Initial implementation

README.md

@@ -1,4 +1,34 @@
-# loopback-context-cls
+# loopback-context
 
 Current context for LoopBack applications, based on
 node-continuation-local-storage.
+
+## Usage
+
+1) Add `per-request-context` middleware to your
+`server/middleware-config.json`:
+
+```json
+{
+  "initial": {
+    "loopback-context#per-request-context": {
+    }
+  }
+}
+```
+
+2) Then you can access the context from your code:
+
+```js
+var LoopBackContext = require('loopback-context');
+
+// ...
+
+MyModel.myMethod = function(cb) {
+  var ctx = LoopBackContext.getCurrentContext();
+  ctx.get('key');
+  ctx.set('key', { foo: 'bar' });
+});
+```
+
+See also https://docs.strongloop.com/display/APIC/Using+current+context

browser/current-context.js

@@ -0,0 +1,17 @@
+// Copyright IBM Corp. 2015. All Rights Reserved.
+// Node module: loopback-context-cls
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+var LoopBackContext = module.exports;
+
+LoopBackContext.getCurrentContext = function() {
+  return null;
+};
+
+LoopBackContext.runInContext =
+LoopBackContext.createContext = function() {
+  throw new Error('Current context is not supported in the browser.');
+};

package.json

@@ -11,19 +11,24 @@
     "type": "git",
     "url": "https://github.com/strongloop/loopback-context"
   },
-  "main": "index.js",
-  "browser": "browser.js",
+  "main": "server/current-context.js",
+  "browser": "browser/current-context.js",
   "scripts": {
     "test": "mocha",
     "posttest": "npm run lint",
     "lint": "eslint ."
   },
   "license": "MIT",
-  "dependencies": {},
+  "dependencies": {
+    "continuation-local-storage": "^3.1.7"
+  },
   "devDependencies": {
+    "chai": "^3.5.0",
+    "dirty-chai": "^1.2.2",
     "eslint": "^2.13.1",
     "eslint-config-loopback": "^4.0.0",
     "loopback": "^3.0.0-alpha.1",
-    "mocha": "^2.5.3"
+    "mocha": "^2.5.3",
+    "supertest": "^1.2.0"
   }
 }

server/current-context.js

@@ -0,0 +1,96 @@
+// Copyright IBM Corp. 2015,2016. All Rights Reserved.
+// Node module: loopback-context-cls
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+var domain = require('domain');
+
+// Require CLS only when using the current context feature.
+// As soon as this require is done, all the instrumentation/patching
+// of async-listener is fired which is not ideal.
+//
+// Some users observed stack overflows due to promise instrumentation
+// and other people have seen similar things:
+//   https://github.com/othiym23/async-listener/issues/57
+// It all goes away when instrumentation is disabled.
+var cls = function() {
+  return require('continuation-local-storage');
+};
+
+var LoopBackContext = module.exports;
+
+/**
+ * Get the current context object. The context is preserved
+ * across async calls, it behaves like a thread-local storage.
+ *
+ * @returns {Namespace} The context object or null.
+ */
+LoopBackContext.getCurrentContext = function() {
+  // A placeholder method, see LoopBackContext.createContext() for the real version
+  return null;
+};
+
+/**
+ * Run the given function in such way that
+ * `LoopBackContext.getCurrentContext` returns the
+ * provided context object.
+ *
+ * **NOTE**
+ *
+ * The method is supported on the server only, it does not work
+ * in the browser at the moment.
+ *
+ * @param {Function} fn The function to run, it will receive arguments
+ * (currentContext, currentDomain).
+ * @param {Namespace} context An optional context object.
+ *   When no value is provided, then the default global context is used.
+ */
+LoopBackContext.runInContext = function(fn, context) {
+  var currentDomain = domain.create();
+  currentDomain.oldBind = currentDomain.bind;
+  currentDomain.bind = function(callback, context) {
+    return currentDomain.oldBind(ns.bind(callback, context), context);
+  };
+
+  var ns = context || LoopBackContext.createContext('loopback');
+
+  currentDomain.run(function() {
+    ns.run(function executeInContext(context) {
+      fn(ns, currentDomain);
+    });
+  });
+};
+
+/**
+ * Create a new LoopBackContext instance that can be used
+ * for `LoopBackContext.runInContext`.
+ *
+ * **NOTES**
+ *
+ * At the moment, `LoopBackContext.getCurrentContext` supports
+ * a single global context instance only. If you call `createContext()`
+ * multiple times, `getCurrentContext` will return the last context
+ * created.
+ *
+ * The method is supported on the server only, it does not work
+ * in the browser at the moment.
+ *
+ * @param {String} scopeName An optional scope name.
+ * @return {Namespace} The new context object.
+ */
+LoopBackContext.createContext = function(scopeName) {
+  // Make the namespace globally visible via the process.context property
+  process.context = process.context || {};
+  var ns = process.context[scopeName];
+  if (!ns) {
+    ns = cls().createNamespace(scopeName);
+    process.context[scopeName] = ns;
+    // Set up LoopBackContext.getCurrentContext()
+    LoopBackContext.getCurrentContext = function() {
+      return ns && ns.active ? ns : null;
+    };
+  }
+  return ns;
+};

