bug 1247942 - Limit concurrency of async workers
bug 1247942 - Limit concurrency of async workers

In Heroku, each worker opens at least one Redis connection, quickly
bumping up against the connection limits.

mdn/browsercompat,mdn/browsercompat,jwhitlock/web-platform-compat,jwhitlock/web-platform-compat,jwhitlock/web-platform-compat,mdn/browsercompat