Sending MongoDB metrics to AWS CloudWatch

The objective is to collect data from a MongoDB service and insert it into a CloudWatch as a custom metric. It gives the capability to create alarms based on this information.

The requirements are:

• Aws CLI installed on the MongoDB server
• Permission to put metrics to CloudWatch (I recommend to use an instance role)

The first step is to create a policy and a role that will permit the instance to put metric into CloudWatch. The following policy is enough to push our metric to CloudWatch.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1523876124974",
      "Action": [
        "cloudwatch:PutMetricData"
      ],
      "Effect": "Allow",
      "Resource": "*"
    }
  ]
}

Then use script bellow to monitor the MongoDB, the script will collect the service status, current connections, and available connections.

#!/bin/bash

EC2_INSTANCE_ID=$(wget -q -O - http://169.254.169.254/latest/meta-data/instance-id)
REGION=$(wget -q -O - http://169.254.169.254/latest/meta-data/placement/availability-zone | awk '{print substr($1, 1, length($1)-1)}')
#!/bin/bash
test -n "$EC2_INSTANCE_ID" || die 'cannot obtain instance-id'
test -n "$REGION" || die 'cannot obtain region'

mongo --eval "printjson(db.serverStatus())" > /dev/null 2>&1
SERVER_STATUS=$?
AWSCLI=$(which aws)

if [[ -z $AWSCLI ]]
then
    echo "awscli not found"
    exit 1
fi


if [[ $SERVER_STATUS -eq 0 ]]
then

    aws cloudwatch put-metric-data --region=$REGION --namespace Services --dimensions MongoDB=$EC2_INSTANCE_ID --metric-name 'Status' --unit 'Count' --value='0'

    CONN_CUR=$(mongo --eval "printjson(db.serverStatus().connections.current)" | tail -1)
    CONN_AVAILABLE=$(mongo --eval "printjson(db.serverStatus().connections.available)" | tail -1)

    aws cloudwatch put-metric-data --region=$REGION --namespace Services --dimensions MongoDB=$EC2_INSTANCE_ID --metric-name 'CurrentConn' --unit 'Count' --value=$CONN_CUR
    aws cloudwatch put-metric-data --region=$REGION --namespace Services --dimensions MongoDB=$EC2_INSTANCE_ID --metric-name 'AvailableConn' --unit 'Count' --value=$CONN_AVAILABLE
else
    aws cloudwatch put-metric-data --region=$REGION --namespace Services --dimensions MongoDB=$EC2_INSTANCE_ID --metric-name 'Status' --unit 'Count' --value='1'
fi

Now is possible to see the metrics on CloudWatch and use it to create alarms.