[GitHub] [hive] szlta commented on a change in pull request #2106: HIVE-24729: Implement strategy for llap cache hydration

[GitBox <gi...@apache.org>]

szlta commented on a change in pull request #2106:
URL: https://github.com/apache/hive/pull/2106#discussion_r603131868



##########
File path: common/src/java/org/apache/hadoop/hive/conf/HiveConf.java
##########
@@ -4648,6 +4648,12 @@ private static void populateLlapDaemonVarsSet(Set<String> llapDaemonVarsSetLocal
     LLAP_LRFU_BP_WRAPPER_SIZE("hive.llap.io.lrfu.bp.wrapper.size", 64, "thread local queue "
         + "used to amortize the lock contention, the idea hear is to try locking as soon we reach max size / 2 "
         + "and block when max queue size reached"),
+    LLAP_CACHE_REPL_STRATEGY_CLASS("hive.llap.cache.repl.strategy.class", "", "Strategy class for managing the "

Review comment:
       Isn't this feature rather about the more general 'hydration' than replication?

##########
File path: llap-server/src/java/org/apache/hadoop/hive/llap/cache/BasicLlapCacheReplication.java
##########
@@ -0,0 +1,125 @@
+/*
+ * 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.hive.llap.cache;
+
+import com.google.common.annotations.VisibleForTesting;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hive.conf.HiveConf;
+import org.apache.hadoop.hive.llap.daemon.rpc.LlapDaemonProtocolProtos;
+import org.apache.hadoop.hive.llap.io.api.LlapIo;
+import org.apache.hadoop.hive.llap.io.api.LlapProxy;
+import org.apache.hadoop.hive.registry.RegistryUtilities;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import static org.apache.hadoop.hive.conf.HiveConf.ConfVars;
+
+/**
+ * Simple cache replication strategy which saves the content info of the cache to a file on the local filesystem on
+ * shutdown, and loads it when the daemon starts.
+ */
+public class BasicLlapCacheReplication implements LlapCacheReplication {

Review comment:
       Same question of naming like above in HiveConf

##########
File path: llap-server/src/java/org/apache/hadoop/hive/llap/cache/LlapCacheReplication.java
##########
@@ -0,0 +1,79 @@
+/*
+ * 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.hive.llap.cache;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.hadoop.conf.Configurable;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hive.conf.HiveConf;
+import org.apache.hadoop.hive.conf.HiveConf.ConfVars;
+import org.apache.hive.common.util.ReflectionUtil;
+import org.apache.hive.common.util.ShutdownHookManager;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Interface to manage the cache content info, so that it can be saved on shutdown and loaded on startup.
+ */
+public interface LlapCacheReplication extends Configurable {
+
+  Logger LOG = LoggerFactory.getLogger(LlapCacheReplication.class);
+
+  /**
+   * Save the state of the cache. Will be attached to the shutdown hook.

Review comment:
       Perhaps we could make it configurable: certain strategies will want to have save() invoked in a shutdown hook, other maybe don't. This could be easily achieved by adding a new method in this API that strategies could implement, such as:
   default boolean shouldSaveDuringShutdown() { return false/true;}




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