Non-technical Description

We have a job running up to once per minute that follows changes in the revalidation database. It keeps track of what the most recent change processed was in order to know where it should pick up next time. We received an alert that the reference to that latest change couldn’t be used. The reference to the latest recommendation change was no longer available. We were fortunate that changes to doctors continue.

We moved the old reference and made a change to the code to enable the job to restart tracking changes.

Between Saturday morning and Monday morning some changes in the Reval Database would not have been reflected on Reval UI, however as there were no changes during this period

Trigger

• There were a lot of Sentry errors at about 2,800. It doesn’t look like anything recommendations were made and so we were fortunate nothing was affected.

• Combination of 3 hour window having elapsed and transaction log rolling over

Detection

Resolution

Timeline

All times in GMT unless indicated

• 02 Feb 2024 18:07 - Last recommendation submitted.

• 03 Feb 2024 05:00-05:29 - Backup window

• 03 Feb 2024 05:00-05:29 - Backup window

• 03 Feb 2024 05:29 - Earliest Slack message identifying an issue with the production CDC Lambda

• 05 Feb 2024 ~06:00 - renamed attribute in the database collection. This caused other issues which were resolved by applying a hotfix to generate a new reference until a more robust solution is implemented

Root Cause(s)

• Sentry errors were caused by a reference which could not be found

• The reference was to the change stream for the last change in the recommendation collection, which was presumably cleaned up

• The change stream was cleaned up*

• The change stream is configured to hold references for at least to 3 hours (default)

Action Items

Lessons Learned