MongoDB副本集调整节点-51CTO.COM

MongoDB的副本集（Replica Set）是一个高可用性、可扩展性和冗余性的数据库解决方案。它能够确保数据库的高可用性，同时保障了数据的安全性。在本文中，我们将探讨如何在一个已经包含三个数据节点的副本集集群中，添加一个仲裁节点，并同时删除原先的一个数据节点。

1、副本集的基本概念

MongoDB副本集由多个数据节点+若干个仲裁节点（可以没有）组成，其中一个数据节点被选举为主节点(Primary），其余节点为次要节点（Secondary）。在故障时，副本集会自动进行主节点的切换，确保服务的高可用性。副本集中的仲裁节点（Arbiter）不存储数据，仅用于选举过程，帮助副本集进行决策。

例如，当前配置一个3节点的数据节点集群，组件集群命令如下：

> use admin
> rs.initiate( {_id: "test1",members: [{ _id: 0, host: "192.168.122.36:27017" },{ _id: 1, host: "192.168.122.36:27018" },{ _id: 2, host: "192.168.122.36:27019" } ] })1.
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查看状态：

test1:PRIMARY> use admin
switched to db admin
test1:PRIMARY> rs.status()
{
        "set" : "test1",
        "date" : ISODate("2023-10-23T02:31:02.345Z"),
        "myState" : 1,
        "term" : NumberLong(1),
        "syncingTo" : "",
        "syncSourceHost" : "",
        "syncSourceId" : -1,
        "heartbeatIntervalMillis" : NumberLong(2000),
        "majorityVoteCount" : 2,
        "writeMajorityCount" : 2,
        "optimes" : {
                "lastCommittedOpTime" : {
                        "ts" : Timestamp(1698028254, 1),
                        "t" : NumberLong(1)
                },
                "lastCommittedWallTime" : ISODate("2023-10-23T02:30:54.919Z"),
                "readConcernMajorityOpTime" : {
                        "ts" : Timestamp(1698028254, 1),
                        "t" : NumberLong(1)
                },
                "readConcernMajorityWallTime" : ISODate("2023-10-23T02:30:54.919Z"),
                "appliedOpTime" : {
                        "ts" : Timestamp(1698028254, 1),
                        "t" : NumberLong(1)
                },
                "durableOpTime" : {
                        "ts" : Timestamp(1698028254, 1),
                        "t" : NumberLong(1)
                },
                "lastAppliedWallTime" : ISODate("2023-10-23T02:30:54.919Z"),
                "lastDurableWallTime" : ISODate("2023-10-23T02:30:54.919Z")
        },
        "lastStableRecoveryTimestamp" : Timestamp(1698028224, 3),
        "lastStableCheckpointTimestamp" : Timestamp(1698028224, 3),
        "electionCandidateMetrics" : {
                "lastElectionReason" : "electionTimeout",
                "lastElectionDate" : ISODate("2023-10-23T02:30:24.838Z"),
                "electionTerm" : NumberLong(1),
                "lastCommittedOpTimeAtElection" : {
                        "ts" : Timestamp(0, 0),
                        "t" : NumberLong(-1)
                },
                "lastSeenOpTimeAtElection" : {
                        "ts" : Timestamp(1698028214, 1),
                        "t" : NumberLong(-1)
                },
                "numVotesNeeded" : 2,
                "priorityAtElection" : 1,
                "electionTimeoutMillis" : NumberLong(10000),
                "numCatchUpOps" : NumberLong(0),
                "newTermStartDate" : ISODate("2023-10-23T02:30:24.912Z"),
                "wMajorityWriteAvailabilityDate" : ISODate("2023-10-23T02:30:25.497Z")
        },
        "members" : [
                {
                        "_id" : 0,
                        "name" : "192.168.122.36:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 183,
                        "optime" : {
                                "ts" : Timestamp(1698028254, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T02:30:54Z"),
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "could not find member to sync from",
                        "electionTime" : Timestamp(1698028224, 1),
                        "electionDate" : ISODate("2023-10-23T02:30:24Z"),
                        "configVersion" : 1,
                        "self" : true,
                        "lastHeartbeatMessage" : ""
                },
                {
                        "_id" : 1,
                        "name" : "192.168.122.36:27018",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 47,
                        "optime" : {
                                "ts" : Timestamp(1698028254, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1698028254, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T02:30:54Z"),
                        "optimeDurableDate" : ISODate("2023-10-23T02:30:54Z"),
                        "lastHeartbeat" : ISODate("2023-10-23T02:31:00.889Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T02:31:01.443Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "192.168.122.36:27017",
                        "syncSourceHost" : "192.168.122.36:27017",
                        "syncSourceId" : 0,
                        "infoMessage" : "",
                        "configVersion" : 1
                },
                {
                        "_id" : 2,
                        "name" : "192.168.122.36:27019",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 47,
                        "optime" : {
                                "ts" : Timestamp(1698028254, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1698028254, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T02:30:54Z"),
                        "optimeDurableDate" : ISODate("2023-10-23T02:30:54Z"),
                        "lastHeartbeat" : ISODate("2023-10-23T02:31:00.890Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T02:31:01.446Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "192.168.122.36:27017",
                        "syncSourceHost" : "192.168.122.36:27017",
                        "syncSourceId" : 0,
                        "infoMessage" : "",
                        "configVersion" : 1
                }
        ],
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1698028254, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1698028254, 1)
}1.
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此时可以用一个程序验证集群的可用情况：

