hadoop RecordStore 源码
haddop RecordStore 代码
文件路径:/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/store/RecordStore.java
/**
* 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.hdfs.server.federation.store;
import java.lang.reflect.Constructor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.server.federation.store.driver.StateStoreDriver;
import org.apache.hadoop.hdfs.server.federation.store.records.BaseRecord;
/**
* Store records in the State Store. Subclasses provide interfaces to operate on
* those records.
*
* @param <R> Record to store by this interface.
*/
@InterfaceAudience.Private
@InterfaceStability.Evolving
public abstract class RecordStore<R extends BaseRecord> {
private static final Logger LOG = LoggerFactory.getLogger(RecordStore.class);
/** Class of the record stored in this State Store. */
private final Class<R> recordClass;
/** State store driver backed by persistent storage. */
private final StateStoreDriver driver;
/**
* Create a new store for records.
*
* @param clazz Class of the record to store.
* @param stateStoreDriver Driver for the State Store.
*/
protected RecordStore(Class<R> clazz, StateStoreDriver stateStoreDriver) {
this.recordClass = clazz;
this.driver = stateStoreDriver;
}
/**
* Report a required record to the data store. The data store uses this to
* create/maintain storage for the record.
*
* @return The class of the required record or null if no record is required
* for this interface.
*/
public Class<R> getRecordClass() {
return this.recordClass;
}
/**
* Get the State Store driver.
*
* @return State Store driver.
*/
protected StateStoreDriver getDriver() {
return this.driver;
}
/**
* Build a state store API implementation interface.
*
* @param clazz The specific interface implementation to create
* @param driver The {@link StateStoreDriver} implementation in use.
* @return An initialized instance of the specified state store API
* implementation.
*/
public static <T extends RecordStore<?>> T newInstance(
final Class<T> clazz, final StateStoreDriver driver) {
try {
Constructor<T> constructor = clazz.getConstructor(StateStoreDriver.class);
T recordStore = constructor.newInstance(driver);
return recordStore;
} catch (Exception e) {
LOG.error("Cannot create new instance for " + clazz, e);
return null;
}
}
}
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