// This file is part of OpenTSDB.
// Copyright (C) 2016 The OpenTSDB Authors.
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 2.1 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 Lesser
// General Public License for more details. You should have received a copy
// of the GNU Lesser General Public License along with this program. If not,
// see <http://www.gnu.org/licenses/>.
package net.opentsdb.meta;
import com.stumbleupon.async.Deferred;
import net.opentsdb.core.TSDB;
import net.opentsdb.stats.StatsCollector;
/**
* This is a first stab at a meta data cache. Initially it only handles
* incrementing TSUID counters in a local database. The class will then
* periodically sync the local counter cache with HBase and generate TSMeta
* objects if necessary. This keeps us from having to maintain thousands or
* millions of callback objects in memory while we wait for individual atomic
* increments per data point.
* @since 2.3
*/
public abstract class MetaDataCache {
/**
* Called by TSDB to initialize the plugin
* Implementations are responsible for setting up any IO they need as well
* as starting any required background threads.
* <b>Note:</b> Implementations should throw exceptions if they can't start
* up properly. The TSD will then shutdown so the operator can fix the
* problem. Please use IllegalArgumentException for configuration issues.
* @param tsdb The parent TSDB object
* @throws IllegalArgumentException if required configuration parameters are
* missing
* @throws Exception if something else goes wrong
*/
public abstract void initialize(final TSDB tsdb);
/**
* Called when the TSD is shutting down to gracefully flush any buffers or
* close open connections.
*/
public abstract Deferred<Object> shutdown();
/**
* Should return the version of this plugin in the format:
* MAJOR.MINOR.MAINT, e.g. 2.0.1. The MAJOR version should match the major
* version of OpenTSDB the plugin is meant to work with.
* @return A version string used to log the loaded version
*/
public abstract String version();
/**
* Called by the TSD when a request for statistics collection has come in. The
* implementation may provide one or more statistics. If no statistics are
* available for the implementation, simply stub the method.
* @param collector The collector used for emitting statistics
*/
public abstract void collectStats(final StatsCollector collector);
/**
* Increments the given TSUID in the cache by 1
* @param tsuid The tsuid to increment
*/
public abstract void increment(final byte[] tsuid);
}