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Apache Jena Fuseki server Kafka connector
/*
* 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 org.apache.kafka.common.utils;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.atomic.AtomicBoolean;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A base class for running a Unix command.
*
* Shell can be used to run unix commands like du or
* df.
*/
abstract public class Shell {
private static final Logger LOG = LoggerFactory.getLogger(Shell.class);
/** Return an array containing the command name and its parameters */
protected abstract String[] execString();
/** Parse the execution result */
protected abstract void parseExecResult(BufferedReader lines) throws IOException;
private final long timeout;
private int exitCode;
private Process process; // sub process used to execute the command
/* If or not script finished executing */
private volatile AtomicBoolean completed;
/**
* @param timeout Specifies the time in milliseconds, after which the command will be killed. -1 means no timeout.
*/
public Shell(long timeout) {
this.timeout = timeout;
}
/** get the exit code
* @return the exit code of the process
*/
public int exitCode() {
return exitCode;
}
/** get the current sub-process executing the given command
* @return process executing the command
*/
public Process process() {
return process;
}
protected void run() throws IOException {
exitCode = 0; // reset for next run
runCommand();
}
/** Run a command */
private void runCommand() throws IOException {
ProcessBuilder builder = new ProcessBuilder(execString());
Timer timeoutTimer = null;
completed = new AtomicBoolean(false);
process = builder.start();
if (timeout > -1) {
timeoutTimer = new Timer();
//One time scheduling.
timeoutTimer.schedule(new ShellTimeoutTimerTask(this), timeout);
}
final BufferedReader errReader = new BufferedReader(
new InputStreamReader(process.getErrorStream(), StandardCharsets.UTF_8));
BufferedReader inReader = new BufferedReader(
new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_8));
final StringBuffer errMsg = new StringBuffer();
// read error and input streams as this would free up the buffers
// free the error stream buffer
Thread errThread = KafkaThread.nonDaemon("kafka-shell-thread", () -> {
try {
String line = errReader.readLine();
while ((line != null) && !Thread.currentThread().isInterrupted()) {
errMsg.append(line);
errMsg.append(System.lineSeparator());
line = errReader.readLine();
}
} catch (IOException ioe) {
LOG.warn("Error reading the error stream", ioe);
}
});
errThread.start();
try {
parseExecResult(inReader); // parse the output
// wait for the process to finish and check the exit code
exitCode = process.waitFor();
try {
// make sure that the error thread exits
errThread.join();
} catch (InterruptedException ie) {
LOG.warn("Interrupted while reading the error stream", ie);
}
completed.set(true);
//the timeout thread handling
//taken care in finally block
if (exitCode != 0) {
throw new ExitCodeException(exitCode, errMsg.toString());
}
} catch (InterruptedException ie) {
throw new IOException(ie.toString());
} finally {
if (timeoutTimer != null)
timeoutTimer.cancel();
// close the input stream
try {
inReader.close();
} catch (IOException ioe) {
LOG.warn("Error while closing the input stream", ioe);
}
if (!completed.get())
errThread.interrupt();
try {
errReader.close();
} catch (IOException ioe) {
LOG.warn("Error while closing the error stream", ioe);
}
process.destroy();
}
}
/**
* This is an IOException with exit code added.
*/
public static class ExitCodeException extends IOException {
int exitCode;
public ExitCodeException(int exitCode, String message) {
super(message);
this.exitCode = exitCode;
}
public int getExitCode() {
return exitCode;
}
}
/**
* A simple shell command executor.
*
* ShellCommandExecutorshould be used in cases where the output
* of the command needs no explicit parsing and where the command, working
* directory and the environment remains unchanged. The output of the command
* is stored as-is and is expected to be small.
*/
public static class ShellCommandExecutor extends Shell {
private final String[] command;
private StringBuffer output;
/**
* Create a new instance of the ShellCommandExecutor to execute a command.
*
* @param execString The command to execute with arguments
* @param timeout Specifies the time in milliseconds, after which the
* command will be killed. -1 means no timeout.
*/
public ShellCommandExecutor(String[] execString, long timeout) {
super(timeout);
command = execString.clone();
}
/** Execute the shell command. */
public void execute() throws IOException {
this.run();
}
protected String[] execString() {
return command;
}
protected void parseExecResult(BufferedReader reader) throws IOException {
output = new StringBuffer();
char[] buf = new char[512];
int nRead;
while ((nRead = reader.read(buf, 0, buf.length)) > 0) {
output.append(buf, 0, nRead);
}
}
/** Get the output of the shell command.*/
public String output() {
return (output == null) ? "" : output.toString();
}
/**
* Returns the commands of this instance.
* Arguments with spaces in are presented with quotes round; other
* arguments are presented raw
*
* @return a string representation of the object.
*/
public String toString() {
StringBuilder builder = new StringBuilder();
String[] args = execString();
for (String s : args) {
if (s.indexOf(' ') >= 0) {
builder.append('"').append(s).append('"');
} else {
builder.append(s);
}
builder.append(' ');
}
return builder.toString();
}
}
/**
* Static method to execute a shell command.
* Covers most of the simple cases without requiring the user to implement
* the Shell interface.
* @param cmd shell command to execute.
* @return the output of the executed command.
*/
public static String execCommand(String... cmd) throws IOException {
return execCommand(cmd, -1);
}
/**
* Static method to execute a shell command.
* Covers most of the simple cases without requiring the user to implement
* the Shell interface.
* @param cmd shell command to execute.
* @param timeout time in milliseconds after which script should be killed. -1 means no timeout.
* @return the output of the executed command.
*/
public static String execCommand(String[] cmd, long timeout) throws IOException {
ShellCommandExecutor exec = new ShellCommandExecutor(cmd, timeout);
exec.execute();
return exec.output();
}
/**
* Timer which is used to timeout scripts spawned off by shell.
*/
private static class ShellTimeoutTimerTask extends TimerTask {
private final Shell shell;
public ShellTimeoutTimerTask(Shell shell) {
this.shell = shell;
}
@Override
public void run() {
Process p = shell.process();
try {
p.exitValue();
} catch (Exception e) {
//Process has not terminated.
//So check if it has completed
//if not just destroy it.
if (p != null && !shell.completed.get()) {
p.destroy();
}
}
}
}
}