VTEX IO provides a logging service that allows developers to keep track of errors, warnings, and informative events within an application. The VTEX IO Logging Service collects data from the cloud infrastructure where VTEX applications run and delivers them via the VTEX IO CLI.

In the following section, you'll learn how to implement the VTEX IO Logging Service in your apps and how to retrieve their logs.

The VTEX IO Logging Service is currently available for Node apps only.

To complete this guide, you must have the VTEX IO CLI installed in your machine. For more information, please refer to this document.

1. Open your Node app in any code editor of your preference.
2. Define an object with the Context interface as a parameter of a function you wish to provide logging messages. Take the following example:

const helloWorld = (Context: ctx) => {
  const { vtex: { logger } } = ctx

  logger.info('Hello World!')
}

In this example, the helloWorld function receives an object with a Context interface as a parameter.

The Context interface contains many implementations inherent to the VTEX IO platform. One of those implementations is called vtex - an object containing all VTEX IO infrastructure related metadata, such as account, workspace, tenant, settings, and some service implementations. In the previous example, we used the logger service, which is an implementation inside vtex responsible for generating log messages.

3. Destructure the logger object from the vtex context and use its methods (i.e., error, warn, info, and debug) to provide error, warning, debugging, or informative messages in the log. Take the following example:

const helloWorld = (Context: ctx) => {
  const { vtex: { logger } } = ctx

  logger.warn('Warning the world!')

  logger.error('Error!!!')

  logger.debug('Verbose debug message!')
}

Every exception that happens inside a VTEX IO service application is intercepted and automatically logged with a logger.error implementation.

Every log written by a running application with the VTEX IO logging service is collected and stored for 7 days. These logs can be retrieved by the VTEX IO CLI as in the following:

1. Log in to your VTEX account.
2. Install the Logs plugin for the VTEX IO CLI by running the following command:

vtex plugins add logs

3. Check if the installation of the Logs plugin was successful by running vtex logs --help.
4. Retrieve logs from all apps installed in your account by running the following command:

vtex logs --all

As an output, you should see a message similar to the following:

vtex logs --all
18:15:26.779 - info: Connecting to logs stream for store components
18:15:26.782 - info: Press CTRL+C to abort

18:15:43.856 - info: Listening to store components logs

  info: { status: 403,
  code: 'FORBIDDEN',
  name: 'ForbiddenError',
  level: 'error',
  message: 'This username is already registered with another email',
  stack:
   'ForbiddenError: This username is already registered with another email[ErrorStack...]
  routeId: 'login' }

You can also retrieve logs from a specific app installed in your account by running the following command: vtex logs {account}.{serviceAppExample}. Remeber to replace account with your account name and serviceAppExample with the desired app name.

We suggest running vtex logs --all > {mylogfile.logs} to save the log messages in a local file. Replace {mylogfile.logs} with the most suitable name for you.

Also, if you want to see log messages that you have previously retrieved, run vtex logs --past.