sails.jssails-mongo

How can I wrap sails-mongo db methods for profiling?


I'm trying to setup a sails hook with miniprofiler to help profile mongo usage. I'm struggling for how to wrap the db methods in a function that will execute the profile. I'm trying to do this via a user hook:

setupMiniprofilerMongo(req, res, next) {
  const adapter = sails.hooks.orm.datastores.default.adapter;
  const adapterPrototype = Object.getPrototypeOf(adapter);
  const originalMethod = adapter.adapter.find;
  methodPrototype.find = function profiledMongoCommand(connectionName, collectionName, options, cb) {
    sails.log.info(`${collectionName}.find`);
    return originalMethod.call(adapter, connectionName, collectionName, options, cb);
  };
}

That causes the following error to be thrown:

TypeError: Cannot read property 'collections' of undefined
    at Object.module.exports.adapter.find (/Users/jgeurts/dev/platform/node_modules/sails-mongo/lib/adapter.js:349:40)
    at Object.profiledMongoCommand [as find] (/Users/jgeurts/dev/platform/config/http.js:234:37)

Any help would be appreciated. I tried to wrap the methods on mongodb package, but that doesn't seem to work either. :/


Solution

  • I got this working by wrapping waterline query methods. There is room for improvement, though.

    setupMiniprofilerWaterline(req, res, next) {
      const dbOperations = [
        'count',
        'create',
        'createEach',
        'define',
        'describe',
        'destroy',
        'drop',
        'find',
        'join',
        //        'native',
        //        'registerConnection',
        'update',
      ];
    
      const waterlineMethodByModels = {};
      const miniprofilerWaterline = () => {
        return {
          name: 'mongodb',
          handler(req, res, next) {
    
            if (!req.miniprofiler || !req.miniprofiler.enabled) {
              return next();
            }
    
            const profiler = req.miniprofiler;
    
            for (const modelName of _.keys(sails.models)) {
              for (const dbOperation of dbOperations) {
                const model = sails.models[modelName];
                if (!model[dbOperation]) {
                  continue;
                }
    
                if (!waterlineMethodByModels[modelName]) {
                  waterlineMethodByModels[modelName] = {};
                }
    
                // Prevent wrapping a method more than once
                if (waterlineMethodByModels[modelName][dbOperation]) {
                  continue;
                }
    
                waterlineMethodByModels[modelName][dbOperation] = true;
    
                const originalMethod = model[dbOperation];
    
                model[dbOperation] = function profiledMongoCommand(...args) {
                  const query = args && args.length ? args[0] : '';
                  const lastArg = args && args.length ? args[args.length - 1] : null;
                  const modelAndMethod = `${modelName}.${dbOperation}`;
    
                  if (lastArg && typeof lastArg === 'function') {
                    sails.log.debug(`mongo::${modelAndMethod}  - ${JSON.stringify(query)}`);
                    const callback = args.pop();
    
                    const timing = profiler.startTimeQuery('mongodb', query ? JSON.stringify(query || '') : '');
                    // In general, the callstack is kind of useless to us for these profiles
                    // The model/db method is more useful in the miniprofiler UI
                    timing.callStack = `\n\nMethod: ${modelAndMethod}`;
    
                    return originalMethod.call(this, ...args, function profiledResult(...results) {
                      profiler.stopTimeQuery(timing);
                      callback(...results);
                    });
                  }
    
                  const methodResult = originalMethod.call(this, ...args);
                  const methodResultPrototype = Object.getPrototypeOf(methodResult);
                  const isDeferred = !!methodResultPrototype.exec;
                  // If methodResult is a Deferred object type, then the query method will be profiled above when the deferred is executed (with a callback)
                  // So we only care to log this if the methodResult is not a deferred object
                  if (!isDeferred) {
                    sails.log.warn(`Was not able to profile mongo::${modelAndMethod}. Maybe its a promise? query: ${JSON.stringify(query)}`);
                  }
    
                  return methodResult;
                };
              }
            }
    
            next();
          },
        };
      };
    
      miniprofiler.express.for(miniprofilerWaterline())(req, res, next);
    },
    

    The code is available as miniprofiler-waterline if you want to contribute/use it in your own projects