add example with bad perfomance when usePCFwildcard equals "true"

Resolves: #49

Author: willardgibbs

README.md

@@ -111,7 +111,9 @@ PCFParameters:
 # If usePCFWildcards equals "true", then all monitored objects will be grouped by object type: QUEUE, CHANNEL and LISTENER. Only one PCF command will be sent for each object type. 
 # If usePCFWildcards equals "false", then PCF command will be send for each object.
 # Each PCF command uses a separate connection, so sending a large number of PCF commands will create a large number of connections to MQ queue manager.
-# For example, for 100 monitoring queues will be opened 100 connections to MQ queue manager, if usePCFwildcard equals "false". 
+# For example, for 100 monitoring queues will be opened 100 connections to MQ queue manager, if usePCFwildcard equals "false".
+# Another example: for usePCFwildcard equals "true", if there are 10.000 queues in the queue manager and just a few queues is need to be monitored, 
+# only one PCF command will be sent. But response will contain metrics for all 10.000 queues and that will lead to performance problems.
   usePCFWildcards: true
 # Interval in seconds between sending PCF commands.
   scrapeInterval: 10

src/main/resources/exporter_config.yaml

@@ -33,12 +33,12 @@ PCFParameters:
 # Collect additional metrics? If false, all settings in this section below are ignored. 
 # If yes, additional metrics will be collected for all queues, channels and listeners listed below. 
   sendPCFCommands: true
-# If usePCFWildcards equals "true", then all monitored objects will be grouped by object type:
-# QUEUE, CHANNEL and LISTENER. Only one PCF command will be send for each object type.
-# Metrics will be obtained from the PCF command response for each object one type.
+# If usePCFWildcards equals "true", then all monitored objects will be grouped by object type: QUEUE, CHANNEL and LISTENER. Only one PCF command will be sent for each object type.
 # If usePCFWildcards equals "false", then PCF command will be send for each object.
-# PCF command are sent in one connection to MQ queue manager, so for many PCF command will be opened many connection to MQ queue manager.
-# For example, for 100 monitoring queue will be opened 100 connection to MQ queue manager, if usePCFwildcard equals "false".
+# Each PCF command uses a separate connection, so sending a large number of PCF commands will create a large number of connections to MQ queue manager.
+# For example, for 100 monitoring queues will be opened 100 connections to MQ queue manager, if usePCFwildcard equals "false".
+# Another example: for usePCFwildcard equals "true", if there are 10.000 queues in the queue manager and just a few queues is need to be monitored,
+# only one PCF command will be sent. But response will contain metrics for all 10.000 queues and that will lead to performance problems.
   usePCFWildcards: true
 # Interval in seconds between sending PCF commands.
   scrapeInterval: 10