Non-technical Description

An issue occurred with an overnight task which meant users were only seeing one trainee in the revalidation search lists. It was continously restarting and retrying until we were able to give it additional resources to work with. It then was able to run and fill out the search lists for recommendations and connections.

Trigger

• As part of the overnight sync job, on calling the GMC’s SOAP endpoint GetDoctorsForDB our service gmc-client-service experienced an out of memory error and crashed

• The message to trigger the sync job remained queued, and presumably kept re-triggering the error every time ECS spun up a new task

Detection

• Slack monitoring channel

  • Also reported & impact confirmed by users

Resolution

• Increased memory available to the task.

Timeline

All times in BST unless indicated

• 22 Jun 2023 00:05 : gmc-client-service crashes attempting to run the overnight sync job due to a lack of memory

• 22 Jun 2023 01:07 - 08:47 : The monitoring channel showed the task was stopping and being replaced.

• 22 Jun 2023 08:53 : User reported (on Teams) revalidation module is showing one person under notice

• 22 Jun 2023 09:30 : Stopped the 2-hourly checks of submitted recommendation, shortly after stopped the service temporarily to stop unhelpful logging

• 22 Jun 2023 09:41 : Moved sync start messages to new queues for debugging

• 22 Jun 2023 09:43 : Found logging to suggest incident started at 00:05 - around the time of the gmc sync job starting

• 22 Jun 2023 ~ 9:45 : Stopped gmc-client task on prod

• 22 Jun 2023 ~10:00 : Restarted gmc-client task on prod, observed the same debug logs (later appeared to be not relevant), task stopped again.

• 22 Jun 2023 10:15 : Changed Log level for gmc-client (set to debug) and pushed to preprod

• 22 Jun 2023 11:30 : Added JAVA_TOOL_OPTIONS in task definition, then updated memory from 512M to 2G. As part of deploying this change, the production issue became an issue for our preprod environment

• 22 Jun 2023 ~ 11:30 Triggered GMC sync again on preprod. Failed due to memory error when making SOAP request to GMC

• 22 Jun 2023 ~12:15 Triggered GMC sync again on preprod after increasing memory allocation, this time it worked

• 22 Jun 2023 ~12:20 Identified separate issue with preprod regarding missing queues, reran jenkins build to restore them

• 22 Jun 2023 ~12:20 Triggered GMC sync again on prod after increasing memory allocation, this time it worked

• 22 Jun 2023 ~12:40 GMC sync appeared healthy on prod and doctors were appearing in connections

5 Whys (or other analysis of Root Cause)

1. Why were no doctors showing in the revalidation recommendations and connections summary lists for most of the day? - Because the GMC overnight sync had failed

2. Why had the GMC overnight sync job failed? - Because the gmc-client-service kept crashing and restarting the sync process

3. Why did the gmc-client-service keep crashing? - Because it was experiencing an out of memory error every time it received a response from GMC
   It kept on crashing on startup because ?!?

4. Why was the gmc-client-service experiencing an out of memory error every time it received a response from GMC? - current unknown

• Why does it take so long for the GMC sync job to repopulate the doctors lists? - Because there’s a bottleneck in the CDC process (lambda)
  

Action Items

Lessons Learned