[WIP] Add interfaces for refactoring work

wrapper/src/main/java/software/amazon/jdbc/util/ItemDisposalFunc.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util;
+
+/**
+ * An optional function defining extra cleanup steps to take when a cache item is cleaned up.
+ *
+ * @param <V> the type of object being disposed
+ */
+public interface ItemDisposalFunc<V> {
+  void dispose(V item);
+}

wrapper/src/main/java/software/amazon/jdbc/util/ShouldDisposeFunc.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util;
+
+/**
+ * An optional function defining the conditions under which an expired entry should be cleaned up
+ * at cleanup time.
+ *
+ * @param <V> the type of object being analyzed for disposal
+ */
+public interface ShouldDisposeFunc<V> {
+  boolean shouldDispose(V item);
+}

wrapper/src/main/java/software/amazon/jdbc/util/SlidingExpirationCache.java

@@ -214,25 +214,6 @@ public void setCleanupIntervalNanos(long cleanupIntervalNanos) {
     this.cleanupTimeNanos.set(System.nanoTime() + cleanupIntervalNanos);
   }
 
-  /**
-   * An optional function defining the conditions under which an expired entry should be cleaned up
-   * at cleanup time.
-   *
-   * @param <V> the type of object being analyzed for disposal
-   */
-  public interface ShouldDisposeFunc<V> {
-    boolean shouldDispose(V item);
-  }
-
-  /**
-   * An optional function defining extra cleanup steps to take when a cache item is cleaned up.
-   *
-   * @param <V> the type of object being disposed
-   */
-  public interface ItemDisposalFunc<V> {
-    void dispose(V item);
-  }
-
   // For testing purposes only
   Map<K, CacheItem> getCache() {
     return cache;

wrapper/src/main/java/software/amazon/jdbc/util/events/Event.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.events;
+
+// A marker interface for events that need to be communicated between different components.
+public interface Event {
+}

wrapper/src/main/java/software/amazon/jdbc/util/events/EventPublisher.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.events;
+
+import java.util.Set;
+
+public interface EventPublisher {
+  /**
+   * Register the given subscriber for the given event classes.
+   *
+   * @param subscriber   the subscriber to be notified when the given event classes occur.
+   * @param eventClasses the classes of event that the subscriber should be notified of.
+   */
+  void subscribe(EventSubscriber subscriber, Set<Class<? extends Event>> eventClasses);
+
+  /**
+   * Unsubscribe the subscriber from the given event classes.
+   *
+   * @param subscriber   the subscriber to unsubscribe from the given event classes.
+   * @param eventClasses the classes of events that the subscriber wants to unsubscribe from.
+   */
+  void unsubscribe(EventSubscriber subscriber, Set<Class<? extends Event>> eventClasses);
+
+  /**
+   * Publish an event. All subscribers to the given event class will be notified of the event.
+   *
+   * @param event the event to publish.
+   */
+  void publish(Event event);
+}

wrapper/src/main/java/software/amazon/jdbc/util/events/EventSubscriber.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.events;
+
+public interface EventSubscriber {
+  /**
+   * Process an event. This method will only be called on this subscriber if it has subscribed to the event class via
+   * {@link EventPublisher#subscribe}.
+   *
+   * @param event the event to process.
+   */
+  void processEvent(Event event);
+}

wrapper/src/main/java/software/amazon/jdbc/util/events/WriterChangedExampleEvent.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.events;
+
+public class WriterChangedExampleEvent implements Event {
+  final String newWriterUrl;
+  final String oldWriterUrl;
+
+  public WriterChangedExampleEvent(String newWriterUrl, String oldWriterUrl) {
+    this.newWriterUrl = newWriterUrl;
+    this.oldWriterUrl = oldWriterUrl;
+  }
+
+  public String getNewWriterUrl() {
+    return newWriterUrl;
+  }
+
+  public String getOldWriterUrl() {
+    return oldWriterUrl;
+  }
+}

wrapper/src/main/java/software/amazon/jdbc/util/monitoring/Monitor.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.monitoring;
+
+public interface Monitor {
+  void start();
+
+  void stop();
+
+  MonitorStatus getStatus();
+}

wrapper/src/main/java/software/amazon/jdbc/util/monitoring/MonitorErrorResponse.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.monitoring;
+
+public enum MonitorErrorResponse {
+  NO_ACTION,
+  RESTART
+}

wrapper/src/main/java/software/amazon/jdbc/util/monitoring/MonitorService.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.monitoring;
+
+import java.util.Set;
+import java.util.function.Supplier;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import software.amazon.jdbc.util.ShouldDisposeFunc;
+
+public interface MonitorService {
+  /**
+   * Register a new monitor type with the monitor service. This method needs to be called before adding new types of
+   * monitors to the monitor service, so that the monitor service knows when a running monitor should be stopped.
+   * Expected monitor types ("topology" and "customEndpoint") will be added automatically during driver initialization,
+   * but this method can be called by users if they want to add a new monitor type.
+   *
+   * @param monitorType       a String representing the monitor type, eg "customEndpoint".
+   * @param errorResponses    a Set defining actions to take if the monitor is in an error state.
+   * @param expirationTimeNs  how long a monitor should be stored before expiring, in nanoseconds. If the monitor is
+   *                          expired and shouldDisposeFunc returns `true`, the monitor will be stopped.
+   * @param shouldDisposeFunc a function defining whether an item should be stopped if expired. If `null` is passed, the
+   *                          monitor will always be stopped if the monitor is expired.
+   */
+  void registerMonitorTypeIfAbsent(
+      String monitorType,
+      Set<MonitorErrorResponse> errorResponses,
+      long expirationTimeNs,
+      @Nullable ShouldDisposeFunc<Monitor> shouldDisposeFunc);
+
+  /**
+   * Creates and starts the given monitor if it does not already exist and stores it under the given monitor type and
+   * key.
+   *
+   * @param monitorType     a String representing the monitor type, eg "customEndpoint".
+   * @param key             the key for the monitor, eg
+   *                        "custom-endpoint.cluster-custom-XYZ.us-east-2.rds.amazonaws.com:5432".
+   * @param monitorSupplier an initialization lambda that can be used to create the monitor if it is absent.
+   */
+  void runIfAbsent(
+      String monitorType,
+      Object key,
+      Supplier<Monitor> monitorSupplier);
+
+  /**
+   * Stops the given monitor and removes it from the monitor service.
+   *
+   * @param monitorType a String representing the monitor type, eg "customEndpoint".
+   * @param key         the key for the monitor, eg
+   *                    "custom-endpoint.cluster-custom-XYZ.us-east-2.rds.amazonaws.com:5432".
+   */
+  void stopAndRemove(String monitorType, Object key);
+
+  /**
+   * Stops all monitors for the given type and removes them from the monitor service.
+   *
+   * @param monitorType a String representing the monitor type, eg "customEndpoint".
+   */
+  void stopAndRemoveMonitors(String monitorType);
+
+  /**
+   * Stops all monitors and removes them from the monitor service.
+   */
+  void stopAndRemoveAll();
+}

wrapper/src/main/java/software/amazon/jdbc/util/monitoring/MonitorState.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed 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 software.amazon.jdbc.util.monitoring;
+
+public enum MonitorState {
+  RUNNING,
+  STOPPED,
+  ERROR
+}