from pymongo import MongoClient
from pymongo.errors import ConnectionFailure


# MongoDB副本集的连接信息
replica_set = "test1"
mongo_host = ["192.168.122.36:27017", "192.168.122.36:27018", "192.168.122.36:27019"]  # 主机和端口号列表


# 尝试连接MongoDB副本集
try:
    client = MongoClient(mongo_host, replicaSet=replica_set, serverSelectinotallow=5000)
    db = client["testdb"]
    print("Successfully connected to MongoDB replica set.")
    collection = db['test1']
    data = {"b":2}
    result = collection.insert_one(data)




except ConnectionFailure:
    print("Failed to connect to MongoDB replica set. Please check your connection settings.")1.
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运行结果如下：

查看数据库中运行结果：

2、添加节点

要添加一个仲裁节点，我们需要在现有副本集中的任一节点上执行如下操作：

rs.add( { host: "IP:PORT", arbiterOnly:true } )1.

执行这个命令后，MongoDB将会在副本集中添加一个仲裁节点，增加了选主的稳定性，同时不会增加数据存储的压力。具体实际案例如下

test1:PRIMARY> use  admin
switched to db admin
test1:PRIMARY> rs.add( { host: "192.168.122.36:27020", arbiterOnly:true } )
{
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1698030806, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1698030806, 1)
}
test1:PRIMARY> rs.status();
{
        "set" : "test1",
        "date" : ISODate("2023-10-23T03:13:32.511Z"),
        "myState" : 1,
        "term" : NumberLong(1),
        "syncingTo" : "",
        "syncSourceHost" : "",
        "syncSourceId" : -1,
        "heartbeatIntervalMillis" : NumberLong(2000),
        "majorityVoteCount" : 3,
        "writeMajorityCount" : 3,
        "optimes" : {
                "lastCommittedOpTime" : {
                        "ts" : Timestamp(1698030806, 1),
                        "t" : NumberLong(1)
                },
                "lastCommittedWallTime" : ISODate("2023-10-23T03:13:26.379Z"),
                "readConcernMajorityOpTime" : {
                        "ts" : Timestamp(1698030806, 1),
                        "t" : NumberLong(1)
                },
                "readConcernMajorityWallTime" : ISODate("2023-10-23T03:13:26.379Z"),
                "appliedOpTime" : {
                        "ts" : Timestamp(1698030806, 1),
                        "t" : NumberLong(1)
                },
                "durableOpTime" : {
                        "ts" : Timestamp(1698030806, 1),
                        "t" : NumberLong(1)
                },
                "lastAppliedWallTime" : ISODate("2023-10-23T03:13:26.379Z"),
                "lastDurableWallTime" : ISODate("2023-10-23T03:13:26.379Z")
        },
        "lastStableRecoveryTimestamp" : Timestamp(1698030805, 1),
        "lastStableCheckpointTimestamp" : Timestamp(1698030805, 1),
        "electionCandidateMetrics" : {
                "lastElectionReason" : "electionTimeout",
                "lastElectionDate" : ISODate("2023-10-23T02:30:24.838Z"),
                "electionTerm" : NumberLong(1),
                "lastCommittedOpTimeAtElection" : {
                        "ts" : Timestamp(0, 0),
                        "t" : NumberLong(-1)
                },
                "lastSeenOpTimeAtElection" : {
                        "ts" : Timestamp(1698028214, 1),
                        "t" : NumberLong(-1)
                },
                "numVotesNeeded" : 2,
                "priorityAtElection" : 1,
