End to End SaaS Serviceability, Metrics, Monitoring, and Alerting by Eamon Maguire

Author:Eamon Maguire
Language: eng
Format: azw3
Published: 2017-07-21T07:00:00+00:00

In this scenario, the "isAlive" check would communicate directly with service C. As a result, the "isAlive" check would find that service C is online and capable of servicing requests as expected, so no alert would be sent. If we had a monitor that informed us when our call volume was below a certain threshold value for a certain amount of time, we could be informed if there were some network issue, or other defect that prevented services from reaching us.

Beyond these couple of odd scenarios, however, we'll be applying monitors on the basis of our previously established reductive reasoning: ingress and egress points of the service, and general resources. That is, we'll apply rules such that all of our buckets of failures have an associated rule which will inform us if an API isn't satisfying QoS or correctness expectations.

How to Monitor

There are competing and varied schools of thought on the best way to approach monitoring, and a lot of depth as well. I've my own opinions based on experiences with a variety of approaches, and I'll expound upon the virtues of those in a moment. First though we should outline what it means to send an alert, and what precisely we expect.

An alert, by definition, is intended to get the attention of an on-call engineer. The expectation is that any monitor we've created has an expressly defined purpose, and reason for existing. An alert based off of a monitor needs to result in the ability of an on-call engineer to take a mitigating action to restore QoS or correctness.

On Apdex for Monitoring

A reasonably recently proposed solution with respect to the actual mechanism we use to implement our rules has emerged called "Apdex". I've worked with systems that utilized Apdex measurements before, and have a few gripes about it. In order to understand what I believe are shortcomings of the approach, we'll first need to have a basic understanding of the principle.

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