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Deploying a shared production ready MongoDB cluster with Ansible
In this example we demonstrate how we can orchestrate the deployment of a production grade MongoDB Cluster. The functionality of this example includes:
- Deploying a N node MongoDB cluster, which has N shards and N replication nodes.
- Scale out capability. Expand the Cluster by adding nodes to the cluster.
- Security, All the mongodb process are secured using the best practices.
###Deployment Architecture.
To better explain the deployment architecture let's take an example where we are deploying a 3 node MongoDB cluster ( Minimum recommended by MongoDB).
The way Ansible configures the three nodes is as follows:
-
Install the mongodb software on all nodes.
-
Creates 3 replication sets, with one primary on each node and the rest two acting as secondaries.
-
Configures MongodDB configuration DB servers as listed in the inventory section[mongocservers]. Recommended number is 3, so it can be the same three servers as the datanodes.
-
Configures a Mongos server as listed in the inventory file [mongosservers].
-
Adds 3 Shards each belonging to individual replication sets.
-
All the processes, mongod,mogos are secured using the keyfiles.
####Once the cluster is deployed, if we want to scale the cluster, Ansible configures it as follows:
-
Install the MongoDB application on the new node.
-
Configure the replication set with primary as the new node and the secondaries as listed in the inventory file [replicationservers]. ( don't forget to add the new node also in the replicationservers section]
-
Adds the new shard to the mongos service pointing to the new replication set.
###The following example deploys a three node MongoDB Cluster
The inventory file looks as follows:
#The site wide list of mongodb servers
[mongoservers]
mongo1
mongo2
mongo3
#The list of servers where replication should happen, by default include all servers
[replicationservers]
mongo1
mongo2
mongo3
#The list of mongodb configuration servers, make sure it is 1 or 3
[mongocservers]
mongo1
mongo2
mongo3
#The list of servers where mongos servers would run.
[mongosservers]
mongos
Build the site with the following command:
ansible-playbook -i hosts site.yml
###Verifying the deployed MongoDB Cluster
Once completed we can check replication set availibitly by connecting to individual primary replication set nodes, 'mongo --host --port and issue the command to query the status of replication set, we should get a similar output.
web2:PRIMARY> rs.status()
{
"set" : "web2",
"date" : ISODate("2013-03-19T10:26:35Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "web2:2013",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 102,
"optime" : Timestamp(1363688755000, 1),
"optimeDate" : ISODate("2013-03-19T10:25:55Z"),
"self" : true
},
{
"_id" : 1,
"name" : "web3:2013",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 40,
"optime" : Timestamp(1363688755000, 1),
"optimeDate" : ISODate("2013-03-19T10:25:55Z"),
"lastHeartbeat" : ISODate("2013-03-19T10:26:33Z"),
"pingMs" : 1
}
],
"ok" : 1
}
we can check the status of the Shards as follows: connect to the mongos service 'mongos --host --port 8888' and issue the following command to get the status of the Shards.
mongos> sh.status()
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards:
{ "_id" : "web2", "host" : "web2/web2:2013,web3:2013" }
{ "_id" : "web3", "host" : "web3/web2:2014,web3:2014" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
We can also make sure the Sharding works by creating a database and collection and populate it with documents and check if the chunks of the collection are balanced equally across nodes.
The above mentioned steps can be tested as follows:
-
Once the Sharded cluster is ready, create a new database and an admin user for the database. This is done from the mongos machine.
/usr/bin/mongo localhost:8888/admin -u admin -p 123456 mongos> use test switched to db test mongos> db.addUser('admin','123456') { "user" : "admin", "readOnly" : false, "pwd" : "95ec4261124ba5951720b199908d892b", "_id" : ObjectId("51519f349cd3a93ca7e17909") } -
Once the DB and the user is created, create a collection and poplulate documents, This deployment add a script to the /tmp location of the mongos server which adds a new collection and 100,000 documents.
$/usr/bin/mongo localhost:8888/test -u admin -p 123456 /tmp/testsharding.js -
After the document's are populated, we have to enable sharding on the database and the collection. which can be done as follows:
$/usr/bin/mongo localhost:8888/admin -u admin -p 123456 mongos> db.runCommand( { enableSharding : "test" } ) { "ok" : 1 } mongos> db.runCommand( { shardCollection : "test.test_collection", key : {"number":1} }) { "collectionsharded" : "test.test_collection", "ok" : 1 } mongos> sh.status() --- Sharding Status --- sharding version: { "_id" : 1, "version" : 3 } shards: { "_id" : "bensible", "host" : "bensible/bensible:20103,web2:20103,web3:20103" } { "_id" : "web2", "host" : "web2/bensible:20102,web2:20102,web3:20102" } { "_id" : "web3", "host" : "web3/bensible:20101,web2:20101,web3:20101" } databases: { "_id" : "admin", "partitioned" : false, "primary" : "config" } { "_id" : "test", "partitioned" : true, "primary" : "bensible" } test.test_collection chunks: web2 1 bensible 19 -
In the above example we can see the chunks being balanced across nodes. After a few minutes if we excute the same command 'sh.status()' we will see the below output, which shows all the chunks being balanced across the three nodes.
mongos> sh.status() --- Sharding Status --- sharding version: { "_id" : 1, "version" : 3 } shards: { "_id" : "bensible", "host" : "bensible/bensible:20103,web2:20103,web3:20103" } { "_id" : "web2", "host" : "web2/bensible:20105,web2:20105,web3:20105" } { "_id" : "web3", "host" : "web3/bensible:20102,web2:20102,web3:20102" } databases: { "_id" : "admin", "partitioned" : false, "primary" : "config" } { "_id" : "test", "partitioned" : true, "primary" : "web3" } test.test_collection chunks: bensible 7 web2 6 web3 7
Adding a new node to the Cluster
To add a new node to the configured MongoDb Cluster, setup the inventory file as follows:
#The site wide list of mongodb servers
[mongoservers]
mongo1
mongo2
mongo3
mongo4
#The list of servers where replication should happen, by default include all servers
[replicationservers]
mongo4
mongo1
mongo2
#The list of mongodb configuration servers, make sure it is 1 or 3
[mongocservers]
mongo1
mongo2
mongo3
#The list of servers where mongos servers would run.
[mongosservers]
mongos
Make sure you have the new node added in the replicationservers section and execute the following command:
ansible-playbook -i hosts playbooks/addnode.yml -e servername=mongo4
###Verification.
The verification of the newly added node can be as easy checking the sharding status and see the chunks being rebalanced to the newly added node.
$/usr/bin/mongo localhost:8888/admin -u admin -p 123456
mongos> sh.status()
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards:
{ "_id" : "bensible", "host" : "bensible/bensible:20103,web2:20103,web3:20103" }
{ "_id" : "web2", "host" : "web2/bensible:20105,web2:20105,web3:20105" }
{ "_id" : "web3", "host" : "web3/bensible:20102,web2:20102,web3:20102" }
{ "_id" : "web4", "host" : "web4/bensible:20101,web3:20101,web4:20101" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : true, "primary" : "bensible" }
test.test_collection chunks:
web4 3
web3 6
web2 6
bensible 5