Bug 62741 - httpd fails to start with error: "undefined symbol: ap_proxy_balancer_get_best_worker" when using mod_lbmethod_byrequests.so and mod_proxy.so is NOT enabled
Summary: httpd fails to start with error: "undefined symbol: ap_proxy_balancer_get_bes...
Alias: None
Product: Apache httpd-2
Classification: Unclassified
Component: mod_proxy (show other bugs)
Version: 2.4.34
Hardware: PC Mac OS X 10.1
: P2 normal (vote)
Target Milestone: ---
Assignee: Apache HTTPD Bugs Mailing List
Depends on:
Reported: 2018-09-19 17:28 UTC by Adrian Salaices
Modified: 2018-09-19 18:51 UTC (History)
0 users


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Description Adrian Salaices 2018-09-19 17:28:25 UTC
The issue comes up when starting apache with the mod_lbmethod_byrequests enabled while mod_proxy module is NOT enabled. 

The error: 

Cannot load lib64/httpd/modules/mod_lbmethod_byrequests.so into server: /usr/lib64/httpd/modules/mod_lbmethod_byrequests.so: undefined symbol: ap_proxy_balancer_get_best_worker. 

There was a post describing a workaround by loading mod_proxy before the mod_lbmethod_byrequests module, the problem with this approach is that now you will have mod_proxy (and a matching bogus config pointing /whatever to a non existent backend server) just to get mod_lbmethod_byrequests working. 

The bottom line is that mod_proxy should NOT be a prereq for using mod_lbmethod_byrequests as it May NOT be needed. 

Please feel free to correct me if I am totally missing something
Comment 1 William A. Rowe Jr. 2018-09-19 18:51:10 UTC
Change your module load order to load mod_proxy first. It is not possible
to use lbmethod modules without mod_proxy.

In 2.4.35 the load order dependency is corrected; but mod_proxy is still

What purpose do you have in loading lbmethod's if you are not loading
mod_proxy_balancer, and ergo mod_proxy, into the given server instance?