[Bug 1429427] [NEW] Unexplainable time jumps in CRON

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Seyeong Kim (xtrusia):

[Impact]

on Trusty

logging to syslog via cron causes timestamp abnormals after several
hours.

[Test Case]

1. run below first,
while true ; do logger "hello syslog" ; sleep 1; done

2. register below script to crontab
for i in {1..100} ; do logger "hello syslog via cron" ; sleep 1; done

3. monitor syslog with below script
tail -f -n 100 /var/log/syslog

You can see weird timestamp in several hours.

[Regression Potential]

it's ratelimiting turn off code, could be issue with being off rate-
limit

[Other Info]

commit

>From 7a2e2473476d2b10a775affd9ac6c62b81c450e5 Mon Sep 17 00:00:00 2001
From: Tomas Heinrich <theinric at redhat.com>
Date: Thu, 24 Jul 2014 13:47:14 +0200
Subject: [PATCH 1/1] bugfix: plug a memleak in imuxsock

The hash table for the system socket was allocated twice. The other
one being in activateListeners().

This commit practically reverts: 34a77cde2423303da72ab773128a2ddcf41
The issue seems to be that the hash table is not initialized (to NULL)
rather then not being allocated.


#####################################################################
## old description

On my main server I see unexplainable time jumps backwards in the syslog. Those jumps affect CRON.
Example:

Feb 10 06:48:01 nostromo CRON[20351]: (root) CMD (    /storage/exec/checkinternet.sh 2>/dev/null 1>/dev/null)
Feb 10 06:49:01 nostromo CRON[20364]: (root) CMD (    /storage/exec/checkinternet.sh 2>/dev/null 1>/dev/null)
Feb 10 06:50:01 nostromo CRON[20386]: (root) CMD (    /storage/exec/status-nostromo.sh >/dev/null 2>&1)
Feb  7 05:40:01 nostromo CRON[20389]: (root) CMD (    /storage/exec/checkinternet.sh 2>/dev/null 1>/dev/null)
Feb 10 06:50:01 nostromo CRON[20390]: (root) CMD (    /storage/exec/checkinternet.sh 2>/dev/null 1>/dev/null)
Feb 10 06:50:01 nostromo CRON[20391]: (root) CMD (    /storage/exec/checkip.sh 2>/dev/null 1>/dev/null)

For debugging I did the following:
Start xclock and watch xclock and tail -f /var/log/syslog in parallel. When CRON logged a wrong time, xclock did NOT show any time jump but seemed to freeze for a fraction of a second.
Open a screen and start a script that will once per second read the time (in unix seconds) and compare the read time with the time read a second ago. If the current time was smaller, the script would send an email with a process list from before and after the jump. The script also never detected any time jump.

In summary, my current impression is that there might be a bug in CRON because no other programm seems to be able to see the "wrong" time. The server in question is syslog server for 4 servers and 3 network devices. The time jumps exclusively show in syslog entries from the local CRON instance. Not in any remote syslog entry and not in any other local syslog entry, e.g. from DHCPD, bind, tftpd, etc. etc.
Also, after a reboot, things work ok for several days upto about 2 or 3 weeks. Then the "time jumps" start to occur with increasing frequency.

I don't use user crontabs but maintain all jobs in /etc/crontab. I have
number of jobs which are triggered every minute and another number of
jobs which are triggered every 5 minutes (maybe some CRON internal
counter overflow problem?).

Hardware:
Asus P9D-V
Intel Xeon E3-1240L V3
16GB ECC RAM
128GB SSD System
3x3TB ZFS RaidZ2 storage
1x3TB Misc. data

CMOS battery already changed and board inspected.

nostromo:~ # lsb_release -rd
Description:    Ubuntu 14.04.2 LTS
Release:        14.04

nostromo:~ # apt-cache policy cron
cron:
  Installed: 3.0pl1-124ubuntu2
  Candidate: 3.0pl1-124ubuntu2
  Version table:
 *** 3.0pl1-124ubuntu2 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

** Affects: rsyslog (Ubuntu)
     Importance: Undecided
         Status: Confirmed

-- 
Unexplainable time jumps in CRON
https://bugs.launchpad.net/bugs/1429427
You received this bug notification because you are a member of Ubuntu Sponsors Team, which is subscribed to the bug report.