At 12:08 PM -0500 3/11/02, Lisa Casey wrote: >Could someone explain to me how chunky writes effect qpopper timeouts?
I don't know that it affects server timeouts, only client timeouts, but I suppose it might have an effect on server timeouts. By default, Qpopper 4.x aggregates small writes into one large packet. This makes TLS/SSL much more efficient, and can be faster in a normal network. However, if there is a lot of network congestion or other problems causing dropped packets between the server and the client, the large packet may get dropped and need to be resent, possibly several times. During this period the client receives nothing from the server. If the client has a very short timeout, it generates an error and closes the connection. Turning chunky writes off (or setting it to TLS only) forces Qpopper to send each network write as its own packet (at least when not under TLS/SSL). This increases the chances that something will reach the client before it times out. It's generally better to fix the network problem, or increase the client timeout, but if neither of those are practical in a situation, fiddling with chunky writes can help. > I'm >having a lot of problems with users getting timeouts when they attempt to >pop their mail. The error message I was seeing in /var/log/messages was: > >Mar 11 10:00:25 i2000 -s[39039]: (v4.0) Timeout (120 secs) during nw read >from username at IP address > >So I changed qpoppers timeout to 600 seconds but now I get a lot of error >messages like: > >Mar 11 10:00:25 i2000 -s[39039]: (v4.0) Timeout (600 secs) during nw read >from username at IP address. This is a server timeout, not a client timeout. > >Most of our customers use Outlook Express and we have changed the server >timeout in their settings from one to five minutes. Then you probably don't need to mess with chunky writes. > >The only other thing I see in the qpopper FAQ that addresses this issue is >the bit about chunky writes, but there's a couple of things I don't >understand. > >Since I already have qpopper installed and running can I just run >./configure again to change the chunky writes? Or should I use a >configuration file? I don't quite understand how I should create the >configuration file and just how to tell qpopper to use it. It's a lot easier to use a run-time configuration file than to recompile Qpopper. Not only do you avoid having to do a 'make realclean' and rerunning ./configure and make, but you can turn it on and off, for everyone or just some users. Just create the file (you can use the sample one in the distribution), put it somewhere, and then modify the flags passed to Qpopper when it is launched to point to it. This should all be covered in the Administrator's Guide.
