Troubles while running neo4j & rails in HA - neo4j

I have configured an HA cluster with 3 nodes.
The first is a Rails server, and the others are two Neo4j server
I started the Rails s, then I started another instance, with the following error
Has anyone an idea?
Paolo
2013-11-21 23:48:57.473+0000 INFO [Cluster] Attempting to join cluster of [127.0.0.1:5001, 127.0.0.1:5002, 127.0.0.1:5003]
2013-11-21 23:49:02.568+0000 INFO [Cluster] Joined cluster:Name:neo4j.ha Nodes:{1=cluster://127.0.0.1:5001, 3=cluster://127.0.0.1:5003} Roles:{coordinator=1}
2013-11-21 23:49:02.582+0000 INFO [Cluster] Instance 3 (this server) joined the cluster
2013-11-21 23:49:06.845+0000 INFO [Cluster] Instance 1 was elected as coordinator
java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2598)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1318)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1990)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1915)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1798)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
at org.neo4j.cluster.member.paxos.PaxosClusterMemberEvents$HighAvailabilitySnapshotProvider.setState(PaxosClusterMemberEvents.java:179)
at org.neo4j.cluster.protocol.snapshot.SnapshotMessage$SnapshotState.setState(SnapshotMessage.java:91)
at org.neo4j.cluster.protocol.snapshot.SnapshotState$2.handle(SnapshotState.java:105)
at org.neo4j.cluster.protocol.snapshot.SnapshotState$2.handle(SnapshotState.java:89)
at org.neo4j.cluster.statemachine.StateMachine.handle(StateMachine.java:88)
at org.neo4j.cluster.StateMachines$1.run(StateMachines.java:135)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)

Related

Can not enable Alwayson sql in DSE

I get this error when start Alwayson sql, tried many ways but the results still same. any ideas why?
Im using 1 cluster, 1 analytics+search center, 2 ubuntu 16.04 nodes.
INFO [ALWAYSON-SQL] 2019-02-14 11:36:01,348 ALWAYSON-SQL AlwaysOnSqlRunner.scala:304 - Shutting down AlwaysOn SQL.
INFO [ALWAYSON-SQL] 2019-02-14 11:36:01,617 ALWAYSON-SQL AlwaysOnSqlRunner.scala:328 - Set status to stopped
INFO [ALWAYSON-SQL] 2019-02-14 11:36:01,620 ALWAYSON-SQL AlwaysOnSqlRunner.scala:382 - Reserve port for AlwaysOn SQL
INFO [ALWAYSON-SQL] 2019-02-14 11:36:04,621 ALWAYSON-SQL AlwaysOnSqlRunner.scala:375 - Release reserved port
INFO [ALWAYSON-SQL] 2019-02-14 11:36:04,622 ALWAYSON-SQL AlwaysOnSqlRunner.scala:805 - Set InCluster token to DseFs client
INFO [ForkJoinPool-1-worker-1] 2019-02-14 11:36:04,650 AlwaysOnSqlRunner.scala:740 - dsefs server heartbeat response: pong
INFO [ForkJoinPool-1-worker-3] 2019-02-14 11:36:04,757 AlwaysOnSqlRunner.scala:704 - Create DseFs directory /var/log/spark/alwayson_sql
INFO [ForkJoinPool-1-worker-3] 2019-02-14 11:36:04,758 AlwaysOnSqlRunner.scala:805 - Set InCluster token to DseFs client
ERROR [ForkJoinPool-1-worker-3] 2019-02-14 11:36:04,788 AlwaysOnSqlRunner.scala:722 - Failed to check dsefs directory alwayson_sql
com.datastax.bdp.fs.model.AccessDeniedException: Insufficient permissions to path /
at com.datastax.bdp.fs.model.DseFsJsonProtocol$ThrowableReader$.read(DseFsJsonProtocol.scala:258)
at com.datastax.bdp.fs.model.DseFsJsonProtocol$ThrowableReader$.read(DseFsJsonProtocol.scala:232)
at spray.json.JsValue.convertTo(JsValue.scala:31)
at com.datastax.bdp.fs.rest.RestResponse$stateMachine$macro$331$1.apply(RestResponse.scala:48)
at com.datastax.bdp.fs.rest.RestResponse$stateMachine$macro$331$1.apply(RestResponse.scala:44)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:465)
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
at java.lang.Thread.run(Thread.java:748)
INFO [ALWAYSON-SQL] 2019-02-14 11:36:04,788 ALWAYSON-SQL AlwaysOnSqlRunner.scala:247 - ALWAYSON-SQL caused an exception in state RUNNING : com.datastax.bdp.fs.model.AccessDeniedException: Insufficient permissions to path /
com.datastax.bdp.fs.model.AccessDeniedException: Insufficient permissions to path /
at com.datastax.bdp.fs.model.DseFsJsonProtocol$ThrowableReader$.read(DseFsJsonProtocol.scala:258)
at com.datastax.bdp.fs.model.DseFsJsonProtocol$ThrowableReader$.read(DseFsJsonProtocol.scala:232)
at spray.json.JsValue.convertTo(JsValue.scala:31)
at com.datastax.bdp.fs.rest.RestResponse$stateMachine$macro$331$1.apply(RestResponse.scala:48)
at com.datastax.bdp.fs.rest.RestResponse$stateMachine$macro$331$1.apply(RestResponse.scala:44)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:465)
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
at java.lang.Thread.run(Thread.java:748)
I have seen this problem too! It was a permissions problem in dsefs! To fix, login with the root Cassandra user, and change permissions of the your alwayson log directory to the alwayson user.

