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Why don't I see the 'system.processes.open_file_descriptors' metric?

Users that enable the process check in a Datadog Agent running on Linux OSs notice that the system.processes.open_file_descriptors metric is not collected or reported by default. This occurs when the process being monitored by the process check runs under a different user than the Agent - the dd-agent user doesn’t have full access to all files in /proc, which is where the Agent looks to collect data for this metric.

Users can enable the try_sudo option in the process check configuration and add the appropriate sudoers rules:

dd-agent ALL=NOPASSWD: /bin/ls /proc/*/fd/

This allows the process check to use sudo to execute the ls command but only to the list of contents of the path /proc/*/fd/.

If users see this line in the Datadog error.log: sudo: sorry, you must have a tty to run sudo, users should visudo and comment out the line Default requiretty.

See the following Github issues for more info on this matter as well as other potential methods of capturing this metric on Linux machines.

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