3.5-MongoDB replica set test
* MongoDB replica set test
Build libraries and collections on the Lord
> use mydb # build a library
> db.acc.insert ({AccountID:1,UserName: "123", password: "123456"}) # insert data
> show dbs # View the library
View from above
> show dbs
If there is an error Error: listDatabases failed: {"note": "from execCommand", "ok": 0, "errmsg": "not master"}, you need to execute
> rs.slaveok ()
* change the weight of MongoDB replica set to simulate the main downtime
By default, the weights of the three machines are all 1. If any one of them is set to a higher weight than the others, the machine will immediately switch to the primary role, so we preset the weights of the three machines as follows: 111vis3, 112, 112, 2 and 101, respectively.
Execute on the Lord
Cfg = rs.conf () # reassign
Cfg.members [0] .priority = 3
Cfg.members [1] .priority = 2
Cfg.members [2] .priority = 1
Rs.reconfig (cfg) # reload
In that case, the second node will be the candidate primary node.
Execute iptables-I INPUT-p tcp-- dport 27017-j DROP on the host
Disadvantages: mongodb can automatically switch between master and slave, but the client cannot automatically switch to the new master. You need to switch manually.
When the original master goes down, the data written by the original master will also be synchronized to the new master before the new master is restored.
