AWS Alarms for Application Errors

by | Apr 17, 2020 | Aggregated, alarms, alerts, aws, Developer tips, devops

Monitoring is key for any real-world application. You have to know what’s happening and be alerted in real time if something wrong is happening. AWS has CloudWatch for that, and gives you a lot of metrics automatically. But there are some that you have to define yourself. And then you need to define proper alarms. Here I’ll focus on hour: High number of application errors High number of application warnings High number of 5xx errors on the load balancer High number of 4xx errors on the load balancer First, the prerequisites: You need to be using CloudFormation to automate everything. You can create all of those things manually, but automation is a big plus If using CloudFormation, you’d preferably have a sub-stack for configuring alarms You need to be collecting your logs with CloudWatch logs If you are not using CloudWatch logs, here’s a simple config file and script to enable them: { "agent": { "metrics_collection_interval": 10, "region": "eu-west-1", "logfile": "/opt/aws/amazon-cloudwatch-agent/logs/amazon-cloudwatch-agent.log" }, "logs": { "logs_collected": { "files": { "collect_list": [ { "file_path": "{{logPath}}", "log_group_name": "{{logGroupName}}", "log_stream_name": "{instance_id}", "timestamp_format": "%Y-%m-%d %H:%M:%S" } ] } } } } # install AWS CloudWatch monitor mkdir cloud-watch-agent cd cloud-watch-agent wget https://s3.amazonaws.com/amazoncloudwatch-agent/linux/amd64/latest/AmazonCloudWatchAgent.zip unzip AmazonCloudWatchAgent.zip ./install.sh aws s3 cp s3://$BUCKET_NAME/cloudwatch-agent-config.json /var/config/cloudwatch-agent-config.json sed -i -- 's|{{logPath}}|/var/log/application.log|g' /var/config/cloudwatch-agent-config.json sed -i -- 's|{{logGroupName}}|app_node|g' /var/config/cloudwatch-agent-config.json sudo /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -c file:/var/config/cloudwatch-agent-config.json -s Now you have to define two things: Log metrics and alarms. The cloudformation code below creates both: "HighAppErrorsNotification": { "Type": "AWS::CloudWatch::Alarm", "Properties": { "AlarmActions": [ { "Ref": "NotificationTopicId" } ], "InsufficientDataActions": [ { "Ref": "NotificationTopicId" } ], "AlarmDescription": "Notify if there are too many application...