Setting up Causal Cluster Fails

I am trying to setup up a Neo4J Causal Cluster with 3 cores (core only). I have three Debian servers all debian 8.5. I have installed Java 8 and Neo4J Enterprise 3.4.0 (package source deb https://debian.neo4j.org/repo stable/) on each server.
My hosts are 192.168.20.163, 192.168.20.164 and 192.168.20.165. The config is the same on each host with the obvious change for IP address. The following is for the .163 host
dbms.connectors.default_listen_address=0.0.0.0
dbms.connectors.default_advertised_address=192.168.20.163
dbms.mode=CORE
causal_clustering.expected_core_cluster_size=3
causal_clustering.minimum_core_cluster_size_at_formation=3
causal_clustering.minimum_core_cluster_size_at_runtime=3
causal_clustering.initial_discovery_members=192.168.20.163:5000,192.168.20.164:5000,192.168.20.165:5000
causal_clustering.discovery_type=LIST
causal_clustering.discovery_listen_address=192.168.20.163:5000
causal_clustering.transaction_listen_address=192.168.20.163:6000
causal_clustering.raft_listen_address=192.168.20.163:7000
The servers go through the election process but the LEADER continues to switch back to FOLLOWER and trigger a new election.
The non-leader servers or 'members' each get the following error:
ERROR [o.n.c.c.s.s.CoreStateDownloader] Store copy failed due to store
ID mismatch
The server that was started first becomes a LEADER but as indicated switches back to FOLLOWER:
2018-05-30 14:58:22.808+0000 INFO [o.n.c.c.c.RaftMachine] Moving to CANDIDATE state after successfully starting election
2018-05-30 14:58:22.825+0000 INFO [o.n.c.m.SenderService] Creating channel to: [192.168.20.165:7000]
2018-05-30 14:58:22.827+0000 INFO [o.n.c.m.SenderService] Creating channel to: [192.168.20.164:7000]
2018-05-30 14:58:22.838+0000 INFO [o.n.c.p.h.HandshakeClientInitializer] Scheduling handshake (and timeout) local null remote null
2018-05-30 14:58:22.848+0000 INFO [o.n.c.p.h.HandshakeClientInitializer] Scheduling handshake (and timeout) local null remote null
2018-05-30 14:58:22.861+0000 INFO [o.n.c.m.SenderService] Connected: [id: 0x2ee2e930, L:/192.168.20.163:50169 - R:/192.168.20.165:7000]
2018-05-30 14:58:22.862+0000 INFO [o.n.c.p.h.HandshakeClientInitializer] Initiating handshake local /192.168.20.163:50169 remote /192.168.20.165:7000
2018-05-30 14:58:22.863+0000 INFO [o.n.c.m.SenderService] Connected: [id: 0x3d670ef3, L:/192.168.20.163:38239 - R:/192.168.20.164:7000]
2018-05-30 14:58:22.863+0000 INFO [o.n.c.p.h.HandshakeClientInitializer] Initiating handshake local /192.168.20.163:38239 remote /192.168.20.164:7000
2018-05-30 14:58:22.928+0000 INFO [o.n.c.p.h.HandshakeClientInitializer] Installing: ProtocolStack{applicationProtocol=RAFT_1, modifierProtocols=[]}
2018-05-30 14:58:22.929+0000 INFO [o.n.c.p.h.HandshakeClientInitializer] Installing: ProtocolStack{applicationProtocol=RAFT_1, modifierProtocols=[]}
2018-05-30 14:58:22.965+0000 INFO [o.n.c.p.h.HandshakeServerInitializer] Installing handshake server local /192.168.20.163:7000 remote /192.168.20.164:41725
2018-05-30 14:58:23.036+0000 INFO [o.n.c.c.c.RaftMachine] Moving to LEADER state at term 111 (I am MemberId{fbdff840}), voted for by [MemberId{4fe121e0}]
