Occam’s razor strikes again!
Tonight we ran into an interesting problem. A web service – with a very simple time-elapsed check – started reporting negatives… Racking our brain, pouring over the code, produced nothing. It was as if the clock were jumping around randomly! No! On a whim Barry checked it and the clock was, indeed, jumping around…
# while [ 1 ]; do date; sleep 1; done Wed May 30 04:37:52 UTC 2007 Wed May 30 04:37:53 UTC 2007 Wed May 30 04:37:54 UTC 2007 Wed May 30 04:37:55 UTC 2007 Wed May 30 04:37:56 UTC 2007 Wed May 30 04:37:57 UTC 2007 Wed May 30 04:37:58 UTC 2007 Wed May 30 04:37:59 UTC 2007 Wed May 30 04:38:00 UTC 2007 Wed May 30 04:38:01 UTC 2007 Wed May 30 04:38:02 UTC 2007 Wed May 30 04:38:19 UTC 2007 Wed May 30 04:38:21 UTC 2007 Wed May 30 04:38:22 UTC 2007 Wed May 30 04:38:23 UTC 2007 Wed May 30 04:38:24 UTC 2007 Wed May 30 04:38:08 UTC 2007 Wed May 30 04:38:09 UTC 2007 Wed May 30 04:38:10 UTC 2007 Wed May 30 04:38:28 UTC 2007 Wed May 30 04:38:12 UTC 2007 Wed May 30 04:38:30 UTC 2007 Wed May 30 04:38:31 UTC 2007 Wed May 30 04:38:32 UTC 2007 Wed May 30 04:38:33 UTC 2007 Wed May 30 04:38:34 UTC 2007 Wed May 30 04:38:35 UTC 2007 Wed May 30 04:38:19 UTC 2007 Wed May 30 04:38:20 UTC 2007 Wed May 30 04:38:21 UTC 2007 Wed May 30 04:38:22 UTC 2007 Wed May 30 04:38:40 UTC 2007 Wed May 30 04:38:41 UTC 2007 Wed May 30 04:38:42 UTC 2007 Wed May 30 04:38:43 UTC 2007 Wed May 30 04:38:44 UTC 2007
Hardware issue then? Battery?
SMP issue, actually…
Ha. Been there!
Years back I was helping a friend debug an ATM-ish program that was doing its stuff over a serial line. The problem was that the code that tested the serial line had this weird heisenbug. One minute working. The other not.
After about a day and a half we finally figured out that maybe… just maybe… there actually was an intermittent fault in the cable. D'oh!