2 files changed, 27 insertions, 4 deletions
diff --git a/jstests/replsets/maxSyncSourceLagSecs.js b/jstests/replsets/maxSyncSourceLagSecs.js
index a9aaa104c59..a00ad8a7bef 100644
--- a/jstests/replsets/maxSyncSourceLagSecs.js
+++ b/jstests/replsets/maxSyncSourceLagSecs.js
@@ -25,6 +25,12 @@
     });
     replTest.awaitNodesAgreeOnPrimary();
 
+    // Disable maxSyncSourceLagSecs behavior until we've established the spanning tree we want.
+    replTest.nodes.forEach(function(node) {
+        assert.commandWorked(node.getDB('admin').runCommand(
+            {configureFailPoint: 'disableMaxSyncSourceLagSecs', mode: 'alwaysOn'}));
+    });
+
     var master = replTest.getPrimary();
     var slaves = replTest.liveNodes.slaves;
     syncFrom(slaves[0], master, replTest);
@@ -32,13 +38,20 @@
     master.getDB("foo").bar.save({a: 1});
     replTest.awaitReplication();
 
+    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("Setting sync target of slave 2 to slave 1");
-    syncFrom(slaves[1], slaves[0], replTest);
-    printjson(replTest.status());
+    // Re-enable maxSyncSourceLagSecs behavior now that we have the spanning tree we want and are
+    // ready to test that behavior.
+    replTest.nodes.forEach(function(node) {
+        assert.commandWorked(node.getDB('admin').runCommand(
+            {configureFailPoint: 'disableMaxSyncSourceLagSecs', mode: 'off'}));
+    });
 
     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 3ca7e66d85b..b97f79c00d1 100644
--- a/jstests/replsets/rslib.js
+++ b/jstests/replsets/rslib.js
@@ -22,14 +22,24 @@ var startSetIfSupportsReadMajority;
      */
     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);