Add basic handshake negotiation

lib/agent.js

@@ -20,6 +20,12 @@ function Agent(backend, stream) {
   this.stream = stream;
 
   this.clientId = hat();
+  // src is a client-configurable "id" which the client will set in its handshake,
+  // and attach to its ops. This should take precedence over clientId if set.
+  // Only legacy clients, or new clients connecting for the first time will use the
+  // Agent-provided clientId. Ideally we'll deprecate clientId in favour of src
+  // in the next breaking change.
+  this.src = null;
   this.connectTime = Date.now();
 
   // We need to track which documents are subscribed by the client. This is a
@@ -38,20 +44,15 @@ function Agent(backend, stream) {
   // active, and it is passed to each middleware call
   this.custom = {};
 
-  // Initialize the remote client by sending it its agent Id.
-  this.send({
-    a: 'init',
-    protocol: 1,
-    id: this.clientId,
-    type: types.defaultType.uri
-  });
+  // Send the legacy message to initialize old clients with the random agent Id
+  this.send(this._initMessage('init'));
 }
 module.exports = Agent;
 
 // Close the agent with the client.
 Agent.prototype.close = function(err) {
   if (err) {
-    logger.warn('Agent closed due to error', this.clientId, err.stack || err);
+    logger.warn('Agent closed due to error', this._src(), err.stack || err);
   }
   if (this.closed) return;
   // This will end the writable stream and emit 'finish'
@@ -190,7 +191,7 @@ Agent.prototype._isOwnOp = function(collection, op) {
   // Detect ops from this client on the same projection. Since the client sent
   // these in, the submit reply will be sufficient and we can silently ignore
   // them in the streams for subscribed documents or queries
-  return (this.clientId === op.src) && (collection === (op.i || op.c));
+  return (this._src() === op.src) && (collection === (op.i || op.c));
 };
 
 Agent.prototype.send = function(message) {
@@ -332,6 +333,9 @@ Agent.prototype._handleMessage = function(request, callback) {
     if (errMessage) return callback(new ShareDBError(ERROR_CODE.ERR_MESSAGE_BADLY_FORMED, errMessage));
 
     switch (request.a) {
+      case 'hs':
+        if (request.id) this.src = request.id;
+        return callback(null, this._initMessage('hs'));
       case 'qf':
         return this._queryFetch(request.id, request.c, request.q, getQueryOptions(request), callback);
       case 'qs':
@@ -352,7 +356,13 @@ Agent.prototype._handleMessage = function(request, callback) {
         return this._unsubscribe(request.c, request.d, callback);
       case 'op':
         // Normalize the properties submitted
-        var op = createClientOp(request, this.clientId);
+        var op = createClientOp(request, this._src());
+        if (op.seq >= util.MAX_SAFE_INTEGER) {
+          return callback(new ShareDBError(
+            ERROR_CODE.ERR_CONNECTION_SEQ_INTEGER_OVERFLOW,
+            'Connection seq has exceeded the max safe integer, maybe from being open for too long'
+          ));
+        }
         if (!op) return callback(new ShareDBError(ERROR_CODE.ERR_MESSAGE_BADLY_FORMED, 'Invalid op message'));
         return this._submit(request.c, request.d, op, callback);
       case 'nf':
@@ -645,6 +655,20 @@ Agent.prototype._fetchSnapshotByTimestamp = function(collection, id, timestamp,
   this.backend.fetchSnapshotByTimestamp(this, collection, id, timestamp, callback);
 };
 
+Agent.prototype._initMessage = function(action) {
+  return {
+    a: action,
+    protocol: 1,
+    protocolMinor: 1,
+    id: this._src(),
+    type: types.defaultType.uri
+  };
+};
+
+Agent.prototype._src = function() {
+  return this.src || this.clientId;
+};
+
 
 function createClientOp(request, clientId) {
   // src can be provided if it is not the same as the current agent,

lib/backend.js

@@ -100,7 +100,7 @@ Backend.prototype.close = function(callback) {
   finish();
 };
 
-Backend.prototype.connect = function(connection, req) {
+Backend.prototype.connect = function(connection, req, callback) {
   var socket = new StreamSocket();
   if (connection) {
     connection.bindToSocket(socket);
@@ -113,6 +113,13 @@ Backend.prototype.connect = function(connection, req) {
   // not used internal to ShareDB, but it is handy for server-side only user
   // code that may cache state on the agent and read it in middleware
   connection.agent = agent;
+
+  if (typeof callback === 'function') {
+    connection.once('connected', function() {
+      callback(connection);
+    });
+  }
+
   return connection;
 };
 

lib/client/connection.js

@@ -52,7 +52,7 @@ function Connection(socket) {
   // A unique message number for the given id
   this.seq = 1;
 
-  // Equals agent.clientId on the server
+  // Equals agent.src on the server
   this.id = null;
 
