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I'm a beginner but I did install fpm to see how it works.
Did you set the fpm acces logs?
; The access log file
; Default: not set
access.log = "/usr/local/etc/php/8.0/log/www.access.log"
And the status page?
; The URI to view the FPM status page.
If this value is not set, no URI will be
; recognized as a status page. It shows the following information:
pm.status_path = /fpm-status
I don't know how ALB works, but does it
make different requests/hit?
If not, that's maybe why FPM coughs
Cordially
Luis
On 20/12/2021 01:08, Dan Washusen
wrote:
Also worth noting that Nginx OS does not experience the
issues (otherwise same setup)...
Yeah, all those parameters are configured and
everything works fine when I switch to the MPM worker
module. The 408 errors are returned by Jetty and ProxyPass
is configured to not reuse connections (which seems to
suggest not a KeepAlive issue), Jetty is erroring because
it receives no request data. Kind of seems like the MPM
event module is missing events/data (when behind the
ALB)...
Given that the TCP network load balancer doesn't show
the issue, maybe it's something to do with how the ALB
sends the data to the instance (e.g. Jumbo frames vs the
standard MTU)...?
I will still say this is a timeout issue. Set the
ALB timeout to 3600 which is the max possible in case
you do not know where to start from. I guess you
already have ALB logs enabled.
In apache check the KeepAliveTimeout,
RequestReadTimeout and ProxyTimeout and make sure they
make sense for your user case. Enable debug logs too
for more details.
It is tough to guess without knowing your relevant
configuration but 408 is usually caused by client
connection being closed while keep-alive in use.
Thanks for the response. Timeouts are
configured appropriately...
To clarify; everything works fine through a TCP
Network Load Balancer pointing at the same
infrastructure. There is something about having a
HTTP based Application Load Balancer in front of
an MPM event configuration that's causing
issues...
In a proxy chains like this
getting the timeouts in sync is the most
important thing. Make sure that you have done
that.
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
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