huaxiangsun commented on a change in pull request #2570: URL: https://github.com/apache/hbase/pull/2570#discussion_r510412184
########## File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/MetaReplicaLoadBalanceReplicaSimpleChooser.java ########## @@ -0,0 +1,248 @@ +/** + * 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.client; + +import org.apache.commons.lang3.builder.ToStringBuilder; +import org.apache.hadoop.hbase.HRegionLocation; +import org.apache.hadoop.hbase.ScheduledChore; +import org.apache.hadoop.hbase.Stoppable; +import org.apache.hadoop.hbase.TableName; +import org.apache.hadoop.hbase.util.Bytes; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import java.util.Iterator; +import java.util.Map; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.ConcurrentNavigableMap; +import java.util.concurrent.ConcurrentSkipListMap; +import java.util.concurrent.ThreadLocalRandom; +import static org.apache.hadoop.hbase.HConstants.DEFAULT_META_REPLICA_NUM; +import static org.apache.hadoop.hbase.HConstants.META_REPLICAS_NUM; +import static org.apache.hadoop.hbase.client.ConnectionUtils.isEmptyStopRow; +import static org.apache.hadoop.hbase.util.Bytes.BYTES_COMPARATOR; +import static org.apache.hadoop.hbase.util.ConcurrentMapUtils.computeIfAbsent; + +/** + * MetaReplicaLoadBalanceReplicaSimpleChooser implements a simple meta replica load balancing + * algorithm. It maintains a stale location cache for each table. Whenever client looks up meta, + * it first check if the row is the stale location cache, if yes, this means the the location from + * meta replica is stale, it will go to the primary meta to look up update-to-date location; + * otherwise, it will randomly pick up a meta replica region for meta lookup. When clients receive + * RegionNotServedException from region servers, it will add these region locations to the stale + * location cache. The stale cache will be cleaned up periodically by a chore. + */ + +/** + * StaleLocationCacheEntry is the entry when a stale location is reported by an client. + */ +class StaleLocationCacheEntry { Review comment: Got it, will make it an inner class. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
