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Common Lib:

A set of decorators and services that are commonly used in our applications.


npm install @alphaapps/nestjs-common


  • GetUser: Used in controllers to get the current authenticated user.
export default class UserController {
  getMe(@GetUser() user: User): User {
    return { user };
  • InjectSentry: Injects Sentry service so it can be called.


  • CrudWrapperInterceptor: User to wrap the response of crud APIs with data key.
  • UserLanguageSetterInterceptor: Updates the language, devicePlatform & appVersion of the user using values passed in headers in the request.
  • LocalizationSetter: Used to update response with the correct language.
  • WinstonLoggingInterceptor: Logs every request to winston


  • rewriteUrls: A middleware for rewriting URLs. This is useful when want to add a param to the request URL without forcing the API consumer to do it.
export default class AppModule implements NestModule {
  configure(consumer: MiddlewareConsumer): void {
        method: 'GET',
        from: '/notifications',
        to: '/notifications?limit=100&sort=createdAt,DESC'
        path: '*',
        method: RequestMethod.ALL


  • ExceptionsFilter: An exception filter that catches all exceptions and check if these are business errors (i.e. User not verified, unique violations) and print them in a pretty way, when an exception is unknown (not one of our known errors) it reports it to Sentry.
This filter also logs the error to winston.

A note about errors:

Every error in the app must be an instance of AlphaError class.
Application errors must be like this:
import { errors } from '@alphaapps/nestjs-common';
import _ from 'lodash';

const localErrors = {
  users: {
    invalidEmail: {
      code: 311,
      message: 'invalid_email_string',
      statusCode: 400
  files: {
    conflictingFiles: {
      code: 400,
      message: 'conflicting_files',
      statusCode: 400

export default _.merge(errors, localErrors);
Then every error should be fired like this: throw new AlphaError('users.invalidEmail')
These errors must be provided in the AppModule so the ExceptionsFilter can identify them.
  providers: [{
    provide: APP_INTERCEPTOR,
    useClass: WinstonLoggingInterceptor
  }, {
    provide: APP_FILTER,
    useClass: ExceptionsFilter
  }, {
    provide: ERRORS_TOKEN,
    useValue: Errors
export default class AppModule {}


  • SentryService: A service to encapsulate Sentry SDK with two methods captureException & captureEvent
This service can be injected with @InjectSentry decorator.
  • SequelizeCrudService: A CRUD service for Sequelize ORM. More info can be viewed at crud github repo
There's some few differences between the original crud service and ours: - getMany method calls 2 sub methods createBuilder & executeQuery to enable some customization in the extending service. - Joins are all allowed by default. - When calling count in getMany function the many associations to get correct results. - getMany uses modelFindAll & modelCount methods to enable more customisation.
  • FirebaseService: Encapsulation for firebase push notification service.
  • MandrillService: Encapsulation for Mandrill email service.
  • SesService: Encapsulation for SES email service.
  • TwilioService: Encapsulation for Twilio SMS service.

Log Reader Service:

This service is used to query logs stored on disk and it's super useful in development environments.
By default when using WinstonLoggingInterceptor and ExceptionsFilter all our requests and failed responses are saved via winston logging lib. So in AppModule we define the following transports
const env = process.env.NODE_ENV || 'development';
const winstonTransports: Transport[] = [
  new winston.transports.Console({
    level: 'debug',
    log: (info, callback) => {
      const {
        level = 'info', http = {}, message, duration
      } = info;
      const { method = 'GET', status_code: statusCode = 200 } = http;
      // eslint-disable-next-line no-console
      console.log(`${level}:  ${method}  ${message} [${statusCode}] ${duration ? `${duration / 1000000}ms` : ''}`);
      return callback();
// only add DatadogTransport if it is configured
if (config.has('datadog.apiKey')) {
  winstonTransports.push(new DatadogTransport({
    level: 'debug',
    apiKey: config.get('datadog.apiKey'),
    host: config.get('datadog.host'),
    port: config.get('datadog.port'),
    metadata: {
      host: `/esc/${env}-api`,
      service: 'api',
      ddsource: 'winston-datadog-transport'
else {
  // if no datadog config is found then add a file transport
  winstonTransports.push(new winston.transports.DailyRotateFile({
    filename: 'logs/%DATE%-all.log',
    datePattern: 'YYYY-MM-DD',
    zippedArchive: true,
    maxSize: '20m',
    maxFiles: '14d'
  imports: [
      format: winston.format.json(),
      transports: winstonTransports
export default class AppModule {}
Basically what we're doing here is using winston to write our log entries, on production env where we usually use DataDog logs are sent there. However, on other envs we save logs to files on disk.
In order to query these logs (the ones stored in files on disk) we use a small cli called log-cli which is included in the @alphaapps/nestjs-common package
sami@Samis-MacBook-Pro project % npx log-cli
Usage: log-cli read:logs

  log-cli read:logs  Query logs from winston

  --help     Show help                                                 [boolean]
  --version  Show version number                                       [boolean]
  --dir      Folder where the logs are              [string] [default: "./logs"]
  --url      URL to match                                               [string]
  --method   Filter by HTTP method
                              [choices: "get", "post", "put", "patch", "delete"]
  --limit    Number of records returned                   [number] [default: 10]
  --sort     Sort the list            [choices: "desc", "asc"] [default: "desc"]
  --last     Show result from last period              [string] [default: "15d"]
  --from     From date (ISO Date)                                       [string]
  --to       To date (ISO Date)                                         [string]
  --userId   Filter by user id                                          [number]
  --level    Fetch only a specific level
                                    [string] [choices: "debug", "info", "error"]
  --status   Filter by response status code                             [number]

  read:logs  npx log-cli read:logs --dir='./logs' --limit=20 --last=2d

copyright Alpha-Apps@2020

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