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Server functionality for HBase
/*
* 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.regionserver;
import java.io.IOException;
import java.util.Collection;
import java.util.List;
import java.util.UUID;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.hbase.client.Durability;
import org.apache.hadoop.hbase.client.Mutation;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
import com.google.protobuf.Message;
/**
* Defines the procedure to atomically perform multiple scans and mutations
* on a HRegion.
*
* This is invoked by HRegion#processRowsWithLocks().
* This class performs scans and generates mutations and WAL edits.
* The locks and MVCC will be handled by HRegion.
*
* The RowProcessor user code could have data that needs to be
* sent across for proper initialization at the server side. The generic type
* parameter S is the type of the request data sent to the server.
* The generic type parameter T is the return type of RowProcessor.getResult().
*/
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
@InterfaceStability.Evolving
public interface RowProcessor {
/**
* Rows to lock while operation.
* They have to be sorted with RowProcessor
* to avoid deadlock.
*/
Collection getRowsToLock();
/**
* Obtain the processing result. All row processor implementations must
* implement this, even if the method is simply returning an empty
* Message.
*/
T getResult();
/**
* Is this operation read only? If this is true, process() should not add
* any mutations or it throws IOException.
* @return ture if read only operation
*/
boolean readOnly();
/**
* HRegion handles the locks and MVCC and invokes this method properly.
*
* You should override this to create your own RowProcessor.
*
* If you are doing read-modify-write here, you should consider using
* IsolationLevel.READ_UNCOMMITTED for scan because
* we advance MVCC after releasing the locks for optimization purpose.
*
* @param now the current system millisecond
* @param region the HRegion
* @param mutations the output mutations to apply to memstore
* @param walEdit the output WAL edits to apply to write ahead log
*/
void process(long now,
HRegion region,
List mutations,
WALEdit walEdit) throws IOException;
/**
* The hook to be executed before process().
*
* @param region the HRegion
* @param walEdit the output WAL edits to apply to write ahead log
*/
void preProcess(HRegion region, WALEdit walEdit) throws IOException;
/**
* The hook to be executed after the process() but before applying the Mutations to region. Also
* by the time this hook is been called, mvcc transaction is started.
* @param region
* @param walEdit the output WAL edits to apply to write ahead log
* @throws IOException
*/
void preBatchMutate(HRegion region, WALEdit walEdit) throws IOException;
/**
* The hook to be executed after the process() and applying the Mutations to region. The
* difference of this one with {@link #postProcess(HRegion, WALEdit, boolean)} is this hook will
* be executed before the mvcc transaction completion.
* @param region
* @throws IOException
*/
void postBatchMutate(HRegion region) throws IOException;
/**
* The hook to be executed after process() and applying the Mutations to region.
*
* @param region the HRegion
* @param walEdit the output WAL edits to apply to write ahead log
* @param success true if batch operation is successful otherwise false.
*/
void postProcess(HRegion region, WALEdit walEdit, boolean success) throws IOException;
/**
* @return The cluster ids that have the change.
*/
List getClusterIds();
/**
* Human readable name of the processor
* @return The name of the processor
*/
String getName();
/**
* This method should return any additional data that is needed on the
* server side to construct the RowProcessor. The server will pass this to
* the {@link #initialize(Message msg)} method. If there is no RowProcessor
* specific data then null should be returned.
* @return the PB message
* @throws IOException
*/
S getRequestData() throws IOException;
/**
* This method should initialize any field(s) of the RowProcessor with
* a parsing of the passed message bytes (used on the server side).
* @param msg
* @throws IOException
*/
void initialize(S msg) throws IOException;
/**
* @return The {@link Durability} to use
*/
Durability useDurability();
}