This charm deploys MongoDB in three configurations:

• Single node
• Replica set
• Sharded clusters

The MongoDB charm allows for certain values to be configurable via a config.yaml file. The options provided are extensive, you should review the options.

Specificlly the following options are important:

• replicaset

  • ie: myreplicaset
  • Each replicaset has a unique name to distinguish it’s members from other replicasets available in the network.
  • The default value of myset should be fine for most single cluster scenarios.

• web_admin_ui

  • MongoDB comes with a basic but very informative web user interface that provides health and status information on the database node as well as the cluster.
  • The default value of yes will start the Admin web UI on port 28017.

• replicaset_master

  • If this node is going to be joining an existing replicaset, you can specify a member of that cluster ( preferably the master node ) so we can join the existing replicaset.
  • The value should be in the form of host[:port]
  • ie: hostname ( will connect to hostname on the default port of 27017 )
  • ie: hostname:port ( will connect to hostname on port number )

Most of the options in config.yaml have been modeled after the default configuration file for mongodb (normally in /etc/mongodb.conf) and should be familiar to most mongodb admins. Each option in this charm have a brief description of what it does.

Deploy the first MongoDB instance

juju deploy mongodb
juju expose mongodb

Deploy the first MongoDB instance

juju deploy mongodb
juju expose mongodb

Your deployment should look similar to this ( juju status ):

environment: amazon
machines:
  "0":
    agent-state: started
    agent-version: 1.16.5
    dns-name: ec2-184-73-7-172.compute-1.amazonaws.com
    instance-id: i-cb55cceb
    instance-state: running
    series: precise
    hardware: arch=amd64 cpu-cores=1 cpu-power=100 mem=1740M root-disk=8192M
  "1":
    agent-state: pending
    dns-name: ec2-54-196-181-161.compute-1.amazonaws.com
    instance-id: i-974bd2b7
    instance-state: pending
    series: precise
    hardware: arch=amd64 cpu-cores=1 cpu-power=100 mem=1740M root-disk=8192M
services:
  mongodb:
    charm: cs:precise/mongodb-20
    exposed: false
    relations:
      replica-set:
      - mongodb
    units:
      mongodb/0:
        agent-state: pending
        machine: "1"
        public-address: ec2-54-196-181-161.compute-1.amazonaws.com

In addition, the MongoDB web interface should also be accessible via the services’ public-address and port 28017 ( ie: http://ec2-50-17-73-255.compute-1.amazonaws.com:28017 ).

juju set mongodb replicaset=<new_replicaset_name>

juju add-unit mongodb

juju add-unit mongodb -n5

We now have a working MongoDB replica-set.

According the the MongoDB documentation found on their website, one way of deploying a Shard Cluster is as follows:

• deploy config servers
• deploy a mongo shell (mongos)
• deploy shards
• connect the config servers to the mongo shell
• add the shards to the mongo shell

Using Juju we can deploy a sharded cluster using the following commands:

shard1:
  replicaset: shard1
shard2:
  replicaset: shard2
shard3:
  replicaset: shard3
configsvr:
  replicaset: configsvr

We'll save this one as ~/mongodb-shard.yaml.

juju bootstrap

juju deploy mongodb configsvr --config ~/mongodb-shard.yaml -n3

juju deploy mongodb mongos

juju deploy mongodb shard1 --config ~/mongodb-shard.yaml -n3
juju deploy mongodb shard2 --config ~/mongodb-shard.yaml -n3
juju deploy mongodb shard3 --config ~/mongodb-shard.yaml -n3

juju add-relation mongos:mongos-cfg configsvr:configsvr

juju add-relation mongos:mongos shard1:database
juju add-relation mongos:mongos shard2:database
juju add-relation mongos:mongos shard3:database

With the above commands, we should now have a three replica-set sharded cluster running. Using the default configuration, here are some details of our sharded cluster:

• mongos is running on port 27021
• configsvr is running on port 27019
• the shards are running on the default mongodb port of 27017
• The web admin is turned on by default and accessible with your browser on port 28017 on each of the shards.

To verify that your sharded cluster is running, connect to the mongo shell and run sh.status():

• mongo --host <mongos_host>:<mongos_port>
• run sh.status() You should see your the hosts for your shards in the status output.

The storage subordinate and block-storage-broker service can automatically handle attaching the volume and mounting it to the unit before MongoDB is setup to use it.

For example if you've created the volumes vol-id-00001 and vol-id-00002 and want to attach them to your 2 mongo units, with your OpenStack or AWS credentials in a credential.yaml file:

juju deploy block-storage-broker --config credentials.yaml
juju deploy storage
juju add-relation block-storage-broker storage
juju set storage provider=block-storage-broker
juju set volume_map="{mongodb/0: vol-id-00001, mongodb/1: vol-id-00002}"
juju add-relation storage mongodb

Note: Although these steps will still work they are now deprecated, you should use the storage subordinate above instead.

To deploy mongodb using permanent volume on Openstack, the permanent volume should be attached to the mongodb unit just after the deployment, then the configuration should be updated like follows.

juju set mongodb volume-dev-regexp="/dev/vdc" volume-map='{"mongodb/0": "vol-id-00000000000000"}' volume-ephemeral-storage=false

Backups can be enabled via config. Note that destroying the service cannot currently remove the backup cron job so it will continue to run. There is a setting for the number of backups to keep, however, to prevent from filling disk space.

To fetch the backups scp the files down from the path in the config.

• If your master/slave/replicaset deployment is not updating correctly, check the log files at /var/log/mongodb/mongodb.log to see if there is an obvious reason ( port not open etc.).
• Ensure that TCP port 27017 is accessible from all of the nodes in the deployment.
• If you are trying to access your MongoDB instance from outside your deployment, ensure that the service has been exposed ( juju expose mongodb )
• Make sure that the mongod process is running ( ps -ef | grep mongo ).
• Try restarting the database ( restart mongodb )
• If all else fails, remove the data directory on the slave ( rm -fr /var/log/mongodb/data/* ) and restart the mongodb-slave daemon ( restart mongodb ).

• MongoDB website
• MongoDB documentation
• MongoDB bug tracker
• MongoDB user mailing list