1 files changed, 122 insertions, 0 deletions
diff --git a/jstests/multiVersion/shell_retryable_writes_downgrade.js b/jstests/multiVersion/shell_retryable_writes_downgrade.js
new file mode 100644
index 00000000000..652d33c0ddc
--- /dev/null
+++ b/jstests/multiVersion/shell_retryable_writes_downgrade.js
@@ -0,0 +1,122 @@
+/**
+ * Tests that the mongo shell doesn't attempt to retry its write operations after downgrading from
+ * 3.6 to 3.4.
+ */
+(function() {
+    "use strict";
+
+    load("jstests/replsets/rslib.js");
+
+    const rst = new ReplSetTest({nodes: 1});
+    rst.startSet();
+    rst.initiate();
+
+    const primary = rst.getPrimary();
+
+    const db = primary.startSession({retryWrites: true}).getDatabase("test");
+    const coll = db.shell_retryable_writes_downgrade;
+
+    function testCommandCanBeRetried(func, {
+        expectedLogicalSessionId: expectedLogicalSessionId = true,
+        expectedTransactionNumber: expectedTransactionNumber = true
+    } = {}) {
+        const mongoRunCommandOriginal = Mongo.prototype.runCommand;
+
+        const sentinel = {};
+        let cmdObjSeen = sentinel;
+
+        Mongo.prototype.runCommand = function runCommandSpy(dbName, cmdObj, options) {
+            cmdObjSeen = cmdObj;
+            return mongoRunCommandOriginal.apply(this, arguments);
+        };
+
+        try {
+            assert.doesNotThrow(func);
+        } finally {
+            Mongo.prototype.runCommand = mongoRunCommandOriginal;
+        }
+
+        if (cmdObjSeen === sentinel) {
+            throw new Error("Mongo.prototype.runCommand() was never called: " + func.toString());
+        }
+
+        let cmdName = Object.keys(cmdObjSeen)[0];
+
+        // If the command is in a wrapped form, then we look for the actual command object inside
+        // the query/$query object.
+        if (cmdName === "query" || cmdName === "$query") {
+            cmdObjSeen = cmdObjSeen[cmdName];
+            cmdName = Object.keys(cmdObjSeen)[0];
+        }
+
+        if (expectedLogicalSessionId) {
+            assert(cmdObjSeen.hasOwnProperty("lsid"),
+                   "Expected operation " + tojson(cmdObjSeen) + " to have a logical session id: " +
+                       func.toString());
+        } else {
+            assert(!cmdObjSeen.hasOwnProperty("lsid"),
+                   "Expected operation " + tojson(cmdObjSeen) +
+                       " to not have a logical session id: " + func.toString());
+        }
+
+        if (expectedTransactionNumber) {
+            assert(cmdObjSeen.hasOwnProperty("txnNumber"),
+                   "Expected operation " + tojson(cmdObjSeen) +
+                       " to be assigned a transaction number since it can be retried: " +
+                       func.toString());
+        } else {
+            assert(!cmdObjSeen.hasOwnProperty("txnNumber"),
+                   "Expected operation " + tojson(cmdObjSeen) +
+                       " to not be assigned a transaction number since it cannot be retried: " +
+                       func.toString());
+        }
+    }
+
+    testCommandCanBeRetried(function() {
+        assert.writeOK(coll.insert({_id: "while fCV=3.6"}));
+    });
+
+    assert.commandWorked(db.adminCommand({setFeatureCompatibilityVersion: "3.4"}));
+
+    // The server continues to accept lsid and txnNumber while in featureCompatibilityVersion=3.4.
+    //
+    // TODO SERVER-31777: The server should return an error if an lsid or txnNumber is specified
+    // while in featureCompatibilityVersion=3.4.
+    testCommandCanBeRetried(function() {
+        assert.writeOK(coll.insert({_id: "while fCV=3.4"}));
+    });
+
+    rst.restart(primary, {binVersion: "3.4"});
+    rst.waitForMaster();
+
+    assert(db.getSession().getOptions().shouldRetryWrites(),
+           "Re-establishing the connection shouldn't change the state of the SessionOptions");
+
+    // After downgrading to MongoDB 3.4, the mongo shell shouldn't attempt to automatically retry
+    // write operations.
+    assert.throws(function() {
+        coll.insert({_id: "while in binVersion=3.4 and disconnected"});
+    });
+
+    // After downgrading to MongoDB 3.4, the mongo shell shouldn't inject an lsid or assign a
+    // transaction number to its write requests.
+    testCommandCanBeRetried(function() {
+        assert.writeOK(coll.insert({_id: "while binVersion=3.4 and reconnected"}));
+    }, {expectedLogicalSessionId: false, expectedTransactionNumber: false});
+
+    rst.restart(primary, {binVersion: "latest", noReplSet: true});
+    rst.waitForMaster();
+    reconnect(primary);
+
+    // When upgrading to MongoDB 3.6 but running as a stand-alone server, the mongo shell should
+    // still assign a transaction number to its write requests (per the Driver's specification).
+    //
+    // TODO SERVER-31777: The server should return an error if an lsid or txnNumber is specified
+    // while in featureCompatibilityVersion=3.4.
+    testCommandCanBeRetried(function() {
+        assert.writeOK(coll.insert({_id: "while binVersion=3.6 as stand-alone and reconnected"}));
+    });
+
+    db.getSession().endSession();
+    rst.stopSet();
+})();