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/*
* Copyright 2015 Google Inc. 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.cloud;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.Callable;
/**
* Exception handling used by {@link RetryHelper}.
*/
public final class ExceptionHandler implements Serializable {
private static final long serialVersionUID = -2460707015779532919L;
private static final ExceptionHandler DEFAULT_INSTANCE =
builder().retryOn(Exception.class).abortOn(RuntimeException.class).build();
private final ImmutableList interceptors;
private final ImmutableSet> retriableExceptions;
private final ImmutableSet> nonRetriableExceptions;
private final Set retryInfo = Sets.newHashSet();
public interface Interceptor extends Serializable {
enum RetryResult {
NO_RETRY, RETRY, CONTINUE_EVALUATION;
}
/**
* This method is called before exception evaluation and could short-circuit the process.
*
* @param exception the exception that is being evaluated
* @return {@link RetryResult} to indicate if the exception should be ignored (
* {@link RetryResult#RETRY}), propagated ({@link RetryResult#NO_RETRY}), or evaluation
* should proceed ({@link RetryResult#CONTINUE_EVALUATION}).
*/
RetryResult beforeEval(Exception exception);
/**
* This method is called after the evaluation and could alter its result.
*
* @param exception the exception that is being evaluated
* @param retryResult the result of the evaluation so far
* @return {@link RetryResult} to indicate if the exception should be ignored (
* {@link RetryResult#RETRY}), propagated ({@link RetryResult#NO_RETRY}), or evaluation
* should proceed ({@link RetryResult#CONTINUE_EVALUATION}).
*/
RetryResult afterEval(Exception exception, RetryResult retryResult);
}
/**
* ExceptionHandler builder.
*/
public static class Builder {
private final ImmutableList.Builder interceptors = ImmutableList.builder();
private final ImmutableSet.Builder> retriableExceptions =
ImmutableSet.builder();
private final ImmutableSet.Builder> nonRetriableExceptions =
ImmutableSet.builder();
private Builder() {}
/**
* Adds the exception handler interceptors. Call order will be maintained.
*
* @param interceptors the interceptors for this exception handler
* @return the Builder for chaining
*/
public Builder interceptor(Interceptor... interceptors) {
for (Interceptor interceptor : interceptors) {
this.interceptors.add(interceptor);
}
return this;
}
/**
* Add the exceptions to ignore/retry-on.
*
* @param exceptions retry should continue when such exceptions are thrown
* @return the Builder for chaining
*/
@SafeVarargs
public final Builder retryOn(Class... exceptions) {
for (Class exception : exceptions) {
retriableExceptions.add(checkNotNull(exception));
}
return this;
}
/**
* Adds the exceptions to abort on.
*
* @param exceptions retry should abort when such exceptions are thrown
* @return the Builder for chaining
*/
@SafeVarargs
public final Builder abortOn(Class... exceptions) {
for (Class exception : exceptions) {
nonRetriableExceptions.add(checkNotNull(exception));
}
return this;
}
/**
* Returns a new ExceptionHandler instance.
