Merge pull request #337 from strongloop/feature/context-propagation

Add context propagation middleware

example/context/app.js

@@ -0,0 +1,29 @@
+var loopback = require('../../');
+var app = loopback();
+
+// Create a LoopBack context for all requests
+app.use(loopback.context());
+
+// Store a request property in the context
+app.use(function saveHostToContext(req, res, next) {
+  var ns = loopback.getCurrentContext();
+  ns.set('host', req.host);
+  next();
+});
+
+app.use(loopback.rest());
+
+var Color = loopback.createModel('color', { 'name': String });
+Color.beforeRemote('**', function (ctx, unused, next) {
+  // Inside LoopBack code, you can read the property from the context
+  var ns = loopback.getCurrentContext();
+  console.log('Request to host', ns && ns.get('host'));
+  next();
+});
+
+app.dataSource('db', { connector: 'memory' });
+app.model(Color, { dataSource: 'db' });
+
+app.listen(3000, function() {
+  console.log('A list of colors is available at http://localhost:3000/colors');
+});

lib/middleware/context.js

@@ -0,0 +1,104 @@
+var loopback = require('../loopback');
+var juggler = require('loopback-datasource-juggler');
+var remoting = require('strong-remoting');
+var cls = require('continuation-local-storage');
+
+module.exports = context;
+
+var name = 'loopback';
+
+function createContext(scope) {
+  // Make the namespace globally visible via the process.context property
+  process.context = process.context || {};
+  var ns = process.context[scope];
+  if (!ns) {
+    ns = cls.createNamespace(scope);
+    process.context[scope] = ns;
+    // Set up loopback.getCurrentContext()
+    loopback.getCurrentContext = function() {
+      return ns;
+    };
+
+    chain(juggler);
+    chain(remoting);
+  }
+  return ns;
+}
+
+function context(options) {
+  options = options || {};
+  var scope = options.name || name;
+  var enableHttpContext = options.enableHttpContext || false;
+  var ns = createContext(scope);
+  // Return the middleware
+  return function contextHandler(req, res, next) {
+    if (req.loopbackContext) {
+      return next();
+    }
+    req.loopbackContext = ns;
+    // Bind req/res event emitters to the given namespace
+    ns.bindEmitter(req);
+    ns.bindEmitter(res);
+    // Create namespace for the request context
+    ns.run(function processRequestInContext(context) {
+      // Run the code in the context of the namespace
+      if (enableHttpContext) {
+        ns.set('http', {req: req, res: res}); // Set up the transport context
+      }
+      next();
+    });
+  };
+}
+
+/**
+ * Create a chained context
+ * @param {Object} child The child context
+ * @param {Object} parent The parent context
+ * @private
+ * @constructor
+ */
+function ChainedContext(child, parent) {
+  this.child = child;
+  this.parent = parent;
+}
+
+/**
+ * Get the value by name from the context. If it doesn't exist in the child
+ * context, try the parent one
+ * @param {String} name Name of the context property
+ * @returns {*} Value of the context property
+ */
+ChainedContext.prototype.get = function(name) {
+  var val = this.child && this.child.get(name);
+  if (val === undefined) {
+    return this.parent && this.parent.get(name);
+  }
+};
+
+ChainedContext.prototype.set = function(name, val) {
+  if (this.child) {
+    return this.child.set(name, val);
+  } else {
+    return this.parent && this.parent.set(name, val);
+  }
+};
+
+ChainedContext.prototype.reset = function(name, val) {
+  if (this.child) {
+    return this.child.reset(name, val);
+  } else {
+    return this.parent && this.parent.reset(name, val);
+  }
+};
+
+function chain(child) {
+  if (typeof child.getCurrentContext === 'function') {
+    var childContext = new ChainedContext(child.getCurrentContext(),
+      loopback.getCurrentContext());
+    child.getCurrentContext = function() {
+      return childContext;
+    };
+  } else {
+    child.getCurrentContext = loopback.getCurrentContext;
+  }
+}

lib/middleware/rest.js

@@ -3,6 +3,7 @@
  */
 
 var loopback = require('../loopback');
+var async = require('async');
 
 /*!
  * Export the middleware.
@@ -22,36 +23,43 @@ module.exports = rest;
  */
 
 function rest() {
-  var tokenParser = null;
-  return function(req, res, next) {
+  return function restApiHandler(req, res, next) {
     var app = req.app;
-    var handler = app.handler('rest');
+    var restHandler = app.handler('rest');
 
