fix(transactions): do not send txnNumber for non-write commands (#308)

* fix(transactions): do not send txnNumber for non-write commands

We started sending txnNumber for non-transaction non-retryable
commands, which causes errors against transaction-enabled servers

Fixes NODE-1466

lib/topologies/mongos.js

@@ -895,6 +895,7 @@ var executeWriteOperation = function(self, op, ns, ops, options, callback) {
   }
 
   // increment and assign txnNumber
+  options.willRetryWrite = true;
   options.session.incrementTransactionNumber();
 
   server[op](ns, ops, options, (err, result) => {

lib/topologies/replset.js

@@ -1231,6 +1231,7 @@ function executeWriteOperation(args, options, callback) {
   // increment and assign txnNumber
   if (willRetryWrite) {
     options.session.incrementTransactionNumber();
+    options.willRetryWrite = willRetryWrite;
   }
 
   // optionally autostart transaction if requested

lib/wireprotocol/3_2_support.js

@@ -18,20 +18,23 @@ var WireProtocol = function(legacyWireProtocol) {
  *
  * @param {Object} command the command to decorate
  * @param {ClientSession} session the session tracking transaction state
+ * @param {boolean} [isRetryableWrite=false] if true, will be decorated for retryable writes
  */
-function decorateWithTransactionsData(command, session) {
+function decorateWithTransactionsData(command, session, isRetryableWrite) {
   if (!session) {
     return;
   }
 
   // first apply non-transaction-specific sessions data
   const serverSession = session.serverSession;
-  if (serverSession.txnNumber) {
+  const inTransaction = session.inTransaction();
+
+  if (serverSession.txnNumber && (isRetryableWrite || inTransaction)) {
     command.txnNumber = BSON.Long.fromNumber(serverSession.txnNumber);
   }
 
   // now try to apply tansaction-specific data
-  if (!session.inTransaction()) {
+  if (!inTransaction) {
     return;
   }
 
@@ -103,7 +106,7 @@ var executeWrite = function(pool, bson, type, opsField, ns, ops, options, callba
   }
 
   // optionally decorate command with transactions data
-  decorateWithTransactionsData(writeCommand, options.session);
+  decorateWithTransactionsData(writeCommand, options.session, options.willRetryWrite);
 
   // Options object
   var opts = { command: true };

test/tests/unit/replset/transactions_feature_decoration_tests.js

@@ -0,0 +1,142 @@
+'use strict';
+
+const expect = require('chai').expect;
+const ReplSet = require('../../../../lib/topologies/replset');
+const mock = require('mongodb-mock-server');
+const ReplSetFixture = require('../common').ReplSetFixture;
+const ClientSession = require('../../../../lib/sessions').ClientSession;
+const ServerSessionPool = require('../../../../lib/sessions').ServerSessionPool;
+
+describe('Transaction Feature Decoration', function() {
+  let test;
+  const ns = 'db.foo';
+  const noop = () => {};
+  const ismaster = Object.assign({}, mock.DEFAULT_ISMASTER_36, { maxWireVersion: 7 });
+
+  before(() => (test = new ReplSetFixture()));
+  afterEach(() => mock.cleanup());
+  beforeEach(() => test.setup({ ismaster }));
+
+  class TestConfig {
+    constructor(config, flags) {
+      this.fnName = config.fnName;
+      this.cmd = config.cmd;
+      this.arg = config.arg();
+      this.flags = flags;
+      this.retryWrites = flags.retryWrites;
+      this.session = flags.session;
+      this.transaction = flags.transaction;
+    }
+
+    get shouldPass() {
+      if (this.session && this.transaction) {
+        return true;
+      }
+
+      if (this.fnName === 'command') {
+        return false;
+      }
+
+      return this.session && this.retryWrites;
+    }
+
+    get description() {
+      const not = this.shouldPass ? '' : 'not ';
+      const flags = JSON.stringify(this.flags);
+
+      return `should ${not}have a txnNumber when command ${this.cmd} is used with ${flags}`;
+    }
+  }
+
+  [
+    { fnName: 'insert', cmd: 'insert', arg: () => [{ foo: 1 }] },
+    { fnName: 'update', cmd: 'update', arg: () => [{ foo: 1 }] },
+    { fnName: 'remove', cmd: 'delete', arg: () => [{ foo: 1 }] },
+    { fnName: 'command', cmd: 'fizzBuzz', arg: () => ({ fizzBuzz: 1 }) }
+  ]
+    .reduce((testConfigs, op) => {
+      for (let i = 0; i < 4; i += 1) {
+        const options = {
+          retryWrites: i % 2 === 1,
+          session: i >= 2
+        };
+
+        testConfigs.push(new TestConfig(op, options));
+
+        if (options.session) {
+          testConfigs.push(new TestConfig(op, Object.assign({ transaction: true }, options)));
+        }
+      }
+      return testConfigs;
+    }, [])
+    .forEach(config => {
+      it(config.description, {
+        metadata: { requires: { topology: 'single', mongodb: '>=3.7.3' } },
+        test: function(done) {
+          const replSet = new ReplSet(
+            [test.primaryServer.address(), test.firstSecondaryServer.address()],
+            {
+              setName: 'rs',
+              connectionTimeout: 3000,
+              socketTimeout: 0,
+              haInterval: 100,
+              size: 1
+            }
+          );
+
+          function shutdown(err) {
+            replSet.destroy();
+            done(err);
+          }
+
+          test.primaryServer.setMessageHandler(request => {
+            try {
+              const doc = request.document;
+
+              if (doc.ismaster) {
+                return request.reply(test.primaryStates[0]);
+              }
+
+              if (doc[config.cmd]) {
+                if (config.shouldPass) {
+                  expect(doc).to.have.property('txnNumber');
+                } else {
+                  expect(doc).to.not.have.property('txnNumber');
+                }
+
+                request.reply({ ok: 1 });
+
+                setTimeout(() => shutdown());
+              }
+            } catch (e) {
+              return shutdown(e);
+            }
+          });
+
+          const sessionPool = new ServerSessionPool(replSet);
+
+          replSet.on('connect', () => {
+            const options = {};
+
+            if (config.retryWrites) {
+              options.retryWrites = true;
+            }
+
+            if (config.session) {
+              options.session = new ClientSession(replSet, sessionPool, {}, {});
+
+              if (config.transaction) {
+                options.session.startTransaction();
+              }
+            }
+
+            replSet[config.fnName](ns, config.arg, options, noop);
+          });
+
+          replSet.on('error', shutdown);
+
+          replSet.connect();
+        }
+      });
+    });
+});