   // This direct reference from connection to agent is not used internal to
@@ -141,6 +141,7 @@ Connection.prototype.bindToSocket = function(socket) {
 
   socket.onopen = function() {
     connection._setState('connecting');
+    connection._initializeHandshake();
   };
 
   socket.onerror = function(err) {
@@ -183,29 +184,9 @@ Connection.prototype.handleMessage = function(message) {
   switch (message.a) {
     case 'init':
       // Client initialization packet
-      if (message.protocol !== 1) {
-        err = new ShareDBError(
-          ERROR_CODE.ERR_PROTOCOL_VERSION_NOT_SUPPORTED,
-          'Unsupported protocol version: ' + message.protocol
-        );
-        return this.emit('error', err);
-      }
-      if (types.map[message.type] !== types.defaultType) {
-        err = new ShareDBError(
-          ERROR_CODE.ERR_DEFAULT_TYPE_MISMATCH,
-          message.type + ' does not match the server default type'
-        );
-        return this.emit('error', err);
-      }
-      if (typeof message.id !== 'string') {
-        err = new ShareDBError(ERROR_CODE.ERR_CLIENT_ID_BADLY_FORMED, 'Client id must be a string');
-        return this.emit('error', err);
-      }
-      this.id = message.id;
-
-      this._setState('connected');
-      return;
-
+      return this._handleLegacyInit(message);
+    case 'hs':
+      return this._handleHandshake(err, message);
     case 'qf':
       var query = this.queries[message.id];
       if (query) query._handleFetch(err, message.data, message.extra);
@@ -305,8 +286,6 @@ Connection.prototype._handleBulkMessage = function(err, message, method) {
 };
 
 Connection.prototype._reset = function() {
-  this.seq = 1;
-  this.id = null;
   this.agent = null;
 };
 
@@ -714,3 +693,43 @@ Connection.prototype._handleSnapshotFetch = function(error, message) {
   delete this._snapshotRequests[message.id];
   snapshotRequest._handleResponse(error, message);
 };
+
+Connection.prototype._handleLegacyInit = function(message) {
+  // If the minor protocol version has been set, we can ignore this legacy
+  // init message, and wait for a response to our handshake message.
+  if (message.protocolMinor) return;
+  this._initialize(message);
+};
+
+Connection.prototype._initializeHandshake = function() {
+  this.send({a: 'hs', id: this.id});
+};
+
+Connection.prototype._handleHandshake = function(error, message) {
+  if (error) return this.emit('error', error);
+  this._initialize(message);
+};
+
+Connection.prototype._initialize = function(message) {
+  if (message.protocol !== 1) {
+    return this.emit('error', new ShareDBError(
+      ERROR_CODE.ERR_PROTOCOL_VERSION_NOT_SUPPORTED,
+      'Unsupported protocol version: ' + message.protocol
+    ));
+  }
+  if (types.map[message.type] !== types.defaultType) {
+    return this.emit('error', new ShareDBError(
+      ERROR_CODE.ERR_DEFAULT_TYPE_MISMATCH,
+      message.type + ' does not match the server default type'
+    ));
+  }
+  if (typeof message.id !== 'string') {
+    return this.emit('error', new ShareDBError(
+      ERROR_CODE.ERR_CLIENT_ID_BADLY_FORMED,
+      'Client id must be a string'
+    ));
+  }
+  this.id = message.id;
+
+  this._setState('connected');
+};

lib/client/doc.js

@@ -2,6 +2,7 @@ var emitter = require('../emitter');
 var logger = require('../logger');
 var ShareDBError = require('../error');
 var types = require('../types');
+var util = require('../util');
 
 var ERROR_CODE = ShareDBError.CODES;
 
@@ -615,9 +616,8 @@ Doc.prototype._otApply = function(op, source) {
 
 // Actually send op to the server.
 Doc.prototype._sendOp = function() {
-  // Wait until we have a src id from the server
+  if (!this.connection.canSend) return;
   var src = this.connection.id;
-  if (!src) return;
 
   // When there is no inflightOp, send the first item in pendingOps. If
   // there is inflightOp, try sending it again
@@ -642,7 +642,16 @@ Doc.prototype._sendOp = function() {
   // reconnect, since an op may still be pending after the reconnection and
   // this.connection.id will change. In case an op is sent multiple times, we
   // also need to be careful not to override the original seq value.
-  if (op.seq == null) op.seq = this.connection.seq++;
+  if (op.seq == null) {
+    if (this.connection.seq >= util.MAX_SAFE_INTEGER) {
+      return this.emit('error', new ShareDBError(
+        ERROR_CODE.ERR_CONNECTION_SEQ_INTEGER_OVERFLOW,
+        'Connection seq has exceeded the max safe integer, maybe from being open for too long'
+      ));
+    }
+
+    op.seq = this.connection.seq++;
+  }
 
   this.connection.sendOp(this, op);
 

