Explain all environment variables used in Shuffle

[frikky]

Across everything in the Shuffle stack:

• Frontend
• Backend
• Orborus
• Worker
• Apps

External:

• Opensearch

[frikky]

• SHUFFLE_ORBORUS_PULL_TIME: Used to control the speed at which Orborus polls for new jobs from the backend. The default is 2, as in it polls every 2 seconds.