Bug 2010947
| Summary: | journalctl -f with MESSAGE_ID= before messages with that ID exist in the journal results in "buffered" output of future messages | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 8 | Reporter: | John Kyros <jkyros> |
| Component: | systemd | Assignee: | David Tardon <dtardon> |
| Status: | CLOSED MIGRATED | QA Contact: | Frantisek Sumsal <fsumsal> |
| Severity: | low | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 8.4 | CC: | andbartl, dornelas, dtardon, systemd-maint-list |
| Target Milestone: | rc | Keywords: | MigratedToJIRA |
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2023-09-21 11:14:20 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 1997404 | ||
I cannot reproduce this. I tried to run journalctl both manually and via a service, with and without tee, but I haven't seen any delay in the output. Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug. This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there. Due to differences in account names between systems, some fields were not replicated. Be sure to add yourself to Jira issue's "Watchers" field to continue receiving updates and add others to the "Need Info From" field to continue requesting information. To find the migrated issue, look in the "Links" section for a direct link to the new issue location. The issue key will have an icon of 2 footprints next to it, and begin with "RHEL-" followed by an integer. You can also find this issue by visiting https://issues.redhat.com/issues/?jql= and searching the "Bugzilla Bug" field for this BZ's number, e.g. a search like: "Bugzilla Bug" = 1234567 In the event you have trouble locating or viewing this issue, you can file an issue by sending mail to rh-issues. You can also visit https://access.redhat.com/articles/7032570 for general account information. |
Description of problem: We were using "journalctl -f" in the OpenShift MCO operator to watch for login events and we noticed that we don't get any (I suspect because we don't ever reach 50+ logins to a RHCOS box) If you: - run "journalctl -f" with a MESSAGE_ID= AND - there are no matching log messages already in the journal at the time the command is run Then: - once messages with that MESSAGE_ID do exist, you will not receive them until some number/amount/size of them accumulate Version-Release number of selected component (if applicable): systemd 239 (239-45.el8_4.2) on RHCOS systemd 248 (v248.7-1.fc34) on FCOS How reproducible: Every time. Steps to Reproduce: 1. Create a unit that logs filtered logs to a text file: sudo cat << EOF > /etc/systemd/system/early_listen.service [Unit] Description=Hang journalctl before anyone logs in by filtering both unit and message id Before=network-online.target [Service] User=root ExecStart=/bin/sh -c "journalctl -b -f -o cat -u systemd-logind.service MESSAGE_ID=8d45620c1a4348dbb17410da57c60c66 | tee /tmp/journal_unit_messageid.txt" [Install] WantedBy=multi-user.target EOF 2.) Enable that unit systemctl enable early_listen 3.) Clear your journal: sudo journalctl --flush sudo journalctl --vacuum-time=1s 4.) Restart your server (may be able to get by without rebooting, I just always did) sudo systemctl reboot 5.) When the server comes back up, login/ssh into the server ssh core.122.16 6.) observe that /tmp/journal_unit_messageid.txt is still empty cat /tmp/journal_unit_messageid.txt 7.) if you repeatedly login in a loop, after some number of logins (usually > 50) it will snap out of it and events start coming out immediately Actual results: Messages do not come out until some unseen/unknown threshold is met Expected results: Messages come out as they occur Additional info: - It *feels* like buffering, and at first I thought it was standard output buffering and I was doing something wrong, but after testing I don't think so. I also ran it with "stdbuf" for good measure and it didn't help. - If MESSAGE_ID is omitted, journalctl works as expected and messages are returned immediately - Any "journalctl -f" process started *after* a login message is present in the journal does return (and continue to return) events immediately - It does not appear to be time based -- the messages do not seem to come out after days or hours, the only time they start coming out again is when there seem to be "enough of them"