SERVER-26261 Expose current() and advance() methods on version iterator.

3 files changed, 77 insertions, 46 deletions

diff --git a/buildscripts/resmokeconfig/suites/multiversion.yml b/buildscripts/resmokeconfig/suites/multiversion.yml
index c97b6fc8d98..95c81adcc12 100644
--- a/buildscripts/resmokeconfig/suites/multiversion.yml
+++ b/buildscripts/resmokeconfig/suites/multiversion.yml
@@ -8,9 +8,6 @@ selector:
     - jstests/multiVersion/transitioning_to_and_from_WT.js
     # TODO: SERVER-21578
     - jstests/multiVersion/balancer_multiVersion_detect.js
-    # TODO: SERVER-26261
-    - jstests/multiVersion/2_test_launching_cluster.js
-    - jstests/multiVersion/dumprestore_sharded.js
 
 # Multiversion tests start their own mongod's.
 executor:
diff --git a/src/mongo/shell/servers.js b/src/mongo/shell/servers.js
index 7b7ee8dbbdf..078f63fb56e 100644
--- a/src/mongo/shell/servers.js
+++ b/src/mongo/shell/servers.js
@@ -118,10 +118,8 @@ var MongoRunner, _startMongod, startMongoProgram, runMongoProgram, startMongoPro
     ];
 
     MongoRunner.getBinVersionFor = function(version) {
-
-        // If this is a version iterator, iterate the version via toString()
         if (version instanceof MongoRunner.versionIterator.iterator) {
-            version = version.toString();
+            version = version.current();
         }
 
         if (version == null)
@@ -227,11 +225,11 @@ var MongoRunner, _startMongod, startMongoProgram, runMongoProgram, startMongoPro
     MongoRunner.toRealFile = MongoRunner.toRealDir;
 
     /**
-     * Returns an iterator object which yields successive versions on toString(), starting from a
-     * random initial position, from an array of versions.
+     * Returns an iterator object which yields successive versions on calls to advance(), starting
+     * from a random initial position, from an array of versions.
      *
      * If passed a single version string or an already-existing version iterator, just returns the
-     * object itself, since it will yield correctly on toString()
+     * object itself, since it will yield correctly on calls to advance().
      *
      * @param {Array.<String>}|{String}|{versionIterator}
      */
@@ -253,12 +251,21 @@ var MongoRunner, _startMongod, startMongoProgram, runMongoProgram, startMongoPro
     };
 
     MongoRunner.versionIterator.iterator = function(i, arr) {
+        if (!Array.isArray(arr)) {
+            throw new Error("Expected an array for the second argument, but got: " + tojson(arr));
+        }
+
+        this.current = function current() {
+            return arr[i];
+        };
 
-        this.toString = function() {
-            i = i % arr.length;
-            print("Returning next version : " + i + " (" + arr[i] + ") from " + tojson(arr) +
-                  "...");
-            return arr[i++];
+        // We define the toString() method as an alias for current() so that concatenating a version
+        // iterator with a string returns the next version in the list without introducing any
+        // side-effects.
+        this.toString = this.current;
+
+        this.advance = function advance() {
+            i = (i + 1) % arr.length;
         };
 
         this.isVersionIterator = true;
@@ -428,6 +435,13 @@ var MongoRunner, _startMongod, startMongoProgram, runMongoProgram, startMongoPro
 
         // Normalize and get the binary version to use
         if (opts.hasOwnProperty('binVersion')) {
+            if (opts.binVersion instanceof MongoRunner.versionIterator.iterator) {
+                // Advance the version iterator so that subsequent calls to
+                // MongoRunner.mongoOptions() use the next version in the list.
+                const iterator = opts.binVersion;
+                opts.binVersion = iterator.current();
+                iterator.advance();
+            }
             opts.binVersion = MongoRunner.getBinVersionFor(opts.binVersion);
         }
 
@@ -874,7 +888,15 @@ var MongoRunner, _startMongod, startMongoProgram, runMongoProgram, startMongoPro
     MongoRunner.runMongoTool = function(binaryName, opts, ...positionalArgs) {
 
         var opts = opts || {};
+
         // Normalize and get the binary version to use
+        if (opts.binVersion instanceof MongoRunner.versionIterator.iterator) {
+            // Advance the version iterator so that subsequent calls to MongoRunner.runMongoTool()
+            // use the next version in the list.
+            const iterator = opts.binVersion;
+            opts.binVersion = iterator.current();
+            iterator.advance();
+        }
         opts.binVersion = MongoRunner.getBinVersionFor(opts.binVersion);
 
         // Recent versions of the mongo tools support a --dialTimeout flag to set for how
diff --git a/src/mongo/shell/shardingtest.js b/src/mongo/shell/shardingtest.js
index c9314aea8b8..ec1f60eb869 100644
--- a/src/mongo/shell/shardingtest.js
+++ b/src/mongo/shell/shardingtest.js
@@ -781,9 +781,6 @@ var ShardingTest = function(params) {
 
