Enable node.js stack locals capture (#902)

Author: waltjones

index.d.ts

@@ -67,6 +67,7 @@ declare namespace Rollbar {
         includeItemsInTelemetry?: boolean;
         inspectAnonymousErrors?: boolean;
         itemsPerMinute?: number;
+        locals?: boolean;
         logLevel?: Level;
         maxItems?: number;
         maxTelemetryEvents?: number;

src/server/locals.js

@@ -0,0 +1,171 @@
+/* globals Map */
+var inspector = require('inspector');
+var async = require('async');
+
+function Locals(config) {
+  if (!(this instanceof Locals)) {
+    return new Locals(config);
+  }
+
+  this.config = config;
+
+  this.initSession();
+}
+
+Locals.prototype.initSession = function() {
+  if (Locals.session) { return; }
+
+  Locals.session = new inspector.Session();
+  Locals.session.connect();
+  Locals.currentErrors = new Map();
+
+  Locals.session.on('Debugger.paused', ({ params }) => {
+    if (params.reason == 'promiseRejection' || params.reason == 'exception') {
+      var key = params.data.description;
+      Locals.currentErrors.set(key, params);
+
+      // Set the max size of the current errors array.
+      // The value should be large enough to preserve each of the errors in
+      // the current cause chain.
+      var CURRENT_ERRORS_MAX_SIZE = 4;
+
+      if (Locals.currentErrors.size > CURRENT_ERRORS_MAX_SIZE) {
+        var firstKey = Locals.currentErrors.keys()[0];
+        Locals.currentErrors.delete(firstKey);
+      }
+    }
+  });
+
+  Locals.session.post('Debugger.enable', (_err, _result) => {
+    Locals.session.post('Debugger.setPauseOnExceptions', { state: 'all'}, (_err, _result) => {
+    });
+  });
+}
+
+Locals.prototype.currentLocalsMap = function() {
+  return new Map(Locals.currentErrors);
+}
+
+Locals.prototype.mergeLocals = function(localsMap, stack, key, callback) {
+  var matchedFrames;
+
+  try {
+    var localParams = localsMap.get(key);
+
+    // If a mapping isn't found return success without mapped locals.
+    if (!localParams) {
+      return callback(null);
+    }
+
+    matchedFrames = matchFrames(localParams, stack.slice().reverse());
+  } catch (e) {
+    return callback(e);
+  }
+
+  getLocalScopesForFrames(matchedFrames, callback);
+}
+
+// Finds frames in localParams that match file and line locations in stack.
+function matchFrames(localParams, stack) {
+  var matchedFrames = [];
+  var localIndex = 0, stackIndex = 0;
+  var stackLength = stack.length;
+  var callFrames = localParams.callFrames;
+  var callFramesLength = callFrames.length;
+
+  for (; stackIndex < stackLength; stackIndex++) {
+    while (localIndex < callFramesLength) {
+      if (firstFrame(localIndex, stackIndex) || matchedFrame(callFrames[localIndex], stack[stackIndex])) {
+        matchedFrames.push({
+          stackLocation: stack[stackIndex],
+          callFrame: callFrames[localIndex]
+        });
+        localIndex++;
+        break;
+      } else {
+        localIndex++;
+      }
+    }
+  }
+
+  return matchedFrames;
+}
+
+function firstFrame(localIndex, stackIndex) {
+  return !localIndex && !stackIndex;
+}
+
+function matchedFrame(callFrame, stackLocation) {
+  if (!callFrame || !stackLocation) {
+    return false;
+  }
+
+  var position = stackLocation.runtimePosition;
+
+  // Node.js prefixes filename some URLs with 'file:///' in Debugger.callFrame,
+  // but with only '/' in the error.stack string. Remove the prefix to facilitate a match.
+  var callFrameUrl = callFrame.url.replace(/file:\/\//,'');
+
+  // lineNumber is zero indexed, so offset it.
+  var callFrameLine = callFrame.location.lineNumber + 1;
+  var callFrameColumn = callFrame.location.columnNumber;
+
+  return callFrameUrl === position.source &&
+    callFrameLine === position.line &&
+    callFrameColumn === position.column;
+}
+
+function getLocalScopesForFrames(matchedFrames, callback) {
+  async.each(matchedFrames, getLocalScopeForFrame, callback);
+}
+
+function getLocalScopeForFrame(matchedFrame, callback) {
+  var scopes = matchedFrame.callFrame.scopeChain;
+
+  var scope = scopes.find(scope => scope.type === 'local');
+
+  if (!scope) {
+    return callback(null); // Do nothing return success.
+  }
+
+  getProperties(scope.object.objectId, function(err, response){
+    if (err) {
+      return callback(err);
+    }
+
+    var locals = response.result;
+    matchedFrame.stackLocation.locals = {};
+    for (var local of locals) {
+      matchedFrame.stackLocation.locals[local.name] = getLocalValue(local);
+    }
+
+    callback(null);
+  });
+}
+
+function getLocalValue(local) {
+  var value;
+
+  switch (local.value.type) {
+    case 'undefined': value = 'undefined'; break;
+    case 'object': value = getObjectValue(local); break;
+    case 'array': value = getObjectValue(local); break;
+    default: value = local.value.value; break;
+  }
+
+  return value;
+}
+
+function getObjectValue(local) {
+  if (local.value.className) {
+    return '<' + local.value.className + ' object>'
+  } else {
+    return '<object>'
+  }
+}
+
+function getProperties(objectId, callback) {
+  Locals.session.post('Runtime.getProperties', { objectId : objectId, ownProperties: true }, callback);
+}
+
+module.exports = Locals;

