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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.net;
import java.util.Map;
import org.apache.cassandra.exceptions.RequestFailureReason;
import org.apache.cassandra.locator.InetAddressAndPort;
/**
* implementors of {@link RequestCallback} need to make sure that any public methods
* are threadsafe with respect to {@link #onResponse} being called from the message
* service. In particular, if any shared state is referenced, making
* response alone synchronized will not suffice.
*/
public interface RequestCallback
{
/**
* @param msg response received.
*/
void onResponse(Message msg);
/**
* Called when there is an exception on the remote node or timeout happens
*/
default void onFailure(InetAddressAndPort from, RequestFailureReason failureReason)
{
}
/**
* Returns true if the callback handles failure reporting - in which case the remove host will be asked to
* report failures to us in the event of a problem processing the request.
*
* TODO: this is an error prone method, and we should be handling failures everywhere
* so we should probably just start doing that, and remove this method
*
* @return true if the callback should be invoked on failure
*/
default boolean invokeOnFailure()
{
return false;
}
/**
* @return true if this callback is on the read path and its latency should be
* given as input to the dynamic snitch.
*/
default boolean trackLatencyForSnitch()
{
return false;
}
static boolean isTimeout(Map failureReasonByEndpoint)
{
// The reason that all must be timeout to be called a timeout is as follows
// Assume RF=6, QUORUM, and failureReasonByEndpoint.size() == 3
// R1 -> TIMEOUT
// R2 -> TIMEOUT
// R3 -> READ_TOO_MANY_TOMBSTONES
// Since we got a reply back, and that was a failure, we should return a failure letting the user know.
// When all failures are a timeout, then this is a race condition with
// org.apache.cassandra.utils.concurrent.Awaitable.await(long, java.util.concurrent.TimeUnit)
// The race is that the message expire path runs and expires all messages, this then casues the condition
// to signal telling the caller "got all replies!".
return failureReasonByEndpoint.values().stream().allMatch(RequestFailureReason.TIMEOUT::equals);
}
}