Apache error "AH01171: balancer://cluster: No workers in balancer"

Question

I'm trying to set up an apache server (run with Docker) to act as a load-balancing reverse proxy, but no matter what I try, I get the error [proxy_balancer:error] [pid 8:tid 140013616056064] [client 172.17.0.1:39376] AH01171: balancer://cluster: No workers in balancer

Here's a minimum working example to demonstrate the problem:

Dockerfile:

FROM httpd:2.4
RUN for mod in \
            slotmem_shm_module lbmethod_byrequests_module \
            proxy_module proxy_http_module proxy_balancer_module; do \
        sed -i "s/^#LoadModule \\($mod\\) /LoadModule \\1 /" conf/httpd.conf; \
    done
RUN echo "Include conf/extra/test.conf" >> conf/httpd.conf

test.conf:

<Proxy "balance://cluster">
    BalancerMember "http://www.google.com/"
    BalancerMember "http://www.xkcd.com/"
</Proxy>

ProxyPass / balancer://cluster/

Run as docker run -it -p 80:80 -v $PWD/test.conf:/usr/local/apache2/conf/extra/test.conf proxy-test

Then try to retrieve http://localhost/ and the error appears in the server stderr.

I've tried putting it in a virtualhost, setting servername, putting in a ProxyPassReverse, putting the ProxyPass inside a <Location /> - none of it helps.

Answer 1

I figured it out - it's a typo. balance://cluster should be balancer://cluster.