副本集中有一个重要的概念“大多数”，意思是说，选择主节点需要大多数决定（本人亲自做了实验）
步骤：
1.开启副本集（如果没有配置好 副本集的 亲参考我的上篇文章 https://www.cnblogs.com/anxbb/p/9482304.html）
2.运行 rs.status(),查看状态
{
"set" : "haibin",
"date" : ISODate("2018-08-16T03:18:05.461Z"),
"myState" : 1,
"term" : NumberLong(9),
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1534389483, 1),
"t" : NumberLong(9)
},
"appliedOpTime" : {
"ts" : Timestamp(1534389483, 1),
"t" : NumberLong(9)
},
"durableOpTime" : {
"ts" : Timestamp(1534389483, 1),
"t" : NumberLong(9)
}
},
"members" : [
{
"_id" : 0,
"name" : "127.0.0.1:27017",
"health" : 1.0,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 788,
"optime" : {
"ts" : Timestamp(1534389483, 1),
"t" : NumberLong(9)
},
"optimeDate" : ISODate("2018-08-16T03:18:03.000Z"),
"electionTime" : Timestamp(1534389270, 1),
"electionDate" : ISODate("2018-08-16T03:14:30.000Z"),
"configVersion" : 2,
"self" : true
},
{
"_id" : 1,
"name" : "127.0.0.1:27018",
"health" : 1.0,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 6,
"optime" : {
"ts" : Timestamp(1534389483, 1),
"t" : NumberLong(9)
},
"optimeDurable" : {
"ts" : Timestamp(1534389483, 1),
"t" : NumberLong(9)
},
"optimeDate" : ISODate("2018-08-16T03:18:03.000Z"),
"optimeDurableDate" : ISODate("2018-08-16T03:18:03.000Z"),
"lastHeartbeat" : ISODate("2018-08-16T03:18:04.903Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:18:03.874Z"),
"pingMs" : NumberLong(0),
"syncingTo" : "127.0.0.1:27017",
"configVersion" : 2
},
{
"_id" : 2,
"name" : "127.0.0.1:27019",
"health" : 1.0,
"state" : 7,
"stateStr" : "ARBITER",
"uptime" : 221,
"lastHeartbeat" : ISODate("2018-08-16T03:18:04.603Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:18:04.103Z"),
"pingMs" : NumberLong(0),
"configVersion" : 2
}
],
"ok" : 1.0
}
3.试着关闭 27017这个端口 然后在运行 rs.status()，结果如下
{
"set" : "haibin",
"date" : ISODate("2018-08-16T03:20:21.708Z"),
"myState" : 1,
"term" : NumberLong(10),
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1534389603, 1),
"t" : NumberLong(9)
},
"appliedOpTime" : {
"ts" : Timestamp(1534389616, 1),
"t" : NumberLong(10)
},
"durableOpTime" : {
"ts" : Timestamp(1534389616, 1),
"t" : NumberLong(10)
}
},
"members" : [
{
"_id" : 0,
"name" : "127.0.0.1:27017",
"health" : 0.0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDurable" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDate" : ISODate("1970-01-01T00:00:00.000Z"),
"optimeDurableDate" : ISODate("1970-01-01T00:00:00.000Z"),
"lastHeartbeat" : ISODate("2018-08-16T03:20:21.009Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:20:02.982Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "����Ŀ�������������ܾ��������ӡ�",
"configVersion" : -1
},
{
"_id" : 1,
"name" : "127.0.0.1:27018",
"health" : 1.0,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 144,
"optime" : {
"ts" : Timestamp(1534389616, 1),
"t" : NumberLong(10)
},
"optimeDate" : ISODate("2018-08-16T03:20:16.000Z"),
"infoMessage" : "could not find member to sync from",
"electionTime" : Timestamp(1534389614, 1),
"electionDate" : ISODate("2018-08-16T03:20:14.000Z"),
"configVersion" : 2,
"self" : true
},
{
"_id" : 2,
"name" : "127.0.0.1:27019",
"health" : 1.0,
"state" : 7,
"stateStr" : "ARBITER",
"uptime" : 142,
"lastHeartbeat" : ISODate("2018-08-16T03:20:20.912Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:20:20.345Z"),
"pingMs" : NumberLong(0),
"configVersion" : 2
}
],
"ok" : 1.0
}
我们发现现在端口 27018 变成了主节点，27017 为断开状态
4.试着关闭 27019 这个端口 然后在运行 rs.status()，结果如下
/* 1 */
{
"set" : "haibin",
"date" : ISODate("2018-08-16T03:21:34.102Z"),
"myState" : 1,
"term" : NumberLong(10),
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1534389603, 1),
"t" : NumberLong(9)
},
"appliedOpTime" : {
"ts" : Timestamp(1534389686, 1),
"t" : NumberLong(10)
},
"durableOpTime" : {
"ts" : Timestamp(1534389686, 1),
"t" : NumberLong(10)
}
},
"members" : [
{
"_id" : 0,
"name" : "127.0.0.1:27017",
"health" : 0.0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDurable" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDate" : ISODate("1970-01-01T00:00:00.000Z"),
"optimeDurableDate" : ISODate("1970-01-01T00:00:00.000Z"),
"lastHeartbeat" : ISODate("2018-08-16T03:21:31.166Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:20:02.982Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "����Ŀ�������������ܾ��������ӡ�",
