com.pinterest.terrapin.server.ResourcePartitionMap.java Source code

Introduction

Here is the source code for com.pinterest.terrapin.server.ResourcePartitionMap.java

Source

/**
* 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 com.pinterest.terrapin.server;

import com.google.common.collect.Maps;
import com.pinterest.terrapin.storage.Reader;
import com.pinterest.terrapin.thrift.generated.TerrapinGetErrorCode;
import com.pinterest.terrapin.thrift.generated.TerrapinGetException;
import org.apache.commons.lang3.tuple.ImmutablePair;
import org.apache.commons.lang3.tuple.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;

/**
 * Maintains a mapping of resources and partitions to their corresponding readers.
 */
public class ResourcePartitionMap {
    private static final Logger LOG = LoggerFactory.getLogger(ResourcePartitionMap.class);

    // Map from (resource,partition) -> reader.
    private final Map<Pair<String, String>, Reader> readerMap;
    // Map from resource->number of partitions for a resource.
    private final Map<String, Integer> partitionCountMap;

    public ResourcePartitionMap() {
        // We use concurrent maps since we require the ability to issue lock free reads. Writes
        // are still synchronized so that we can update both maps together.
        this.readerMap = Maps.newConcurrentMap();
        this.partitionCountMap = Maps.newConcurrentMap();
    }

    private void incrementPartitionCount(String resource) {
        Integer resourceCount = partitionCountMap.get(resource);
        if (resourceCount == null) {
            partitionCountMap.put(resource, 1);
        } else {
            partitionCountMap.put(resource, resourceCount + 1);
        }
    }

    private void decrementPartitionCount(String resource) {
        Integer resourceCount = partitionCountMap.get(resource);
        if (resourceCount == null || resourceCount <= 1) {
            partitionCountMap.remove(resource);
        } else {
            partitionCountMap.put(resource, resourceCount - 1);
        }
    }

    public void addReader(String resource, String partition, Reader r) throws UnsupportedOperationException {
        Pair<String, String> readerMapKey = new ImmutablePair(resource, partition);
        synchronized (this) {
            if (readerMap.containsKey(readerMapKey)) {
                // If we already have a reader available, log as an error and return.
                LOG.warn("Resource : " + resource + " Partition : " + partition + " already exists.");
                return;
            }
            readerMap.put(readerMapKey, r);
            incrementPartitionCount(resource);
        }
    }

    public Reader removeReader(String resource, String partition) throws UnsupportedOperationException {
        Pair<String, String> readerMapKey = new ImmutablePair(resource, partition);
        synchronized (this) {
            Reader r = this.readerMap.get(readerMapKey);
            if (r != null) {
                readerMap.remove(readerMapKey);
                decrementPartitionCount(resource);
                return r;
            } else {
                throw new UnsupportedOperationException(
                        "Partition " + partition + " not found for Resource " + resource);
            }
        }
    }

    public Reader getReader(String resource, String partition) throws TerrapinGetException {
        Pair<String, String> readerMapKey = new ImmutablePair(resource, partition);
        Reader r = readerMap.get(readerMapKey);
        if (r == null) {
            Integer partitionCount = partitionCountMap.get(resource);
            if (partitionCount == null || partitionCount < 1) {
                throw new TerrapinGetException("Resource " + resource + " not found.",
                        TerrapinGetErrorCode.NOT_SERVING_RESOURCE);
            } else {
                throw new TerrapinGetException("Resource " + resource + " Partition " + partition + " not found.",
                        TerrapinGetErrorCode.NOT_SERVING_PARTITION);
            }
        }
        return r;
    }

    public void close() {
        // TODO(varun): stop accepting any more open/close commands and close all readers/release
        // file descriptors.
    }
}