Installing MongoDB

MongoDB is configured as a replica set across multiple nodes with an arbiter, and includes user and role setup. Monitoring is enabled using MongoDB Exporter.

Install MongoDB on the designated VMs and configure replica set with required ports and users.

To install the MongoDB, follow the steps below:

Configure MongoDB repository and install.

vi /etc/yum.repos.d/mongodb-org-6.0.repo

 [mongodb-org-6.0]
 name=MongoDB Repository
 baseurl=https://repo.mongodb.org/yum/redhat/8/mongodb-org/6.0/x86_64/
 gpgcheck=1
 enabled=1
 gpgkey=https://pgp.mongodb.com/server-6.0.asc
 
yum install -y mongodb-org

Update systemd configuration for replica set.

echo "exclude=mongodb-org,mongodb-org-database,mongodb-org-server,mongodb-mongosh,mongodb-org-mongos,mongodb-org-tools" >> /etc/yum.conf
sed -i "s|OPTIONS=-f /etc/mongod.conf|OPTIONS=--replSet cdprsg -f /etc/mongod.conf" /usr/lib/systemd/system/mongod.service
vi /etc/mongod.conf

Configure data directories and SELinux permissions.

chown -R mongod: /sdd
 chcon -R --reference=/var/lib/mongo /sdd
 semanage port -a -t mongod_port_t -p tcp 51090
 systemctl daemon-reload
 systemctl restart mongod
 systemctl status mongod

 nc -zv  puapso1bhxcdmgodbs1002.hxcd.aws.hclsw.internal 5190
 nc -zv puapso1ahxcdmgodbs1003.hxcd.aws.hclsw.internal 5190
 nc -zv puapso1bhxcdmgodbs1004.hxcd.aws.hclsw.internal 5190
 nc -zv  puapso1ahxcdmgodbs1005 5190

Configure replica set.

mongosh --host <primary-host> --port 51090

 use admin;

 conf = {
  _id: "cdprsg",
  members: [
    { _id: 0, host: "<host1>:51090", tags: { usage:
        "schedule" } },
    { _id: 1, host: "<host2>:51090", tags: { usage:
        "schedule" } },
    { _id: 2, host: "<host3>:51090", tags: { usage:
        "segloader" } },
    { _id: 3, host: "<host4>:51090", tags: { usage:
        "analytics" } }
  ]
 }
 rs.initiate(conf)
 rs.addArb("<arbiter-host>:51090") 
 conf = rs.conf()
 conf.members[3].hidden = true
 rs.status()

Create required MongoDB users.

use admin;

 db.createUser({ user: "rtsms", pwd: "<password>", roles: [{ role: "readWrite",
        db: "segmentation" }, { role: "dbAdmin", db: "segmentation" }] });

 db.createUser({ user: "segdbconnector", pwd: "<password>", roles: [{ role:
        "readWrite", db: "segmentation" }] });

 db.createUser({ user: "pmm", pwd: "<password>", roles: [
  { role: "backup", db: "admin" },
  { role: "clusterMonitor", db: "admin" },
  { role: "read", db: "local" },
  { role: "readWrite", db: "admin" },
  { role: "restore", db: "admin" }
 ]
        });
  openssl rand -base64 16

Node Exporter

Node Exporter installed on MongoDB virtual machines collect systems metrics such as CPU, memory, disk, and network usage. These metrics are then scraped by Prometheus for monitoring and visualization.

To install node exporter, follow the steps below:

Download and extract Node Exporter.

wget  https://github.com/prometheus/node_exporter/releases/download/v1.7.0/node_exporter-1.7.0.linux-amd64.tar.gz
 tar xfz node_exporter-1.7.0.linux-amd64.tar.gz

Move binary and create system user.

sudo mv node_exporter-1.7.0.linux-amd64/node_exporter /usr/local/bin/
 sudo useradd -rs /bin/false node_exporter

Create a systemd service unit.

vi /etc/systemd/system/node_exporter.service

Paste the following contents:


 [Unit]
 Description=Node Exporter
 After=network.target

 [Service]
 User=node_exporter
 Group=node_exporter
 Type=simple
 ExecStart=/usr/local/bin/node_exporter

 [Install]
 WantedBy=multi-user.target

Start and enable service.

restorecon -Rv /usr/local/bin
systemctl daemon-reload
 systemctl start node_
 systemctl status node_exporter
 systemctl enable node_exporter

To validate metrics endpoint and exporter status, run this command to confirm the service is up.
```
  curl -kv http://localhost:9100/metrics
```

MongoDB Prometheus Exporter

This section details how to install and configure Percona's MongoDB Exporter to expose MongoDB metrics to Prometheus for scraping and monitoring. To install Prometheus exporter, follow the steps below:

Install the Exporter Package.

wget https://github.com/percona/mongodb_exporter/releases/download/v0.40.0/mongodb_exporter-0.40.0.linux-64-bit.rpm

rpm -Uhv mongodb_exporter-0.40.0.linux-64-bit.rpm

Create a systemd Unit File.

vi /etc/systemd/system/mongodb_exporter.service

Paste the following contents:


 [Unit]
 Description=Prometheus MongoDB Exporter
 After=network.target

 [Service]
 Type=simple
 User=mongodb_exporter
 Group=mongodb_exporter

        Environment="OPTIONS=--mongodb.uri=mongodb://pmm:<password>@<mongo-host>:51090
        --compatible-mode"
 ExecStart=/usr/bin/mongodb_exporter $OPTIONS
 Restart=always

 [Install]
 WantedBy=multi-user.target

Note: Replace <password> and <mongo-host> with actual credentials and hostname.

Reload and Start the Service.

systemctl daemon-reload
 systemctl start mongodb_exporter
 systemctl status mongodb_exporter
 systemctl enable mongodb_exporter

Run this command to validate and confirm the service is up.
```
curl -kv http://localhost:9216/metrics
```