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Extract HA's IdReuseEligibility in a top level class
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enterprise/ha/src/main/java/org/neo4j/kernel/ha/id/HaIdReuseEligibility.java
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| /* | ||
| * Copyright (c) 2002-2016 "Neo Technology," | ||
| * Network Engine for Objects in Lund AB [http://neotechnology.com] | ||
| * | ||
| * This file is part of Neo4j. | ||
| * | ||
| * Neo4j 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 Affero 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 <http://www.gnu.org/licenses/>. | ||
| */ | ||
| package org.neo4j.kernel.ha.id; | ||
|
|
||
| import org.neo4j.helpers.Clock; | ||
| import org.neo4j.kernel.ha.cluster.HighAvailabilityModeSwitcher; | ||
| import org.neo4j.kernel.ha.cluster.member.ClusterMembers; | ||
| import org.neo4j.kernel.impl.api.KernelTransactionsSnapshot; | ||
| import org.neo4j.kernel.impl.store.id.IdReuseEligibility; | ||
|
|
||
| /** | ||
| * This {@link IdReuseEligibility} only buffer ids for reuse when we're the master. | ||
| * This is mostly an optimization since when in slave role the ids are thrown away anyway. | ||
| */ | ||
| public class HaIdReuseEligibility implements IdReuseEligibility | ||
| { | ||
| private final ClusterMembers members; | ||
| private final Clock clock; | ||
| private final long idReuseSafeZone; | ||
|
|
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| public HaIdReuseEligibility( ClusterMembers members, Clock clock, long idReuseSafeZone ) | ||
| { | ||
| this.members = members; | ||
| this.clock = clock; | ||
| this.idReuseSafeZone = idReuseSafeZone; | ||
| } | ||
|
|
||
| @Override | ||
| public boolean isEligible( KernelTransactionsSnapshot snapshot ) | ||
| { | ||
| switch ( members.getCurrentMemberRole() ) | ||
| { | ||
| case HighAvailabilityModeSwitcher.SLAVE: | ||
| // If we're slave right now then just release them because the id generators in slave mode | ||
| // will throw them away anyway, no need to keep them in memory. The architecture around | ||
| // how buffering is done isn't a 100% fit for HA since the wrapping if IdGeneratorFactory | ||
| // where the buffering takes place is done in a place which is oblivious to HA and roles | ||
| // which means that buffering will always take place. For now we'll have to live with | ||
| // always buffering and only just release them as soon as possible when slave. | ||
| return true; | ||
| case HighAvailabilityModeSwitcher.MASTER: | ||
| // If we're master then we have to keep these ids around during the configured safe zone time | ||
| // so that slaves have a chance to read consistently as well (slaves will know and compensate | ||
| // for falling outside of safe zone). Let's keep this separate from SLAVE since they | ||
| // have different reasons for doing what they do. | ||
| return clock.currentTimeMillis() - snapshot.snapshotTime() >= idReuseSafeZone; | ||
| default: | ||
| // If we're anything other than slave, i.e. also pending then retain the ids since we're | ||
| // not quite sure what state we're in at the moment and we clear the id buffers anyway | ||
| // during state switch. | ||
| return false; | ||
| } | ||
| } | ||
| } |