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Library implementing Paxos and Heartbeat components required for High Availability Neo4j
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/*
* Copyright (c) 2018-2020 "Graph Foundation"
* Graph Foundation, Inc. [https://graphfoundation.org]
*
* Copyright (c) 2002-2018 "Neo4j,"
* Neo4j Sweden AB [http://neo4j.com]
*
* This file is part of ONgDB Enterprise Edition. The included source
* code can be redistributed and/or modified under the terms of the
* GNU AFFERO GENERAL PUBLIC LICENSE Version 3
* (http://www.fsf.org/licensing/licenses/agpl-3.0.html) as found
* in the associated LICENSE.txt file.
*
* 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 Affero General Public License for more details.
*/
package org.neo4j.cluster;
import java.time.Duration;
import java.util.List;
import java.util.function.Function;
import org.neo4j.configuration.Description;
import org.neo4j.configuration.Internal;
import org.neo4j.configuration.LoadableConfig;
import org.neo4j.graphdb.config.Setting;
import org.neo4j.helpers.HostnamePort;
import org.neo4j.kernel.configuration.Settings;
import static org.neo4j.kernel.configuration.Settings.ANY;
import static org.neo4j.kernel.configuration.Settings.BOOLEAN;
import static org.neo4j.kernel.configuration.Settings.DURATION;
import static org.neo4j.kernel.configuration.Settings.FALSE;
import static org.neo4j.kernel.configuration.Settings.HOSTNAME_PORT;
import static org.neo4j.kernel.configuration.Settings.INTEGER;
import static org.neo4j.kernel.configuration.Settings.NO_DEFAULT;
import static org.neo4j.kernel.configuration.Settings.STRING;
import static org.neo4j.kernel.configuration.Settings.TRUE;
import static org.neo4j.kernel.configuration.Settings.buildSetting;
import static org.neo4j.kernel.configuration.Settings.illegalValueMessage;
import static org.neo4j.kernel.configuration.Settings.list;
import static org.neo4j.kernel.configuration.Settings.matches;
import static org.neo4j.kernel.configuration.Settings.min;
import static org.neo4j.kernel.configuration.Settings.setting;
/**
* Settings for cluster members
*/
@Description( "Cluster configuration settings" )
public class ClusterSettings implements LoadableConfig
{
public static final Function INSTANCE_ID = new Function()
{
@Override
public InstanceId apply( String value )
{
try
{
return new InstanceId( Integer.parseInt( value ) );
}
catch ( NumberFormatException e )
{
throw new IllegalArgumentException( "not a valid integer value" );
}
}
@Override
public String toString()
{
return "an instance id, which has to be a valid integer";
}
};
@Description( "Id for a cluster instance. Must be unique within the cluster." )
public static final Setting server_id = setting( "ha.server_id", INSTANCE_ID, NO_DEFAULT );
@Description( "The name of a cluster." )
@Internal
public static final Setting cluster_name = buildSetting( "unsupported.ha.cluster_name", STRING, "neo4j.ha" ).constraint(
illegalValueMessage( "must be a valid cluster name", matches( ANY ) ) ).build();
@Description( "A comma-separated list of other members of the cluster to join." )
public static final Setting> initial_hosts = setting( "ha.initial_hosts",
list( ",", HOSTNAME_PORT ), NO_DEFAULT );
@Description( "Host and port to bind the cluster management communication." )
public static final Setting cluster_server = setting( "ha.host.coordination", HOSTNAME_PORT,
"0.0.0.0:5001-5099" );
@Description( "Whether to allow this instance to create a cluster if unable to join." )
public static final Setting allow_init_cluster = setting( "ha.allow_init_cluster", BOOLEAN, TRUE );
// Timeout settings
/*
* ha.heartbeat_interval
* ha.paxos_timeout
* ha.learn_timeout
*/
@Description( "Default timeout used for clustering timeouts. Override specific timeout settings with proper" +
" values if necessary. This value is the default value for the ha.heartbeat_interval," +
" ha.paxos_timeout and ha.learn_timeout settings." )
public static final Setting default_timeout = setting( "ha.default_timeout", DURATION, "5s" );
@Description( "How often heartbeat messages should be sent. Defaults to ha.default_timeout." )
public static final Setting heartbeat_interval = buildSetting( "ha.heartbeat_interval", DURATION ).inherits(
default_timeout ).build();
@Description( "How long to wait for heartbeats from other instances before marking them as suspects for failure. " +
