Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/3524#discussion_r108670567
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/SharedStateRegistry.java
---
@@ -0,0 +1,192 @@
+/*
+ * 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.flink.runtime.state;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.java.tuple.Tuple2;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A {@code SharedStateRegistry} will be deployed in the
+ * {@link org.apache.flink.runtime.checkpoint.CheckpointCoordinator} to
+ * maintain the reference count of those state objects shared among
different
+ * checkpoints. Each shared state object must be identified by a unique
key.
+ */
+public class SharedStateRegistry implements Serializable {
+
+ private static final long serialVersionUID = -8357254413007773970L;
+
+ /** All registered state objects */
+ private final Map<String, Tuple2<StateObject, Integer>>
registeredStates = new HashMap<>();
+
+ /** All state objects that are not referenced any more */
+ private transient final List<StateObject> discardedStates = new
ArrayList<>();
+
+ /**
+ * Register the state in the registry
+ *
+ * @param key The key of the state to register
+ * @param state The state to register
+ */
+ public void register(String key, StateObject state) {
+ Tuple2<StateObject, Integer> stateAndRefCnt =
registeredStates.get(key);
+
+ if (stateAndRefCnt == null) {
+ registeredStates.put(key, new Tuple2<>(state, 1));
+ } else {
+ if (!stateAndRefCnt.f0.equals(state)) {
+ throw new IllegalStateException("Cannot
register a key with different states.");
+ }
+
+ stateAndRefCnt.f1++;
+ }
+ }
+
+ /**
+ * Decrease the reference count of the state in the registry
+ *
+ * @param key The key of the state to unregister
+ */
+ public void unregister(String key) {
+ Tuple2<StateObject, Integer> stateAndRefCnt =
registeredStates.get(key);
+
+ if (stateAndRefCnt == null) {
+ throw new IllegalStateException("Cannot unregister an
unexisted state.");
+ }
+
+ stateAndRefCnt.f1--;
+
+ // Remove the state from the registry when it's not referenced
any more.
+ if (stateAndRefCnt.f1 == 0) {
+ registeredStates.remove(key);
+ discardedStates.add(stateAndRefCnt.f0);
+ }
+ }
+
+ /**
+ * Register all the shared states in the given state handles.
+ *
+ * @param stateHandles The state handles to register their shared states
+ */
+ public void registerAll(Collection<? extends CompositeStateHandle>
stateHandles) {
+ synchronized (this) {
+ if (stateHandles != null) {
+ for (CompositeStateHandle stateHandle :
stateHandles) {
+ stateHandle.register(this);
+ }
+ }
+ }
+ }
+
+ /**
+ * Register all the shared states in the given state handle.
+ *
+ * @param stateHandle The state handle to register its shared states
+ */
+ public void registerAll(CompositeStateHandle stateHandle) {
+ if (stateHandle != null) {
+ synchronized (this) {
+ stateHandle.register(this);
+ }
+ }
+ }
+
+ /**
+ * Unregister all the shared states in the given state handles and
return
+ * those unreferenced states after these shared states are unregistered.
+ *
+ * @param stateHandles The state handles to unregister their shared
states
+ * @return The states that are not referenced any more
+ */
+ public List<StateObject> unregisterAll(Collection<? extends
CompositeStateHandle> stateHandles) {
+ synchronized (this) {
+ discardedStates.clear();
+
+ if (stateHandles != null) {
+ for (CompositeStateHandle stateHandle :
stateHandles) {
+ stateHandle.unregister(this);
+ }
+ }
+
+ return discardedStates;
+ }
+
+ }
+
+ /**
+ * Unregister all the shared states in the given state handles and
return
+ * those unreferenced states after these shared states are unregistered.
+ *
+ * @param stateHandle The state handle to unregister its shared states
+ * @return The states that are not referenced any more
+ */
+ public List<StateObject> unregisterAll(CompositeStateHandle
stateHandle) {
+ if (stateHandle == null) {
+ return null;
+ } else {
+ synchronized (this) {
+ discardedStates.clear();
+
+ stateHandle.unregister(this);
+
+ return discardedStates;
+ }
+ }
+ }
+
+ @VisibleForTesting
+ int getReferenceCount(String key) {
+ Tuple2<StateObject, Integer> stateAndRefCnt =
registeredStates.get(key);
+
+ return stateAndRefCnt == null ? 0 : stateAndRefCnt.f1;
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ if (this == o) {
--- End diff --
I think `equals()` and `hashCode()` are not really well defined on the
state registry, and not needed. I would remove them.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
