[Config] Add readWorkerThreadsThrottlingEnabled to conf/bookkeeper.co…

…nf (apache#12666)

- apache/bookkeeper#2646 added "Auto-throttle read operations" which is
  enabled by default

conf/bookkeeper.conf

@@ -166,6 +166,11 @@ maxPendingReadRequestsPerThread=2500
 # avoid the executor queue to grow indefinitely
 maxPendingAddRequestsPerThread=10000
 
+# Use auto-throttling of the read-worker threads. This is done
+# to ensure the bookie is not using unlimited amount of memory
+# to respond to read-requests.
+readWorkerThreadsThrottlingEnabled=true
+
 # Option to enable busy-wait settings. Default is false.
 # WARNING: This option will enable spin-waiting on executors and IO threads in order to reduce latency during
 # context switches. The spinning will consume 100% CPU even when bookie is not doing any work. It is recommended to