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From StephanEwen <...@git.apache.org>
Subject [GitHub] flink pull request #3524: [FLINK-6014][checkpoint] Allow the registration of...
Date Wed, 29 Mar 2017 13:16:02 GMT
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.


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