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From: joshelser <git@git.apache.org>
To: dev@accumulo.apache.org
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Subject: [GitHub] accumulo pull request: ACCUMULO-4173: Host Regex Table Load
 Balanc...
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Message-Id: <20160412140845.1EF5BDFBA0@git1-us-west.apache.org>
Date: Tue, 12 Apr 2016 14:08:45 +0000 (UTC)

Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/83#discussion_r59382019
  
    --- Diff: server/base/src/main/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancer.java ---
    @@ -0,0 +1,334 @@
    +/*
    + * 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.accumulo.server.master.balancer;
    +
    +import java.net.InetAddress;
    +import java.net.UnknownHostException;
    +import java.util.ArrayList;
    +import java.util.Collections;
    +import java.util.HashMap;
    +import java.util.List;
    +import java.util.Map;
    +import java.util.Map.Entry;
    +import java.util.Set;
    +import java.util.SortedMap;
    +import java.util.TreeMap;
    +import java.util.regex.Pattern;
    +
    +import org.apache.accumulo.core.client.admin.TableOperations;
    +import org.apache.accumulo.core.conf.AccumuloConfiguration;
    +import org.apache.accumulo.core.conf.Property;
    +import org.apache.accumulo.core.data.impl.KeyExtent;
    +import org.apache.accumulo.core.master.thrift.TabletServerStatus;
    +import org.apache.accumulo.core.tabletserver.thrift.TabletStats;
    +import org.apache.accumulo.server.conf.ServerConfiguration;
    +import org.apache.accumulo.server.master.state.TServerInstance;
    +import org.apache.accumulo.server.master.state.TabletMigration;
    +import org.apache.thrift.TException;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +/**
    + * This balancer will create pools of tablet servers by grouping tablet servers that match a regex into the same pool and calling the balancer set on the table
    + * to balance within the set of matching tablet servers. All tablet servers that do not match a regex are grouped into a default pool.<br>
    + * Regex properties for this balancer are specified as:<br>
    + * <b>table.custom.balancer.host.regex.&lt;tablename&gt;=&lt;regex&gt;</b><br>
    + * Periodically (default 5m) this balancer will check to see if a tablet server is hosting tablets that it should not be according to the regex configuration.
    + * If this occurs then the offending tablets will be reassigned. This would cover the case where the configuration is changed and the master is restarted while
    + * the tablet servers are up. To change the out of bounds check time period, set the following property:<br>
    + * <b>table.custom.balancer.host.regex.oob.period=5m</b><br>
    + * Periodically (default 5m) this balancer will regroup the set of current tablet servers into pools based on regexes applied to the tserver host names. This
    + * would cover the case of tservers dying or coming online. To change the host pool check time period, set the following property: <br>
    + * <b>table.custom.balancer.host.regex.pool.check=5m</b><br>
    + * Regex matching can be based on either the host name (default) or host ip address. To set this balancer to match the regular expressions to the tablet server
    + * IP address, then set the following property:<br>
    + * <b>table.custom.balancer.host.regex.is.ip=true</b>
    + *
    + */
    +public class HostRegexTableLoadBalancer extends TableLoadBalancer {
    +
    +  private static final Logger LOG = LoggerFactory.getLogger(HostRegexTableLoadBalancer.class);
    +  public static final String HOST_BALANCER_PREFIX = Property.TABLE_ARBITRARY_PROP_PREFIX.getKey() + "balancer.host.regex.";
    +  public static final String HOST_BALANCER_OOB_CHECK = Property.TABLE_ARBITRARY_PROP_PREFIX.getKey() + "balancer.host.regex.oob.period";
    +  private static final String HOST_BALANCER_OOB_DEFAULT = "5m";
    +  public static final String HOST_BALANCER_POOL_RECHECK_KEY = Property.TABLE_ARBITRARY_PROP_PREFIX.getKey() + "balancer.host.regex.pool.check";
    +  private static final String HOST_BALANCER_POOL_RECHECK_DEFAULT = "5m";
    +  public static final String HOST_BALANCER_REGEX_USING_IPS = Property.TABLE_ARBITRARY_PROP_PREFIX.getKey() + "balancer.host.regex.is.ip";
    +  protected static final String DEFAULT_POOL = "HostTableLoadBalancer.ALL";
    +
    +  protected long oobCheckMillis = AccumuloConfiguration.getTimeInMillis(HOST_BALANCER_OOB_DEFAULT);
    +  protected long poolRecheckMillis = AccumuloConfiguration.getTimeInMillis(HOST_BALANCER_POOL_RECHECK_DEFAULT);
    +
    +  private Map<String,String> tableIdToTableName = null;
    +  private Map<String,Pattern> poolNameToRegexPattern = null;
    +  private volatile long lastOOBCheck = System.currentTimeMillis();
    +  private volatile long lastPoolRecheck = 0;
    +  private boolean isIpBasedRegex = false;
    +  private Map<String,SortedMap<TServerInstance,TabletServerStatus>> pools = new HashMap<String,SortedMap<TServerInstance,TabletServerStatus>>();
    +
    +  /**
    +   * Group the set of current tservers by pool name. Tservers that don't match a regex are put into a default pool.
    +   *
    +   * @param current
    +   *          map of current tservers
    +   * @return current servers grouped by pool name, if not a match it is put into a default pool.
    +   */
    +  protected synchronized Map<String,SortedMap<TServerInstance,TabletServerStatus>> splitCurrentByRegex(SortedMap<TServerInstance,TabletServerStatus> current) {
    +    if ((System.currentTimeMillis() - lastPoolRecheck) > poolRecheckMillis) {
    --- End diff --
    
    This is probably fine when the defaults are on the order of minutes, but could be problematic if someone reduces the period. Maybe worthy of a comment to state the expectation that `poolRecheckMillis` is commonly order-minutes.


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