2018-05-30 14:58:23.036+0000 INFO [o.n.c.c.c.s.RaftState] First leader elected: MemberId{fbdff840}
2018-05-30 14:58:23.044+0000 INFO [o.n.c.c.c.s.RaftLogShipper] Starting log shipper: MemberId{f202d023}[matchIndex: -1, lastSentIndex: 0, localAppendIndex: 3, mode: MISMATCH]
2018-05-30 14:58:23.045+0000 INFO [o.n.c.c.c.s.RaftLogShipper] Starting log shipper: MemberId{4fe121e0}[matchIndex: -1, lastSentIndex: 0, localAppendIndex: 3, mode: MISMATCH]
2018-05-30 14:58:23.045+0000 INFO [o.n.c.c.c.m.RaftMembershipChanger] Idle{}
2018-05-30 14:58:23.046+0000 INFO [c.n.c.d.SslHazelcastCoreTopologyService] Leader MemberId{fbdff840} updating leader info for database default and term 111
2018-05-30 14:58:24.105+0000 INFO [o.n.c.p.h.HandshakeServerInitializer] Installing handshake server local /192.168.20.163:6000 remote /192.168.20.164:58041
2018-05-30 14:58:26.841+0000 INFO [o.n.c.p.h.HandshakeServerInitializer] Installing handshake server local /192.168.20.163:7000 remote /192.168.20.165:48317
2018-05-30 14:58:30.881+0000 INFO [o.n.c.p.h.HandshakeServerInitializer] Installing handshake server local /192.168.20.163:6000 remote /192.168.20.165:47015
2018-05-30 14:58:38.462+0000 INFO [o.n.c.c.c.m.MembershipWaiter] Leader commit unknown
2018-05-30 14:58:40.411+0000 INFO [o.n.c.c.c.RaftMachine] Moving to FOLLOWER state after not receiving heartbeat responses in this election timeout period. Heartbeats received: []
2018-05-30 14:58:40.411+0000 INFO [o.n.c.c.c.s.RaftState] Leader changed from MemberId{fbdff840} to null
2018-05-30 14:58:40.412+0000 INFO [o.n.c.c.c.s.RaftLogShipper] Stopping log shipper MemberId{f202d023}[matchIndex: -1, lastSentIndex: 3, localAppendIndex: 3, mode: MISMATCH]
2018-05-30 14:58:40.413+0000 INFO [o.n.c.c.c.s.RaftLogShipper] Stopping log shipper MemberId{4fe121e0}[matchIndex: -1, lastSentIndex: 3, localAppendIndex: 3, mode: MISMATCH]
2018-05-30 14:58:40.413+0000 INFO [o.n.c.c.c.m.RaftMembershipChanger] Inactive{}
2018-05-30 14:58:40.413+0000 INFO [c.n.c.d.SslHazelcastCoreTopologyService] Step down event detected. This topology member, with MemberId MemberId{fbdff840}, was leader in term 111, now moving to follower.
2018-05-30 14:58:48.342+0000 INFO [o.n.c.c.c.RaftMachine] Election timeout triggered
Eventually servers fail with:
ERROR [o.n.c.c.c.m.MembershipWaiterLifecycle] Server failed to join cluster within catchup time limit [600000 ms]
Based on the messages you have I assume you are trying to seed the cluster with a backup from somewhere ? Here's what you should do :
Check if the cluster forms correctly with no seeding (so with an empty database). That way you verify if all your settings are correct.
When seeding the cluster with a backup you need to neo4j-admin unbind the database on each of the instances before starting. Check https://neo4j.com/docs/operations-manual/current/clustering/causal-clustering/seed-cluster/ to find out the specific instructions for your case. The store ID mismatch is what you get if you don't unbind.
If 1. and 2. don't solve your problem, check with Neo4j support (since you are using the EE I assume you do have support).
Hope this helps.
Regards,
Tom

