a-quality-log-message

Here is an example of a great log message in the "cause" section below:

It covers:

• when
• what happened
  • "instance i-0196831f293cc4677 was taken out of service"
• why it was done (what motivated this action?)
  • "in response to a user request"
• additional effects it had (things you might want to know)
  • "shrinking the capacity from 4 to 3"

Details

aws autoscaling terminate-instance-in-auto-scaling-group --instance-id i-0196831f293cc4677 --should-decrement-desired-capacity
{
    "Activity": {
        "Description": "Terminating EC2 instance: i-0196831f293cc4677",
        "ActivityId": "8468db2f-7127-4930-b95f-b8de05de9e64",
        "Details": "{\"Subnet ID\":\"subnet-e0908d97\",\"Availability Zone\":\"us-east-1b\"}",
        "StartTime": "2016-10-11T18:26:50.564Z",
        "Progress": 0,
        "Cause": "At 2016-10-11T18:26:50Z instance i-0196831f293cc4677 was taken out of service in response to a user request, shrinking the capacity from 4 to 3.",
        "StatusCode": "InProgress"
    }
}

This type of message is motivated by understandability-as-a-design-goal, since it helps with the understandability of the overall system. Consider that these types of logs could be part of the user-facing part of the system, not just external to the system. For example, they could be shown in an admin interface, as opposed to only being available in a log aggregation tool.

Referring Pages