Manual server configuration is always a nightmare, especially when there is a large fleet of servers to manage. However, with Infrastructure as Code(IaC) automation tools like Ansible, all that pain goes away. In this blog, we shall leverage the automation tool to create a MongoDB sharded cluster from scratch in just a few minutes using . this Ansible role Prerequisites Ansible installed on your control node Seven (or more) target servers running any Ubuntu OS version SSH access to the target servers Getting our hands dirty Install the Ansible Role As I mentioned earlier, we shall be using an existing Ansible role, so we won't have to write all the playbooks by ourselves from scratch. However, to install the role, we shall need a file that has its installation information. A file. Run the commands below to create the file and the directory, which we shall be working. requirements.yml ansible_mongodb, mkdir ~/ansible_mongodb
echo "-   name: 123mwanjemike.ansible_mongodb
    src: https://github.com/123MwanjeMike/ansible-mongodb
    version: v1.0.4" > ~/ansible_mongodb/requirements.yml Note on version v1.0.4 The latest version of the role, 123mwanjemike.ansible_mongodb, at the time of writing this blog, was v1.0.4. There may, however, be more recent release versions at the time you read this, which are recommended to use instead. You can now install the role using the Ansible Galaxy command below. ansible-galaxy install -r ~/ansible_mongodb/requirements.yml Output: The Inventory File Create an inventory using the command below. mkdir ~/ansible_mongodb/inventory
touch ~/ansible_mongodb/inventory/hosts Next, populate the inventory with the target servers grouped according to the respective replicaSets. That is to say, the Config servers replicaSet servers in their group, and the Shard servers in the corresponding group. Also, make sure to use the Fully Qualified Domain Names(FQDN) of the servers when adding them to the inventory. Below is what my inventory looks like. all:
  children:            
    mongo_cluster:
      children:
        mongos_routers:
          hosts:
            mongos-router-0.europe-north1-b.c.oceanic-muse-408212.internal:
        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:
        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: The Variables There will be a number of variables at play when using this role. Let's get them right. Run the commands below to put them in place Host Variables All hosts mkdir ~/ansible_mongodb/inventory/group_vars
 echo "ansible_python_interpreter: /usr/bin/python3" > ~/ansible_mongodb/inventory/group_vars/all.yml Router(s) echo "cluster_role: 'router'" > ~/ansible_mongodb/inventory/group_vars/mongos_routers.yml Config Servers echo "cluster_role: 'config'

 replica_set:
   name: 'cfgsvr'
   group: 'config_servers'" > ~/ansible_mongodb/inventory/group_vars/config_servers.yml Shard_0 Servers echo "cluster_role: 'shard'

 replica_set:
   name: 'shard-0'
   group: 'shard_0'" > ~/ansible_mongodb/inventory/group_vars/shard_0.yml Configuration Variables You can find in the file at the path where the role was installed. For example, in my case, it was installed at . the role's preset configuration variables var/main.yml ~/.ansible/roles/123mwanjemike.ansible_mongodb You can change them as you wish, especially the versions and public keys given that they point to Ubuntu Jammy's MongoDB version 7.0 public keys. mongo_configs Cluster Variables As for the MongoDB cluster configuration variables, they have been documented on the role's README on GitHub . here A Playbook We're almost good to go. We now just need a playbook to install and configure the MongoDB sharded cluster. I build from the provided in the README of the role on GitHub. Below is my file sample playbook ~/ansible_mongodb/sample_playbook.yml - hosts: mongo_cluster
  become: true
  vars:
    adminUser: "myAdminUser"
    adminPass: "" # Secret password here
    new_shard:
      name: "shard-0"
      group: "shard_0"
    tgt_db: "myDatabase"
    roles: ["readWrite", "userAdmin"]
    userName: "targetUser"
    userPass: "" # Secret password here
    keyfile_src: "./keyfile"
    cfg_server:
      name: "cfgsvr"
      group: "config_servers"

  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,
      } The moment of truth has now come. We shall be running the playbook with the command below and see what happens. cd ~/ansible_mongodb/
ansible-playbook sample_playbook.yml -i inventory/hosts Output: Checking out the cluster 🎉💃🏽🕺🏽😎 Closing Remarks With this Ansible role, we've been able to create and configure a MongoDB sharded cluster in under 10 minutes without writing any single configuration for the servers by ourselves. In case you were wondering, I am indeed the author of the role we have just used to create the cluster. I am also working on that can be used to create the server instances for the sharded cluster used herein. Currently, I have only set up the provider for Google Cloud Platform(GCP), but I will be adding Azure, AWS, and other service providers soon. I hope you enjoy them as much as I did when creating them. this Terraform project Cheers! Additional resources Ansible [Ansible] Roles What Is a “Fully Qualified Domain Name”? [MongoDB] Sharded Cluster Components What is a virtual private cloud (VPC)? Also published . here

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