Allow specifying preferred replica set members

conf/mongodb-consistent-backup.example.conf

@@ -28,6 +28,7 @@ production:
   #  max_priority: [2-1000]                    (default: 1000)
   #  hidden_only: [true|false]                 (default: false)
   #  read_pref_tags: [key:value,key:value,...] (default: none)
+  #  preferred_members: rsname/host:port[,...] (default: none)
   #sharding:
   #  balancer:
   #    wait_secs: [1+] (default: 300)

mongodb_consistent_backup/Replication/Replset.py

@@ -17,6 +17,10 @@ def __init__(self, config, db):
         self.min_priority   = self.config.replication.min_priority
         self.max_priority   = self.config.replication.max_priority
         self.hidden_only    = self.config.replication.hidden_only
+        self.preferred_members = []
+        if self.config.replication.preferred_members:
+            self.preferred_members = self.config.replication.preferred_members.split(",")
+            logging.debug("Preferred members: %s" % self.preferred_members)
 
         self.state_primary   = 1
         self.state_secondary = 2
@@ -234,6 +238,10 @@ def find_secondary(self, force=False, quiet=False):
                     logging.info("Found SECONDARY %s that is non-hidden and hidden-only mode is enabled! Skipping" % member_uri)
                     continue
 
+                if member_uri.str() in self.preferred_members:
+                    logging.info("Bumping preferred SECONDARY member %s's score", member_uri)
+                    score = 10000
+
                 rep_lag, optime_ts = self.get_repl_lag(member)
                 score = ceil((score - rep_lag) * score_scale)
                 if rep_lag < self.max_lag_secs:

mongodb_consistent_backup/Replication/__init__.py

@@ -13,4 +13,7 @@ def config(parser):
                         help="Only use hidden secondary members for backup (default: false)")
     parser.add_argument("--replication.read_pref_tags", dest="replication.read_pref_tags", default=None, type=str,
                         help="Only use members that match replication tags in comma-separated key:value format (default: none)")
+    parser.add_argument("--replication.preferred_members", dest="replication.preferred_members", default=None, type=str,
+                        help="Prefer members with these names; comma-separated URIs in rs/host:port format (default: none)")
+
     return parser