Date |
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Authors | |
Status | Done |
Summary | |
Impact | Applicants and notifications were exported a few hours later than usual |
Non-technical Description
There were a significant number of errors that occurred when we received files from ESR on Thursday afternoon. This is because of an issue with the service that checks login details. We processed the files again to ensure all information had been received before re-enabling the processes that generate applicant and notification information that goes to ESR.
Trigger
Slack alerting
Detection
There were 2358 messages in the dlq until we got the notification in #monitoring-prod Slack channel and shovelled them.
Resolution
Processed the files a second time.
Timeline
BST unless otherwise stated
14:45 noticed the alert: “RabbitMQ PROD too many messages in the DLQ” in #monitoring-prod channel, then shovelled them to another queue “esr.dlq.2024.03.13“
14:50 messages still coming through to dlq, initially an additional 157 followed by a further 589
15:15 Noticed errors in sentry-esr channel - ResourceAccessException: I/O error on GET request
15:33 had a huddle and looked into the messages in queue “esr.dlq.2024.03.13“
15:45 observed one of the TCS nodes had deregistered.. Further investigation showed TCS had spiked at 100% CPU and memory - see attached
16:00 Agreed to wait until 17:00 and observe the dlq to check if any additional messages.
17:00 Processed RMC files from 13th March (moved messages into the normal flow for processing)
Root Cause(s)
The quantity of messages in the dead letter queue showed a variety of types of messages failed. Messages which relied on enrichment from information in TCS seem to be the ones which failed.
TCS was busy but still functional. There were timeouts when TCS requested information about the user making the request.
Profile was experiencing a short spike in CPU usage.
Action Items
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