com.splout.db.hazelcast.CoordinationStructures Maven / Gradle / Ivy
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package com.splout.db.hazelcast;
/*
* #%L
* Splout SQL Server
* %%
* Copyright (C) 2012 Datasalt Systems S.L.
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see > that keeps the version that is being served currently for each tablespace
* It only keeps one entry in the map with the full versions, keyed by KEY_FOR_VERSIONS_BEING_SERVED.
* This is done that way, instead having one entry per tablespace because of atomicity:
* Each time one, or severals tablespaces versions have changes, we receive ALL CHANGES
* all together.
*/
public static final String VERSIONS_BEING_SERVED = "com.splout.db.versionsBeingServed";
public static final String KEY_FOR_VERSIONS_BEING_SERVED = "versions";
// Map that keeps the registry of which DNodes are available currently
public static final String DNODES = "com.splout.db.dnodes";
// Distributed CountDownLatch prefix name used as barrier to wait for DNodes. Used in
// conjuntion with the version as postfix
public static final String GLOBAL_DEPLOY_COUNT_DOWN = "com.splout.db.deploy.countdown-";
// Error panel used in deployment to inform that the deployment on a DNode failed. This is
// a prefix, and the version is used as postfix
public static final String GLOBAL_DEPLOY_ERROR_PANEL = "com.splout.db.deploy.errorPanel-";
// Version generator. Generates unique version id across the cluster
public static final String VERSION_GENERATOR = "com.splout.db.versionGenerator";
// Key for #getDNodeReplicaBalanceActionsSet()
public static final String DNODE_REPLICA_BALANCE_ACTIONS_SET = "com.splout.db.replicaBalanceActions";
private HazelcastInstance hz;
// A JVM-local static flag for unit testing (not associated with Hazelcast) set / unset by {@link com.splout.db.qnode.Deployer}
// This is only to be used for testing purposes. It is an integer since there might be more than one deploy happening at once.
public static final AtomicInteger DEPLOY_IN_PROGRESS = new AtomicInteger(0);
public CoordinationStructures(HazelcastInstance hz) {
this.hz = hz;
}
/**
* Returns the set that shows what {@link ReplicaBalancer.BalanceAction}s
* are currently being performed in the cluster. If some QNode wants to trigger a balance
* action it has to update this map only in the case that the key doesn't already exist.
*
*
*/
public IMap getDNodeReplicaBalanceActionsSet() {
return hz.getMap(CoordinationStructures.DNODE_REPLICA_BALANCE_ACTIONS_SET);
}
/**
* Map> that keeps the version that is being served currently for each tablespace
* It only keeps one entry in the map with the full versions, keyed by {@link #KEY_FOR_VERSIONS_BEING_SERVED}.
* This is done that way, instead having one entry per tablespace because of atomicity:
* Each time one, or severals tablespaces versions have changes, we receive ALL CHANGES
* all together.
*/
public IMap> getVersionsBeingServed() {
return hz.getMap(CoordinationStructures.VERSIONS_BEING_SERVED);
}
/**
* Returns a map with the current version being served per each tablespace.
* BE CAREFUL: this map is not "managed" by Hazelcast, so changes to it
* are not shared to the rest of the cluster. If you want so, use
* {@link #updateVersionsBeingServed(Map, Map)}. It can be null at the
* startup.
*/
@SuppressWarnings("unchecked")
public Map getCopyVersionsBeingServed() {
return (Map) hz.getMap(CoordinationStructures.VERSIONS_BEING_SERVED).get(KEY_FOR_VERSIONS_BEING_SERVED);
}
/**
* Updates the versions being served in the cluster. You should provide
* the old version you based on to create the new version. If the old version
* that you used differs with the current version on the cluster, then the
* update will fail. In this case, you should load the new "oldVersion",
* reconstruct your new version based on it, and retry.
*
* If oldVersion is null, then we imagine that the value
* was not present in the map. BE CAREFUL: If null is present in the
* map, the update will fail.
*/
public boolean updateVersionsBeingServed(Map oldVersion, Map newVersion) {
IMap> ver = getVersionsBeingServed();
boolean success;
if (oldVersion == null) {
success = (ver.putIfAbsent(KEY_FOR_VERSIONS_BEING_SERVED, newVersion) != null);
} else {
success = ver.replace(KEY_FOR_VERSIONS_BEING_SERVED, oldVersion, newVersion);
}
return success;
}
/**
* Map that keeps the registry of which DNodes are available currently.
* Related with {@link DistributedRegistry}
*/
public IMap getDNodes() {
return hz.getMap(CoordinationStructures.DNODES);
}
/**
* A reasonable method for generating unique version ids: combining a timestamp (in seconds)
* with a distributed unique Id from Hazelcast. In this way if the Hazelcast counter is restarted
* (for example after a cluster shutdown or restart) then the Ids will still be unique afterwards.
*/
public long uniqueVersionId() {
IdGenerator idGenerator = hz.getIdGenerator(CoordinationStructures.VERSION_GENERATOR);
long id = idGenerator.newId();
int timeSeconds = (int)(System.currentTimeMillis() / 1000);
long paddedId = id << 32;
return paddedId + timeSeconds;
}
/**
* Return a {@link ICountDownLatch} used to know when a deploy
* process has finished. The version is used to compose the
* name of the latch, so make it unique for each deployment.
*/
public ICountDownLatch getCountDownLatchForDeploy(long version) {
return hz.getCountDownLatch(GLOBAL_DEPLOY_COUNT_DOWN + version);
}
/**
* Return a map used as panel tu publish errors of deployments
* on DNodes. The key is the DNode id. QNode is informed
* on errors in DNodes using this map.
*/
public IMap getDeployErrorPanel(long version) {
return hz.getMap(GLOBAL_DEPLOY_ERROR_PANEL + version);
}
}