一、HA高可用集群搭建
版本采用的是neo4j-enterprise-3.5.3-unix.tar.gz
1.1、集群ip規划
192.168.56.10 neo4j-node1
192.168.56.11 neo4j-node2
192.168.56.12 neo4j-node3
192.168.56.13 neo4j-node4
192.168.56.14 neo4j-node5
1.2、免密登錄配置
$ ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa #生成秘鑰
$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys #cp公鑰到驗證文件中
$ chmod 0600 ~/.ssh/authorized_keys
如上做免密登錄，這里只做了neo4j-node1 免密登錄其他節點
這里做不做免密，都可以，我做免密主要是為了方便，不需要一直輸入密碼，在正式環境中還是不用免密的好
1.3、修改主機名配置
/etc/hosts配置
192.168.56.10 neo4j-node1
192.168.56.11 neo4j-node2
192.168.56.12 neo4j-node3
192.168.56.13 neo4j-node4
/etc/sysconfig/network配置
hostname neo4j-node1
重啟網卡
$ systemctl restart network
如上內容完成之后退出重新登錄，修改主機名的設置就能生效
1.4、neo4j文件配置
官方配置參數詳細列表
https://neo4j.com/docs/operations-manual/current/ha-cluster/tutorial/setup-cluster/
官方HA配置模式
https://neo4j.com/docs/operations-manual/current/ha-cluster/tutorial/setup-cluster/
分別在三台不同機器上進行修改配置文件，conf/neo4j.conf
neo4j-node1
# Unique server id for this Neo4j instance
# can not be negative id and must be unique
ha.server_id=1
# List of other known instances in this cluster
ha.initial_hosts=neo4j-node1:5001,neo4j-node2:5001,neo4j-node3:5001
# Alternatively, use IP addresses:
#ha.initial_hosts=192.168.0.20:5001,192.168.0.21:5001,192.168.0.22:5001
# HA - High Availability
# SINGLE - Single mode, default.
dbms.mode=HA
# HTTP Connector
dbms.connector.http.enabled=true
dbms.connector.http.listen_address=:7474
neo4j-node2
# Unique server id for this Neo4j instance
# can not be negative id and must be unique
ha.server_id=2
# List of other known instances in this cluster
ha.initial_hosts=neo4j-node1:5001,neo4j-node2:5001,neo4j-node3:5001
# Alternatively, use IP addresses:
#ha.initial_hosts=192.168.0.20:5001,192.168.0.21:5001,192.168.0.22:5001
# HA - High Availability
# SINGLE - Single mode, default.
dbms.mode=HA
# HTTP Connector
dbms.connector.http.enabled=true
dbms.connector.http.listen_address=:7474
neo4j-node3
# Unique server id for this Neo4j instance
# can not be negative id and must be unique
ha.server_id=3
# List of other known instances in this cluster
ha.initial_hosts=neo4j-node1:5001,neo4j-node2:5001,neo4j-node3:5001
# Alternatively, use IP addresses:
#ha.initial_hosts=192.168.0.20:5001,192.168.0.21:5001,192.168.0.22:5001
# HA - High Availability
# SINGLE - Single mode, default.
dbms.mode=HA
# HTTP Connector
dbms.connector.http.enabled=true
dbms.connector.http.listen_address=:7474
根據上面官方給出的配置，啟動的時候會報錯的，報錯信息如下：
logs/neo4j.log
2019-03-07 03:43:22.176+0000 INFO ======== Neo4j 3.5.3 ========
2019-03-07 03:43:22.194+0000 INFO Starting...
2019-03-07 03:43:24.254+0000 INFO Write transactions to database disabled
2019-03-07 03:43:24.662+0000 INFO Initiating metrics...
2019-03-07 03:43:26.000+0000 INFO Attempting to join cluster of [neo4j-node1:5001, neo4j-node2:5001, neo4j-node3:5001]
2019-03-07 03:44:56.174+0000 ERROR Failed to start Neo4j: Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase@1e141e42' was successfully initialized, but failed to start. Please see the attached cause exception "Conversation-response mapping:
{1/13#=ResponseFuture{conversationId='1/13#', initiatedByMessageType=join, response=null}}". Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase@1e141e42' was successfully initialized, but failed to start. Please see the attached cause exception "Conversation-response mapping:
{1/13#=ResponseFuture{conversationId='1/13#', initiatedByMessageType=join, response=null}}".