                "electionTimeoutMillis" : NumberLong(10000),
                "numCatchUpOps" : NumberLong(0),
                "newTermStartDate" : ISODate("2023-10-23T02:30:24.912Z"),
                "wMajorityWriteAvailabilityDate" : ISODate("2023-10-23T02:30:25.497Z")
        },
        "members" : [
                {
                        "_id" : 0,
                        "name" : "192.168.122.36:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 2733,
                        "optime" : {
                                "ts" : Timestamp(1698030806, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T03:13:26Z"),
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "electionTime" : Timestamp(1698028224, 1),
                        "electionDate" : ISODate("2023-10-23T02:30:24Z"),
                        "configVersion" : 2,
                        "self" : true,
                        "lastHeartbeatMessage" : ""
                },
                {
                        "_id" : 1,
                        "name" : "192.168.122.36:27018",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 2597,
                        "optime" : {
                                "ts" : Timestamp(1698030806, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1698030806, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T03:13:26Z"),
                        "optimeDurableDate" : ISODate("2023-10-23T03:13:26Z"),
                        "lastHeartbeat" : ISODate("2023-10-23T03:13:32.393Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T03:13:32.420Z"),
                        "pingMs" : NumberLong(1),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 2
                },
                {
                        "_id" : 2,
                        "name" : "192.168.122.36:27019",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 2597,
                        "optime" : {
                                "ts" : Timestamp(1698030806, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1698030806, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T03:13:26Z"),
                        "optimeDurableDate" : ISODate("2023-10-23T03:13:26Z"),
                        "lastHeartbeat" : ISODate("2023-10-23T03:13:32.393Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T03:13:32.445Z"),
                        "pingMs" : NumberLong(1),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 2
                },
                {
                        "_id" : 3,
                        "name" : "192.168.122.36:27020",
                        "health" : 1,
                        "state" : 7,
                        "stateStr" : "ARBITER",
                        "uptime" : 6,
                        "lastHeartbeat" : ISODate("2023-10-23T03:13:32.405Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T03:13:32.455Z"),
                        "pingMs" : NumberLong(4),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 2
                }
        ],
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1698030806, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1698030806, 1)
}1.
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此时修改python中程序（插入的数据），运行结果如下：

3、删除数据节点

如果你需要删除一个数据节点，首先，你要确保副本集的健康状态，然后执行如下操作来删除一个Secondary节点。

rs.remove("IP:PORT");1.

