SERVER-28813 drop collection before doing dummy write in syncFrom helper

2 files changed, 15 insertions, 5 deletions

diff --git a/jstests/replsets/maxSyncSourceLagSecs.js b/jstests/replsets/maxSyncSourceLagSecs.js
index 96d6a530aee..3e0dc7bd3b1 100644
--- a/jstests/replsets/maxSyncSourceLagSecs.js
+++ b/jstests/replsets/maxSyncSourceLagSecs.js
@@ -28,14 +28,14 @@
     master.getDB("foo").bar.save({a: 1});
     replTest.awaitReplication();
 
-    // need to put at least maxSyncSourceLagSecs b/w first op and subsequent ops
-    // so that the shouldChangeSyncSource logic goes into effect
-    sleep(4000);
-
     jsTestLog("Setting sync target of slave 2 to slave 1");
     syncFrom(slaves[1], slaves[0], replTest);
     printjson(replTest.status());
 
+    // need to put at least maxSyncSourceLagSecs b/w first op and subsequent ops
+    // so that the shouldChangeSyncSource logic goes into effect
+    sleep(4000);
+
     jsTestLog("Lock slave 1 and add some docs. Force sync target for slave 2 to change to primary");
     assert.commandWorked(slaves[0].getDB("admin").runCommand({fsync: 1, lock: 1}));
 
diff --git a/jstests/replsets/rslib.js b/jstests/replsets/rslib.js
index 93fa1393984..1471824bd8f 100644
--- a/jstests/replsets/rslib.js
+++ b/jstests/replsets/rslib.js
@@ -29,14 +29,24 @@ var getLastOpTime;
      */
     syncFrom = function(syncingNode, desiredSyncSource, rst) {
         jsTestLog("Forcing " + syncingNode.name + " to sync from " + desiredSyncSource.name);
-        stopServerReplication(syncingNode);
+
+        // Ensure that 'desiredSyncSource' doesn't already have the dummy write sitting around from
+        // a previous syncFrom attempt.
         var dummyName = "dummyForSyncFrom";
+        rst.getPrimary().getDB(dummyName).getCollection(dummyName).drop();
+        assert.soonNoExcept(function() {
+            return desiredSyncSource.getDB(dummyName).getCollection(dummyName).findOne() == null;
+        });
+
+        stopServerReplication(syncingNode);
+
         assert.writeOK(rst.getPrimary().getDB(dummyName).getCollection(dummyName).insert({a: 1}));
         // Wait for 'desiredSyncSource' to get the dummy write we just did so we know it's
         // definitely ahead of 'syncingNode' before we call replSetSyncFrom.
         assert.soonNoExcept(function() {
             return desiredSyncSource.getDB(dummyName).getCollection(dummyName).findOne({a: 1});
         });
+
         assert.commandWorked(syncingNode.adminCommand({replSetSyncFrom: desiredSyncSource.name}));
         restartServerReplication(syncingNode);
         rst.awaitSyncSource(syncingNode, desiredSyncSource);