In a proxy chains like this getting the timeouts in sync is the most important thing. Make sure that you have done that.
On Mon, 20 Dec 2021, 08:37 Dan Washusen, <d...@reactive.org> wrote: > Hi All, > I've been experimenting with the MPM event module with Apache instances > sitting behind an AWS Application Load Balancer (ALB) and it really doesn't > seem to be working well. Response times shoot up (compared to MPM event > worker) and we see a fair few 502 errors returned (by the AWS ALB. > > The basic layout is: AWS Application Load Balancer -> Apache 2.4.x -> AWS > Internal TCP Load Balancer (NLB) -> Jetty App Servers > > Debugging the issue I think I traced it down to Jetty returning a 408 > error because it can't read the request body in a timely manner. So it > seems like for some reason MPM is sending the request body...? > > We're running Ubuntu 20.04 with Apache 2.4.41-4ubuntu3.8 with the > following worker configuration: > > ServerLimit 250 > StartServers 100 > MinSpareThreads 75 > MaxSpareThreads 250 > ThreadLimit 64 > ThreadsPerChild 64 > MaxRequestWorkers 8000 > > I've come across several random posts mentioning that the MPM event module > doesn't work behind an ALB but no-one seems to be into any detail. Anyone > have some debugging/configuration suggestions? > > Thanks, > Dan > > p.s. I've created a serverfault post showing graphs etc: > https://serverfault.com/questions/1087747/apache-2-4-mpm-event-module-causing-intermittent-502-errors-and-slow-response-ti >
