What is the problem with celery: Substantial drift from celery@abc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:35:37.001612 recv: 2014-04-14 14:36:06.011759]

The celery workers keep outputting those kind of warning message below and they seem not work well. Is there any one who can help me work out this problem?

[2014-04-14 14:33:42,123: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:42.123609 recv: 2014-04-14 14:34:11.140435]

[2014-04-14 14:33:44,125: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:44.125058 recv: 2014-04-14 14:34:13.141632]

[2014-04-14 14:33:46,126: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:46.126766 recv: 2014-04-14 14:34:15.143480]

[2014-04-14 14:33:48,129: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:48.129440 recv: 2014-04-14 14:34:17.145398]

[2014-04-14 14:33:49,776: WARNING/Worker-1312] the length of content: 2415 [Apr 14 14:33:49] Fetched original text: now 2415 bytes vs. was 170 bytes [2014-04-14 14:33:50,131: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:50.131493 recv: 2014-04-14 14:34:19.147759]

[2014-04-14 14:33:52,133: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:52.133548 recv: 2014-04-14 14:34:21.149592]

[2014-04-14 14:33:54,947: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is 29 seconds. [orig: 2014-04-14 14:33:54.947904 recv: 2014-04-14 14:34:23.963787]

[2014-04-14 14:33:55,246: WARNING/Worker-1312] the length of content: 5752 [Apr 14 14:33:55] Fetched original text: now 5752 bytes vs. was 954 bytes [2014-04-14 14:33:56,949: WARNING/MainProcess] Substantial drift from celeryabc03 may mean clocks are out of sync. Current drift is

29 seconds. [orig: 2014-04-14 14:33:56.949390 recv: 2014-04-14 14:34:25.965050]

And the time zone of the server is:

date -R

Mon, 14 Apr 2014 14:39:40 +0800

The time zone of celery is:

from celery.utils.timeutils import utcoffset /usr/local/lib/python2.7/dist-packages/kombu/utils/init.py:393: UserWarning: Module readline was already imported from /usr/lib/python2.7/lib-dynload/readline.so, but /usr/local/lib/python2.7/dist-packages is being added to sys.path from pkg_resources import iter_entry_points utcoffset() 8

Any one know what cause the problem? Any one know how to solve them?