Raise error if we try to reconfig redis after it's been established, fixes #1309

Changes.md

@@ -1,3 +1,10 @@
+HEAD
+-----------
+
+- Raise error if application tries to configure Redis after the pool has been
+  established.  Sidekiq's redis connection cannot be dynamically changed
+  at runtime. [#1309]
+
 2.17.0
 -----------
 

lib/sidekiq.rb

@@ -68,6 +68,7 @@ module Sidekiq
   end
 
   def self.redis=(hash)
+    raise "Sidekiq's redis pool has already been established, cannot configure" if @redis && !$TESTING
     return @redis = hash if hash.is_a?(ConnectionPool)
 
     if hash.is_a?(Hash)