Graphaware Framework and UUID not starting on Neo4j GrapheneDB

I am trying to get the Graphaware Framework and UUID running on a GrapheneDB instance. I have followed the instructions to zip the JAR and neo4j.properties files and uploaded using the GrapheneDB Web Interface but UUID's are not added when I create a new node.
neo4j.properties file
dbms.unmanaged_extension_classes=com.graphaware.server=/graphaware
com.graphaware.runtime.enabled=true
#UIDM becomes the module ID:
com.graphaware.module.UIDM.1=com.graphaware.module.uuid.UuidBootstrapper
#optional, default is uuid:
com.graphaware.module.UIDM.uuidProperty=uuid
#optional, default is false:
com.graphaware.module.UIDM.stripHyphens=true
#optional, default is all nodes:
#com.graphaware.module.UIDM.node=hasLabel('Label1') || hasLabel('Label2')
#optional, default is no relationships:
#com.graphaware.module.UIDM.relationship=isType('Type1')
com.graphaware.module.UIDM.relationship=com.graphaware.runtime.policy.all.IncludeAllBusinessRelationships
#optional, default is uuidIndex
com.graphaware.module.UIDM.uuidIndex=uuidIndex
#optional, default is uuidRelIndex
com.graphaware.module.UIDM.uuidRelationshipIndex=uuidRelIndex
Log Output
2017-03-02 10:20:40.184+0000 INFO Neo4j Server shutdown initiated by
request 2017-03-02 10:20:40.209+0000 INFO
[c.g.s.f.b.GraphAwareServerBootstrapper] stopped 2017-03-02
10:20:40.209+0000 INFO Stopping... 2017-03-02 10:20:40.982+0000 INFO
Stopped. 2017-03-02 10:20:43.402+0000 INFO Starting... 2017-03-02
10:20:43.820+0000 INFO Bolt enabled on 0.0.0.0:7475. 2017-03-02
10:20:45.153+0000 INFO [c.g.r.b.RuntimeKernelExtension] GraphAware
Runtime disabled. 2017-03-02 10:20:48.130+0000 INFO Started.
2017-03-02 10:20:48.343+0000 INFO
[c.g.s.f.b.GraphAwareServerBootstrapper] started 2017-03-02
10:20:48.350+0000 INFO Mounted unmanaged extension
[com.graphaware.server] at [/graphaware] 2017-03-02 10:20:48.724+0000
INFO Mounting GraphAware Framework at /graphaware 2017-03-02
10:20:48.755+0000 INFO Will try to scan the following packages:
{com..graphaware.,org..graphaware.,net..graphaware.}
2017-03-02 10:20:52.633+0000 INFO Remote interface available at
http://localhost:7474/
Messages.log Extract
2017-03-02 10:33:59.991+0000 INFO [o.n.k.i.DiagnosticsManager] ---
STARTED diagnostics for KernelDiagnostics:StoreFiles END ---
2017-03-02 10:34:01.846+0000 INFO [o.n.k.i.DiagnosticsManager] ---
SERVER STARTED START --- 2017-03-02 10:34:02.526+0000 INFO
[c.g.s.f.b.GraphAwareBootstrappingFilter] Mounting GraphAware
Framework at /graphaware 2017-03-02 10:34:02.547+0000 INFO
[c.g.s.f.c.GraphAwareWebContextCreator] Will try to scan the following
packages:
{com..graphaware.,org..graphaware.,net..graphaware.}
2017-03-02 10:34:06.100+0000 INFO [o.n.k.i.DiagnosticsManager] ---
SERVER STARTED END ---
It looks like the framework is not started but I have set enabled=true in the properties file.
Environment Setup
Neo4j Community Edition 3.1.1
graphaware-server-3.1.0.44
graphaware-uuid-3.1.0.44.13
Thanks

