AWS Logging using Cloudwatch

To see logs:

  • Click Services, top left
  • Select Cloudwatch (in the “Management Tools” group)
  • Click Logs (LHS)
  • Select the environment you want
  • To see more columns (eg ingestion time), click the cog icon, top right
  • Most recent logs are at the bottom by default
  • To change the time period, see the options top right

Health checks and unhealthy instances

CloudWatch Alarms

  • CloudWatch alarms can be configured to alert us in particular circumstances
    • Eg we had them set up for 0 healthy hosts and over a certain threshold of 5xx alarms
    • Note that notifications are handled via topics - use the SNS service in AWS
  • CloudWatch alarms and monitoring can be accessed via load balancers
  • You can view load balancers if you select them on the right in the EC2 management console
  • You can select load balancers one by one and check “Instances” to see whether you have the right one – or make a note somewhere!
  • In the load balancer, you can click “View all CloudWatch alarms” to view other alarms, and to edit alarms: In the list of alarms, click View (on the right), then select Actions | Modify from the dropdown at the top.
  • When you view all alarms, you will see several in ALARM status
    • These will mostly have names that include “AWSEBCloudwatchAlarm” then will be labelled either Low or High
    • These are the default alarms created as a result of setting scaling triggers in EBS | Configuration | Scaling | Scaling Trigger, where “High” alarms are triggered by breaching the upper threshold, and “Low” alarms by breaching the lower threshold
    • These alarms all have auto-scaling actions attached - ie either add or remove an instance (unless the min or max instance values prevent you)
    • Their names are based on AutoScaling group names
    • To see AutoScaling groups, go to EC2 and click AutoScaling Groups on the left
    • AutoScaling group names are reasonably easy to parse because they include environment Ids - as do the alarms

      Useful debugging tools in Cloudwatch

  • Logs
  • Alarms History
  • Metrics
  • View individual alarms (see below)

Viewing Individual Alarms

  • Go here:
  • Cloudwatch
  • Alarms (LHS)
  • Find the healthy host count one (“HealthyHostCount < 1 for 1 minute”) for ryfzuqamvb
    • It will either be in Red (“ALARM”) or green (“OK”) (or maybe “insufficient”?)
  • Select / click
  • Click the graph on the Details tab
  • Select “1w” at the top
  • …or Cloudwatch | Metrics – All Metrics, select ELB, then “Per LB” or “Per LB, per A-Z”
    • (to find out which LB you are looking at, go to EC2 and select load balancers on the left, then select a particular load balancer and view tags to get a cross reference)
    • To see healthy host count, see notes above
    • …or you can go to Elastic Beanstalk | Monitoring and fiddle about with the date range