     if (req.url === '/routes') {
-      res.send(handler.adapter.allRoutes());
+      return res.send(restHandler.adapter.allRoutes());
     } else if (req.url === '/models') {
       return res.send(app.remotes().toJSON());
-    } else if (app.isAuthEnabled) {
-      if (!tokenParser) {
+    }
+
+    var preHandlers;
+
+    if (!preHandlers) {
+      preHandlers = [];
+      var remotingOptions = app.get('remoting') || {};
+
+      var contextOptions = remotingOptions.context;
+      if (contextOptions !== false) {
+        if (typeof contextOptions !== 'object')
+          contextOptions = {};
+        preHandlers.push(loopback.context(contextOptions));
+      }
+
+      if (app.isAuthEnabled) {
         // NOTE(bajtos) It would be better to search app.models for a model
         // of type AccessToken instead of searching all loopback models.
         // Unfortunately that's not supported now.
         // Related discussions:
         // https://github.com/strongloop/loopback/pull/167
         // https://github.com/strongloop/loopback/commit/f07446a
         var AccessToken = loopback.getModelByType(loopback.AccessToken);
-        tokenParser = loopback.token({ model: AccessToken });
+        preHandlers.push(loopback.token({ model: AccessToken }));
       }
-
-      tokenParser(req, res, function(err) {
-        if (err) {
-          next(err);
-        } else {
-          handler(req, res, next);
-        }
-      });
-    } else {
-      handler(req, res, next);
     }
+
+    async.eachSeries(preHandlers.concat(restHandler), function(handler, done) {
+      handler(req, res, done);
+    }, next);
   };
 }

package.json

@@ -46,7 +46,8 @@
     "strong-remoting": "^2.4.0",
     "uid2": "0.0.3",
     "underscore": "~1.7.0",
-    "underscore.string": "~2.3.3"
+    "underscore.string": "~2.3.3",
+    "continuation-local-storage": "~3.1.1"
   },
   "peerDependencies": {
     "loopback-datasource-juggler": "^2.8.0"

test/rest.middleware.test.js

@@ -130,6 +130,107 @@ describe('loopback.rest', function() {
     });
   });
 
+  describe('context propagation', function() {
+    var User;
+
+    beforeEach(function() {
+      User = givenUserModelWithAuth();
+      User.getToken = function(cb) {
+        var context = loopback.getCurrentContext();
+        var req = context.get('http').req;
+        expect(req).to.have.property('accessToken');
+
+        var juggler = require('loopback-datasource-juggler');
+        expect(juggler.getCurrentContext().get('http').req)
+          .to.have.property('accessToken');
+
+        var remoting = require('strong-remoting');
+        expect(remoting.getCurrentContext().get('http').req)
+          .to.have.property('accessToken');
+
+        cb(null, req && req.accessToken ? req.accessToken.id : null);
+      };
+      // Set up the ACL
+      User.settings.acls.push({principalType: 'ROLE',
+        principalId: '$authenticated', permission: 'ALLOW',
+        property: 'getToken'});
+
+      loopback.remoteMethod(User.getToken, {
+        accepts: [],
+        returns: [
+          { type: 'object', name: 'id' }
+        ]
+      });
+    });
+
+    function invokeGetToken(done) {
+      givenLoggedInUser(function(err, token) {
+        if (err) return done(err);
+        request(app).get('/users/getToken')
+          .set('Authorization', token.id)
+          .expect(200)
+          .end(function(err, res) {
+            if (err) return done(err);
+            expect(res.body.id).to.equal(token.id);
+            done();
+          });
+      });
+    }
+
+    it('should enable context using loopback.context', function(done) {
+      app.use(loopback.context({ enableHttpContext: true }));
+      app.enableAuth();
+      app.use(loopback.rest());
+
+      invokeGetToken(done);
+    });
+
+    it('should enable context with loopback.rest', function(done) {
+      app.enableAuth();
+      app.set('remoting', { context: { enableHttpContext: true } });
+      app.use(loopback.rest());
+
+      invokeGetToken(done);
+    });
+
+    it('should support explicit context', function(done) {
+      app.enableAuth();
+      app.use(loopback.context());
+      app.use(loopback.token(
+        { model: loopback.getModelByType(loopback.AccessToken) }));
+      app.use(function(req, res, next) {
+        loopback.getCurrentContext().set('accessToken', req.accessToken);
+        next();
+      });
+      app.use(loopback.rest());
+
+      User.getToken = function(cb) {
+        var context = loopback.getCurrentContext();
+        var accessToken = context.get('accessToken');
+        expect(context.get('accessToken')).to.have.property('id');
+
+        var juggler = require('loopback-datasource-juggler');
+        context = juggler.getCurrentContext();
+        expect(context.get('accessToken')).to.have.property('id');
+
+        var remoting = require('strong-remoting');
+        context = remoting.getCurrentContext();
+        expect(context.get('accessToken')).to.have.property('id');
+
+        cb(null, accessToken ? accessToken.id : null);
+      };
+
+      loopback.remoteMethod(User.getToken, {
+        accepts: [],
+        returns: [
+          { type: 'object', name: 'id' }
+        ]
+      });
+
+      invokeGetToken(done);
+    });
+  });
+
   function givenUserModelWithAuth() {
     // NOTE(bajtos) It is important to create a custom AccessToken model here,
     // in order to overwrite the entry created by previous tests in