Seeing NULLs in my Log::Log4perl log file

talexb has asked for the wisdom of the Perl Monks concerning the following question:

I'm seeing a blob of NULLs in the log file for a script that's using Log::Log4perl, like this:

2315760   616f    2064    7661    7265    6761    7365    203a    2e30
         o   a   d  sp   a   v   e   r   a   g   e   s   :  sp   0   .
2316000   3133    3020    332e    2035    2e30    3233    000a    0000
         3   1  sp   0   .   3   5  sp   0   .   3   2  nl nul nul nul
2316020   0000    0000    0000    0000    0000    0000    0000    0000
       nul nul nul nul nul nul nul nul nul nul nul nul nul nul nul nul
*
2320000   3032    3432    302f    2f35    3130    3020    3a37    3034
         2   0   2   4   /   0   5   /   0   1  sp   0   7   :   4   0
2320020   303a    2032    5245    4f52    2052    203a    2f2e    7263
         :   0   2  sp   E   R   R   O   R  sp   :  sp   .   /   c   r
[download]

The output is from the command od -ha cpt3.log.1 | less. Based only on the fact that the NULLs end on a block boundary, I'm wondering if this might be a problem with the hard drive. Thoughts?

Alex / talexb / Toronto

Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.

Comment on Seeing NULLs in my Log::Log4perl log file Select or Download Code

Replies are listed 'Best First'.
Re: Seeing NULLs in my Log::Log4perl log file by NERDVANA (Priest) on May 01, 2024 at 20:11 UTC
Was there a reboot around that time? I sometimes see blocks of NULs written to log files (unrelated to Perl) if a machine lost power. I suspect it has something to do with the file metadata (saying the file now includes that block) getting committed to the drive before the contents of that block are fully written.	[reply]
Re^2: Seeing NULLs in my Log::Log4perl log file by talexb (Chancellor) on May 02, 2024 at 01:46 UTC
Huh. Good catch. The response I was ready to post was "Nope, there were no reboots, and there were about a dozen other scripts that didn't exhibit this behaviour." -- but I thought, Meh, I better have a look. No one's supposed to touch this server, and (I believe) it's on a UPS, but it looks like someone power cycled it this morning at about 0730. That's not good. I'll have to investigate some more. Alex / talexb / Toronto Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.	[reply]