Since with request #13893 (git #tuleap/stable/8ef9da3cdb45742126e4872f36c0ce1f021052cd) workers are way more resilient to errors (redis deconnexions).
Unfortunately it put under the spotlight that current implementation of worker "init" (magically hidden behind tuleap system events) was broken since ages.
As we should not try to re-invent an init system (and even if we do, php is probably not the best language to achieve that AND stay healthy), then the start of backend workers should be grouped with "start of tuleap backend".