"configVersion" : -1
},
{
"_id" : 1,
"name" : "127.0.0.1:27018",
"health" : 1.0,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 217,
"optime" : {
"ts" : Timestamp(1534389686, 1),
"t" : NumberLong(10)
},
"optimeDate" : ISODate("2018-08-16T03:21:26.000Z"),
"infoMessage" : "could not find member to sync from",
"electionTime" : Timestamp(1534389614, 1),
"electionDate" : ISODate("2018-08-16T03:20:14.000Z"),
"configVersion" : 2,
"self" : true
},
{
"_id" : 2,
"name" : "127.0.0.1:27019",
"health" : 0.0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"lastHeartbeat" : ISODate("2018-08-16T03:21:31.966Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:21:25.358Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "����Ŀ�������������ܾ��������ӡ�",
"configVersion" : -1
}
],
"ok" : 1.0
}
发现现在 27018这个端口还是主节点，那么我们过一会在运行 rs.tatus(),在看下结果
/* 1 */
{
"set" : "haibin",
"date" : ISODate("2018-08-16T03:23:20.966Z"),
"myState" : 2,
"term" : NumberLong(10),
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1534389603, 1),
"t" : NumberLong(9)
},
"appliedOpTime" : {
"ts" : Timestamp(1534389686, 1),
"t" : NumberLong(10)
},
"durableOpTime" : {
"ts" : Timestamp(1534389686, 1),
"t" : NumberLong(10)
}
},
"members" : [
{
"_id" : 0,
"name" : "127.0.0.1:27017",
"health" : 0.0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDurable" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDate" : ISODate("1970-01-01T00:00:00.000Z"),
"optimeDurableDate" : ISODate("1970-01-01T00:00:00.000Z"),
"lastHeartbeat" : ISODate("2018-08-16T03:23:20.305Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:20:02.982Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "����Ŀ�������������ܾ��������ӡ�",
"configVersion" : -1
},
{
"_id" : 1,
"name" : "127.0.0.1:27018",
"health" : 1.0,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 323,
"optime" : {
"ts" : Timestamp(1534389686, 1),
"t" : NumberLong(10)
},
"optimeDate" : ISODate("2018-08-16T03:21:26.000Z"),
"infoMessage" : "could not find member to sync from",
"configVersion" : 2,
"self" : true
},
{
"_id" : 2,
"name" : "127.0.0.1:27019",
"health" : 0.0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"lastHeartbeat" : ISODate("2018-08-16T03:23:13.088Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:21:25.358Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "����Ŀ�������������ܾ��������ӡ�",
"configVersion" : -1
}
],
"ok" : 1.0
}
发现此时的27018 已经不是主节点了，变成了备份节点。
经过上面的实验可以让大家知道，副本集的大多数概念，一定要记住。
最后我们再次重启一个节点（27019）过一段时间按发现 27018又变回了主节点
/* 1 */
{
"set" : "haibin",
"date" : ISODate("2018-08-16T03:25:34.676Z"),
"myState" : 1,
"term" : NumberLong(11),
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1534389603, 1),
"t" : NumberLong(9)
},
"appliedOpTime" : {
"ts" : Timestamp(1534389931, 1),
"t" : NumberLong(11)
},
"durableOpTime" : {
"ts" : Timestamp(1534389931, 1),
"t" : NumberLong(11)
}
},
"members" : [
{
"_id" : 0,
"name" : "127.0.0.1:27017",
"health" : 0.0,
"state" : 8,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDurable" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"optimeDate" : ISODate("1970-01-01T00:00:00.000Z"),
"optimeDurableDate" : ISODate("1970-01-01T00:00:00.000Z"),
"lastHeartbeat" : ISODate("2018-08-16T03:25:31.632Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:20:02.982Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "����Ŀ�������������ܾ��������ӡ�",
"configVersion" : -1
},
{
"_id" : 1,
"name" : "127.0.0.1:27018",
"health" : 1.0,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 457,
"optime" : {
"ts" : Timestamp(1534389931, 1),
"t" : NumberLong(11)
},
"optimeDate" : ISODate("2018-08-16T03:25:31.000Z"),
"infoMessage" : "could not find member to sync from",
"electionTime" : Timestamp(1534389928, 1),
"electionDate" : ISODate("2018-08-16T03:25:28.000Z"),
"configVersion" : 2,
"self" : true
},
{
"_id" : 2,
"name" : "127.0.0.1:27019",
"health" : 1.0,
"state" : 7,
"stateStr" : "ARBITER",
"uptime" : 7,
"lastHeartbeat" : ISODate("2018-08-16T03:25:34.640Z"),
"lastHeartbeatRecv" : ISODate("2018-08-16T03:25:32.362Z"),
"pingMs" : NumberLong(0),
"configVersion" : 2
}
],
"ok" : 1.0
}
截取书上的文字说明，说明下为什么要使用这样的规则：
