I am using slony_logshipper for admittedly the first time. I keep
getting errors like this:

INFO  2008-06-26 17:31:31 > Processing archive file
/foo/logship/in/slony1_log_2_00000000000000000121.sql
ERROR 2008-06-26 17:31:31 > PGRES_FATAL_ERROR: ERROR:  Slony-I: node
is on archive counter 118, this archive log expects 120
Query was: select "_slony".archiveTracking_offline('121', '2008-06-25
18:21:35.407583');
WARN  2008-06-26 17:31:31 > waiting for resume

I can simply kill the slony_logshipper process and restart and it will
make it a little further before stopping on the same error but with
higher numbers. This seems odd. Seems if there is a problem, it should
continue to be a problem each time I run slony_logshipper. What is
this error and why does it make it a little further each time?

Another user explains this exact same issue, but there was not a
resolution in the thread:
http://www.nabble.com/node-is-on-archive-counter-44,-this-archive-log-expects-45-td16970660.html

On a side note, the way slony_logshipper works seems kind of odd, but
then again, there is a lot I don't know about it. It is odd to me that
it reaches a fatal error yet does not actually stop the process. You
have to either kill it, or run the command again with a -r option to
"resume from error". However, the resume option never allows the
process to continue past the error. If instead, I kill the
slony_logshipper process, then restart it, it is always able to apply
a few more log files before barfing the error.