Merge pull request rails#52468 from heka1024/available-processor-count-in-async-adapter

Use `RAILS_MAX_THREADS` in `ActiveJob::AsyncAdapter`

Author: byroot

activejob/CHANGELOG.md

@@ -1,2 +1,5 @@
+*   Use `RAILS_MAX_THREADS` in `ActiveJob::AsyncAdapter`. If it is not set, use 5 as default.
+
+    *heka1024*
 
 Please check [7-2-stable](https://github.com/rails/rails/blob/7-2-stable/activejob/CHANGELOG.md) for previous changes.

activejob/lib/active_job/queue_adapters/async_adapter.rb

@@ -74,7 +74,7 @@ def perform
       class Scheduler # :nodoc:
         DEFAULT_EXECUTOR_OPTIONS = {
           min_threads:     0,
-          max_threads:     Concurrent.processor_count,
+          max_threads:     ENV.fetch("RAILS_MAX_THREADS", 5).to_i,
           auto_terminate:  true,
           idletime:        60, # 1 minute
           max_queue:       0, # unlimited