MongoDB Shard (sharding) feature implementation

MongoDB Shard Overview Shards

In MongoDB there is another cluster, that is, the Shard technology, can meet the requirements of a large number of MONGODB data volume growth.

When MongoDB stores massive amounts of data, a machine may not be enough to store data, or it may not be sufficient to provide acceptable read and write throughput. At this point, we can divide the data on multiple machines so that the database system can store and process more data.

Why use Shards

• Copy all write operations to the master node

• Deferred sensitive data is queried on the master node

• A single replica set is limited to 12 nodes

• When the volume of requests is large, there is insufficient memory.

• Insufficient Local Disk

• Vertical expansion is expensive

MongoDB Shard

Shows the use of shard cluster structure distribution in MongoDB:

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There are three main components as described below:

• Shard:

  Used to store actual blocks of data, a Shard server role in the actual production environment can be assumed by several machines, one replica set, to prevent a single point of failure of the host

• Config Server:

  The Mongod instance, which stores the entire clustermetadata, including chunk information.

• Query Routers:

  Front-end routing, which the client accesses, and makes the entire cluster look like a single database, the front-end application can be used transparently.

Shard Instance

192.168.1.100:mongos

192.168.1.110:config Server

192.168.1.101:shard1

192.168.1.102:shard2

The MongoDB database is installed on all four of the above hosts.

I. Configuring CONFIG server

To edit a configuration file mongod.conf:

Vim/etc/mongod.conf

Add the following and enable the Config Server service:

Configsvr=true

To restart the MongoDB service:

Service Mongod Restart

Note: The default listener is 27019 ports. You can also start the Mongod process using the following command.

# Mongod--configsvr--dbpath <path>--port <port>

At this point, the default port is changed from 27017 to 27019:

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Two. Configuring MONGOs instances

Install MONGOs:

Yum Install mongodb-org-mongos-2.6.1-1.x86_64.rpm

Start MONGOs:

MONGOs--configdb=192.168.1.110--fork--logpath=/var/log/mongodb/mongos.log

Note: MONGOs is a lightweight application that can run on the same node as other services, and at startup, it is necessary to specify the access address of each config server for the MONGOs instance;

By default, MONGOs listens on port 27017, and the MONGOs instance can be started using the following command.

# mongos--configdb <config server hostnames (ip| Hostname) >:P ort)

You can also edit the configuration file directly:

1, note dbpath directive;

2, add configdb instruction, and specify the address of config server;

Then use the following command to start the MONGOs instance:

# mongos-f/etc/mongod.conf

Log in to MONGOs and configure the Shard node:

MONGO--host 192.168.1.100mongos> sh.addshard ("192.168.1.101") {"shardadded": "shard0000", "OK": 1}mongos> sh.ad Dshard ("192.168.1.102") {"shardadded": "shard0001", "OK": 1}

View Shard Status:

mongos> sh.status ()---sharding status---sharding version: {"_id": 1, "Version": 4, "Mincompatibleversion": 4, "cur Rentversion ": 5," Clusterid ": ObjectId (" 58d4bd8a102ad4bdad74aa1d ")} shards:{" _id ":" shard0000 "," host ":" 192.168.1. " 101:27017 "} {" _id ":" shard0001 "," host ":" 192.168.1.102:27017 "} databases:{" _id ":" admin "," partitioned ": Fals E, "PRIMARY": "Config"}

To start the sharding function:

Mongos> sh.enablesharding ("TestDB"); {"OK": 1}

Note: MongoDB's shard feature is implemented at the collection level, but to start Shard on collection, it also needs to be enabled on its associated database beforehand. When the Shard feature is enabled on the database, MongoDB assigns it a Master shard.

The Enable procedure needs to be implemented on MONGOs instances, you can use the Sh.enablesharding () method, or you can use the enablesharding command of Db.runcommand (), which uses the following format, respectively:

Sh.enablesharding ("<database>") Db.runcommand ({enablesharding: <database>})

At this point, look again at the Shard status:

mongos> sh.status ()---sharding status---sharding version: {"_id": 1, "Version": 4, "Mincompatibleversion": 4, "cur Rentversion ": 5," Clusterid ": ObjectId (" 58d4bd8a102ad4bdad74aa1d ")} shards:{" _id ":" shard0000 "," host ":" 192.168.1. " 101:27017 "} {" _id ":" shard0001 "," host ":" 192.168.1.102:27017 "} databases:{" _id ":" TestDB "," Partitioned ": Tru E, "PRIMARY": "shard0000"}

Test:

Sharding on the collection:

Mongos> sh.shardcollection ("Testdb.student", {"Age": 1}) {"collectionsharded": "Testdb.student", "OK": 1}

Insert data:

Mongos> for (i=1;i<=100000;i++) Db.student.insert ({name: "Student" +i,age: (i%120), classes: "Class+ (I%10)"}); Writeresult ({"ninserted": 1})

At this point we re-view the sharding status as follows:

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MongoDB Shard (sharding) feature implementation