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Asked: 2026-05-25T22:06:37+00:00

Background: I had an issue with my Rails server recently where it would stop

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Background:

I had an issue with my Rails server recently where it would stop responding, requiring a bounce to get it back up and running. This issue was due to a controller that does some forking upon receiving a POST, to do some heavy-weight concurrent processing — server response time kept increasing until the server completely stopped responding. I’m pretty sure I have fixed that issue (DB connections copied upon fork weren’t getting closed in child processes), but it would be great to authoritatively test that.

Question:

Is there a way to monitor open file descriptors from inside my Rails app? It’s running on Linux, so I’ve been mucking around with the proc filesystem and the lsof command to observe the open file descriptors; this is messy, because it only gives you a snapshot of the current processes. Ideally I would like to print the open file descriptors in the parent and child processes before, during, and after the processing, to ensure that file descriptors don’t stay open past their welcome.

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1 Answer

  1. Editorial Team

    One method to consider (probably the simplest) is using a background worker of some sort, such as with Workling, and making it run lsof in intervals, and getting output using syntax:

    `lsof | grep something` # shell command example.

    Programs like lsof can really hurt performance if run too frequently. Perhaps every 10s to 30s. Perhaps down to maybe 5s, but that’s really pushing it. I’m assuming you have a dedicated server or a beasty virtual machine.

    In your background worker, you can store these command results into a variable, or grep it down to what you’re really looking for (as demonstrated), and access/manipulate the data as you please.

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