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本文主要研究一下ElasticsearchUncaughtExceptionHandler
ElasticsearchUncaughtExceptionHandler
class ElasticsearchUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
private static final Logger logger = LogManager.getLogger(ElasticsearchUncaughtExceptionHandler.class);
@Override
public void uncaughtException(Thread t, Throwable e) {
if (isFatalUncaught(e)) {
try {
onFatalUncaught(t.getName(), e);
} finally {
// we use specific error codes in case the above notification failed, at least we
// will have some indication of the error bringing us down
if (e instanceof InternalError) {
halt(128);
} else if (e instanceof OutOfMemoryError) {
halt(127);
} else if (e instanceof StackOverflowError) {
halt(126);
} else if (e instanceof UnknownError) {
halt(125);
} else if (e instanceof IOError) {
halt(124);
} else {
halt(1);
}
}
} else {
onNonFatalUncaught(t.getName(), e);
}
}
static boolean isFatalUncaught(Throwable e) {
return e instanceof Error;
}
void onFatalUncaught(final String threadName, final Throwable t) {
logger.error(() -> new ParameterizedMessage("fatal error in thread [{}], exiting", threadName), t);
}
void onNonFatalUncaught(final String threadName, final Throwable t) {
logger.warn(() -> new ParameterizedMessage("uncaught exception in thread [{}]", threadName), t);
}
void halt(int status) {
AccessController.doPrivileged(new PrivilegedHaltAction(status));
}
static class PrivilegedHaltAction implements PrivilegedAction<Void> {
private final int status;
private PrivilegedHaltAction(final int status) {
this.status = status;
}
@SuppressForbidden(reason = "halt")
@Override
public Void run() {
// we halt to prevent shutdown hooks from running
Runtime.getRuntime().halt(status);
return null;
}
}
}
复制代码- ElasticsearchUncaughtExceptionHandler实现了Thread.UncaughtExceptionHandler接口
- uncaughtException方法首先判断throwable是否是Error类型，是的话则执行onFatalUncaught(
logger.error)，然后执行halt方法，不是则执行onNonFatalUncaught(logger.warn) - halt方法AccessController.doPrivileged来执行对应status的PrivilegedHaltAction，该action执行的是Runtime.getRuntime().halt(status)
Bootstrap.init
elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java
final class Bootstrap {
private static volatile Bootstrap INSTANCE;
private volatile Node node;
private final CountDownLatch keepAliveLatch = new CountDownLatch(1);
private final Thread keepAliveThread;
private final Spawner spawner = new Spawner();
//......
static void init(
final boolean foreground,
final Path pidFile,
final boolean quiet,
final Environment initialEnv) throws BootstrapException, NodeValidationException, UserException {
// force the class initializer for BootstrapInfo to run before
// the security manager is installed
BootstrapInfo.init();
INSTANCE = new Bootstrap();
final SecureSettings keystore = loadSecureSettings(initialEnv);
final Environment environment = createEnvironment(pidFile, keystore, initialEnv.settings(), initialEnv.configFile());
LogConfigurator.setNodeName(Node.NODE_NAME_SETTING.get(environment.settings()));
try {
LogConfigurator.configure(environment);
} catch (IOException e) {
throw new BootstrapException(e);
}
if (environment.pidFile() != null) {
try {
PidFile.create(environment.pidFile(), true);
} catch (IOException e) {
throw new BootstrapException(e);
}
}
final boolean closeStandardStreams = (foreground == false) || quiet;
try {
if (closeStandardStreams) {
final Logger rootLogger = LogManager.getRootLogger();
final Appender maybeConsoleAppender = Loggers.findAppender(rootLogger, ConsoleAppender.class);
if (maybeConsoleAppender != null) {
Loggers.removeAppender(rootLogger, maybeConsoleAppender);
}
closeSystOut();
}
// fail if somebody replaced the lucene jars
checkLucene();
// install the default uncaught exception handler; must be done before security is
// initialized as we do not want to grant the runtime permission
// setDefaultUncaughtExceptionHandler
Thread.setDefaultUncaughtExceptionHandler(new ElasticsearchUncaughtExceptionHandler());
INSTANCE.setup(true, environment);
try {
// any secure settings must be read during node construction
IOUtils.close(keystore);
} catch (IOException e) {
throw new BootstrapException(e);
}
INSTANCE.start();
if (closeStandardStreams) {
closeSysError();
}
} catch (NodeValidationException | RuntimeException e) {
// disable console logging, so user does not see the exception twice (jvm will show it already)
final Logger rootLogger = LogManager.getRootLogger();
final Appender maybeConsoleAppender = Loggers.findAppender(rootLogger, ConsoleAppender.class);
if (foreground && maybeConsoleAppender != null) {
Loggers.removeAppender(rootLogger, maybeConsoleAppender);
}
Logger logger = LogManager.getLogger(Bootstrap.class);
// HACK, it sucks to do this, but we will run users out of disk space otherwise
if (e instanceof CreationException) {
// guice: log the shortened exc to the log
file
ByteArrayOutputStream os = new ByteArrayOutputStream();
PrintStream ps = null;
try {
ps = new PrintStream(os, false, "UTF-8");
} catch (UnsupportedEncodingException uee) {
assert false;
e.addSuppressed(uee);
}
new StartupException(e).printStackTrace(ps);
ps.flush();
try {
logger.error("Guice Exception: {}", os.toString("UTF-8"));
} catch (UnsupportedEncodingException uee) {
assert false;
e.addSuppressed(uee);
}
} else if (e instanceof NodeValidationException) {
logger.error("node validation exception\n{}", e.getMessage());
} else {
// full exception
logger.error("Exception", e);
}
// re-enable it if appropriate, so they can see any logging during the shutdown process
if (foreground && maybeConsoleAppender != null) {
Loggers.addAppender(rootLogger, maybeConsoleAppender);
}
throw e;
}
}
//......
}
复制代码- Bootstrap的init静态方法使用Thread.setDefaultUncaughtExceptionHandler(new ElasticsearchUncaughtExceptionHandler())来给线程设置defaultUncaughtExceptionHandler
小结
- ElasticsearchUncaughtExceptionHandler实现了Thread.UncaughtExceptionHandler接口；uncaughtException方法首先判断throwable是否是Error类型，是的话则执行onFatalUncaught(
logger.error)，然后执行halt方法，不是则执行onNonFatalUncaught(logger.warn) - halt方法AccessController.doPrivileged来执行对应status的PrivilegedHaltAction，该action执行的是Runtime.getRuntime().halt(status)
- Bootstrap的init静态方法使用Thread.setDefaultUncaughtExceptionHandler(new ElasticsearchUncaughtExceptionHandler())来给线程设置defaultUncaughtExceptionHandler
