MongoDB副本集調整節點
作者：懂點IT的耿小廚
在本文中，我們將探討如何在一個已經包含三個數據節點的副本集集群中，添加一個仲裁節點，并同時刪除原先的一個數據節點。
MongoDB的副本集（Replica Set）是一個高可用性、可擴展性和冗余性的數據庫解決方案。它能夠確保數據庫的高可用性，同時保障了數據的安全性。在本文中，我們將探討如何在一個已經包含三個數據節點的副本集集群中，添加一個仲裁節點，并同時刪除原先的一個數據節點。
1、副本集的基本概念
MongoDB副本集由多個數據節點+若干個仲裁節點（可以沒有）組成，其中一個數據節點被選舉為主節點(Primary），其余節點為次要節點（Secondary）。在故障時，副本集會自動進行主節點的切換，確保服務的高可用性。副本集中的仲裁節點（Arbiter）不存儲數據，僅用于選舉過程，幫助副本集進行決策。
例如，當前配置一個3節點的數據節點集群，組件集群命令如下：
> 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" } ] })
查看狀態：
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,
"$clusterTime" : {
"clusterTime" : Timestamp(1698028254, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1698028254, 1)
}此時可以用一個程序驗證集群的可用情況：
from pymongo import MongoClient
from pymongo.errors import ConnectionFailure
# MongoDB副本集的連接信息
replica_set = "test1"
mongo_host = ["192.168.122.36:27017", "192.168.122.36:27018", "192.168.122.36:27019"] # 主機和端口號列表
# 嘗試連接MongoDB副本集
try:
client = MongoClient(mongo_host, replicaSet=replica_set, serverSelectinotallow=5000)
db = client["testdb"]
print("Successfully connected to MongoDB replica set.")
collection = db['test1']
data = {"b":2}
result = collection.insert_one(data)
except ConnectionFailure:
print("Failed to connect to MongoDB replica set. Please check your connection settings.")運行結果如下：
查看數據庫中運行結果：
2、添加節點
要添加一個仲裁節點，我們需要在現有副本集中的任一節點上執行如下操作：
rs.add( { host: "IP:PORT", arbiterOnly:true } )執行這個命令后，MongoDB將會在副本集中添加一個仲裁節點，增加了選主的穩定性，同時不會增加數據存儲的壓力。具體實際案例如下
test1:PRIMARY> use admin
switched to db admin
test1:PRIMARY> rs.add( { host: "192.168.122.36:27020", arbiterOnly:true } )
{
"ok" : 1,
"$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,
"$clusterTime" : {
"clusterTime" : Timestamp(1698030806, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1698030806, 1)
}此時修改python中程序（插入的數據），運行結果如下：
3、刪除數據節點
如果你需要刪除一個數據節點，首先，你要確保副本集的健康狀態，然后執行如下操作來刪除一個Secondary節點。
rs.remove("IP:PORT");執行這個命令后，MongoDB將從副本集中移除該數據節點，副本集會重新進行選舉，確保副本集的高可用性。
test1:PRIMARY> rs.remove("192.168.122.36:27019")
{
"ok" : 1,
"$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"); # 選舉中
}
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)
}注意：復制集將會短暫的關閉連接并進入選舉，選舉出一個新的主節點。接口將會自動重連。接口可能將會報錯 DBClientCursor::init call() failed 。
責任編輯：姜華
來源：
數據庫干貨鋪