             // If the mongos is being restarted with a newer version, make sure we remove any
             // options that no longer exist in the newer version.
-            // Note: If a jstest specifies the mongos binVersion as an array, calling
-            // MongoRunner.areBinVersionsTheSame() will advance the binVersion iterator over that
-            // array (SERVER-26261).
             if (MongoRunner.areBinVersionsTheSame('latest', opts.binVersion)) {
                 delete opts.noAutoSplit;
             }
@@ -1240,6 +1237,40 @@ var ShardingTest = function(params) {
     // Wait for master to be elected before starting mongos
     var csrsPrimary = this.configRS.getPrimary();
 
+    // If 'otherParams.mongosOptions.binVersion' is an array value, then we'll end up constructing a
+    // version iterator. We initialize the options for the mongos processes before checking whether
+    // we need to run {setFeatureCompatibilityVersion: "3.2"} on the CSRS primary so we know
+    // definitively what binVersions will be used for the mongos processes.
+    const mongosOptions = [];
+    for (var i = 0; i < numMongos; ++i) {
+        let options = {
+            useHostname: otherParams.useHostname,
+            pathOpts: Object.merge(pathOpts, {mongos: i}),
+            verbose: mongosVerboseLevel,
+            keyFile: keyFile,
+        };
+
+        if (otherParams.mongosOptions && otherParams.mongosOptions.binVersion) {
+            otherParams.mongosOptions.binVersion =
+                MongoRunner.versionIterator(otherParams.mongosOptions.binVersion);
+        }
+
+        options = Object.merge(options, otherParams.mongosOptions);
+        options = Object.merge(options, otherParams["s" + i]);
+
+        options.port = options.port || allocatePort();
+
+        // TODO(esha): remove after v3.4 ships.
+        // Legacy mongoses use a command line option to disable autosplit instead of reading the
+        // config.settings collection.
+        if (options.binVersion && MongoRunner.areBinVersionsTheSame('3.2', options.binVersion) &&
+            !otherParams.enableAutoSplit) {
+            options.noAutoSplit = "";
+        }
+
+        mongosOptions.push(options);
+    }
+
     /**
      * Helper method to check whether we should set featureCompatibilityVersion to 3.2 on the CSRS.
      * We do this if we have a 3.2 shard or a 3.2 mongos and a 3.4 CSRS because older versions of
@@ -1285,7 +1316,14 @@ var ShardingTest = function(params) {
     const configRS = this.configRS;
     if (shouldSetFeatureCompatibilityVersion32()) {
         function setFeatureCompatibilityVersion() {
-            assert.commandWorked(csrsPrimary.adminCommand({setFeatureCompatibilityVersion: '3.2'}));
+            const res = csrsPrimary.adminCommand({setFeatureCompatibilityVersion: '3.2'});
+            if (res.ok === 0) {
+                // The "setFeatureCompatibilityVersion" command is unrecognized by versions of
+                // MongoDB earlier than 3.4.
+                assert.commandFailedWithCode(res, ErrorCodes.CommandNotFound);
+                return;
+            }
+            assert.commandWorked(res);
 
             // We wait for setting the featureCompatibilityVersion to "3.2" to propagate to all
             // nodes in the CSRS to ensure that older versions of mongos can successfully connect.
@@ -1335,34 +1373,8 @@ var ShardingTest = function(params) {
 
     // Start the MongoS servers
     for (var i = 0; i < numMongos; i++) {
-        options = {
-            useHostname: otherParams.useHostname,
-            pathOpts: Object.merge(pathOpts, {mongos: i}),
-            configdb: this._configDB,
-            verbose: mongosVerboseLevel,
-            keyFile: keyFile,
-        };
-
-        if (otherParams.mongosOptions && otherParams.mongosOptions.binVersion) {
-            otherParams.mongosOptions.binVersion =
-                MongoRunner.versionIterator(otherParams.mongosOptions.binVersion);
-        }
-
-        options = Object.merge(options, otherParams.mongosOptions);
-        options = Object.merge(options, otherParams["s" + i]);
-
-        options.port = options.port || allocatePort();
-
-        // TODO(esha): remove after v3.4 ships.
-        // Legacy mongoses use a command line option to disable autosplit instead of reading the
-        // config.settings collection.
-        // Note: If a jstest specifies the mongos binVersion as an array, calling
-        // MongoRunner.areBinVersionsTheSame() will advance the binVersion iterator over that array
-        // (SERVER-26261).
-        if (options.binVersion && MongoRunner.areBinVersionsTheSame('3.2', options.binVersion) &&
-            !otherParams.enableAutoSplit) {
-            options.noAutoSplit = "";
-        }
+        const options = mongosOptions[i];
+        options.configdb = this._configDB;
 
         if (otherParams.useBridge) {
             var bridgeOptions =