Two commonly used [Galaxy][galaxy] server configurations are the use of [uWSGI Zerg Mode][uwsgi-zerg-mode] and [uWSGI Mules][uwsgi-mules] as [Galaxy job handlers][galaxy-scaling]. These features are not easily compatible because Galaxy job handlers rely heavily on having unique server names, and handlers' server names must be persistent across restarts. Because zerg mode results in running two Galaxy servers simultaneously (however briefly), using mules with zerg mode would necessarily mean running mules with overlapping server names.
In a typical Galaxy zerg mode setup, the newly started zergling (B) terminates the old zergling (A) once B is ready to serve requests. Zergling B then continues to serve requests until another zergling (C) is started and terminates B.
It is possible to get both zerg mode and mules working together by configuring zergling B to start without mules, and perform a double zerg dance on each restart: