[GitHub] [hbase] virajjasani commented on a change in pull request #2261: HBASE-24528 : BalancerDecision queue implementation in HMaster with Admin API

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virajjasani commented on a change in pull request #2261:
URL: https://github.com/apache/hbase/pull/2261#discussion_r471677530



##########
File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/BalancerDecisionRecords.java
##########
@@ -0,0 +1,147 @@
+/*
+ *
+ * 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.util.GsonUtil;
+import org.apache.hbase.thirdparty.com.google.gson.Gson;
+import org.apache.hbase.thirdparty.com.google.gson.JsonSerializer;
+import org.apache.yetus.audience.InterfaceAudience;
+import java.util.List;
+
+/**
+ * History of balancer decisions taken for region movements.
+ */
+@InterfaceAudience.Private
+final public class BalancerDecisionRecords {
+
+  private final String initialFunctionCosts;
+  private final String finalFunctionCosts;
+  private final double initTotalCost;
+  private final double computedTotalCost;
+  private final long computedSteps;
+  private final List<String> regionPlans;
+
+  // used to convert object to pretty printed format
+  // used by toJsonPrettyPrint()
+  private static final Gson GSON = GsonUtil.createGson()
+    .setPrettyPrinting()
+    .registerTypeAdapter(OnlineLogRecord.class, (JsonSerializer<OnlineLogRecord>)
+      (slowLogPayload, type, jsonSerializationContext) -> {

Review comment:
       Can't believe this miss! This Gson serialization function was a copy paste :|

##########
File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/BalancerDecisionRecords.java
##########
@@ -0,0 +1,147 @@
+/*
+ *
+ * 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.util.GsonUtil;
+import org.apache.hbase.thirdparty.com.google.gson.Gson;
+import org.apache.hbase.thirdparty.com.google.gson.JsonSerializer;
+import org.apache.yetus.audience.InterfaceAudience;
+import java.util.List;
+
+/**
+ * History of balancer decisions taken for region movements.
+ */
+@InterfaceAudience.Private
+final public class BalancerDecisionRecords {

Review comment:
       Sure

##########
File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/AdminOverAsyncAdmin.java
##########
@@ -1057,4 +1057,9 @@ public void updateRSGroupConfig(String groupName, Map<String, String> configurat
       throws IOException {
     get(admin.updateRSGroupConfig(groupName, configuration));
   }
+
+  @Override
+  public List<BalancerDecisionRecords> getBalancerDecisions() throws IOException {

Review comment:
       Definitely, adding new APIs not desirable, however the reason why I had to choose this way: 
   
   1. slowLog released in 2.3 already.
   2. slowLog is in each RS and the API has flexibility to choose serverName to get records from (filter by serverName) whereas balancer is HMaster queue meaning activeMasterStub is to be identified by client, hence no need of serverName filter.
   3. client has to identify whom to make a call - HMaster or RegionServer (or limited no of RS) based on use-case, not a big deal but maybe too much logic for client interface?
   4. genericAPI might need to include abstract request and response classes, and respective use-cases to ensure if filter is required at server side (not a big deal)
   
   For 1), I believe trunk and 2.4.0 both can have generic API end-point.
   2) and 3) seem bit of headache for single API.




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