[GitHub] [incubator-pinot] jihaozh commented on a change in pull request #4842: [TE] add detection health for the alerts list

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

jihaozh commented on a change in pull request #4842: [TE] add detection health for the alerts list
URL: https://github.com/apache/incubator-pinot/pull/4842#discussion_r349300642
 
 

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 File path: thirdeye/thirdeye-pinot/src/main/java/org/apache/pinot/thirdeye/datasource/cache/metadata/MetaDataCollectionCache.java
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+/*
+ *  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.pinot.thirdeye.datasource.cache.metadata;
+
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * The cache for a meta-data collection.
+ * This cache will hold a collection of meta-data and periodically reloads it using the cache loader.
+ *
+ * It's designed to cache the original or derived meta-data collection for ThirdEye Dashboard server, for example, a
+ * list of all applications, subscription groups, and detection configs. Loading a collection of metadata has been
+ * a pain point for ThirdEye. It requires data base to scan the index table and then do a look up for each config in the
+ * generic json table, which is slow. This cache makes such loading asynchronous and returns user the cached result
+ * when opening page.
+ *
+ * @param <T> the type of the value to be cached.
+ */
+public class MetaDataCollectionCache<T> {
+  private static final String META_DATA_KEY = "metaData";
+  protected static final Logger LOG = LoggerFactory.getLogger(MetaDataCollectionCache.class);
+  private final LoadingCache<String, T> loadingCache;
+
+  /**
+   * Create a Metadata collection cache
+   * @param cacheLoader the cache loader for the meta data collection
+   * @param reloadPeriod the period of the reloading frequency
+   * @param reloadUnit the unit for the reload period
+   */
+  public MetaDataCollectionCache(MetadataCacheLoader<T> cacheLoader, int reloadPeriod, TimeUnit reloadUnit) {
+    this.loadingCache = CacheBuilder.newBuilder()
+        .expireAfterWrite(10, TimeUnit.MINUTES)
 
 Review comment:
   Good point. Yes, it should. It will trigger a cache refresh whenever the user changes the config.

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