YARN-6228: EntityGroupFSTimelineStore should allow configurable cache

stores. Contributed by Li Lu

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java

@@ -1890,6 +1890,9 @@ public class YarnConfiguration extends Configuration {
   public static final String TIMELINE_SERVICE_ENTITYGROUP_FS_STORE_PREFIX =
       TIMELINE_SERVICE_PREFIX + "entity-group-fs-store.";
 
+  public static final String TIMELINE_SERVICE_ENTITYGROUP_FS_STORE_CACHE_STORE =
+      TIMELINE_SERVICE_ENTITYGROUP_FS_STORE_PREFIX + "cache-store-class";
+
   public static final String TIMELINE_SERVICE_ENTITYGROUP_FS_STORE_ACTIVE_DIR =
       TIMELINE_SERVICE_ENTITYGROUP_FS_STORE_PREFIX + "active-dir";
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/resources/yarn-default.xml

@@ -2096,6 +2096,11 @@
   </property>
 
   <!-- Timeline Service v1.5 Configuration -->
+  <property>
+    <name>yarn.timeline-service.entity-group-fs-store.cache-store-class</name>
+    <value>org.apache.hadoop.yarn.server.timeline.MemoryTimelineStore</value>
+    <description>Caching storage timeline server v1.5 is using. </description>
+  </property>
 
   <property>
     <name>yarn.timeline-service.entity-group-fs-store.active-dir</name>

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timeline-pluginstorage/src/main/java/org/apache/hadoop/yarn/server/timeline/EntityCacheItem.java

@@ -17,8 +17,10 @@
 package org.apache.hadoop.yarn.server.timeline;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.Time;
 import org.apache.hadoop.yarn.api.records.timeline.TimelineEntityGroupId;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.server.timeline.security.TimelineACLsManager;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -95,8 +97,11 @@ public class EntityCacheItem {
       }
       if (!appLogs.getDetailLogs().isEmpty()) {
         if (store == null) {
-          store = new LevelDBCacheTimelineStore(groupId.toString(),
-              "LeveldbCache." + groupId);
+          store = ReflectionUtils.newInstance(config.getClass(
+              YarnConfiguration
+                  .TIMELINE_SERVICE_ENTITYGROUP_FS_STORE_CACHE_STORE,
+              MemoryTimelineStore.class, TimelineStore.class),
+              config);
           store.init(config);
           store.start();
         } else {