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As the other child comment said, are you shipping _all_ logs? For a K8s cluster of a few nodes, sure, you might send `/var/log/*` out, but that doesn't scale. I
by sgarland 4y ago
As the other child comment said, are you shipping _all_ logs? For a K8s cluster of a few nodes, sure, you might send `/var/log/*` out, but that doesn't scale. If you have weird Kubernetes problems like mysteriously dying containers that don't trip 137 (hello, non-init processes [0]), you will need to dive into kernel messages. For this particular example, there is to my knowledge one poorly-maintained package [1] that fixes this, but it also requires at the very least some Linux capabilities that might raise eyebrows with security, and as written it requires privileged containers. Thankfully this particular example will hopefully be fixed with cgroupsv2, but still.
SaaS DB like RDS is another example. I've seen mysterious growth on a read replica, which was fixed by restarting it. Temporary intrinsic tables were not the cause, if you were wondering. No noted errors were logged in its error log it shipped out, and of course the general log wasn't enabled because it generally gets absurdly large. Had this been a self-hosted installation, there may well have been clues that would have been available only by logging into the host.
"Cattle, not pets" is an admirable goal, but sometimes you have to play veterinarian on a few of your herd to figure out what illness is spreading, and how to inoculate against it.
[0] https://github.com/kubernetes/kubernetes/issues/50632 https://github.com/kubernetes/kubernetes/issues/50632
[1] https://github.com/transferwise/oomie https://github.com/transferwise/oomie
- amtamt 4y agoSeems "not well deployed system" or "system not well understood by developer", what stops one reducing retention to few hours for node kernel logs or having read only access to certain parts, if at all there are so many kernel/ sys logs. I have never come across a system where application logs were not multiple orders of magnitude more in volume than syslogs. Not sure what RDS vs in-house DB example was meant to convey. Ironically, these examples are only proving the point made in first comment.