Configure dogpile.cache to deal with memcached pods failures #511
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gibizer
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Nov 27, 2024
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The direction looks good. Thanks @lmiccini !
I agree that it would be worth trying this out in nova-operator as well with some manual update testing to see the timing differences. But I will not have time to do it soon.
cc @mrkisaolamb for awareness.
bogdando
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Nov 27, 2024
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Whenever one of the mecached pods disappears, because of a rolling restart during a minor update or as result of a failure, APIs can take a long time to detect that the pod went away and keep trying to reconnect. From a quick round of tests we saw downtimes up to ~150s. By enabling the retry_client and limiting the number of retries the behavior seems much more acceptable. Similarly, when TLS is not in use, we may want to set a lower value for memcache_dead_retry so to eventually reconnect to a new pod (having the same dns name but different ip) much faster.
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Whenever one of the mecached pods disappears, because of a rolling restart during a minor update or as result of a failure, APIs can take a long time to detect that the pod went away and keep trying to reconnect.
From a quick round of tests we saw downtimes up to ~150s.
By enabling the retry_client and limiting the number of retries the behavior seems much more acceptable.
Similarly, when TLS is not in use, we may want to set a lower value for memcache_dead_retry so to eventually reconnect to a new pod (having the same dns name but different ip) much faster.
Jira: https://issues.redhat.com/browse/OSPRH-11935