Unable to load webadmin for Neo4j High Availability

I have installed 3 instances of neo4j version 1.9.4 on a linux machine, in 3 different directories: Neo4j01, neo4j02, neo4j03.
I have updated the configuration files neo4j.properties and neo4j-server.properties as mentioned in the link (http://docs.neo4j.org/chunked/milestone/ha-setup-tutorial.html).
When I start all the neo4j instances one after the other, they are successfully installing, but after some time 2 of the 3 neo4j process/instances are automatically disappearing. I noticed it via ps -aef | grep neo4j.
When I checked console logs then i found below errors:
2013-11-12 16:37:32.512+0000 INFO [Cluster] Checking store consistency with master
2013-11-12 16:37:33.174+0000 INFO [Cluster] Store is consistent
2013-11-12 16:37:33.176+0000 INFO [Cluster] Catching up with master
2013-11-12 16:37:33.276+0000 INFO [Cluster] Now consistent with master
2013-11-12 16:37:34.442+0000 INFO [Cluster] ServerId 2, successfully moved to slave for master ha://localhost.localdomain:6363?serverId=1
2013-11-12 16:37:34.689+0000 INFO [Cluster] Instance 1 is available as backup at backup://localhost.localdomain:6366
2013-11-12 16:37:34.798+0000 INFO [Cluster] Instance 2 (this server) is available as slave at ha://localhost.localdomain:6364?serverId=2
2013-11-12 16:37:35.036+0000 INFO [Cluster] Database available for write transactions
2013-11-12 16:37:35.360+0000 INFO [API] Successfully started database
2013-11-12 16:37:36.079+0000 INFO [API] Starting HTTP on port :7474 with 10 threads available
2013-11-12 16:37:40.596+0000 INFO [Cluster] Instance 3 has failed
2013-11-12 16:37:43.654+0000 INFO [API] Enabling HTTPS on port :7473
2013-11-12 16:38:01.081+0000 INFO [API] Mounted REST API at: /db/manage/
2013-11-12 16:38:01.158+0000 INFO [API] Mounted discovery module at [/]
2013-11-12 16:38:02.375+0000 INFO [API] Loaded server plugin "CypherPlugin"
2013-11-12 16:38:02.449+0000 INFO [API] Loaded server plugin "GremlinPlugin"
2013-11-12 16:38:02.462+0000 INFO [API] Mounted REST API at [/db/data/]
2013-11-12 16:38:02.534+0000 INFO [API] Mounted management API at [/db/manage/]
2013-11-12 16:38:03.568+0000 INFO [API] Mounted webadmin at [/webadmin]
2013-11-12 16:38:06.189+0000 INFO [API] Mounting static content at [/webadmin] from [webadmin-html]
2013-11-12 16:38:30.844+0000 DEBUG [API] Failed to start Neo Server on port [7474], reason [org.mortbay.util.MultiException[java.net.BindException: Address already in use, java.net.BindException: Address already in use]]
2013-11-12 16:38:30.880+0000 DEBUG [API] org.neo4j.server.ServerStartupException: Starting Neo4j Server failed: org.mortbay.util.MultiException[java.net.BindException: Address already in use, java.net.BindException: Address already in use]
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:211) ~[neo4j-server-1.9.4.jar:1.9.4]
at org.neo4j.server.Bootstrapper.start(Bootstrapper.java:86) [neo4j-server-1.9.4.jar:1.9.4]
at org.neo4j.server.Bootstrapper.main(Bootstrapper.java:49) [neo4j-server-1.9.4.jar:1.9.4]
Caused by: java.lang.RuntimeException: org.mortbay.util.MultiException[java.net.BindException: Address already in use, java.net.BindException: Address already in use]
at org.neo4j.server.web.Jetty6WebServer.startJetty(Jetty6WebServer.java:334) ~[neo4j-server-1.9.4.jar:1.9.4]
at org.neo4j.server.web.Jetty6WebServer.start(Jetty6WebServer.java:154) ~[neo4j-server-1.9.4.jar:1.9.4]
at org.neo4j.server.AbstractNeoServer.startWebServer(AbstractNeoServer.java:344) ~[neo4j-server-1.9.4.jar:1.9.4]
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:187) ~[neo4j-server-1.9.4.jar:1.9.4]
... 2 common frames omitted
Caused by: org.mortbay.util.MultiException: Multiple exceptions
at org.mortbay.jetty.Server.doStart(Server.java:188) ~[jetty-6.1.25.jar:6.1.25]
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50) ~[jetty-util-6.1.25.jar:6.1.25]
at org.neo4j.server.web.Jetty6WebServer.startJetty(Jetty6WebServer.java:330) ~[neo4j-server-1.9.4.jar:1.9.4]
... 5 common frames omitted
2013-11-12 16:38:30.894+0000 DEBUG [API] Failed to start Neo Server on port [7474]
Now, only neo4j01 process is running and neo4j02 and neo4j03 processes are disappeared. But even though neo4j01 process is up and running I am unable to access the webadmin page at http://htname:7474/webadmin/#/info/org.neo4j/High%20Availability/.
Please, can someone shed some light on this?
You might want to take a look at https://github.com/neo-technology/neo4j-enterprise-local-qa. This contains a rakefile that automates a local setup of 3 instances. Clone the repo locally, and use
rake setup_cluster start_cluster
to bring a locally running cluster online. Shutdown can be done via
rake stop_cluster
Find the configs in machine[ABC]/conf/.

