Mongodb Study Notes 09, mongodb Study Notes

Mongodb Study Notes 09, mongodb Study Notes
Overview

Shard sharding divides different data into different servers.

Model

Where:
All user operations on mongodb are requested from mongs.
Configsvr is used to save a piece of data on which shard

How to use parts

Start two nodes as shard

mongd --dbpath ~/db/mongo1/databse --logpath ~/db/mongo1/log/mongo.log --port 27017 --fork --smallfilesmongd --dbpath ~/db/mongo2/databse --logpath ~/db/mongo2/log/mongo.log --port 27018 --fork --smallfiles

Start configsvr-Configsvr

mongd --dbpath ~/db/mongo3/databse --logpath ~/db/mongo3/log/mongo.log --port 27019 --fork --smallfiles --configsvr

Start mongosNote:-configdb specifies configsvr

mongos --logpath ~/db/mongo4/log/mongs.log --port 27020  --configdb 127.0.0.1:27020 --fork

Connect to mongos

mongo --port 27020

Add the preceding two nodes

sh.addShard("127.0.0.1:27017")sh.addShard("127.0.0.1:27018")

View status

sh.status()

Define sharding rulesFor example, declare that the test database can be sharded first, and then define the partitions Based on the my_id of my table.

sh.enableSharding('test')sh.shardCollection('test.my',{'my_id':1})

Sharding Principle
N documents form a "chunk" and put it on a shard first. When the chunk number on this shard is different from the chunk number on other shard, move the chunk to another shard.

Modify the chunk size: For example, to 4 m
The default chunk size is 64 MB.

use configdb.setting.save({_id:'chunksize',value:4m})

Manual pre-partitioning

In the previous sharding method, shards are based on the number of chunks, which may affect IO.
You can manually pre-create parts, for example, define my_id 0 ~ 1000 put in shard1, 1001 ~ 2000 put in shard2, 2001 ~ Put in shard3 in 3000

sh.enableSharding('test')sh.shardCollection('test.my',{'my_id':1})sh.splitAt('my',{my_id:1000})sh.splitAt('my',{my_id:2000})sh.splitAt('my',{my_id:3000})

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