Improvements to documentation and error messages. (#221)

scripts/stop_ray.sh

@@ -1,3 +1,9 @@
 #!/usr/bin/env bash
 
-killall redis-server global_scheduler plasma_store plasma_manager photon_scheduler
+killall global_scheduler plasma_store plasma_manager photon_scheduler
+
+# Find the PID of the Redis process and kill it.
+kill $(ps aux | grep redis-server | awk '{ print $2 }') 2> /dev/null
+
+# Find the PIDs of the worker processes and kill them.
+kill $(ps aux | grep default_worker.py | awk '{ print $2 }') 2> /dev/null