org.neo4j.server.ServerStartupException: Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase@1e141e42' was successfully initialized, but failed to start. Please see the attached cause exception "Conversation-response mapping:
{1/13#=ResponseFuture{conversationId='1/13#', initiatedByMessageType=join, response=null}}".
at org.neo4j.server.exception.ServerStartupErrors.translateToServerStartupError(ServerStartupErrors.java:45)
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:184)
at org.neo4j.server.ServerBootstrapper.start(ServerBootstrapper.java:123)
at org.neo4j.server.ServerBootstrapper.start(ServerBootstrapper.java:90)
at com.neo4j.server.enterprise.CommercialEntryPoint.main(CommercialEntryPoint.java:22)
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.server.database.LifecycleManagingDatabase@1e141e42' was successfully initialized, but failed to start. Please see the attached cause exception "Conversation-response mapping:
{1/13#=ResponseFuture{conversationId='1/13#', initiatedByMessageType=join, response=null}}".
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:473)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:111)
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:177)
... 3 more
如上錯誤說明三台機器之間訪問出現了問題，不能相互感知，不能加入集群，還需要增加下面配置
#在neo4j-node1 neo4j.conf中添加
dbms.connectors.default_listen_address=192.168.56.10
dbms.connector.bolt.enabled=true
dbms.connector.bolt.listen_address=:7687
#在neo4j-node2 neo4j.conf中添加
dbms.connectors.default_listen_address=192.168.56.11
dbms.connector.bolt.enabled=true
dbms.connector.bolt.listen_address=:7687
#在neo4j-node3 neo4j.conf中添加
dbms.connectors.default_listen_address=192.168.56.12
dbms.connector.bolt.enabled=true
dbms.connector.bolt.listen_address=:7687
如上配置完成之后啟動相關機器，啟動沒有順序區別，依次進行啟動
$ neo4j-node1$ ./bin/neo4j start
$ neo4j-node2$ ./bin/neo4j start
$ neo4j-node3$ ./bin/neo4j start
2019-03-07 06:01:26.887+0000 INFO ======== Neo4j 3.5.3 ========
2019-03-07 06:01:26.892+0000 INFO Starting...
2019-03-07 06:01:28.897+0000 INFO Write transactions to database disabled
2019-03-07 06:01:29.255+0000 INFO Initiating metrics...
2019-03-07 06:01:30.911+0000 INFO Attempting to join cluster of [neo4j-node1:5001, neo4j-node2:5001, neo4j-node3:5001]
2019-03-07 06:01:42.993+0000 INFO Could not join cluster of [neo4j-node1:5001, neo4j-node2:5001, neo4j-node3:5001]
2019-03-07 06:01:42.993+0000 INFO Creating new cluster with name [neo4j.ha]...
2019-03-07 06:01:42.998+0000 INFO Instance 1 (this server) entered the cluster
2019-03-07 06:01:43.012+0000 INFO Instance 1 (this server) was elected as coordinator
2019-03-07 06:01:43.094+0000 INFO I am 1, moving to master
2019-03-07 06:01:43.170+0000 INFO Instance 1 (this server) was elected as coordinator
2019-03-07 06:01:43.256+0000 INFO I am 1, successfully moved to master
2019-03-07 06:01:43.264+0000 INFO Instance 1 (this server) is available as master at ha://192.168.56.10:6001?serverId=1 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:43.288+0000 INFO Sending metrics to CSV file at /root/neo4j-e-3.5.3/metrics
2019-03-07 06:01:43.300+0000 INFO Database available for write transactions
2019-03-07 06:01:43.357+0000 INFO Instance 1 (this server) is available as backup at backup://127.0.0.1:6362 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:43.787+0000 INFO Instance 2 joined the cluster
2019-03-07 06:01:43.893+0000 INFO Instance 3 joined the cluster
2019-03-07 06:01:43.905+0000 INFO Instance 1 (this server) was elected as coordinator
2019-03-07 06:01:43.955+0000 INFO Instance 1 (this server) is available as master at ha://192.168.56.10:6001?serverId=1 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:43.973+0000 INFO Instance 1 (this server) is available as backup at backup://127.0.0.1:6362 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:44.082+0000 INFO Bolt enabled on 192.168.56.10:7687.
2019-03-07 06:01:44.703+0000 INFO Instance 2 is available as slave at ha://192.168.56.11:6001?serverId=2 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:46.444+0000 WARN Server thread metrics not available (missing neo4j.server.threads.jetty.all)
2019-03-07 06:01:46.455+0000 WARN Server thread metrics not available (missing neo4j.server.threads.jetty.idle)
2019-03-07 06:01:46.979+0000 INFO Started.
