Add performance test to monitor capture time

Adds a test which captures a breakpoint with large watch expressions and
ensures that it takes less than 20ms e2e after node 1.6 and less than
110ms e2e before node 1.6. Actual capture time is shorter as it does not
include code running before breakpoint is hit or simulated network
operation afterwards. Capturing state is too slow on travis so this test
does not run with unit tests.

Addresses #71

test/e2e/test-capture-time.js

@@ -0,0 +1,98 @@
+/**
+ * Copyright 2015 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+'use strict';
+
+var assert = require('assert');
+var request = require('request');
+var logger = require('@google/cloud-diagnostics-common').logger;
+var config = require('../../config.js');
+var semver = require('semver');
+var Debuglet = require('../../lib/debuglet.js');
+
+var DEBUGGEE_ID = 'bar';
+var API = 'https://clouddebugger.googleapis.com';
+var REGISTER_PATH = '/v2/controller/debuggees/register';
+var BPS_PATH = '/v2/controller/debuggees/' + DEBUGGEE_ID + '/breakpoints';
+
+var nock = require('nock');
+nock.disableNetConnect();
+
+var debuglet;
+
+describe(__filename, function(){
+  beforeEach(function() {
+    process.env.GCLOUD_PROJECT_NUM = 0;
+    debuglet = new Debuglet(
+      config, logger.create(config.logLevel, '@google/cloud-debug'));
+    debuglet.once('started', function() {
+      debuglet.debugletApi_.request_ = request; // Avoid authing.
+    });
+  });
+
+  afterEach(function() {
+    debuglet.stop();
+  });
+
+  it('should capture breakpoint quickly', function(done) {
+    var h = require('../fixtures/expensive-capture.js');
+    var hitMillis;
+    var reportedMillis;
+    var expensiveBp = {
+      id: 'test',
+      location: { path: 'fixtures/expensive-capture.js', line: 7},
+      condition: 'n===7',
+      expressions: ['a', 'process']
+    };
+
+    var scope = nock(API)
+      .post(REGISTER_PATH)
+      .reply(200, {
+        debuggee: {
+          id: DEBUGGEE_ID
+        }
+      })
+      .get(BPS_PATH)
+      .reply(200, {
+        breakpoints: [expensiveBp]
+      })
+      .put(BPS_PATH + '/test', function(body) {
+        reportedMillis = Date.now();
+        return body.breakpoint.isFinalState && !body.breakpoint.status;
+      })
+      .reply(200);
+
+    debuglet.once('registered', function(id) {
+      assert(id === DEBUGGEE_ID);
+      setTimeout(function() {
+        hitMillis = Date.now();
+        h.rec(7);
+        setTimeout(function() {
+          // See slowdown in state.js#resolveMirror_
+          if (semver.satisfies(process.version, '<1.6')) {
+            assert(reportedMillis - hitMillis < 110);
+          } else {
+            assert(reportedMillis - hitMillis < 20);
+          }
+          scope.done();
+          done();
+        }, 10);
+      }, 500);
+    });
+
+    debuglet.start();
+  });
+});
+

test/fixtures/expensive-capture.js

@@ -0,0 +1,9 @@
+'use strict';
+var a = new Array(50).map(function() { return ','; });
+module.exports.rec = function rec(n) {
+  if (n === 0) {
+    return 5;
+  } else {
+    return rec(n - 1);
+  }
+};