server/middleware/per-request-context.js

@@ -0,0 +1,60 @@
+// Copyright IBM Corp. 2014,2016. All Rights Reserved.
+// Node module: loopback-context-cls
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+var LoopBackContext = require('../current-context');
+
+module.exports = context;
+
+var name = 'loopback';
+
+/**
+ * Context middleware.
+ * ```js
+ * var perRequestContext = require(
+ *   'loopback-context/server/middleware/per-request-context.js');
+ * var app = loopback();
+ * app.use(perRequestContext(options);
+ * app.use(loopback.rest());
+ * app.listen();
+ * ```
+ * @options {Object} [options] Options for context
+ * @property {String} name Context scope name.
+ * @property {Boolean} enableHttpContext Whether HTTP context is enabled. Default is false.
+ */
+
+function context(options) {
+  options = options || {};
+  var scope = options.name || name;
+  var enableHttpContext = options.enableHttpContext || false;
+  var ns = LoopBackContext.createContext(scope);
+
+  // Return the middleware
+  return function contextHandler(req, res, next) {
+    if (req.loopbackContext) {
+      return next();
+    }
+
+    LoopBackContext.runInContext(function processRequestInContext(ns, domain) {
+      req.loopbackContext = ns;
+
+      // Bind req/res event emitters to the given namespace
+      ns.bindEmitter(req);
+      ns.bindEmitter(res);
+
+      // Add req/res event emitters to the current domain
+      domain.add(req);
+      domain.add(res);
+
+      // Run the code in the context of the namespace
+      if (enableHttpContext) {
+        // Set up the transport context
+        ns.set('http', {req: req, res: res});
+      }
+      next();
+    });
+  };
+}

test/helpers/expect.js

@@ -0,0 +1,6 @@
+'use strict';
+
+var chai = require('chai');
+chai.use(require('dirty-chai'));
+
+module.exports = chai.expect;

test/main.test.js

@@ -0,0 +1,101 @@
+// Copyright IBM Corp. 2013,2016. All Rights Reserved.
+// Node module: loopback-context-cls
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+var ClsContext = require('..');
+var Domain = require('domain');
+var EventEmitter = require('events').EventEmitter;
+var expect = require('./helpers/expect');
+var loopback = require('loopback');
+var request = require('supertest');
+
+describe('LoopBack Context', function() {
+  var runInOtherDomain, runnerInterval;
+
+  before(function setupRunInOtherDomain() {
+    var emitterInOtherDomain = new EventEmitter();
+    Domain.create().add(emitterInOtherDomain);
+
+    runInOtherDomain = function(fn) {
+      emitterInOtherDomain.once('run', fn);
+    };
+
+    runnerInterval = setInterval(function() {
+      emitterInOtherDomain.emit('run');
+    }, 10);
+  });
+
+  after(function tearDownRunInOtherDomain() {
+    clearInterval(runnerInterval);
+  });
+
+  // See the following two items for more details:
+  // https://github.com/strongloop/loopback/issues/809
+  // https://github.com/strongloop/loopback/pull/337#issuecomment-61680577
+  it('preserves callback domain', function(done) {
+    var app = loopback({localRegistry: true, loadBuiltinModels: true});
+    app.set('remoting', {context: false});
+    app.set('legacyExplorer', false);
+    app.use(require('../server/middleware/per-request-context')());
+    app.use(loopback.rest());
+    app.dataSource('db', {connector: 'memory'});
+
+    var TestModel = loopback.createModel({name: 'TestModel'});
+    app.model(TestModel, {dataSource: 'db', public: true});
+
+    // function for remote method
+    TestModel.test = function(inst, cb) {
+      var tmpCtx = ClsContext.getCurrentContext();
+      if (tmpCtx) tmpCtx.set('data', 'a value stored in context');
+      if (process.domain) cb = process.domain.bind(cb);  // IMPORTANT
+      runInOtherDomain(cb);
+    };
+
+    // remote method
+    TestModel.remoteMethod('test', {
+      accepts: {arg: 'inst', type: 'TestModel'},
+      returns: {root: true},
+      http: {path: '/test', verb: 'get'},
+    });
+
+    // after remote hook
+    TestModel.afterRemote('**', function(ctxx, inst, next) {
+      var tmpCtx = ClsContext.getCurrentContext();
+      if (tmpCtx) {
+        ctxx.result.data = tmpCtx.get('data');
+      } else {
+        ctxx.result.data = 'context not available';
+      }
+
+      next();
+    });
+
+    request(app)
+      .get('/TestModels/test')
+      .end(function(err, res) {
+        if (err) return done(err);
+
+        expect(res.body.data).to.equal('a value stored in context');
+
+        done();
+      });
+  });
+
+  it('works outside REST middleware', function(done) {
+    ClsContext.runInContext(function() {
+      var ctx = ClsContext.getCurrentContext();
+      expect(ctx).is.an('object');
+      ctx.set('test-key', 'test-value');
+      process.nextTick(function() {
+        var ctx = ClsContext.getCurrentContext();
+        expect(ctx).is.an('object');
+        expect(ctx.get('test-key')).to.equal('test-value');
+
+        done();
+      });
+    });
+  });
+});