DRAFT KB-XXXX HTTP 500 Internal Server Error with "Could not find a worker for worker name" in mod_jk.log

Symptoms

Tomcat and Apache start successfully, but a HTTP 500 Internal Server Error appears when trying to access the Appian login page.

The <APACHE_HOME>/logs/mod_jk.log file shows the following error:
[info] init_jk::mod_jk.c (3595): mod_jk/1.2.42 initialized
[info] jk_handler::mod_jk.c (3003): Could not find a worker for worker name=LoadBalancer”

Cause

The 'JKWorkerProperty' fields from Setup Worker Properties are specified in a file outside <APACHE_HOME>/conf/httpd.conf, rather than directly within httpd.conf. Apache documentation indicates this is possible with the 'JkWorkersFile' directive to reference the 'JKWorkerProperty' fields as a separate file called workers.properties.

However, the 'JkWorkersFile' directive doesn't make the contents of the 'workers.properties' accessible within httpd.conf. Trying to reference any names specified by the 'JKWorkerProperty' field 'worker.list' within httpd.conf will fail, causing the error in mod_jk.log

Action

Follow the Appian Documentation Configuring Apache Web Server with Appian under Setup Worker Properties (or Configuring Apache Web Server with Jboss in 18.2 and below) when configuring the JKWorkerProperty fields.
1) Remove the line JkWorkerFile /path/to/workers.properties
2) Directly add the contents of workers.properties to httpd.conf

Workaround

Instead of following the action steps, add the line Include conf/workers.properties after the line JkWorkerFile /path/to/workers.properties file.

Affected Versions

This article applies to Appian 17.1 and later