2019-03-07 06:01:47.403+0000 INFO Mounted REST API at: /db/manage
2019-03-07 06:01:47.514+0000 INFO Server thread metrics have been registered successfully
2019-03-07 06:01:49.508+0000 INFO Remote interface available at http://localhost:7474/
2019-03-07 06:01:49.895+0000 INFO Instance 1 (this server) was elected as coordinator
2019-03-07 06:01:49.923+0000 INFO Instance 1 (this server) is available as master at ha://192.168.56.10:6001?serverId=1 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:49.971+0000 INFO Instance 1 (this server) is available as backup at backup://127.0.0.1:6362 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:49.992+0000 INFO Instance 2 is available as slave at ha://192.168.56.11:6001?serverId=2 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:50.222+0000 INFO Instance 3 is available as slave at ha://192.168.56.12:6001?serverId=3 with StoreId{creationTime=1551928418454, randomId=5747408418777003467, storeVersion=16094931155187206, upgradeTime=1551928418454, upgradeId=1}
2019-03-07 06:01:50.872+0000 WARN The client is unauthorized due to authentication failure.
如上日志中可以看出來，機器分別都已經加入到集群中，訪問集群
如上圖，點擊之后查詢出集群的詳細信息，可以看到配置的ha.server_id機器分別都加入集群中，並且可以看出那台機器為master節點
說明配置成功，隨便訪問任何一台機器都能夠提供服務，可以自己新建一個node或者relation分別在不同的機器提供的訪問接口查看是否創建成功，數據是否同步成功
二、Causal Clustering（因果集群）搭建
官方文檔：https://neo4j.com/docs/operations-manual/current/
2.1、因果集群架構和集群規划
如上圖所示就是因果集群的架構圖，架構中主要分為兩種角色類型，一種是Replica Servers和Core Servers兩種角色，下面對兩種角色進行介紹：
Core Servers：此角色是邏輯划分，在該系統角色中由多台物理實體機組成，主要提供數據的存儲和數據一致性，事務處理等功能，同時在Core集群中是支持HA的，所以有Leader和Follower兩中角色，這兩種角色能夠互相進行切換，Leader角色主要提供管理集群的作用，存儲元數據信息和處理集群心跳、數據分發等工作，Core節點是能夠進行writer and read，Core集群中是能夠進行集群拓撲的
Replica Servers：該角色系統中的節點主要提供的是對數據的查詢，他能提供查詢任意在Core集群中的圖數據，這里的數據是由Core集群發送給Replica集群的副本，所以在Replica中，數據丟失不會影響到整個集群的使用，他主要的作用就是擴展集群的工作負載例如查詢等
因果一致性：neo4j采用的是因果一致性來保證數據的一致性，使用到的協議是Raft協議來復制所有事務來實現數據的安全和數據一致性；這和其他的分布式系統中采用的Paxos協議不同
Raft協議原理解釋https://www.jianshu.com/p/8e4bbe7e276c
官方提供的一個應用程序對圖進行讀寫操作的一個流程圖，這里Core和Read Replicas都是集群的方式進行展示
在上面的圖中能夠看出數據是怎么流動的，Core是能夠寫和讀，reads是只能被讀的，但是Core只能是Leader提供寫操作，否則報錯如下：
Neo.ClientError.Cluster.NotALeader: No write operations are allowed directly on this database. Writes must pass through the leader. The role of this server is: FOLLOWER
本次的搭建中的節點規划是:
neo4j-node2 core
neo4j-node3 core
neo4j-node4 core
neo4j-node5 add core OR add Read
2.2、因果集群配置
因果集群的Core集群配置
neo4j-node2
dbms.connectors.default_listen_address=192.168.56.11
dbms.connectors.default_advertised_address=192.168.56.11
dbms.mode=CORE
causal_clustering.minimum_core_cluster_size_at_formation=3
causal_clustering.minimum_core_cluster_size_at_runtime=3
causal_clustering.discovery_members=192.168.56.11:5000,192.168.56.12:5000,192.168.56.13:5000
neo4j-node3
dbms.connectors.default_listen_address=192.168.56.12
dbms.connectors.default_advertised_address=192.168.56.12
dbms.mode=CORE
causal_clustering.minimum_core_cluster_size_at_formation=3
causal_clustering.minimum_core_cluster_size_at_runtime=3
causal_clustering.discovery_members=192.168.56.11:5000,192.168.56.13:5000,192.168.56.13:5000
neo4j-node4
dbms.connectors.default_listen_address=192.168.56.13
dbms.connectors.default_advertised_address=192.168.56.13
dbms.mode=CORE
causal_clustering.minimum_core_cluster_size_at_formation=3
causal_clustering.minimum_core_cluster_size_at_runtime=3
causal_clustering.discovery_members=192.168.56.11:5000,192.168.56.12:5000,192.168.56.13:5000
如上內容配置完成之后依次啟動集群中core節點
$ neo4j-node2$ ./bin/neo4j start
$ neo4j-node3$ ./bin/neo4j start
$ neo4j-node4$ ./bin/neo4j start
啟動完成之后登陸到響應的web界面，然后查詢集群詳情就能看出來相關集群的配置是否正確
2.3、添加新的Core節點進入集群
添加新的節點到集群中，這里使用新的節點neo4j-node5來進行操作
conf/neo4j.conf
dbms.connectors.default_listen_address=192.168.56.14
dbms.connectors.default_advertised_address=192.168.56.14
dbms.mode=CORE
causal_clustering.minimum_core_cluster_size_at_formation=3
causal_clustering.minimum_core_cluster_size_at_runtime=3
causal_clustering.discovery_members=192.168.56.11:5000,192.168.56.12:5000,192.168.56.13:5000
在配置新的機器到Core集群中作為Core節點時配置基本和上面的一樣，但是需要注意的是causal_clustering.discovery_members這個配置，這個配置還是上面的配置，並沒有將目前的機器加入，是因為當前的機器是新加入的，不是永久存在的集群，當不使用的時候可以將當前機器剔除集群，如果一開始就規划好了集群，那么開始就配置完整
neo4j-node5配置完成之后，啟動該節點，啟動完成之后需要登錄當前節點，登錄完成之后查看當前節點是否加入集群中，查看方式和上面的查看方式相同，或者可以看日志，是否加入集群，並且擁有集群id
啟動
$ neo4j-node5$ ./bin/neo4j start
2.4、添加新的Replicas節點進入集群
下面是添加Replicas角色節點，在集群中他是可有可無的，沒有他集群也能夠正常的工作，有他的存在是擴展了查詢和過程分析能夠多了一些節點來進行處理，但是該節點的數據均是來源於Core節點
還是用neo4j-node5來進行試驗
conf/neo4j.conf配置
dbms.connectors.default_listen_address=192.168.56.14
dbms.mode=READ_REPLICA
causal_clustering.discovery_members=192.168.56.11:5000,192.168.56.12:5000,192.168.56.13:5000
該節點不參與集群中的Leader選舉所以配置相對簡單
修改完成之后啟動
$ neo4j-node5$ ./bin/neo4j start
啟動完成之后如果是新節點需要先訪問當前的web服務設置好密碼之后，接着可以到集群中任意節點查詢節點是否添加到集群中
如上圖所示，說明成功添加到集群中
三、通過驅動（driver）訪問neo4j 因果集群方式
pom.xml
<dependency>
<groupId>org.neo4j.driver</groupId>
<artifactId>neo4j-java-driver</artifactId>
<version>1.7.2</version>
</dependency>
訪問實例：
public Driver createDriver() throws URISyntaxException {
List<URI> rout = new ArrayList<>();
rout.add(new URI("bolt+routing://192.168.8.106"));
rout.add(new URI("bolt+routing://192.168.8.107"));
rout.add(new URI("bolt+routing://192.168.8.108"));
Driver driver = GraphDatabase.routingDriver(rout,AuthTokens.basic("neo4j","123456"),null);
return driver;
}
Driver訪問集群：在訪問因果集群的時候設置好集群的相關訪問地址，驅動能夠自己判斷當前訪問應該走那台機器，負載由集群自己實現，程序不用關心集群機器可用性，驅動會自己發現集群可用性，並且選擇能夠操作的機器進行操作！
web方式訪問：上面的方式是通過代碼的方式進行訪問，這里是通過web進行訪問，在web訪問的時候寫數據只能在leader節點，查詢數據在所有節點都能進行查詢，這里和上面的驅動訪問是有區別的
四、多群集群搭建
注：這里暫時省略了，目前還沒使用，一般的公司也用不到，而且還是收費的