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Showing posts from September, 2020

An apache OOM (out of memory) emergency in a container

On Sunday last, a (Linux) server in my infrastructure that was running a fairly conservative number of docker containers in production was brought to its knees. The monitoring data (from prometheus) showed that cpu was all gobbled up (from an average of less than 2% to a steady 75%-ish) and remained gobbled up until the server was rebooted. Notably, the disk usage and throughput went down during the event, and memory usage did not change notably, nor was it notable high. On review of the messages log, one of the last entries before the event was documentation of an apache OOM (out of memory) event. On this server, apache is only running inside containers, which are generally limited to 500Mb (by docker). So presumably, a docker container running apache ran out of memory and tried to recover some memory and that was what triggered the event. Reviewing the log of requests before the emergency, it's not clear which container or url or urls might have been generating so much memory u