December Failed Jobs Postmortem

In December 2018 we had two incidents (2018-12-14 and 2018-12-19) which resulted in a number of failed jobs. The first one caused 0.8% of jobs to fail (in a 24h window) and the second one caused 1.2% of jobs to fail (in a 24h window). 

Both incidents were caused by unavailability of the Docker container registry (Amazon ECR). In the first incident we were receiving exceeded quota errors and we initially thought that these were related to higher infrastructure load. A thorough investigation showed that we were nowhere near the limits and now we finally got a confirmation from Amazon that this was an error on their side. The second incident was caused by complete unavailability of the ECR for approximately 30 minutes.

Technical background:

The Docker container registry is used to store the executable code for each component running in Keboola Connection. It is accessed on every job run to make sure that a job is run with the most recent version of the component code. During 2017 we moved most of our components to the Amazon ECR which proved to be very reliable. The outage mentioned above is the first one since 2016 when we began using it. 

Most of the Keboola's infrastructure is duplicated with automatic fail-safe mechanisms in place. That means that minor outages in the underlying services are not noticeable by the end-users. Duplicating the Docker container registry, however, is not an easy task because Docker is not really ready for that yet. So this remains a single point of failure.

Measures already taken and yet to be taken:

  • We have immediately implemented a retry mechanism in our code which will handle short outages, the retry mechanism will also be further improved.
  • We have already started (prior to the incident) reworking the component code validation tooling so that the number of queries to the ECR is reduced by several orders. This will help reduce the impact, should a similar incident happen again.
  • We'll use a dedicated ECR for each Keboola Connection region which will reduce the affected scope for any similar incident in the future.