lib/error.js

@@ -16,6 +16,7 @@ ShareDBError.CODES = {
   ERR_APPLY_OP_VERSION_DOES_NOT_MATCH_SNAPSHOT: 'ERR_APPLY_OP_VERSION_DOES_NOT_MATCH_SNAPSHOT',
   ERR_APPLY_SNAPSHOT_NOT_PROVIDED: 'ERR_APPLY_SNAPSHOT_NOT_PROVIDED',
   ERR_CLIENT_ID_BADLY_FORMED: 'ERR_CLIENT_ID_BADLY_FORMED',
+  ERR_CONNECTION_SEQ_INTEGER_OVERFLOW: 'ERR_CONNECTION_SEQ_INTEGER_OVERFLOW',
   ERR_CONNECTION_STATE_TRANSITION_INVALID: 'ERR_CONNECTION_STATE_TRANSITION_INVALID',
   ERR_DATABASE_ADAPTER_NOT_FOUND: 'ERR_DATABASE_ADAPTER_NOT_FOUND',
   ERR_DATABASE_DOES_NOT_SUPPORT_SUBSCRIBE: 'ERR_DATABASE_DOES_NOT_SUPPORT_SUBSCRIBE',

lib/util.js

@@ -22,3 +22,5 @@ exports.isValidVersion = function(version) {
 exports.isValidTimestamp = function(timestamp) {
   return exports.isValidVersion(timestamp);
 };
+
+exports.MAX_SAFE_INTEGER = 9007199254740991;

package.json

@@ -18,6 +18,7 @@
     "lolex": "^5.1.1",
     "mocha": "^6.2.2",
     "nyc": "^14.1.1",
+    "sharedb-legacy": "npm:sharedb@=1.1.0",
     "sinon": "^7.5.0"
   },
   "scripts": {

test/client/connection.js

@@ -1,6 +1,8 @@
 var expect = require('chai').expect;
 var Backend = require('../../lib/backend');
 var Connection = require('../../lib/client/connection');
+var LegacyConnection = require('sharedb-legacy/lib/client').Connection;
+var StreamSocket = require('../../lib/stream-socket');
 
 describe('client connection', function() {
   beforeEach(function() {
@@ -197,4 +199,66 @@ describe('client connection', function() {
       });
     });
   });
+
+  it('persists its id and seq when reconnecting', function(done) {
+    var backend = this.backend;
+    backend.connect(null, null, function(connection) {
+      var id = connection.id;
+      expect(id).to.be.ok;
+      var doc = connection.get('test', '123');
+      doc.create({foo: 'bar'}, function(error) {
+        if (error) return done(error);
+        expect(connection.seq).to.equal(2);
+        connection.close();
+        backend.connect(connection, null, function() {
+          expect(connection.id).to.equal(id);
+          expect(connection.seq).to.equal(2);
+          done();
+        });
+      });
+    });
+  });
+
+  it('still connects to legacy clients, whose ID changes on reconnection', function(done) {
+    var currentBackend = this.backend;
+    var socket = new StreamSocket();
+    var legacyClient = new LegacyConnection(socket);
+    currentBackend.connect(legacyClient);
+
+    var doc = legacyClient.get('test', '123');
+    doc.create({foo: 'bar'}, function(error) {
+      if (error) return done(error);
+      var initialId = legacyClient.id;
+      expect(initialId).to.equal(legacyClient.agent.clientId);
+      expect(legacyClient.agent.src).to.be.null;
+      legacyClient.close();
+      currentBackend.connect(legacyClient);
+      doc.submitOp({p: ['baz'], oi: 'qux'}, function(error) {
+        if (error) return done(error);
+        var newId = legacyClient.id;
+        expect(newId).not.to.equal(initialId);
+        expect(newId).to.equal(legacyClient.agent.clientId);
+        expect(legacyClient.agent.src).to.be.null;
+        done();
+      });
+    });
+  });
+
+  it('errors when submitting an op with a very large seq', function(done) {
+    this.backend.connect(null, null, function(connection) {
+      var doc = connection.get('test', '123');
+      doc.create({foo: 'bar'}, function(error) {
+        if (error) return done(error);
+        connection.sendOp(doc, {
+          op: {p: ['foo'], od: 'bar'},
+          src: connection.id,
+          seq: Number.MAX_SAFE_INTEGER
+        });
+        doc.once('error', function(error) {
+          expect(error.code).to.equal('ERR_CONNECTION_SEQ_INTEGER_OVERFLOW');
+          done();
+        });
+      });
+    });
+  });
 });

test/client/doc.js

@@ -49,6 +49,17 @@ describe('Doc', function() {
     doc.destroy();
   });
 
+  it('errors when trying to set a very large seq', function(done) {
+    var connection = this.connection;
+    connection.seq = Number.MAX_SAFE_INTEGER;
+    var doc = connection.get('dogs', 'fido');
+    doc.create({name: 'fido'});
+    doc.once('error', function(error) {
+      expect(error.code).to.equal('ERR_CONNECTION_SEQ_INTEGER_OVERFLOW');
+      done();
+    });
+  });
+
   describe('when connection closed', function() {
     beforeEach(function(done) {
       this.op1 = [{p: ['snacks'], oi: true}];