fix(topology): always emit SDAM unrecoverable errors

The SDAM changes introduced for the "Connections survive primary
stepdown" project were erroneously implemented in this driver as
guarding whether a server should be transitioned to an `Unknown`
state, where the real intent is around whether a connection pool
is cleared or not.

NODE-2408

lib/cmap/connection.js

@@ -248,7 +248,7 @@ function messageHandler(conn) {
         return;
       }
 
-      if (document.ok === 0 || document.$err || document.errmsg) {
+      if (document.ok === 0 || document.$err || document.errmsg || document.code) {
         callback(new MongoError(document));
         return;
       }

lib/core/error.js

@@ -1,7 +1,6 @@
 'use strict';
 
 const mongoErrorContextSymbol = Symbol('mongoErrorContextSymbol');
-const maxWireVersion = require('./utils').maxWireVersion;
 
 /**
  * Creates a new MongoError
@@ -237,20 +236,15 @@ function isNodeShuttingDownError(err) {
  * @ignore
  * @see https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#not-master-and-node-is-recovering
  * @param {MongoError|Error} error
- * @param {Server} server
  */
-function isSDAMUnrecoverableError(error, server) {
+function isSDAMUnrecoverableError(error) {
   // NOTE: null check is here for a strictly pre-CMAP world, a timeout or
   //       close event are considered unrecoverable
   if (error instanceof MongoParseError || error == null) {
     return true;
   }
 
   if (isRecoveringError(error) || isNotMasterError(error)) {
-    if (maxWireVersion(server) >= 8 && !isNodeShuttingDownError(error)) {
-      return false;
-    }
-
     return true;
   }
 
@@ -266,5 +260,6 @@ module.exports = {
   MongoWriteConcernError,
   mongoErrorContextSymbol,
   isRetryableError,
-  isSDAMUnrecoverableError
+  isSDAMUnrecoverableError,
+  isNodeShuttingDownError
 };

lib/core/sdam/server.js

@@ -286,7 +286,7 @@ class Server extends EventEmitter {
             options.session.serverSession.isDirty = true;
           }
 
-          if (isSDAMUnrecoverableError(err, this)) {
+          if (isSDAMUnrecoverableError(err)) {
             this.emit('error', err);
           }
         }
@@ -319,7 +319,7 @@ class Server extends EventEmitter {
             options.session.serverSession.isDirty = true;
           }
 
-          if (isSDAMUnrecoverableError(err, this)) {
+          if (isSDAMUnrecoverableError(err)) {
             this.emit('error', err);
           }
         }
@@ -352,7 +352,7 @@ class Server extends EventEmitter {
             options.session.serverSession.isDirty = true;
           }
 
-          if (isSDAMUnrecoverableError(err, this)) {
+          if (isSDAMUnrecoverableError(err)) {
             this.emit('error', err);
           }
         }
@@ -382,7 +382,7 @@ class Server extends EventEmitter {
       if (err) return cb(err);
 
       conn.killCursors(ns, cursorState, (err, result) => {
-        if (err && isSDAMUnrecoverableError(err, this)) {
+        if (err && isSDAMUnrecoverableError(err)) {
           this.emit('error', err);
         }
 
@@ -489,7 +489,7 @@ function executeWriteOperation(args, options, callback) {
           options.session.serverSession.isDirty = true;
         }
 
-        if (isSDAMUnrecoverableError(err, server)) {
+        if (isSDAMUnrecoverableError(err)) {
           server.emit('error', err);
         }
       }

lib/core/sdam/topology.js

@@ -14,7 +14,8 @@ const deprecate = require('util').deprecate;
 const BSON = require('../connection/utils').retrieveBSON();
 const createCompressionInfo = require('../topologies/shared').createCompressionInfo;
 const isRetryableError = require('../error').isRetryableError;
-const isSDAMUnrecoverableError = require('../error').isSDAMUnrecoverableError;
+const isNodeShuttingDownError = require('../error').isNodeShuttingDownError;
+const maxWireVersion = require('../utils').maxWireVersion;
 const ClientSession = require('../sessions').ClientSession;
 const MongoError = require('../error').MongoError;
 const resolveClusterTime = require('../topologies/shared').resolveClusterTime;
@@ -881,14 +882,12 @@ function serverErrorEventHandler(server, topology) {
       return;
     }
 
-    if (isSDAMUnrecoverableError(err, server)) {
-      // NOTE: this must be commented out until we switch to the new CMAP pool because
-      //       we presently _always_ clear the pool on error.
-      resetServerState(server, err, { clearPool: true });
+    if (maxWireVersion(server) >= 8 && !isNodeShuttingDownError(err)) {
+      resetServerState(server, err);
       return;
     }
 
-    resetServerState(server, err);
+    resetServerState(server, err, { clearPool: true });
   };
 }
 

test/unit/sdam/topology.test.js

@@ -113,4 +113,84 @@ describe('Topology (unit)', function() {
       });
     });
   });
+
+  describe('error handling', function() {
+    let mockServer;
+    beforeEach(() => mock.createServer().then(server => (mockServer = server)));
+    afterEach(() => mock.cleanup());
+
+    it('should set server to unknown and reset pool on `node is recovering` error', function(done) {
+      mockServer.setMessageHandler(request => {
+        const doc = request.document;
+        if (doc.ismaster) {
+          request.reply(Object.assign({}, mock.DEFAULT_ISMASTER, { maxWireVersion: 9 }));
+        } else if (doc.insert) {
+          request.reply({ ok: 0, message: 'node is recovering', code: 11600 });
+        } else {
+          request.reply({ ok: 1 });
+        }
+      });
+
+      const topology = new Topology(mockServer.uri());
+      topology.connect(err => {
+        expect(err).to.not.exist;
+
+        topology.selectServer('primary', (err, server) => {
+          expect(err).to.not.exist;
+          this.defer(() => topology.close());
+
+          let serverError;
+          server.on('error', err => (serverError = err));
+
+          let poolCleared = false;
+          topology.on('connectionPoolCleared', () => (poolCleared = true));
+
+          server.command('test.test', { insert: { a: 42 } }, (err, result) => {
+            expect(result).to.not.exist;
+            expect(err).to.exist;
+            expect(err).to.eql(serverError);
+            expect(poolCleared).to.be.true;
+            done();
+          });
+        });
+      });
+    });
+
+    it('should set server to unknown and NOT reset pool on stepdown errors', function(done) {
+      mockServer.setMessageHandler(request => {
+        const doc = request.document;
+        if (doc.ismaster) {
+          request.reply(Object.assign({}, mock.DEFAULT_ISMASTER, { maxWireVersion: 9 }));
+        } else if (doc.insert) {
+          request.reply({ ok: 0, message: 'not master' });
+        } else {
+          request.reply({ ok: 1 });
+        }
+      });
+
+      const topology = new Topology(mockServer.uri());
+      topology.connect(err => {
+        expect(err).to.not.exist;
+
+        topology.selectServer('primary', (err, server) => {
+          expect(err).to.not.exist;
+          this.defer(() => topology.close());
+
+          let serverError;
+          server.on('error', err => (serverError = err));
+
+          let poolCleared = false;
+          topology.on('connectionPoolCleared', () => (poolCleared = true));
+
+          server.command('test.test', { insert: { a: 42 } }, (err, result) => {
+            expect(result).to.not.exist;
+            expect(err).to.exist;
+            expect(err).to.eql(serverError);
+            expect(poolCleared).to.be.false;
+            done();
+          });
+        });
+      });
+    });
+  });
 });