Clarify usage of dequeue_from_legacy option

Change-Id: Iae9aa7a91b9afc19cb8613b5bc31de463b853dde

etc/object-server.conf-sample

@@ -474,10 +474,34 @@ use = egg:swift#recon
 # rsync_tempfile_timeout = auto
 
 # [object-expirer]
+# If this true, this expirer will execute tasks from legacy expirer task queue,
+# at least one object server should run with dequeue_from_legacy = true
+# dequeue_from_legacy = false
+#
 # Note: Be careful not to enable ``dequeue_from_legacy`` on too many expirers
 # as all legacy tasks are stored in a single hidden account and the same hidden
 # containers. On a large cluster one may inadvertently make the
-# acccount/container server for the hidden ones busy.
+# acccount/container server for the hidden too busy.
+#
+# Note: the processes and process options can only be used in conjunction with
+# notes using `dequeue_from_legacy = true`.  These options are ignored on nodes
+# with `dequeue_from_legacy = false`.
+#
+# processes is how many parts to divide the legacy work into, one part per
+# process that will be doing the work
+# processes set 0 means that a single legacy process will be doing all the work
+# processes can also be specified on the command line and will override the
+# config value
+# processes = 0
+#
+# process is which of the parts a particular legacy process will work on
+# process can also be specified on the command line and will override the config
+# value
+# process is "zero based", if you want to use 3 processes, you should run
+# processes with process set to 0, 1, and 2
+# process = 0
+#
+# internal_client_conf_path = /etc/swift/internal-client.conf
 #
 # You can override the default log routing for this app here (don't use set!):
 # log_name = object-expirer
@@ -487,29 +511,6 @@ use = egg:swift#recon
 #
 # interval = 300
 #
-# If this true, expirer execute tasks in legacy expirer task queue
-# dequeue_from_legacy = false
-#
-# internal_client_conf_path = /etc/swift/internal-client.conf
-#
-# processes can only be used in conjunction with `dequeue_from_legacy`.
-# So this option is ignored if dequeue_from_legacy=false.
-# processes is how many parts to divide the legacy work into, one part per
-# process that will be doing the work
-# processes set 0 means that a single legacy process will be doing all the work
-# processes can also be specified on the command line and will override the
-# config value
-# processes = 0
-#
-# process can only be used in conjunction with `dequeue_from_legacy`.
-# So this option is ignored if dequeue_from_legacy=false.
-# process is which of the parts a particular legacy process will work on
-# process can also be specified on the command line and will override the config
-# value
-# process is "zero based", if you want to use 3 processes, you should run
-# processes with process set to 0, 1, and 2
-# process = 0
-#
 # report_interval = 300
 #
 # request_tries is the number of times the expirer's internal client will

swift/obj/expirer.py

@@ -268,9 +268,11 @@ class ObjectExpirer(Daemon):
         # This if-clause will be removed when general task queue feature is
         # implemented.
         if not self.dequeue_from_legacy:
-            self.logger.info('Until general task queue has been released '
+            self.logger.info('This node is not configured to dequeue tasks '
-                             '`dequeue_from_legacy == False` means an '
+                             'from the legacy queue.  This node will '
-                             'object-expirer run is a no-op.')
+                             'not process any expiration tasks.  At least '
+                             'one node in your cluster must be configured '
+                             'with dequeue_from_legacy == true.')
             return
 
         self.get_process_values(kwargs)