | ||
|
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| /** | ||
| * @param process the process which should be handled | ||
| * @param stdoutLineConsumer called asynchronously with the lines read from stdout. The consumer | ||
| * must either be thread-safe, or the result it is building must only be used after | ||
| * {@link #exitValue(long, TimeUnit)} has returned without throwing an exception. The | ||
| * consumer must not block, otherwise this could prevent the process from writing any | ||
| * output, causing it to get stuck. | ||
| */ | ||
| public ProcessHandler(Process process, Consumer<String> stdoutLineConsumer) { | ||
| this.process = Objects.requireNonNull(process); | ||
| Objects.requireNonNull(stdoutLineConsumer); | ||
|
|
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| // 2 threads, one for stdout, one for stderr | ||
| // The process output is consumed concurrently by separate threads because otherwise the process | ||
| // could get stuck if the output is not consumed and the output buffer is full | ||
| ThreadFactory threadFactory = Executors.defaultThreadFactory(); | ||
| outputReaderExecutor = Executors.newFixedThreadPool(2, runnable -> { | ||
| Thread t = threadFactory.newThread(runnable); | ||
| // Don't prevent JVM exit | ||
| t.setDaemon(true); | ||
| return t; | ||
| }); | ||
|
|
||
| String processInfo; | ||
| try { | ||
| processInfo = this.process.info().command().orElse("?") + " [" + this.process.pid() + "]"; | ||
| } catch (UnsupportedOperationException e) { | ||
| processInfo = "<unknown-process>"; | ||
| } | ||
| stdoutFuture = | ||
| outputReaderExecutor.submit(new ProcessOutputReader<>("stdout reader (" + processInfo + ")", | ||
| this.process.getInputStream(), stdoutLineConsumer, | ||
| // Don't create a 'result', `stdoutLineConsumer` will do that itself if needed | ||
| () -> null)); | ||
|
|
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| StringBuilder stderrBuilder = new StringBuilder(); | ||
| stderrFuture = | ||
| outputReaderExecutor.submit(new ProcessOutputReader<>("stderr reader (" + processInfo + ")", | ||
| this.process.getErrorStream(), line -> stderrBuilder.append(line).append('\n'), | ||
| stderrBuilder::toString)); | ||
| } | ||
|
|
||
| /** | ||
| * Waits for the process to finish and returns the exit value. | ||
| * | ||
| * @throws TimeoutException if waiting for the process to finish times out | ||
| */ | ||
| public int exitValue(long timeout, TimeUnit timeUnit) throws InterruptedException, TimeoutException, ExecutionException { | ||
| boolean finished = process.waitFor(timeout, timeUnit); | ||
| if (finished) { | ||
|
|
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| outputReaderExecutor.shutdown(); | ||
| try { | ||
| stdoutFuture.get(); | ||
| } catch (ExecutionException e) { | ||
| throw new ExecutionException("Failed waiting for stdout", e.getCause()); | ||
| } | ||
| try { | ||
| stderrOutput = stderrFuture.get(); | ||
| } catch (ExecutionException e) { | ||
| throw new ExecutionException("Failed waiting for stderr", e.getCause()); | ||
| } | ||
| return process.exitValue(); | ||
| } | ||
| throw new TimeoutException(); | ||
| } | ||
|
|
||
| /** | ||
| * Gets the stderr output. Must only be called after {@link #exitValue(long, TimeUnit)} has | ||
| * returned successfully. | ||
| */ | ||
| public String getStderr() { | ||
| if (stderrOutput == null) { | ||
| throw new IllegalStateException("Process has not finished"); | ||
| } | ||
| return stderrOutput; | ||
| } | ||
|
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| @Override | ||
| public void close() { | ||
| // Perform clean-up; has no effect if process or executor have already been stopped | ||
| process.destroy(); | ||
| outputReaderExecutor.shutdownNow(); | ||
| } | ||
|
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| private static class ProcessOutputReader<T> implements Callable<T> { | ||
| private final String threadName; | ||
| private final InputStream is; | ||
| private final Consumer<String> lineConsumer; | ||
| private final Supplier<T> resultCreator; | ||
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| ProcessOutputReader(String threadName, InputStream is, Consumer<String> lineConsumer, Supplier<T> resultCreator) { | ||
| this.threadName = threadName; | ||
| this.is = is; | ||
| this.lineConsumer = lineConsumer; | ||
| this.resultCreator = resultCreator; | ||
| } | ||
|
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| @Override | ||
| public T call() throws Exception { | ||
| Thread.currentThread().setName(threadName); | ||
|
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| try (BufferedReader br = new BufferedReader(new InputStreamReader(is, StandardCharsets.UTF_8))) { | ||
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| String line; | ||
| while ((line = br.readLine()) != null) { | ||
| lineConsumer.accept(line); | ||
| } | ||
| } | ||
| return resultCreator.get(); | ||
| } | ||
| } | ||
| } |
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