Mongodb shared cluster consists of:

Shards: each shard needs to be deployed as a replica set, which is responsible for storing data. Multiple shards can be deployed
mongos: equivalent to routing
config servers: the configuration server of the entire cluster, which is also a replica set

The development environment can be simpler:

docker builds a simple fragment cluster

One mongos node, two shard s (each replica set has two nodes, and one node can also be used), and one configuration server (replica set has only one node)

Create network

Create a network for the whole cluster to facilitate interworking between nodes

docker network create mongo_shard_net

Start configuration server

docker run --name rs_config --network mongo_shard_net \
	-d mongo mongod --configsvr --replSet rs_config_server \
	--bind_ip_all 

Connect to the configuration database, execute rs.initiate, and configure the replica set. Note that the port number is 27019

docker exec -it rs_config mongosh --port 27019 

Note here that the configsvr attribute is true

rs.initiate(
  {
    _id : "rs_config_server",
   	configsvr: true,
    members: [
      { _id : 0, host : "rs_config:27019" }
    ]
  }
);

Create shard

Start a shard with replica set name rs_shard_g1, containing two nodes

docker run --name rs_shard_11 --network mongo_shard_net \
	-d mongo mongod --shardsvr --replSet rs_shard_g1  \
	--bind_ip_all 

docker run --name rs_shard_12 --network mongo_shard_net \
	-d mongo mongod --shardsvr --replSet rs_shard_g1  \
	--bind_ip_all 

Connect to any of these nodes and perform configuration

docker exec -it rs_shard_11 mongosh --port 27018

rs.initiate(
  {
    _id : "rs_shard_g1",
    members: [
      { _id : 0, host : "rs_shard_11:27018" },
      { _id : 1, host : "rs_shard_12:27018" }
    ]
  }
);

Start the second shard, replica set name rs_shard_g2

docker run --name rs_shard_21 --network mongo_shard_net \
	-d mongo mongod --shardsvr --replSet rs_shard_g2  \
	--bind_ip_all 
	
docker run --name rs_shard_22 --network mongo_shard_net \
	-d mongo mongod --shardsvr --replSet rs_shard_g2  \
	--bind_ip_all 

docker exec -it rs_shard_21 mongosh --port 27018

Configure second replica set

rs.initiate(
  {
    _id : "rs_shard_g2",
    members: [
      { _id : 0, host : "rs_shard_21:27018" },
      { _id : 1, host : "rs_shard_22:27018" }
    ]
  }
);

Start mongos

To start mongos, you need to specify the replica set of the configuration database

docker run --name shard_mongos --network mongo_shard_net \
	-d mongo mongos --configdb rs_config_server/rs_config:27019 \
	--bind_ip_all 

Connect mongos nodes on mongosh and add Shards

docker exec -it shard_mongos mongosh --port 27017

sh.addShard( "rs_shard_g1/rs_shard_11:27018,rs_shard_12:27018");
sh.addShard( "rs_shard_g2/rs_shard_21:27018,rs_shard_22:27018");

Enable sharding for the specified database and specify the collection to be fragmented

sh.enableSharding("somedb");
sh.shardCollection("somedb.helloDoc", { "name" : "hashed" } )

Verify slicing effect

Connect to mongos, switch to somedb and insert 1000 pieces of data

[direct: mongos] test> use somedb
switched to db somedb
[direct: mongos] somedb> for(var i = 0; i < 1000; i++) db.helloDoc.insert({age:i, name:"ly"+i})
{
  acknowledged: true,
  insertedIds: { '0': ObjectId("6198bd3eea75ef2ba111591a") }
}

Connect to two shard s respectively, and you can see that some data is stored respectively

rs_shard_g1 [direct: primary] somedb> db.helloDoc.count()
508

rs_shard_g2 [direct: primary] somedb> db.helloDoc.count()
492
rs_shard_g2 [direct: primary] somedb>

be careful

• There can also be only one replica set of the local test shard, and the slave node of the default replica set cannot directly connect to read data, so it is necessary to
• If the host machine wants to access the database, it should at least configure mongos port mapping; The default port of the configuration node is 27019, the default port of the shard node is 27018, and the default port of mongos is 27017

  -p 27017:27017
  

• You can also mount local folders to place database files as needed

   -v /my/own/datadir:/data/db
  

• For more usage of mongo image, please refer to dockerhub official document