Bug 1253649 - Regression: journalctl -f broken with initially empty filter result
Summary: Regression: journalctl -f broken with initially empty filter result
Alias: None
Product: Fedora
Classification: Fedora
Component: systemd
Version: 22
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Jan Synacek
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2015-08-14 11:27 UTC by Marius Vollmer
Modified: 2015-09-11 06:42 UTC (History)
11 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2015-09-11 06:42:43 UTC
Type: Bug

Attachments (Terms of Use)

Description Marius Vollmer 2015-08-14 11:27:40 UTC
Description of problem:

journalctl --follow will exit immediately if there are initially no matching entries.  Instead, it should block until a matching entry is appended to the journal.

Example: If you have a new service unit that has never been started, the following will not give the expected result:

 term1# journalctl -f -u new-service
 -- No entries --

 term2# systemctl start new-service

I would expect journalctl in term1 to block and then show the entries produced by new-service.unit when it is eventually started in term2.

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

How reproducible:

Steps to Reproduce:
1. journalctl -f -u nonexisting.service; echo Status $?

Actual results:
-- No entries --
Status 0

Expected results:
<no output and journalctl blocks forever>

Additional info:
This is a regression.

Comment 1 Stef Walter 2015-08-14 12:14:16 UTC
This breaks Cockpit: https://github.com/cockpit-project/cockpit/issues/2571

Comment 2 Marius Vollmer 2015-08-14 12:37:08 UTC
This is caused by


which causes journalctl to exit early when there no matches, even with --follow.

That patch should probably look like this:

diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -2057,6 +2057,10 @@ int main(int argc, char *argv[]) {
                 log_error_errno(r, "Failed to iterate through journal: %m");
                 return EXIT_FAILURE;
+        if (r == 0 && !arg_follow) {
+                printf("-- No entries --\n");
+                goto finish;
+        }
         if (!arg_follow)

Comment 3 Stef Walter 2015-08-14 14:09:08 UTC
This regression is in systemd-219-21

systemd-219-20 isn't affected.

Comment 4 Stef Walter 2015-08-14 14:16:21 UTC
The commit containing the regression:

commit 02ab86c732576a71179ce12e97d44c289833236d
Author: Lennart Poettering <lennart>
Date:   Fri Jul 24 02:10:32 2015 +0200

    journalctl: properly detect empty journal files
    When we encounter a journal file with exactly zero entries, print a nice
    message and exit, and don't print a weird error message.

Comment 5 Stef Walter 2015-08-14 14:54:39 UTC
The fix posted by Marius above still has the symptom of printing strange messages like: Failed to get realtime timestamp: Cannot assign requested address

Posted a patch upstream which accounts for that: https://github.com/systemd/systemd/pull/958

Comment 6 Stef Walter 2015-08-17 09:24:06 UTC
Fix merged upstream: https://github.com/systemd/systemd/pull/958

Comment 7 Stef Walter 2015-08-17 13:21:01 UTC
Cockpit has temporarily disabled testing the journal in its test suite for this regressed systemd version: 219-21

However Cockpit is still broken by this bug.

Comment 9 Jan Synacek 2015-09-11 06:42:43 UTC
Fixed by https://bodhi.fedoraproject.org/updates/systemd-219-23.fc22

Note You need to log in before you can comment on or make changes to this bug.