Ketch: Simple map of running leader instances
Supports use in basic daemons where RepositoryCache is also effective. Change-Id: Ia736b32c2c710b5a802233badc0d30818de763cd
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/*
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* Copyright (C) 2016, Google Inc.
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* and other copyright owners as documented in the project's IP log.
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*
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* This program and the accompanying materials are made available
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* under the terms of the Eclipse Distribution License v1.0 which
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* accompanies this distribution, is reproduced below, and is
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* available at http://www.eclipse.org/org/documents/edl-v10.php
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* - Neither the name of the Eclipse Foundation, Inc. nor the
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* names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package org.eclipse.jgit.internal.ketch;
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import java.net.URISyntaxException;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.locks.Lock;
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import java.util.concurrent.locks.ReentrantLock;
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import org.eclipse.jgit.internal.storage.dfs.DfsRepository;
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import org.eclipse.jgit.lib.Repository;
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/**
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* A cache of live leader instances, keyed by repository.
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* <p>
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* Ketch only assigns a leader to a repository when needed. If
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* {@link #get(Repository)} is called for a repository that does not have a
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* leader, the leader is created and added to the cache.
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*/
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public class KetchLeaderCache {
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private final KetchSystem system;
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private final ConcurrentMap<String, KetchLeader> leaders;
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private final Lock startLock;
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/**
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* Initialize a new leader cache.
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*
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* @param system
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* system configuration for the leaders
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*/
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public KetchLeaderCache(KetchSystem system) {
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this.system = system;
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leaders = new ConcurrentHashMap<>();
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startLock = new ReentrantLock(true /* fair */);
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}
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/**
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* Lookup the leader instance for a given repository.
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*
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* @param repo
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* repository to get the leader for.
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* @return the leader instance for the repository.
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* @throws URISyntaxException
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* remote configuration contains an invalid URL.
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*/
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public KetchLeader get(Repository repo)
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throws URISyntaxException {
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String key = computeKey(repo);
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KetchLeader leader = leaders.get(key);
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if (leader != null) {
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return leader;
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}
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return startLeader(key, repo);
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}
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private KetchLeader startLeader(String key, Repository repo)
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throws URISyntaxException {
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startLock.lock();
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try {
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KetchLeader leader = leaders.get(key);
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if (leader != null) {
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return leader;
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}
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leader = system.createLeader(repo);
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leaders.put(key, leader);
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return leader;
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} finally {
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startLock.unlock();
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}
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}
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private static String computeKey(Repository repo) {
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if (repo instanceof DfsRepository) {
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DfsRepository dfs = (DfsRepository) repo;
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return dfs.getDescription().getRepositoryName();
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}
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if (repo.getDirectory() != null) {
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return repo.getDirectory().toURI().toString();
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}
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throw new IllegalArgumentException();
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}
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}
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