Support readPreference on mongodump 3.4.0+, set to secondary to enforce safety

Author: timvaillancourt

mongodb_consistent_backup/Backup/Mongodump/Mongodump.py

@@ -40,9 +40,8 @@ def __init__(self, manager, config, timer, base_dir, backup_dir, replsets, shard
         with hide('running', 'warnings'), settings(warn_only=True):
             self.version = local("%s --version|awk 'NR >1 {exit}; /version/{print $NF}'" % self.binary, capture=True)
 
-        if self.can_gzip():
-            if self.compression() == 'none':
-                self.compression('gzip')
+        if self.can_gzip() and self.compression() == 'none':
+            self.compression('gzip')
         elif self.compression() == 'gzip':
             logging.warning("mongodump gzip compression requested on binary that does not support gzip!")
 
@@ -121,8 +120,9 @@ def run(self):
                 self.authdb,
                 self.backup_dir,
                 self.binary,
+                self.version,
                 self.threads(),
-                self.do_gzip,
+                self.do_gzip(),
                 self.verbose
             )
             self.dump_threads.append(thread)
@@ -152,8 +152,9 @@ def run(self):
                     self.authdb,
                     self.backup_dir,
                     self.binary,
+                    self.version,
                     self.threads(),
-                    self.do_gzip,
+                    self.do_gzip(),
                     self.verbose
                 )]
                 self.dump_threads[0].start()

mongodb_consistent_backup/Backup/Mongodump/MongodumpThread.py

@@ -14,20 +14,21 @@
 
 # noinspection PyStringFormat
 class MongodumpThread(Process):
-    def __init__(self, state, uri, timer, user, password, authdb, base_dir, binary,
+    def __init__(self, state, uri, timer, user, password, authdb, base_dir, binary, version,
                  threads=0, dump_gzip=False, verbose=False):
         Process.__init__(self)
-        self.state       = state
-        self.uri         = uri
-        self.timer       = timer
-        self.user        = user
-        self.password    = password
-        self.authdb      = authdb
-        self.base_dir    = base_dir
-        self.binary      = binary
-        self.threads     = threads
-        self.dump_gzip   = dump_gzip
-        self.verbose     = verbose
+        self.state     = state
+        self.uri       = uri
+        self.timer     = timer
+        self.user      = user
+        self.password  = password
+        self.authdb    = authdb
+        self.base_dir  = base_dir
+        self.binary    = binary
+        self.version   = version
+        self.threads   = threads
+        self.dump_gzip = dump_gzip
+        self.verbose   = verbose
 
         self.timer_name = "%s-%s" % (self.__class__.__name__, self.uri.replset)
         self.exit_code  = 1
@@ -85,6 +86,8 @@ def mongodump_cmd(self):
             mongodump_flags.extend(["--numParallelCollections="+str(self.threads)])
         if self.dump_gzip:
             mongodump_flags.extend(["--gzip"])
+        if tuple("3.4.0".split(".")) <= tuple(self.version.split(".")):
+            mongodump_flags.extend(["--readPreference=secondary"])
         if self.authdb and self.authdb != "admin":
             logging.debug("Using database %s for authentication" % self.authdb)
             mongodump_flags.extend(["--authenticationDatabase", self.authdb])