Date |
|
Authors | |
Status | Documenting |
Summary | TIS21-3846 - Getting issue details... STATUS |
Impact | The recommendations search page was not being updated for a number of hours through the day |
Non-technical Description
The list on the revalidation recommendation doctors page is maintained in a searchable index by aggregating 1)data from updates to TIS and 2)GMC data we store ourselves. The mechanism for keeping this aggregated data up-to-date had stopped running - so no updates were coming through to this list. They were queued up, waiting to be processed. The details pages for each of doctors were unaffected and recommendations could be made without issue.
On each of several restarts, some of the queued updates were used and the service started working again normally. We’ve reduced the frequency of checking if submitted recommendations have been accepted because that also sends updates to the searchable index.
Trigger
GMC doctors that should have been under notice were not showing up in the “Under Notice” list.
Detection
Message from 2 users
Resolution
A “force redeployment” update of the recommendation service
Gave users links to details pages for doctors which could not be found
Timeline
BST unless otherwise stated
02:26 Earliest identifiable point of “something going wrong” - still unknown
02:26 to 08:07 - Queue to recommendation for ‘doctor view’ update built steadily to ~83K
08:21 - First report in user channel
12:07 - Picked up for investigation
12:07 to 14:00ish - Checked database & ElasticSearch index
13:00 - Checked the return list of GMC for north west
14:00ish - Found messages in reval.queue.masterdoctorview.updated.recommendation didn’t get consumed
14:14ish - Having found that there were “recommendation status checks” being processed from overlapping runs, we reduced the frequency of checking for updates on submitted recommendations
16:00ish - Force a new start of recommendation service
16:00ish - Identified that rabbitMq was reporting 0 consumers
17:00ish to 18:00ish - Identified error in queue declaration. Raised, merged and pushed a PR
18:00ish - Noticed that messages are briefly consumed on startup but number of consumers quickly drops to 0
18:40ish - Final redeploy of recommendation service cleared out backlog and appeared to restore consumers stably
18:40ish - Identified that there was still some discrepancies in the data between masterdoctorindex and recommendation index, decided to wait until after overnight doctor sync to do quick reindex
~07:30 - Checked for doctors that were mentioned and found both were appearing
09:08 - Informed users of reindex (brief downtime expected)
11:09 - Reindex complete, service restored
Root Cause(s)
Doctors reported as not showing in the search list
ElasticSearch Index for Recommendation Service isn’t being updated
Large backlog of messages stuck on a queue for updating the index
Message Consumers disappeared but after the final
aws ecs update-service --force-new-deploymentdropped to one before going back up to 3This may have been related to load & thread starvation.
Action Items
Action Items | Comments | Owner |
|---|---|---|
Monitoring for queue depth, consumption or some other combined metric to say whether messages are being processed ‘acceptably’, e.g. Number of consumers, message rate while there are messages, message depth for a period of time / latency | ||
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| |
Test / Replicate in stage… by loading c.100K messages onto the queue that was affected to see if this was likely a cause of the defect | ||
Compare indexes/indices composite doctor view & recommendation view to check for the potential scale of the problem | ||
Can we get extra application insights / metrics about thread usage & other resources | ||
Consider a “drop & rebuild” of the index? | Will consider as part of TIS21-3416 - Getting issue details... STATUS |
Lessons Learned
We need more monitoring on our rabbitmq queues and activity
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