"This value reflects considerations of network latency, expected duration of garbage collection pauses " +
"and other factors that can delay message sending and processing. Larger values will result in more " +
"stable masters but also will result in longer waits before a failover in case of master failure. This " +
"value should not be set to less than twice the ha.heartbeat_interval value otherwise there is a high " +
"risk of frequent master switches and possibly branched data occurrence." )
public static final Setting heartbeat_timeout = setting( "ha.heartbeat_timeout", DURATION, "40s" );
/*
* ha.join_timeout
* ha.leave_timeout
*/
@Description( "Timeout for broadcasting values in cluster. Must consider end-to-end duration of Paxos algorithm." +
" This value is the default value for the ha.join_timeout and ha.leave_timeout settings." )
public static final Setting broadcast_timeout = setting( "ha.broadcast_timeout", DURATION, "30s" );
@Description( "Timeout for joining a cluster. Defaults to ha.broadcast_timeout. " +
"Note that if the timeout expires during cluster formation, the operator may have to restart the instance or instances." )
public static final Setting join_timeout = buildSetting( "ha.join_timeout", DURATION ).inherits( broadcast_timeout ).build();
@Description( "Timeout for waiting for configuration from an existing cluster member during cluster join." )
public static final Setting configuration_timeout = setting( "ha.configuration_timeout", DURATION, "1s" );
@Description( "Timeout for waiting for cluster leave to finish. Defaults to ha.broadcast_timeout." )
public static final Setting leave_timeout = buildSetting( "ha.leave_timeout", DURATION ).inherits( broadcast_timeout ).build();
/*
* ha.phase1_timeout
* ha.phase2_timeout
* ha.election_timeout
*/
@Description( "Default value for all Paxos timeouts. This setting controls the default value for the ha.phase1_timeout, " +
"ha.phase2_timeout and ha.election_timeout settings. If it is not given a value it " +
"defaults to ha.default_timeout and will implicitly change if ha.default_timeout changes. This is an " +
"advanced parameter which should only be changed if specifically advised by Neo4j Professional Services." )
public static final Setting paxos_timeout = buildSetting( "ha.paxos_timeout", DURATION ).inherits( default_timeout ).build();
@Description( "Timeout for Paxos phase 1. If it is not given a value it defaults to ha.paxos_timeout and will " +
"implicitly change if ha.paxos_timeout changes. This is an advanced parameter which should only be " +
"changed if specifically advised by Neo4j Professional Services. " )
public static final Setting phase1_timeout = buildSetting( "ha.phase1_timeout", DURATION ).inherits( paxos_timeout ).build();
@Description( "Timeout for Paxos phase 2. If it is not given a value it defaults to ha.paxos_timeout and will " +
"implicitly change if ha.paxos_timeout changes. This is an advanced parameter which should only be " +
"changed if specifically advised by Neo4j Professional Services. " )
public static final Setting phase2_timeout = buildSetting( "ha.phase2_timeout", DURATION ).inherits( paxos_timeout ).build();
@Description( "Timeout for learning values. Defaults to ha.default_timeout." )
public static final Setting learn_timeout = buildSetting( "ha.learn_timeout", DURATION ).inherits( default_timeout ).build();
@Description( "Timeout for waiting for other members to finish a role election. Defaults to ha.paxos_timeout." )
public static final Setting election_timeout = buildSetting( "ha.election_timeout", DURATION ).inherits( paxos_timeout ).build();
@Internal
public static final Setting instance_name = setting("unsupported.ha.instance_name", STRING, Settings.NO_DEFAULT );
@Description( "Maximum number of servers to involve when agreeing to membership changes. " +
"In very large clusters, the probability of half the cluster failing is low, but protecting against " +
"any arbitrary half failing is expensive. Therefore you may wish to set this parameter to a value less " +
"than the cluster size." )
public static final Setting max_acceptors = buildSetting( "ha.max_acceptors", INTEGER, "21" ).constraint( min( 1 ) ).build();
@Internal
public static final Setting strict_initial_hosts = setting( "ha.strict_initial_hosts", BOOLEAN, FALSE);
}