SERVER-49269: Add 'previousVersion' field to FCV document when in downgrading states

3 files changed, 35 insertions, 16 deletions

diff --git a/jstests/multiVersion/genericSetFCVUsage/repair_feature_compatibility_version.js b/jstests/multiVersion/genericSetFCVUsage/repair_feature_compatibility_version.js
index e9da9ce7735..ec06f436333 100644
--- a/jstests/multiVersion/genericSetFCVUsage/repair_feature_compatibility_version.js
+++ b/jstests/multiVersion/genericSetFCVUsage/repair_feature_compatibility_version.js
@@ -66,9 +66,10 @@ assert.neq(null,
            connection,
            "mongod was unable to start up with version=" + latest + " and existing data files");
 adminDB = connection.getDB("admin");
-assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version,
-          lastStableFCV);
-assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).targetVersion, null);
+const fcvDoc = adminDB.system.version.findOne({_id: "featureCompatibilityVersion"});
+assert.eq(fcvDoc.version, lastStableFCV);
+assert.eq(fcvDoc.targetVersion, undefined);
+assert.eq(fcvDoc.previousVersion, undefined);
 MongoRunner.stopMongod(connection);
 
 // If the featureCompatibilityVersion document is present, --repair should just return success.
diff --git a/jstests/noPassthrough/feature_compatibility_version.js b/jstests/noPassthrough/feature_compatibility_version.js
index a413ac02542..47f992f3b22 100644
--- a/jstests/noPassthrough/feature_compatibility_version.js
+++ b/jstests/noPassthrough/feature_compatibility_version.js
@@ -23,31 +23,49 @@ assert.commandWorked(
                                   {$set: {version: lastStableFCV, targetVersion: latestFCV}}));
 checkFCV(adminDB, lastStableFCV, latestFCV);
 
-assert.commandWorked(
-    adminDB.system.version.update({_id: "featureCompatibilityVersion"},
-                                  {$set: {version: lastStableFCV, targetVersion: lastStableFCV}}));
+assert.commandWorked(adminDB.system.version.update(
+    {_id: "featureCompatibilityVersion"},
+    {$set: {version: lastStableFCV, targetVersion: lastStableFCV, previousVersion: latestFCV}}));
 checkFCV(adminDB, lastStableFCV, lastStableFCV);
 
-assert.commandWorked(
-    adminDB.system.version.update({_id: "featureCompatibilityVersion"},
-                                  {$set: {version: latestFCV}, $unset: {targetVersion: true}}));
+// When present, "previousVersion" will always be the latestFCV.
+assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                                        {$set: {previousVersion: lastStableFCV}}),
+                          4926901);
+checkFCV(adminDB, lastStableFCV, lastStableFCV);
+
+// Downgrading FCV must have a 'previousVersion' field.
+assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                                        {$unset: {previousVersion: true}}),
+                          4926902);
+checkFCV(adminDB, lastStableFCV, lastStableFCV);
+
+assert.commandWorked(adminDB.system.version.update(
+    {_id: "featureCompatibilityVersion"},
+    {$set: {version: latestFCV}, $unset: {targetVersion: true, previousVersion: true}}));
 checkFCV(adminDB, latestFCV);
 
 // Updating the featureCompatibilityVersion document with an invalid version fails.
 assert.writeErrorWithCode(
     adminDB.system.version.update({_id: "featureCompatibilityVersion"}, {$set: {version: "3.2"}}),
-    ErrorCodes.BadValue);
+    4926900);
 checkFCV(adminDB, latestFCV);
 
 // Updating the featureCompatibilityVersion document with an invalid targetVersion fails.
 assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
                                                         {$set: {targetVersion: lastStableFCV}}),
-                          ErrorCodes.BadValue);
+                          4926904);
 checkFCV(adminDB, latestFCV);
 
 assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
                                                         {$set: {targetVersion: latestFCV}}),
-                          ErrorCodes.BadValue);
+                          4926904);
+checkFCV(adminDB, latestFCV);
+
+// Setting an unknown field.
+assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                                        {$set: {unknownField: "unknown"}}),
+                          40415);
 checkFCV(adminDB, latestFCV);
 
 MongoRunner.stopMongod(conn);
diff --git a/jstests/noPassthroughWithMongod/isMaster_feature_compatibility_version.js b/jstests/noPassthroughWithMongod/isMaster_feature_compatibility_version.js
index 7dcc280c066..9cace458341 100644
--- a/jstests/noPassthroughWithMongod/isMaster_feature_compatibility_version.js
+++ b/jstests/noPassthroughWithMongod/isMaster_feature_compatibility_version.js
@@ -36,10 +36,10 @@ assert.eq(res.minWireVersion, res.maxWireVersion, tojson(res));
 
 // When the featureCompatibilityVersion is downgrading, running isMaster with internalClient
 // returns minWireVersion == maxWireVersion.
-assert.commandWorked(
-    adminDB.system.version.update({_id: "featureCompatibilityVersion"},
-                                  {$set: {version: lastStableFCV, targetVersion: lastStableFCV}},
-                                  {writeConcern: {w: 1}}));
+assert.commandWorked(adminDB.system.version.update(
+    {_id: "featureCompatibilityVersion"},
+    {$set: {version: lastStableFCV, targetVersion: lastStableFCV, previousVersion: latestFCV}},
+    {writeConcern: {w: 1}}));
 res = adminDB.runCommand(isMasterCommand);
 assert.commandWorked(res);
 assert.eq(res.minWireVersion, res.maxWireVersion, tojson(res));