Does Neo4j clustering require atleast 3 nodes?

I'm playing with Neo4J high availability clustering. Whilst the documentation indicates a cluster requires at least 3 nodes, or 2 with a arbitrator, I'm wondering what the implications of running with only 2 nodes are?
If i set up a 3 node cluster, and remove a node, i have no issues adding data. Likewise if i set-up the cluster with only 2 nodes i can still add data and don't seem to be restricted functionality. What should i expect to experience as limitations? For example, the following indicates the trace of a slave started in a 2 node cluster. Data can be added to the master with no issues - and be queried.
2013-11-06 10:34:50.403+0000 INFO [Cluster] Attempting to join cluster of [127.0.0.1:5001, 127.0.0.1:5002]
2013-11-06 10:34:54.473+0000 INFO [Cluster] Joined cluster:Name:neo4j.ha Nodes:{1=cluster://127.0.0.1:5001, 2=cluster://127.0.0.1:5002} Roles:{coordinator=1}
2013-11-06 10:34:54.477+0000 INFO [Cluster] Instance 2 (this server) joined the cluster
2013-11-06 10:34:54.512+0000 INFO [Cluster] Instance 1 was elected as coordinator
2013-11-06 10:34:54.530+0000 INFO [Cluster] Instance 1 is available as master at ha://localhost:6363?serverId=1
2013-11-06 10:34:54.531+0000 INFO [Cluster] Instance 1 is available as backup at backup://localhost:6366
2013-11-06 10:34:54.537+0000 INFO [Cluster] ServerId 2, moving to slave for master ha://localhost:6363?serverId=1
2013-11-06 10:34:54.564+0000 INFO [Cluster] Checking store consistency with master
2013-11-06 10:34:54.620+0000 INFO [Cluster] The store does not represent the same database as master. Will remove and fetch a new one from master
2013-11-06 10:34:54.646+0000 INFO [Cluster] ServerId 2, moving to slave for master ha://localhost:6363?serverId=1
2013-11-06 10:34:54.658+0000 INFO [Cluster] Copying store from master
2013-11-06 10:34:54.687+0000 INFO [Cluster] Copying index/lucene-store.db
2013-11-06 10:34:54.688+0000 INFO [Cluster] Copied index/lucene-store.db
2013-11-06 10:34:54.688+0000 INFO [Cluster] Copying neostore.nodestore.db
2013-11-06 10:34:54.689+0000 INFO [Cluster] Copied neostore.nodestore.db
2013-11-06 10:34:54.689+0000 INFO [Cluster] Copying neostore.propertystore.db
2013-11-06 10:34:54.689+0000 INFO [Cluster] Copied neostore.propertystore.db
2013-11-06 10:34:54.689+0000 INFO [Cluster] Copying neostore.propertystore.db.arrays
2013-11-06 10:34:54.690+0000 INFO [Cluster] Copied neostore.propertystore.db.arrays
2013-11-06 10:34:54.690+0000 INFO [Cluster] Copying neostore.propertystore.db.index
2013-11-06 10:34:54.690+0000 INFO [Cluster] Copied neostore.propertystore.db.index
2013-11-06 10:34:54.690+0000 INFO [Cluster] Copying neostore.propertystore.db.index.keys
2013-11-06 10:34:54.691+0000 INFO [Cluster] Copied neostore.propertystore.db.index.keys
2013-11-06 10:34:54.691+0000 INFO [Cluster] Copying neostore.propertystore.db.strings
2013-11-06 10:34:54.691+0000 INFO [Cluster] Copied neostore.propertystore.db.strings
2013-11-06 10:34:54.691+0000 INFO [Cluster] Copying neostore.relationshipstore.db
2013-11-06 10:34:54.692+0000 INFO [Cluster] Copied neostore.relationshipstore.db
