/**
* 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.hadoop.hbase.errorhandling;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hbase.protobuf.generated.ErrorHandlingProtos.ForeignExceptionMessage;
import org.apache.hadoop.hbase.protobuf.generated.ErrorHandlingProtos.GenericExceptionMessage;
import org.apache.hadoop.hbase.protobuf.generated.ErrorHandlingProtos.StackTraceElementMessage;
import com.google.protobuf.InvalidProtocolBufferException;
/**
* A ForeignException is an exception from another thread or process.
* <p>
* ForeignExceptions are sent to 'remote' peers to signal an abort in the face of failures.
* When serialized for transmission we encode using Protobufs to ensure version compatibility.
* <p>
* Foreign exceptions contain a Throwable as its cause. This can be a "regular" exception
* generated locally or a ProxyThrowable that is a representation of the original exception
* created on original 'remote' source. These ProxyThrowables have their their stacks traces and
* messages overridden to reflect the original 'remote' exception. The only way these
* ProxyThrowables are generated are by this class's {@link #deserialize(byte[])} method.
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
@SuppressWarnings("serial")
public class ForeignException extends IOException {
/**
* Name of the throwable's source such as a host or thread name. Must be non-null.
*/
private final String source;
/**
* Create a new ForeignException that can be serialized. It is assumed that this came form a
* local source.
* @param source
* @param cause
*/
public ForeignException(String source, Throwable cause) {
super(cause);
assert source != null;
assert cause != null;
this.source = source;
}
/**
* Create a new ForeignException that can be serialized. It is assumed that this is locally
* generated.
* @param source
* @param msg
*/
public ForeignException(String source, String msg) {
super(new IllegalArgumentException(msg));
this.source = source;
}
public String getSource() {
return source;
}
/**
* The cause of a ForeignException can be an exception that was generated on a local in process
* thread, or a thread from a 'remote' separate process.
*
* If the cause is a ProxyThrowable, we know it came from deserialization which usually means
* it came from not only another thread, but also from a remote thread.
*
* @return true if went through deserialization, false if locally generated
*/
public boolean isRemote() {
return getCause() instanceof ProxyThrowable;
}
@Override
public String toString() {
String className = getCause().getClass().getName() ;
return className + " via " + getSource() + ":" + getLocalizedMessage();
}
/**
* Convert a stack trace to list of {@link StackTraceElement}.
* @param trace the stack trace to convert to protobuf message
* @return <tt>null</tt> if the passed stack is <tt>null</tt>.
*/
private static List<StackTraceElementMessage> toStackTraceElementMessages(
StackTraceElement[] trace) {
// if there is no stack trace, ignore it and just return the message
if (trace == null) return null;
// build the stack trace for the message
List<StackTraceElementMessage> pbTrace =
new ArrayList<StackTraceElementMessage>(trace.length);
for (StackTraceElement elem : trace) {
StackTraceElementMessage.Builder stackBuilder = StackTraceElementMessage.newBuilder();
stackBuilder.setDeclaringClass(elem.getClassName());
stackBuilder.setFileName(elem.getFileName());
stackBuilder.setLineNumber(elem.getLineNumber());
stackBuilder.setMethodName(elem.getMethodName());
pbTrace.add(stackBuilder.build());
}
return pbTrace;
}
/**
* This is a Proxy Throwable that contains the information of the original remote exception
*/
private static class ProxyThrowable extends Throwable {
ProxyThrowable(String msg, StackTraceElement[] trace) {
super(msg);
this.setStackTrace(trace);
}
}
/**
* Converts a ForeignException to an array of bytes.
* @param source the name of the external exception source
* @param t the "local" external exception (local)
* @return protobuf serialized version of ForeignException
*/
public static byte[] serialize(String source, Throwable t) {
GenericExceptionMessage.Builder gemBuilder = GenericExceptionMessage.newBuilder();
gemBuilder.setClassName(t.getClass().getName());
if (t.getMessage() != null) {
gemBuilder.setMessage(t.getMessage());
}
// set the stack trace, if there is one
List<StackTraceElementMessage> stack =
ForeignException.toStackTraceElementMessages(t.getStackTrace());
if (stack != null) {
gemBuilder.addAllTrace(stack);
}
GenericExceptionMessage payload = gemBuilder.build();
ForeignExceptionMessage.Builder exception = ForeignExceptionMessage.newBuilder();
exception.setGenericException(payload).setSource(source);
ForeignExceptionMessage eem = exception.build();
return eem.toByteArray();
}
/**
* Takes a series of bytes and tries to generate an ForeignException instance for it.
* @param bytes
* @return the ForeignExcpetion instance
* @throws InvalidProtocolBufferException if there was deserialization problem this is thrown.
*/
public static ForeignException deserialize(byte[] bytes) throws InvalidProtocolBufferException {
// figure out the data we need to pass
ForeignExceptionMessage eem = ForeignExceptionMessage.parseFrom(bytes);
GenericExceptionMessage gem = eem.getGenericException();
StackTraceElement [] trace = ForeignException.toStackTrace(gem.getTraceList());
ProxyThrowable dfe = new ProxyThrowable(gem.getMessage(), trace);
ForeignException e = new ForeignException(eem.getSource(), dfe);
return e;
}
/**
* Unwind a serialized array of {@link StackTraceElementMessage}s to a
* {@link StackTraceElement}s.
* @param traceList list that was serialized
* @return the deserialized list or <tt>null</tt> if it couldn't be unwound (e.g. wasn't set on
* the sender).
*/
private static StackTraceElement[] toStackTrace(List<StackTraceElementMessage> traceList) {
if (traceList == null || traceList.size() == 0) {
return new StackTraceElement[0]; // empty array
}
StackTraceElement[] trace = new StackTraceElement[traceList.size()];
for (int i = 0; i < traceList.size(); i++) {
StackTraceElementMessage elem = traceList.get(i);
trace[i] = new StackTraceElement(
elem.getDeclaringClass(), elem.getMethodName(), elem.getFileName(), elem.getLineNumber());
}
return trace;
}
}