Refactoring the persistence layer to be able to persist any Java Object

src/main/java/com/amazon/opendistro/elasticsearch/performanceanalyzer/rca/persistence/Persistable.java

@@ -20,11 +20,15 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.gson.JsonElement;
 import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
 import java.sql.SQLException;
 import java.util.List;
 import java.util.Map;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.jooq.Record;
 import org.jooq.Result;
+import org.jooq.exception.DataAccessException;
 
 public interface Persistable {
   /**
@@ -48,6 +52,21 @@ public interface Persistable {
    */
   JsonElement read(String rca);
 
+  /**
+   * This API reads the latest row from the table corresponding to the Object.
+   * @param clz The Class whose Object is desired.
+   * @param <T> The generic type of the class
+   * @return An instantiated Object of the class with the fields populated with the data from the latest row in the table and other
+   *     referenced tables or null if the table does not exist yet.
+   * @throws NoSuchMethodException If the expected setter does not exist.
+   * @throws IllegalAccessException If the setter is not Public
+   * @throws InvocationTargetException If invoking the setter by reflection threw an exception.
+   * @throws InstantiationException Creating an Object of the class failed for some reason.
+   * @throws DataAccessException Thrown by the DB layer.
+   */
+  <T> @Nullable T read(Class<T> clz)
+      throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException, DataAccessException;
+
   /**
    * Write data to the database.
    *
@@ -56,6 +75,36 @@ public interface Persistable {
    */
   <T extends ResourceFlowUnit> void write(Node<?> node, T flowUnit) throws SQLException, IOException;
 
+  /**
+   * This API helps us write any Java Object into the Database and it does not need to be a Graph node anymore.
+   * This is required because:
+   * - in future we would like to persist 'remediation Actions' and they are not necessarily
+   *    FlowUnits or Graph nodes.
+   * - This removes de-coupling of the persistence layer from the RCA runtime.
+   * Restrictions on the Object
+   * --------------------------
+   * The Object that can be persisted has certain restrictions:
+   * - The Fields of the class that are to be persisted should be annotated with '@ValueColumn' or '@RefColumn'.
+   *    A Field should be annotated as @ValueColumn if the field type is a Java primitive type or String type.
+   *    The accepted types are boolean, byte, char, short, int, long, float, and double and their Boxed counterparts.
+   *    A Column can be marked as @RefColumn if the class Field is an user defined Java Class or a collection of the same.
+   * - The annotated Fields should have a 'getter' and a 'setter'. getters are expected to be named as 'get' or 'is'
+   *     prepended to the _capitalized_ fieldName. And the setters are expected to be named 'set' and the capitalized
+   *     field name. The type of the field should match the type of the getter's return type or the setter's argument
+   *     type. Remember, int and Integer are two different types. Therefore, if the field is of type 'int' and your
+   *     'getter' returns a value of type Integer, you will still get NoSuchMethodException.
+   * - The annotated fields and the getter/setters should be declared in the Object and not in a Super class of it.
+   * @param object The Object that needs to be persisted.
+   * @param <T> The type of the Object.
+   * @throws SQLException This is thrown if the underlying DB throws an error.
+   * @throws IOException This is thrown in case the DB file rotation fails.
+   * @throws IllegalAccessException If the getters and setters of the fields to be persisted are not Public.
+   * @throws NoSuchMethodException If getter or setters don't exist with the expected naming convention.
+   * @throws InvocationTargetException Invoking the getter or setter throws an exception.
+   */
+  <T> void write(@NonNull T object) throws SQLException, IOException, IllegalAccessException, NoSuchMethodException,
+      InvocationTargetException;
+
   void close() throws SQLException;
 
   /**

src/main/java/com/amazon/opendistro/elasticsearch/performanceanalyzer/rca/persistence/PersistorBase.java

@@ -23,6 +23,7 @@
 import com.google.gson.JsonElement;
 import java.io.File;
 import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.sql.Connection;
@@ -34,6 +35,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import org.apache.logging.log4j.LogManager;
@@ -188,6 +190,30 @@ public synchronized <T extends ResourceFlowUnit> void write(Node<?> node, T flow
     }
   }
 
+  public synchronized <T> void write(T obj)
+      throws SQLException, IOException, IllegalAccessException, NoSuchMethodException, InvocationTargetException {
+    Objects.requireNonNull(obj);
+    rotateRegisterGarbageThenCreateNewDB(RotationType.TRY_ROTATE);
+    try {
+      writeImpl(obj);
+    } catch (IllegalStateException | IllegalArgumentException | IllegalAccessException | InvocationTargetException | NoSuchMethodException
+        illegalEx) {
+      throw illegalEx;
+    } catch (SQLException e) {
+      LOG.info("RCA: Fail to write.", e);
+      rotateRegisterGarbageThenCreateNewDB(RotationType.FORCE_ROTATE);
+      try {
+        writeImpl(obj);
+      } catch (SQLException ex) {
+        LOG.error("Failed to write multiple times. Giving up.");
+        // We rethrow this exception so that framework can take appropriate action.
+        throw e;
+      }
+    }
+  }
+
+  abstract <T> void writeImpl(T obj) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException, SQLException;
+
   private synchronized void rotateRegisterGarbageThenCreateNewDB(RotationType type) throws IOException, SQLException {
     Path rotatedFile = null;
     long currTime = System.currentTimeMillis();

src/main/java/com/amazon/opendistro/elasticsearch/performanceanalyzer/rca/persistence/RefColumn.java

@@ -0,0 +1,11 @@
+package com.amazon.opendistro.elasticsearch.performanceanalyzer.rca.persistence;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.FIELD)
+public @interface RefColumn {
+}