[Spread-users] mod_log_spread and RELIABLE_MESS

[John David Duncan]

> Daniel Rall wrote:
>> John David Duncan <jdd at greatschools.net> writes:
>>> So here's a simple question:  is there any advantage in having
>>> mod_log_spread send messages as UNRELIABLE_MESS rather than
>>> RELIABLE_MESS?
>> Indeed.  Without flow control built in to the Spread server, the
>> "reliable" messages aren't nearly so reliable.
>


Well, there is certainly some flow control built into spread, and there 
might not be any good way for mod_log_spread (as a sender) to implement 
application-level flow control, because of the way apache processes come 
and go.

My problem isn't that my logging machine can't keep up -- it's that the 
slowest webserver/sender occasionally gets bogged down, and that this 
effects the rest of the segment.

What I'm asking, since I don't need the semantics of reliable messages, 
is whether it actually makes life any easier for spread if I send 
unreliable ones.



> I have mod_log_spread logging fine in a decent size production cluster 
> (4 million hits/day) and see almost no message loss on the Spread 
> level, so even if I did change the RELIABLE_MESS to UNRELIABLE_MESS, I 
> would have only lost a handful (<100) messages over the past week.
>
> If you are seeing message loss on the link layer or are overflowing 
> your recv buffers, then you need to investigate the way you have Spread 
> set up.