ansible-mongodb

Purpose: Create a MongoDB sharded cluster from scratch.

Getting started

1. Start by adding the following to your requirements.yml file:

   -   name: 123mwanjemike.ansible_mongodb
       src: https://github.com/123MwanjeMike/ansible-mongodb
       version: v1.0.4

2. Install the role by running the ansible-galaxy install command:

   ansible-galaxy install -r requirements.yml

Required ansible host/group variables

For each host/group, the cluster_role is either of replicaSet, router, config or shard.

The replica_set is also required for host groups that are in a replica set and is a dictionary with the following keys:

• name: The name of the replica set
• group: The name of the host group in the inventory that the replica set belongs to

Below is an example:

cluster_role: "config"
replica_set:
    name: "cfgsvr"
    group: "config_servers"

You may also checkout the values in the vars/main.yml file and change them according to needs.

Sample inventory

all:
  vars:
    ansible_python_interpreter: /usr/bin/python3
  children:            
    mongo_cluster:
      children:
        mongos_routers:
          hosts:
            mongos-router-0.europe-north1-b.c.oceanic-muse-408212.internal:
          vars:
            cluster_role: "router"
        config_servers:
          hosts:
            mongod-cfgsvr-0.europe-north1-b.c.oceanic-muse-408212.internal:
            mongod-cfgsvr-1.europe-north1-c.c.oceanic-muse-408212.internal:
            mongod-cfgsvr-2.europe-north1-a.c.oceanic-muse-408212.internal:
          vars:
            cluster_role: "config"
            replica_set:
              name: "cfgsvr"
              group: "config_servers"
        shard_0:
          hosts:
            mongod-shard-0-0.europe-north1-b.c.oceanic-muse-408212.internal:
            mongod-shard-0-1.europe-north1-c.c.oceanic-muse-408212.internal:
            mongod-shard-0-2.europe-north1-a.c.oceanic-muse-408212.internal:
          vars:
            cluster_role: "shard"
            replica_set:
              name: "shard-0"
              group: "shard_0"
        plain_replica_set:
          hosts:
            mongod-rs0-0.europe-north1-b.c.oceanic-muse-408212.internal:
            mongod-rs0-1.europe-north1-c.c.oceanic-muse-408212.internal:
            mongod-rs0-0-2.europe-north1-a.c.oceanic-muse-408212.internal:
          vars:
            cluster_role: "replicaSet"
            replica_set:
              name: "rs0"
              group: "plain_replica_set"

NOTE: It is important that the hostnames are the FQDNs of the hosts as shown in the example above.

Flags and Variables

Flag	Variables	Description
install_mongo	none	Installs mongo packages
start_mongo	none	Starts mongo database and/or server
stop_mongo	none	Stops mongo database and/or server
configure_mongo	cfg_server	Configures mongo
prepare_members	keyfile_src	Prepares the mongodb sharded cluster members. Deletes existing mongodb data!
init_replica	none	Creates a mongodb replica set
create_admin	adminUser, adminPass	Creates the admin user
add_shard	new_shard	Adds a shard replicaset server to the sharded cluster
create_database	tgt_db, roles, userName, userPass	Creates a database with sharding enabled. Creates respective user if not present
clear_logs	none	Clears all the sharded cluster logs

Sample playbook

- hosts: all
  become: true
  vars:
    # Used to create admin user
    adminUser: ""
    adminPass: ""
    # Used to add a shard replicaset
    new_shard:
      name: "shard-0" # shard name
      group: "shard_0" # group name from inventories/hosts
    # Used to create a database instance on the cluster
    tgt_db: ""
    roles: ["readWrite", "userAdmin"]
    # Used to create a basic user for the database instance above
    userName: ""
    userPass: ""
    # Used to prepare the members of the sharded cluster
    keyfile_src: "./keyfile" # Path to the keyfile on the ansible controller
    # Used to configure the cluster members
    cfg_server:
      name: "cfgsvr"
      group: "config_servers"

  # Generate a keyfile
  pre_tasks:
    - name: Generate random string with OpenSSL on ansible controller
      shell: openssl rand -base64 756 > keyfile
      delegate_to: localhost
      args:
        creates: keyfile

  roles:
    - { role: 123mwanjemike.ansible_mongodb, flags: ["install_mongo"] }
    - { role: 123mwanjemike.ansible_mongodb, flags: ["configure_mongo"] }
    - { role: 123mwanjemike.ansible_mongodb, flags: ["clear_logs"] }
    - { role: 123mwanjemike.ansible_mongodb, flags: ["prepare_members"] }
    - { role: 123mwanjemike.ansible_mongodb, flags: ["start_mongo"] }
    - {
        role: 123mwanjemike.ansible_mongodb,
        flags: ["init_replica"],
        when: cluster_role != 'router',
      }
    - {
        role: 123mwanjemike.ansible_mongodb,
        flags: ["create_admin"],
        when: cluster_role != 'router',
        delegate_to: "{{ groups[replica_set.group] | first }}",
      }
    - {
        role: 123mwanjemike.ansible_mongodb,
        flags: ["add_shard"],
        when: cluster_role == 'router',
        run_once: true,
      }
    - {
        role: 123mwanjemike.ansible_mongodb,
        flags: ["create_database"],
        when: cluster_role == 'router',
        run_once: true,
      }
    - { role: 123mwanjemike.ansible_mongodb, flags: ["stop_mongo"] }

Notes:

1. The setup is best suited for implementation behind a VPC and thus implements authentication using a keyfile. If you need to use x509 certificates, you can use the x509 security documentation to guide you on how to implement it.
2. This ansible role was originally templated from this role. This particular one is however intended to be light weight and easy to use and thus users that may need a more sophisticated setup can still checkout the original role.