2013-11-06 10:34:54.692+0000 INFO [Cluster] Copying neostore.relationshiptypestore.db
2013-11-06 10:34:54.692+0000 INFO [Cluster] Copied neostore.relationshiptypestore.db
2013-11-06 10:34:54.692+0000 INFO [Cluster] Copying neostore.relationshiptypestore.db.names
2013-11-06 10:34:54.693+0000 INFO [Cluster] Copied neostore.relationshiptypestore.db.names
2013-11-06 10:34:54.693+0000 INFO [Cluster] Copying nioneo_logical.log.v0
2013-11-06 10:34:54.693+0000 INFO [Cluster] Copied nioneo_logical.log.v0
2013-11-06 10:34:54.693+0000 INFO [Cluster] Copying neostore
2013-11-06 10:34:54.694+0000 INFO [Cluster] Copied neostore
2013-11-06 10:34:54.694+0000 INFO [Cluster] Done, copied 12 files
2013-11-06 10:34:55.101+0000 INFO [Cluster] Finished copying store from master
2013-11-06 10:34:55.117+0000 INFO [Cluster] Checking store consistency with master
2013-11-06 10:34:55.123+0000 INFO [Cluster] Store is consistent
2013-11-06 10:34:55.124+0000 INFO [Cluster] Catching up with master
2013-11-06 10:34:55.125+0000 INFO [Cluster] Now consistent with master
2013-11-06 10:34:55.172+0000 INFO [Cluster] ServerId 2, successfully moved to slave for master ha://localhost:6363?serverId=1
2013-11-06 10:34:55.207+0000 INFO [Cluster] Instance 2 (this server) is available as slave at ha://localhost:6364?serverId=2
2013-11-06 10:34:55.261+0000 INFO [API] Successfully started database
2013-11-06 10:34:55.265+0000 INFO [Cluster] Database available for write transactions
2013-11-06 10:34:55.318+0000 INFO [API] Starting HTTP on port :8574 with 40 threads available
2013-11-06 10:34:55.614+0000 INFO [API] Enabling HTTPS on port :8575
2013-11-06 10:34:56.256+0000 INFO [API] Mounted REST API at: /db/manage/
2013-11-06 10:34:56.261+0000 INFO [API] Mounted discovery module at [/]
2013-11-06 10:34:56.341+0000 INFO [API] Loaded server plugin "CypherPlugin"
2013-11-06 10:34:56.344+0000 INFO [API] Loaded server plugin "GremlinPlugin"
2013-11-06 10:34:56.347+0000 INFO [API] Mounted REST API at [/db/data/]
2013-11-06 10:34:56.355+0000 INFO [API] Mounted management API at [/db/manage/]
2013-11-06 10:34:56.435+0000 INFO [API] Mounted webadmin at [/webadmin]
2013-11-06 10:34:56.477+0000 INFO [API] Mounting static content at [/webadmin] from [webadmin-html]
2013-11-06 10:34:57.923+0000 INFO [API] Remote interface ready and available at [http://localhost:8574/]
2013-11-06 10:35:52.829+0000 INFO [API] Available console sessions: SHELL: class org.neo4j.server.webadmin.console.ShellSessionCreator
CYPHER: class org.neo4j.server.webadmin.console.CypherSessionCreator
GREMLIN: class org.neo4j.server.webadmin.console.GremlinSessionCreator
Thanks
There is no implications in terms of functionality Neo4j server.
But in terms of high availability is better to have more then 2 servers in cluster.
If there is a network failure between the 2 nodes and they are running but can't see each other, they will both promote themselves to master.
This may result in problems reforming the cluster when the network recovers.
Adding a 3rd node ensures that only one of the 3 nodes can ever be master.

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