org.apache.activemq.leveldb.replicated.MasterElector.scala Maven / Gradle / Ivy
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/**
* 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.activemq.leveldb.replicated
import org.apache.activemq.leveldb.replicated.groups._
import com.fasterxml.jackson.annotation.JsonProperty
import org.apache.activemq.leveldb.util.{Log, JsonCodec}
import java.io.IOException
class LevelDBNodeState extends NodeState {
@JsonProperty
var id: String = _
@JsonProperty
var container: String = _
@JsonProperty
var address: String = _
@JsonProperty
var position: Long = -1
@JsonProperty
var weight: Int = 0
@JsonProperty
var elected: String = _
override def equals(obj: Any): Boolean = {
obj match {
case x:LevelDBNodeState =>
x.id == id &&
x.container == container &&
x.address == address &&
x.position == position &&
x.elected == elected
case _ => false
}
}
override
def toString = JsonCodec.encode(this).ascii().toString
}
object MasterElector extends Log
/**
*/
class MasterElector(store: ElectingLevelDBStore) extends ClusteredSingleton[LevelDBNodeState](classOf[LevelDBNodeState]) {
import MasterElector._
var last_state: LevelDBNodeState = _
var elected: String = _
var position: Long = -1
var address: String = _
var updating_store = false
var next_connect: String = _
var connected_address: String = _
def join: Unit = this.synchronized {
last_state = create_state
join(last_state)
add(change_listener)
}
def elector = this
def update: Unit = elector.synchronized {
var next = create_state
if (next != last_state) {
last_state = next
join(next)
}
}
def create_state = {
val rc = new LevelDBNodeState
rc.id = store.brokerName
rc.elected = elected
rc.position = position
rc.weight = store.weight
rc.address = address
rc.container = store.container
rc.address = address
rc
}
object change_listener extends ChangeListener {
def connected = changed
def disconnected = {
changed
}
var stopped = false;
def changed:Unit = elector.synchronized {
debug("ZooKeeper group changed: %s", members)
// info(eid+" cluster state changed: "+members)
if (isMaster) {
// We are the master elector, we will choose which node will startup the MasterLevelDBStore
members.get(store.brokerName) match {
case None =>
info("Not enough cluster members connected to elect a new master.")
case Some(members) =>
if (members.size > store.replicas) {
warn("Too many cluster members are connected. Expected at most "+store.replicas+
" members but there are "+members.size+" connected.")
}
if (members.size < store.clusterSizeQuorum) {
info("Not enough cluster members connected to elect a master.")
elected = null
} else {
// If we already elected a master, lets make sure he is still online..
if (elected != null) {
val by_eid = Map(members: _*)
if (by_eid.get(elected).isEmpty) {
info("Previously elected master is not online, staring new election")
elected = null
}
}
// Do we need to elect a new master?
if (elected == null) {
// Find the member with the most updates.
val sortedMembers = members.filter(_._2.position >= 0).sortWith {
(a, b) => {
a._2.position > b._2.position ||
(a._2.position == b._2.position && a._2.weight > b._2.weight )
}
}
if (sortedMembers.size != members.size) {
info("Not enough cluster members have reported their update positions yet.")
} else {
// We now have an election.
elected = sortedMembers.head._1
}
}
// Sort by the positions in the cluster..
}
}
} else {
// Only the master sets the elected field.
elected = null
}
val master_elected = if(eid==null) null else master.map(_.elected).getOrElse(null)
// If no master is currently elected, we need to report our current store position.
// Since that will be used to select the master.
val connect_target = if (master_elected != null) {
position = -1
members.get(store.brokerName).get.find(_._1 == master_elected).map(_._2.address).getOrElse(null)
} else {
// Once we are not running a master or server, report the position..
if( connected_address==null && address==null && !updating_store ) {
position = store.position
}
null
}
// Do we need to stop the running master?
if ((eid==null || master_elected != eid) && address!=null && !updating_store) {
info("Demoted to slave")
updating_store = true
store.stop_master {
elector.synchronized {
updating_store = false
info("Master stopped")
address = null
changed
}
}
}
// Have we been promoted to being the master?
if (eid!=null && master_elected == eid && address==null && !updating_store ) {
info("Promoted to master")
updating_store = true
store.start_master { port =>
elector.synchronized {
updating_store = false
address = store.address(port)
info("Master started: "+address)
changed
}
}
}
// Can we become a slave?
if ( (eid==null || master_elected != eid) && address == null) {
// Did the master address change?
if (connect_target != connected_address) {
// Do we need to setup a new slave.
if (connect_target != null && !updating_store) {
updating_store = true
store.start_slave(connect_target) {
elector.synchronized {
updating_store=false
info("Slave started")
connected_address = connect_target
changed
}
}
}
// Lets stop the slave..
if (connect_target == null && !updating_store) {
updating_store = true
store.stop_slave {
elector.synchronized {
updating_store=false
info("Slave stopped")
connected_address = null
changed
}
}
}
}
}
if( group.zk.isConnected ) {
update
}
}
}
}
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