Greetings, An ongoing issue in container environments where Kubernetes is being used is that setting the overcommit parameters on the base system will impact all of the processes on that system and not all of them handle malloc failing as gracefully as PG does and may allocate more than what they really need with the expectation that it'll work. Folks have already started hacking around this issue by using things like LD_PRELOAD'd libraries to put code between palloc and malloc, but that could cause any malloc to fail and it strikes me that, in an ideal world, we could give users a way to constrain the total amount of memory allocated by regular backends (or those where a user is able to control how much memory is allocated, more generally) while not impacting the processes which keep the server running.
I wanted to bring this general idea up for discussion here to get feedback on the concept before going off to write code for it. Seems unlikely that it would be a huge amount of code while there's likely to need to be discussion about how one would configure this and how we might handle parallel query and such. Empirically, the LD_PRELOAD hack does, in fact, seem to work, so even a simple approach would be helpful, but certainly there is an angle to this where we might eventually allow certain backends (perhaps certain roles, etc) to allocate more and others to not be allowed to allocate as much, etc. Ideally we would look to go with the simple approch first and then we can contemplate making it more complicated in the future and not try to accomplish it all in the first pass. Of course, we should keep in mind such ideas and try to avoid anything which would preclude us for adding that flexibility in the future. Thoughts? Thanks, Stephen
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