Jenkins master node polls for idle executors and scales in.

nmg-jenkins-scaling-in-agents.sh

#!/bin/bash

for i in {1..3};
do
    AGENT_ASG="$(aws autoscaling describe-auto-scaling-groups --region ${aws_region} | jq -r '.AutoScalingGroups[] | select(.AutoScalingGroupName | startswith("${application}-agent-")) | .AutoScalingGroupName')"

    BUILD_ACTIVE_QUEUE_VALUE1="$(curl -s -m 60 -u 'admin:APIKEY' 'http://localhost:8080/computer/api/json' | jq -r '.busyExecutors')"
    BUILD_ACTIVE_QUEUE_VALUE2="$(curl -s -m 60 -u 'admin:APIKEY' 'http://localhost:8080/jqs-monitoring/api/json' | jq -r '.buildQueue.numberOfJobs')"
    BUILD_ACTIVE_QUEUE_VALUE=$(( $BUILD_ACTIVE_QUEUE_VALUE1 + $BUILD_ACTIVE_QUEUE_VALUE2 ))
        
    TOTAL_EXECUTORS="$(curl -s -m 60 -u 'admin:APIKEY' 'http://localhost:8080/computer/api/json' | jq -r '.totalExecutors')"
        
    if [ $TOTAL_EXECUTORS -gt ${executors_min} ] && [ $BUILD_ACTIVE_QUEUE_VALUE -eq 0 ]; then
        aws cloudwatch put-metric-data --namespace JenkinsBuildActiveQueue --metric-name IdleExecutors --value 0 --dimensions AutoScalingGroupName=$AGENT_ASG --unit Count --region ${aws_region}
    else
        aws cloudwatch put-metric-data --namespace JenkinsBuildActiveQueue --metric-name IdleExecutors --value 1 --dimensions AutoScalingGroupName=$AGENT_ASG --unit Count --region ${aws_region}
    fi

    sleep 15
done