Add Memoization class and supports

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/memoization/Memoization.java

@@ -0,0 +1,155 @@
+/*
+ * QQQ - Low-code Application Framework for Engineers.
+ * Copyright (C) 2021-2023.  Kingsrook, LLC
+ * 651 N Broad St Ste 205 # 6917 | Middletown DE 19709 | United States
+ * contact@kingsrook.com
+ * https://github.com/Kingsrook/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.kingsrook.qqq.backend.core.utils.memoization;
+
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Optional;
+import com.kingsrook.qqq.backend.core.logging.QLogger;
+
+
+/*******************************************************************************
+ ** Basic memoization functionality - with result timeouts (only when doing a get -
+ ** there's no cleanup thread), and max-size.
+ *******************************************************************************/
+public class Memoization<K, V>
+{
+   private static final QLogger LOG = QLogger.getLogger(Memoization.class);
+
+   private final Map<K, MemoizedResult<V>> map = Collections.synchronizedMap(new LinkedHashMap<>());
+
+   private Duration timeout = Duration.ofSeconds(600);
+   private Integer  maxSize = 1000;
+
+
+
+   /*******************************************************************************
+    ** Constructor
+    **
+    *******************************************************************************/
+   public Memoization()
+   {
+   }
+
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   public Optional<V> getResult(K key)
+   {
+      MemoizedResult<V> result = map.get(key);
+      if(result != null)
+      {
+         if(result.getTime().isAfter(Instant.now().minus(timeout)))
+         {
+            return (Optional.of(result.getResult()));
+         }
+      }
+
+      return (Optional.empty());
+   }
+
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   public void storeResult(K key, V value)
+   {
+      map.put(key, new MemoizedResult<>(value));
+
+      //////////////////////////////////////
+      // make sure map didn't get too big //
+      // do this thread safely, please    //
+      //////////////////////////////////////
+      try
+      {
+         if(map.size() > maxSize)
+         {
+            synchronized(map)
+            {
+               Iterator<Map.Entry<K, MemoizedResult<V>>> iterator = null;
+               while(map.size() > maxSize)
+               {
+                  if(iterator == null)
+                  {
+                     iterator = map.entrySet().iterator();
+                  }
+
+                  if(iterator.hasNext())
+                  {
+                     iterator.next();
+                     iterator.remove();
+                  }
+                  else
+                  {
+                     break;
+                  }
+               }
+            }
+         }
+      }
+      catch(Exception e)
+      {
+         LOG.error("Error managing size of a Memoization", e);
+      }
+   }
+
+
+
+   /*******************************************************************************
+    ** Setter for timeoutSeconds
+    **
+    *******************************************************************************/
+   public void setTimeout(Duration timeout)
+   {
+      this.timeout = timeout;
+   }
+
+
+
+   /*******************************************************************************
+    ** Setter for maxSize
+    **
+    *******************************************************************************/
+   public void setMaxSize(Integer maxSize)
+   {
+      this.maxSize = maxSize;
+   }
+
+
+
+   /*******************************************************************************
+    ** package-private - for tests to look at the map.
+    **
+    *******************************************************************************/
+   Map<K, MemoizedResult<V>> getMap()
+   {
+      return map;
+   }
+}

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/utils/memoization/MemoizedResult.java

@@ -0,0 +1,70 @@
+/*
+ * QQQ - Low-code Application Framework for Engineers.
+ * Copyright (C) 2021-2023.  Kingsrook, LLC
+ * 651 N Broad St Ste 205 # 6917 | Middletown DE 19709 | United States
+ * contact@kingsrook.com
+ * https://github.com/Kingsrook/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.kingsrook.qqq.backend.core.utils.memoization;
+
+
+import java.time.Instant;
+
+
+/*******************************************************************************
+ ** Object stored in the Memoization class.  Shouldn't need to be visible outside
+ ** its package.
+ *******************************************************************************/
+class MemoizedResult<T>
+{
+   private T       result;
+   private Instant time;
+
+
+
+   /*******************************************************************************
+    ** Constructor
+    **
+    *******************************************************************************/
+   public MemoizedResult(T result)
+   {
+      this.result = result;
+      this.time = Instant.now();
+   }
+
+
+
+   /*******************************************************************************
+    ** Getter for result
+    **
+    *******************************************************************************/
+   public T getResult()
+   {
+      return result;
+   }
+
+
+
+   /*******************************************************************************
+    ** Getter for time
+    **
+    *******************************************************************************/
+   public Instant getTime()
+   {
+      return time;
+   }
+}