/*
* 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.geode.cache.execute;
import java.util.concurrent.TimeUnit;
import org.apache.geode.distributed.DistributedMember;
/**
* <p>
* Defines the interface for a container that gathers results from function execution.<br>
* GemFire provides a default implementation for ResultCollector. Applications can choose to
* implement their own custom ResultCollector. A custom ResultCollector facilitates result sorting
* or aggregation. Aggregation functions like sum, minimum, maximum and average can also be applied
* to the result using a custom ResultCollector. Results arrive as they are sent using the
* {@link ResultSender#sendResult(Object)} and can be used as they arrive. To indicate that all
* results have been received {@link #endResults()} is called.
*
* </p>
* Example: <br>
*
* <pre>
* Region region ;
* Set keySet = Collections.singleton("myKey");
* Function multiGetFunction ;
* Object args ;
* ResultCollector rc = FunctionService.onRegion(region)
* .withArgs(args)
* .withFilter(keySet)
* .withCollector(new MyCustomResultCollector())
* .execute(multiGetFunction.getId());
* Application can do something else here before retrieving the result
* Or it can have some logic in {{@link #addResult(DistributedMember, Object)} to use the partial results.
* If it wants to see all the results it can use
* Object functionResult = rc.getResult();
* or
* Object functionResult = rc.getResult(timeout,TimeUnit);
* depending on if it wants to wait for all the results or wait for a timeout period.
* </pre>
*
* GemFire provides default implementation of ResultCollector which collects results in Arraylist.
* There is no need to provide a synchronization mechanism in the user implementations of
* ResultCollector
*
* @since GemFire 6.0
*
*/
public interface ResultCollector<T, S> {
/**
* Method used to pull results from the ResultCollector. It returns the result of function
* execution, potentially blocking until {@link #endResults() all the results are available} has
* been called.
*
* @return the result
* @throws FunctionException if result retrieval fails
* @since GemFire 6.0
*/
public S getResult() throws FunctionException;
/**
* Method used to pull results from the ResultCollector. It returns the result of function
* execution, blocking for the timeout period until {@link #endResults() all the results are
* available}. If all the results are not received in provided time a FunctionException is thrown.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return the result
* @throws FunctionException if result retrieval fails within timeout provided
* @throws InterruptedException if the current thread was interrupted while waiting
* @since GemFire 6.0
*
*/
public S getResult(long timeout, TimeUnit unit) throws FunctionException, InterruptedException;
/**
* Method used to feed result to the ResultCollector. It adds a single function execution result
* to the ResultCollector It is invoked every time a result is sent using ResultSender.
*
* @param resultOfSingleExecution
* @since GemFire 6.0
* @param memberID DistributedMember ID to which result belongs
*/
public void addResult(DistributedMember memberID, T resultOfSingleExecution);
/**
* GemFire will invoke this method when function execution has completed and all results for the
* execution have been obtained and {@link #addResult(DistributedMember, Object) added to the
* ResultCollector} Unless the {@link ResultCollector} has received
* {@link ResultSender#lastResult(Object) last result} from all the executing nodes, it keeps
* waiting for more results to come.
*
* @since GemFire 6.0
*
* @see ResultSender#lastResult(Object)
*/
public void endResults();
/**
* GemFire will invoke this method before re-executing function (in case of Function Execution
* HA). This is to clear the previous execution results from the result collector
*
* @since GemFire 6.5
*/
public void clearResults();
}