We have mod_proxy doing balancing and working great with the exception of
one thing, the health check. I'm talking about the heartbeat interval that
tells mod_proxy if our java app instances are ok.

I read the docs here:
https://httpd.apache.org/docs/current/mod/mod_proxy_hcheck.html

I'm pretty sure the issue is that the health check is not picking up the
custom header I need to talk to a WebObjects application (java). I'm
wondering if there is a way to configure it or if it simply isn't possible
and am looking for advice on appending this header.

When setting up the proxy balancer, I initially had the same problem but it
was quickly solved by adding the following line before the proxy balancer
definition:
RequestHeader append x-webobjects-adaptor-version "mod_proxy"

What that did was add an arcane header that the java app (NeXT/Apple
WebObjects) instances need to see in order for them to want to respond.
Without it, they will drop the connection. Essentially what I'm doing here
is replacing a special mod_webobjects Apache module with the built-in
mod_proxy. This header is just something WO needs to see to allow
communication.

But now, when I add health check parameters to the proxy balancer it thinks
the app instances are all dead. It's because, for some reason, the custom
header is not being used for the health check and the connection
immediately drops. To confirm that was true, I modified the java
application to force the header to be set when an incoming java HTTP
request was received. While that did allow communication with health check,
it causes other problems for me so is not a good workaround.

Does anyone know how to configure the mod_proxy health check to use a
custom header? Or is it not possible currently? Thank you :-)

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