Add an __str__ method to brokers

A few uses of broker.db_file are in printouts where we do need
them, so the administrator may know what's up. Seems like an easy
way to get rid of those is to make brokers identify themselves
with common __str__. Alternative back-end implementations may
supply something other than a filename here, for example a cluster
name and a volume name.

Note that I'm not sure if correct coercion would occur when
brokers are bounced through dictionaries, hence explicit str().

Change-Id: I329788ebd1fbe39ffadcf9f9d5194a74a88dde58

swift/account/auditor.py

@@ -118,10 +118,10 @@ class AccountAuditor(Daemon):
                 broker.get_info()
                 self.logger.increment('passes')
                 self.account_passes += 1
-                self.logger.debug(_('Audit passed for %s') % broker.db_file)
+                self.logger.debug(_('Audit passed for %s') % broker)
         except (Exception, Timeout):
             self.logger.increment('failures')
             self.account_failures += 1
             self.logger.exception(_('ERROR Could not get account info %s'),
-                                  (broker.db_file))
+                                  path)
         self.logger.timing_since('timing', start_time)

swift/common/db.py

@@ -187,6 +187,14 @@ class DatabaseBroker(object):
         self.container = container
         self._db_version = -1
 
+    def __str__(self):
+        """
+        Returns a string indentifying the entity under broker to a human.
+        The baseline implementation returns a full pathname to a database.
+        This is vital for useful diagnostics.
+        """
+        return self.db_file
+
     def initialize(self, put_timestamp=None):
         """
         Create the DB

swift/common/db_replicator.py

@@ -296,8 +296,8 @@ class Replicator(Daemon):
         if objects:
             self.logger.debug(_(
                 'Synchronization for %s has fallen more than '
-                '%s rows behind; moving on and will try again next pass.') %
+                '%s rows behind; moving on and will try again next pass.'),
-                (broker.db_file, self.max_diffs * self.per_diff))
+                broker, self.max_diffs * self.per_diff)
             self.stats['diff_capped'] += 1
             self.logger.increment('diff_caps')
         else:
@@ -606,7 +606,7 @@ class ReplicatorRpc(object):
             info = broker.get_replication_info()
         except (Exception, Timeout) as e:
             if 'no such table' in str(e):
-                self.logger.error(_("Quarantining DB %s") % broker.db_file)
+                self.logger.error(_("Quarantining DB %s"), broker)
                 quarantine_db(broker.db_file, broker.db_type)
                 return HTTPNotFound()
             raise

swift/container/auditor.py

@@ -118,10 +118,10 @@ class ContainerAuditor(Daemon):
                 broker.get_info()
                 self.logger.increment('passes')
                 self.container_passes += 1
-                self.logger.debug(_('Audit passed for %s'), broker.db_file)
+                self.logger.debug(_('Audit passed for %s'), broker)
         except (Exception, Timeout):
             self.logger.increment('failures')
             self.container_failures += 1
             self.logger.exception(_('ERROR Could not get container info %s'),
-                                  broker.db_file)
+                                  path)
         self.logger.timing_since('timing', start_time)

swift/container/sync.py

@@ -245,7 +245,7 @@ class ContainerSync(Daemon):
                 if err:
                     self.logger.info(
                         _('ERROR %(db_file)s: %(validate_sync_to_err)s'),
-                        {'db_file': broker.db_file,
+                        {'db_file': str(broker),
                          'validate_sync_to_err': err})
                     self.container_failures += 1
                     self.logger.increment('failures')
@@ -299,7 +299,7 @@ class ContainerSync(Daemon):
             self.container_failures += 1
             self.logger.increment('failures')
             self.logger.exception(_('ERROR Syncing %s'),
-                                  broker.db_file if broker else path)
+                                  broker if broker else path)
 
     def container_sync_row(self, row, sync_to, sync_key, broker, info):
         """
@@ -397,14 +397,14 @@ class ContainerSync(Daemon):
             else:
                 self.logger.exception(
                     _('ERROR Syncing %(db_file)s %(row)s'),
-                    {'db_file': broker.db_file, 'row': row})
+                    {'db_file': str(broker), 'row': row})
             self.container_failures += 1
             self.logger.increment('failures')
             return False
         except (Exception, Timeout) as err:
             self.logger.exception(
                 _('ERROR Syncing %(db_file)s %(row)s'),
-                {'db_file': broker.db_file, 'row': row})
+                {'db_file': str(broker), 'row': row})
             self.container_failures += 1
             self.logger.increment('failures')
             return False