执行这个命令后，MongoDB将从副本集中移除该数据节点，副本集会重新进行选举，确保副本集的高可用性。

test1:PRIMARY> rs.remove("192.168.122.36:27019")
{
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1698038888, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1698038888, 1)
}
test1:PRIMARY> rs.status
function() {
    return db._adminCommand("replSetGetStatus");  # 选举中
}
test1:PRIMARY> rs.status()
{
        "set" : "test1",
        "date" : ISODate("2023-10-23T05:28:15.398Z"),
        "myState" : 1,
        "term" : NumberLong(1),
        "syncingTo" : "",
        "syncSourceHost" : "",
        "syncSourceId" : -1,
        "heartbeatIntervalMillis" : NumberLong(2000),
        "majorityVoteCount" : 2,
        "writeMajorityCount" : 2,
        "optimes" : {
                "lastCommittedOpTime" : {
                        "ts" : Timestamp(1698038888, 1),
                        "t" : NumberLong(1)
                },
                "lastCommittedWallTime" : ISODate("2023-10-23T05:28:08.335Z"),
                "readConcernMajorityOpTime" : {
                        "ts" : Timestamp(1698038888, 1),
                        "t" : NumberLong(1)
                },
                "readConcernMajorityWallTime" : ISODate("2023-10-23T05:28:08.335Z"),
                "appliedOpTime" : {
                        "ts" : Timestamp(1698038888, 1),
                        "t" : NumberLong(1)
                },
                "durableOpTime" : {
                        "ts" : Timestamp(1698038888, 1),
                        "t" : NumberLong(1)
                },
                "lastAppliedWallTime" : ISODate("2023-10-23T05:28:08.335Z"),
                "lastDurableWallTime" : ISODate("2023-10-23T05:28:08.335Z")
        },
        "lastStableRecoveryTimestamp" : Timestamp(1698038845, 1),
        "lastStableCheckpointTimestamp" : Timestamp(1698038845, 1),
        "electionCandidateMetrics" : {
                "lastElectionReason" : "electionTimeout",
                "lastElectionDate" : ISODate("2023-10-23T02:30:24.838Z"),
                "electionTerm" : NumberLong(1),
                "lastCommittedOpTimeAtElection" : {
                        "ts" : Timestamp(0, 0),
                        "t" : NumberLong(-1)
                },
                "lastSeenOpTimeAtElection" : {
                        "ts" : Timestamp(1698028214, 1),
                        "t" : NumberLong(-1)
                },
                "numVotesNeeded" : 2,
                "priorityAtElection" : 1,
                "electionTimeoutMillis" : NumberLong(10000),
                "numCatchUpOps" : NumberLong(0),
                "newTermStartDate" : ISODate("2023-10-23T02:30:24.912Z"),
                "wMajorityWriteAvailabilityDate" : ISODate("2023-10-23T02:30:25.497Z")
        },
        "members" : [
                {
                        "_id" : 0,
                        "name" : "192.168.122.36:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 10816,
                        "optime" : {
                                "ts" : Timestamp(1698038888, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T05:28:08Z"),
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "electionTime" : Timestamp(1698028224, 1),
                        "electionDate" : ISODate("2023-10-23T02:30:24Z"),
                        "configVersion" : 3,
                        "self" : true,
                        "lastHeartbeatMessage" : ""
                },
                {
                        "_id" : 1,
                        "name" : "192.168.122.36:27018",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 10680,
                        "optime" : {
                                "ts" : Timestamp(1698038888, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1698038888, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2023-10-23T05:28:08Z"),
                        "optimeDurableDate" : ISODate("2023-10-23T05:28:08Z"),
                        "lastHeartbeat" : ISODate("2023-10-23T05:28:14.347Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T05:28:15.388Z"),
                        "pingMs" : NumberLong(1),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 3
                },
                {
                        "_id" : 3,
                        "name" : "192.168.122.36:27020",
                        "health" : 1,
                        "state" : 7,
                        "stateStr" : "ARBITER",
                        "uptime" : 8088,
                        "lastHeartbeat" : ISODate("2023-10-23T05:28:14.342Z"),
                        "lastHeartbeatRecv" : ISODate("2023-10-23T05:28:14.369Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 3
                }
        ],
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1698038888, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1698038888, 1)
}1.
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注意：复制集将会短暂的关闭连接并进入选举，选举出一个新的主节点。接口将会自动重连。接口可能将会报错 DBClientCursor::init call() failed 。