[colug-432] named pipe vs tail -F /path/to/file

[Jeff Frontz]

I'm not sure I completely understand the intent/implementation but wouldn't this work?

while true
do
    processPipeContents < namedPipe
done

The alternative would be to (if I remember the FIFO semantics) write something that opens the FIFO in non-blocking mode and then poll/select it.

Jeff

On Aug 2, 2012, at 19:50, Rick Hornsby <richardjhornsby at gmail.com> wrote:

> Curious about opinions/thoughts.  I have haproxy logging activity via
> syslog.  HAproxy logs contain lots of useful information about HTTP
> transactions (request, timing, result code, etc).  I'd like to process
> the logs in real time, so I set up syslog to not only write the log to
> a file, but also to a named pipe, /tmp/haproxy.log.pipe.  I figured
> this would be the ideal way to peel off and process log data as it
> happened (using awk, etc) - realtime.
> 
> Except for one thing - when syslog restarts for logrotate, the pipe is
> broken for a moment.  Anything reading from the pipe dies, because
> that's how pipes work.  So the script that was processing the log data
> coming off the pipe goes away.
> 
> One alternative is to tail -F /var/log/haproxy.log |
> /path/to/processor, but boy that just seems hackish - and not in the
> good way.
> 
> Is a named pipe the right tool?  Does it make sense to somehow trap
> the signal that is causing the script to bail?  It isn't critical that
> every single log event be processed, but we want to make a best effort
> so that we're not losing information.
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