| // Copyright (C) 2019 The Android Open Source Project |
| // |
| // 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.gerrit.server; |
| |
| import com.google.gerrit.extensions.annotations.ExtensionPoint; |
| import java.util.Optional; |
| |
| /** |
| * Allows implementors to control how certain exceptions should be handled. |
| * |
| * <p>This interface is intended to be implemented for multi-master setups to control the behavior |
| * for handling exceptions that are thrown by a lower layer that handles the consensus and |
| * synchronization between different server nodes. E.g. if an operation fails because consensus for |
| * a Git update could not be achieved (e.g. due to slow responding server nodes) this interface can |
| * be used to retry the request instead of failing it immediately. |
| */ |
| @ExtensionPoint |
| public interface ExceptionHook { |
| /** |
| * Whether an operation should be retried if it failed with the given throwable. |
| * |
| * <p>Only affects operations that are executed with {@link |
| * com.google.gerrit.server.update.RetryHelper}. |
| * |
| * <p>Should return {@code true} only for exceptions that are caused by temporary issues where a |
| * retry of the operation has a chance to succeed. |
| * |
| * <p>If {@code false} is returned the operation is still retried once to capture a trace, unless |
| * {@link #skipRetryWithTrace(Throwable)} skips the auto-retry. |
| * |
| * @param throwable throwable that was thrown while executing the operation |
| * @return whether the operation should be retried |
| */ |
| default boolean shouldRetry(Throwable throwable) { |
| return false; |
| } |
| |
| /** |
| * Whether auto-retrying of an operation with tracing should be skipped for the given throwable. |
| * |
| * <p>Only affects operations that are executed with {@link |
| * com.google.gerrit.server.update.RetryHelper}. |
| * |
| * <p>This method is only called for exceptions for which the operation should not be retried |
| * ({@link #shouldRetry(Throwable)} returned {@code false}). |
| * |
| * <p>By default this method returns {@code false}, so that by default traces for unexpected |
| * exceptions are captured, which allows to investigate them. |
| * |
| * <p>Implementors may use this method to skip retry with tracing for exceptions that occur due to |
| * known causes that are permanent and where a trace is not needed for the investigation. For |
| * example, if an operation fails because persisted data is corrupt, it makes no sense to retry |
| * the operation with a trace, because the trace will not help with fixing the corrupt data. |
| * |
| * <p>This method is only invoked if retry with tracing is enabled on the server ({@code |
| * retry.retryWithTraceOnFailure} in {@code gerrit.config} is set to {@code true}). |
| * |
| * @param throwable throwable that was thrown while executing the operation |
| * @return whether auto-retrying of an operation with tracing should be skipped for the given |
| * throwable |
| */ |
| default boolean skipRetryWithTrace(Throwable throwable) { |
| return false; |
| } |
| |
| /** |
| * Formats the cause of an exception for use in metrics. |
| * |
| * <p>This method allows implementors to group exceptions that have the same cause into one metric |
| * bucket. |
| * |
| * @param throwable the exception cause |
| * @return formatted cause or {@link Optional#empty()} if no formatting was done |
| */ |
| default Optional<String> formatCause(Throwable throwable) { |
| return Optional.empty(); |
| } |
| |
| /** |
| * Returns a message that should be returned to the user. |
| * |
| * <p>This message is included into the HTTP response that is sent to the user. |
| * |
| * @param throwable throwable that was thrown while executing an operation |
| * @return error message that should be returned to the user, {@link Optional#empty()} if no |
| * message should be returned to the user |
| */ |
| default Optional<String> getUserMessage(Throwable throwable) { |
| return Optional.empty(); |
| } |
| |
| /** |
| * Returns the HTTP status code that should be returned to the user. |
| * |
| * <p>If no value is returned ({@link Optional#empty()}) the HTTP status code defaults to {@code |
| * 500 Internal Server Error}. |
| * |
| * <p>{@link #getUserMessage(Throwable)} allows to define which message should be included into |
| * the body of the HTTP response. |
| * |
| * <p>Implementors may use this method to change the status code for certain exceptions (e.g. |
| * using this method it would be possible to return {@code 409 Conflict} for {@link |
| * com.google.gerrit.git.LockFailureException}s instead of {@code 500 Internal Server Error}). |
| * |
| * @param throwable throwable that was thrown while executing an operation |
| * @return HTTP status code that should be returned to the user, {@link Optional#empty()} if the |
| * exception should result in {@code 500 Internal Server Error} |
| */ |
| default Optional<Integer> getStatusCode(Throwable throwable) { |
| return Optional.empty(); |
| } |
| } |