Created attachment 1402536 [details]
Reproducer: dummy program opening the journal and waiting forever

Description of problem:

This is a continuation of BZ 1540132 (rsyslogd not logging to /var/log/*).
It appears that the sd-journal implementation is very basic, causing 1 file descriptor to be consume for every file in the journal directory, even if these files will never be used later.
When there are many files, e.g.
- because of many users and with mode SplitMode!=none
- because of many rotated files, which can happen if system is alive since a long time

this leads to sd-journal consumers (e.g. rsyslogd/imjournal) to lack from file descriptors.

This is an issue since sd-journal consumers have to be "tuned" one by one and even with tuning, we can never know whether this will work in the future (on long living systems).


Version-Release number of selected component (if applicable):

systemd-219 (RHEL7), systemd-233 (Fedora26)


How reproducible:

Always


Steps to Reproduce:
1. Create persistent journal

  # mkdir -p /var/log/journal
  # systemctl restart systemd-journald

2. Create 2000 users

  # for i in $(seq 1 2000); do useradd user$i; passwd --stdin user$i <<< pass; done

3. Create the journal files for the users (e.g. connect to the system as the user using ssh)

4. Run reproducer in attachment


Actual results:

All filedescriptors from reproducer (default limit is 1024) are consumed by sd-journal