Shulou(Shulou.com)05/31 Report--

In this issue, the editor will bring you about how to manage replica sets in MongoDB. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

1) diagnosis

A machine in a set of copies can use the

> db.printReplicationInfo ()

View the status of replication for the primary database.

Use

> db.printSlaveReplicationInfo ()

To check the status of replication from the database, you can check whether there is replication delay between the master and slave

2) oplog sets and changes the oplog size

Full synchronization, very time-consuming, manually resynchronize using commands:

> db.runCommand ({"resync": 1})

Use the-- oplogSize parameter to set a larger oplog size.

Assuming that the MongoDB data directory is / data/db, use the command after shutting down the mongod service on the primary node:

> rm / data/db/local.*

> mongod-oplog=8038-master

The parameter noprealloc is used when starting MongoDB to turn off space pre-allocation.

For example, to generate the filespace for 20GB, use the command:

Cd / tmp/local

For i in {0..9}

Do

Echo $I

Head-c 2146435072 / dev/zero > local.$i

Done

Then close the MongoDB master node to move the data file

Mv / data/db/local.* / safe/data

Mv / tmp/local/* / data/db/

First back up the data in the original local folder to the / safe/data directory, and then move our pre-allocated space file / tmp/local/* to the data directory / data/db/, thus completing the manual pre-allocation of oplog space.

When you restart the master node, you can set the size of the oplog to 20g. Use the following command:

Mongod-master-oplogSize=20000

3) blocking replication use

When the replication of the slave node can not keep up with the write operation of the master node, in addition to changing the size of the oplog, there is another way to solve it, that is to block the write of the master node until the slave node slowly comes up and then release the blocking. Use the command as follows:

> db.runCommand ({getLastError:1,w:2})

The value of w indicates that at least 2 servers, including the primary node, have recorded the write operation before returning the write result. The value of w can be modified, the larger the value, the more obvious the blocking, and the slower the write operation.

This is how to manage the replica set in the MongoDB shared by the editor. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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