*/
public ExceptionHandler build() {
return new ExceptionHandler(this);
}
}
@VisibleForTesting
static final class RetryInfo implements Serializable {
private static final long serialVersionUID = -4264634837841455974L;
private final Class exception;
private final Interceptor.RetryResult retry;
private final Set children = Sets.newHashSet();
RetryInfo(Class exception, Interceptor.RetryResult retry) {
this.exception = checkNotNull(exception);
this.retry = checkNotNull(retry);
}
@Override
public int hashCode() {
return exception.hashCode();
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof RetryInfo)) {
return false;
}
// We only care about exception in equality as we allow only one instance per exception
return ((RetryInfo) obj).exception.equals(exception);
}
}
private ExceptionHandler(Builder builder) {
interceptors = builder.interceptors.build();
retriableExceptions = builder.retriableExceptions.build();
nonRetriableExceptions = builder.nonRetriableExceptions.build();
Preconditions.checkArgument(
Sets.intersection(retriableExceptions, nonRetriableExceptions).isEmpty(),
"Same exception was found in both retryable and non-retryable sets");
for (Class exception : retriableExceptions) {
addRetryInfo(new RetryInfo(exception, Interceptor.RetryResult.RETRY), retryInfo);
}
for (Class exception : nonRetriableExceptions) {
addRetryInfo(new RetryInfo(exception, Interceptor.RetryResult.NO_RETRY), retryInfo);
}
}
private static void addRetryInfo(RetryInfo retryInfo, Set dest) {
for (RetryInfo current : dest) {
if (current.exception.isAssignableFrom(retryInfo.exception)) {
addRetryInfo(retryInfo, current.children);
return;
}
if (retryInfo.exception.isAssignableFrom(current.exception)) {
retryInfo.children.add(current);
}
}
dest.removeAll(retryInfo.children);
dest.add(retryInfo);
}
private static RetryInfo findMostSpecificRetryInfo(Set retryInfo,
Class exception) {
for (RetryInfo current : retryInfo) {
if (current.exception.isAssignableFrom(exception)) {
RetryInfo match = findMostSpecificRetryInfo(current.children, exception);
return match == null ? current : match;
}
}
return null;
}
// called for Class, therefore a "call" method must be found.
private static Method getCallableMethod(Class clazz) {
try {
return clazz.getDeclaredMethod("call");
} catch (NoSuchMethodException e) {
// check parent
return getCallableMethod(clazz.getSuperclass());
} catch (SecurityException e) {
// This should never happen
throw new IllegalStateException("Unexpected exception", e);
}
}
void verifyCaller(Callable callable) {
Method callMethod = getCallableMethod(callable.getClass());
for (Class exceptionOrError : callMethod.getExceptionTypes()) {
Preconditions.checkArgument(Exception.class.isAssignableFrom(exceptionOrError),
"Callable method exceptions must be derived from Exception");
@SuppressWarnings("unchecked")
Class exception = (Class) exceptionOrError;
Preconditions.checkArgument(findMostSpecificRetryInfo(retryInfo, exception) != null,
"Declared exception '" + exception + "' is not covered by exception handler");
}
}
public Set> retriableExceptions() {
return retriableExceptions;
}
public Set> nonRetriableExceptions() {
return nonRetriableExceptions;
}
boolean shouldRetry(Exception ex) {
for (Interceptor interceptor : interceptors) {
Interceptor.RetryResult retryResult = checkNotNull(interceptor.beforeEval(ex));
if (retryResult != Interceptor.RetryResult.CONTINUE_EVALUATION) {
return retryResult == Interceptor.RetryResult.RETRY;
}
}
RetryInfo retryInfo = findMostSpecificRetryInfo(this.retryInfo, ex.getClass());
Interceptor.RetryResult retryResult =
retryInfo == null ? Interceptor.RetryResult.NO_RETRY : retryInfo.retry;
for (Interceptor interceptor : interceptors) {
Interceptor.RetryResult interceptorRetry =
checkNotNull(interceptor.afterEval(ex, retryResult));
if (interceptorRetry != Interceptor.RetryResult.CONTINUE_EVALUATION) {
retryResult = interceptorRetry;
}
}
return retryResult == Interceptor.RetryResult.RETRY;
}
@Override
public int hashCode() {
return Objects.hash(interceptors, retriableExceptions, nonRetriableExceptions, retryInfo);
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof ExceptionHandler)) {
return false;
}
ExceptionHandler other = (ExceptionHandler) obj;
return Objects.equals(interceptors, other.interceptors)
&& Objects.equals(retriableExceptions, other.retriableExceptions)
&& Objects.equals(nonRetriableExceptions, other.nonRetriableExceptions)
&& Objects.equals(retryInfo, other.retryInfo);
}
/**
* Returns an instance which retry any checked exception and abort on any runtime exception.
*/
public static ExceptionHandler defaultInstance() {
return DEFAULT_INSTANCE;
}
public static Builder builder() {
return new Builder();
}
}