src/server/parser.js

@@ -127,7 +127,7 @@ function mapPosition(position, diagnostic) {
 }
 
 function parseFrameLine(line, callback) {
-  var matched, curLine, data, frame;
+  var matched, curLine, data, frame, position;
 
   curLine = line;
   matched = curLine.match(jadeTracePattern);
@@ -141,20 +141,23 @@ function parseFrameLine(line, callback) {
   }
 
   data = matched.slice(1);
-  var position = {
+  var runtimePosition = {
     source: data[1],
     line: Math.floor(data[2]),
     column: Math.floor(data[3]) - 1
   };
   if (this.useSourceMaps) {
-    position = mapPosition(position, this.diagnostic);
+    position = mapPosition(runtimePosition, this.diagnostic);
+  } else {
+    position = runtimePosition;
   }
 
   frame = {
     method: data[0] || '<unknown>',
     filename: position.source,
     lineno: position.line,
-    colno: position.column
+    colno: position.column,
+    runtimePosition: runtimePosition // Used to match frames for locals
   };
 
   // For coffeescript, lineno and colno refer to the .coffee positions
@@ -306,7 +309,19 @@ exports.parseException = function (exc, options, item, callback) {
       ret.message = jadeData.message;
       ret.frames.push(jadeData.frame);
     }
-    return callback(null, ret);
+
+    if (item.localsMap) {
+      item.notifier.locals.mergeLocals(item.localsMap, stack, exc.stack, function (err) {
+        if (err) {
+          logger.error('could not parse locals, err: ' + err);
+          return callback(err);
+        }
+
+        return callback(null, ret);
+      });
+    } else {
+      return callback(null, ret);
+    }
   });
 };
 

src/server/rollbar.js

@@ -16,6 +16,7 @@ var transforms = require('./transforms');
 var sharedTransforms = require('../transforms');
 var sharedPredicates = require('../predicates');
 var truncation = require('../truncation');
+var Locals = require('./locals');
 var polyfillJSON = require('../../vendor/JSON-js/json3');
 
 function Rollbar(options, client) {
@@ -40,6 +41,13 @@ function Rollbar(options, client) {
   var api = new API(this.options, transport, urllib, truncation, jsonBackup);
   var telemeter = new Telemeter(this.options)
   this.client = client || new Client(this.options, api, logger, telemeter, 'server');
+  if (options.locals) {
+    // Capturing stack local variables is only supported in Node 10 and higher.
+    var nodeMajorVersion = process.versions.node.split('.')[0];
+    if (nodeMajorVersion >= 10) {
+      this.locals = new Locals(this.options)
+    }
+  }
   addTransformsToNotifier(this.client.notifier);
   addPredicatesToQueue(this.client.queue);
   this.setupUnhandledCapture();
@@ -521,7 +529,13 @@ function addPredicatesToQueue(queue) {
 
 Rollbar.prototype._createItem = function (args) {
   var requestKeys = ['headers', 'protocol', 'url', 'method', 'body', 'route'];
-  return _.createItem(args, logger, this, requestKeys, this.lambdaContext);
+  var item = _.createItem(args, logger, this, requestKeys, this.lambdaContext);
+
+  if (item.err && item.notifier.locals) {
+    item.localsMap = item.notifier.locals.currentLocalsMap();
+  }
+
+  return item;
 };
 
 function _getFirstFunction(args) {