1 files changed, 21 insertions, 7 deletions

diff --git a/jstests/multiVersion/delay_secs_field_changes_on_upgrade_downgrade.js b/jstests/multiVersion/delay_secs_field_changes_on_upgrade_downgrade.js
index d44c2013ca9..daf51e42ccb 100644
--- a/jstests/multiVersion/delay_secs_field_changes_on_upgrade_downgrade.js
+++ b/jstests/multiVersion/delay_secs_field_changes_on_upgrade_downgrade.js
@@ -37,18 +37,32 @@ function runTest(downgradeFCV) {
     assert.commandWorked(primary.adminCommand({setFeatureCompatibilityVersion: downgradeFCV}));
 
     config = primary.adminCommand({replSetGetConfig: 1}).config;
-    assert.eq(config.members[1].slaveDelay, 10, tojson(config));
-    assert.eq(config.members[1].hasOwnProperty('secondaryDelaySecs'), false, tojson(config));
+
+    // 'slaveDelay' is disallowed starting in FCV 4.9, so only check for it if
+    // downgradeFCV < 4.9. Otherwise, check that the config is still  using 'secondaryDelaySecs'.
+    if (MongoRunner.compareBinVersions(downgradeFCV, "4.9") >= 0) {
+        assert.eq(config.members[1].secondaryDelaySecs, 10, tojson(config));
+        assert.eq(config.members[1].hasOwnProperty('slaveDelay'), false, tojson(config));
+    } else {
+        assert.eq(config.members[1].slaveDelay, 10, tojson(config));
+        assert.eq(config.members[1].hasOwnProperty('secondaryDelaySecs'), false, tojson(config));
+    }
 
     config.version++;
-    // Test that a reconfig with 'slaveDelay' works.
+    // The following reconfig will use 'slaveDelay' if FCV < 4.9 and 'secondaryDelaySecs' if
+    // FCV >= 4.9. Both should succeed.
     assert.commandWorked(primary.adminCommand({replSetReconfig: config}));
 
-    delete config.members[1].slaveDelay;
-    config.members[1].secondaryDelaySecs = 10;
+    if (MongoRunner.compareBinVersions(downgradeFCV, "4.9") >= 0) {
+        delete config.members[1].secondaryDelaySecs;
+        config.members[1].slaveDelay = 10;
+    } else {
+        delete config.members[1].slaveDelay;
+        config.members[1].secondaryDelaySecs = 10;
+    }
     config.version++;
 
-    // Test that a reconfig with 'secondaryDelaySecs' fails.
+    // Test that a reconfig with an incompatible field name fails.
     assert.commandFailedWithCode(primary.adminCommand({replSetReconfig: config}),
                                  ErrorCodes.NewReplicaSetConfigurationIncompatible);
 
@@ -76,4 +90,4 @@ function runTest(downgradeFCV) {
 }
 
 runFeatureFlagMultiversionTest('featureFlagUseSecondaryDelaySecs', runTest);
-}());
\ No newline at end of file
+}());