Date |
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Authors | |
Status | Done |
Summary | the system is really slow and when I try to select records they don't open sometimes and the error below has been appearing for a few days |
Impact | Users were unable to retrieve information as a result slowness from Recommendation and Connection detail list as the system was reported slow. |
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Non-technical Description
The message broker is a service that helps to connect systems without needing them all to be 100% available and responding instantly all of the time.
The broker has several coordinated computers (nodes) to ensure it functions properly. In the weekly maintenance period, there were so many “in-flight” messages that when one of the nodes was replaced and needed to catch up with the other two, it used too much of the memory from those 2 remaining nodes. That placed the broker into a protective “quarantine” mode, allowing messages to be read but restricting the publishing of messages.
We use the message broker for most of how we process information to and from ESR, also for some of how we pull information from the GMC and for recording when Conditions of Joining are signed by trainees.
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Trigger
Automated maintenance with large queue
Detection
Alerts in monitoring channel
Resolution
Stopped the synchronisation across nodes in the cluster
Horizontal scaling consumers of queues with lots of message
Timeline
22:00-23:59 - Message Broker maintenance window
22:50 - Broker nodes begin being restarted
22:56 - One of the secondary nodes becomes unreachable from the primary
23:28 - Primary and 1 secondary enter an “Memory Alarm”state, although memory reported for the broker did not reflect this
08:41 - First of 3 failed attempts of a trainee to digitally sign conditions of joining
08:45 - Picked up alert and began identifying the issue. We paused some of the feeds in order to free up some
12:11 - Cancelled Sync of largest queue
12:13 - Other queue finished synchronising
- Further maintenance window forced synchronisation, this time with much smaller queues
Revalidation system is really slow when users tries to select records they don't open sometimes an error message occurs" oops something went wrong" which has been appearing for a few days. A user in a different region states it is clearly a speed / data retrieval issue. Three users from three different had raised this issue via the UR Teams Channel.(North West, South East and South West).
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Trigger
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Detection
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Resolution
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Timeline
10:04 - Message received from user to inform that the application is slow followed with error messages
10:06 - First responder informed that the Team did work on this and requested if users could report if performance is still impacted.
15:22 - another user from a different Region reported still having the same issue
15:25 - User raised “clearly a speed / data retrieval issue - we are having this problem also, even using a direct URL is incredibly slow”.
11:00 - Further investigation was commenced to establish the cause of the issue
12:00- We restarted the Core service in Production 1
12:34 - No responses or timeout since
5 Whys (or other analysis of Root Cause)
We received “connection timeout” alerts because the message broker was unavailable.
The broker was in a “Memory Quarantine State”
There was a node started and required synchronising over 1.5M messages
Message broker underwent maintenance (restarts/replacement) with too many messages queued up
2 microservices with audit queues had stopped consuming messages.
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Action Items
Action Items | Owner | Comments |
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Simulate the failure / test pre-emptive alerting | Mini-hack PoC prep | |
Rearchitect:
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Alert on a certain queue size |
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