medusa-store/www/apps/book/app/learn/debugging-and-testing/logging/page.mdx

export const metadata = {
  title: `${pageNumber} Logging`,
}

# {metadata.title}

In this chapter, you’ll learn how to use Medusa’s logging utility.

## Logger Class

Medusa provides a `Logger` class with advanced logging functionalities. This includes configuring logging levels or saving logs to a file.

By default, the `Logger` class logs messages to the console. You can also override the default logger with your custom implementation, as explained in the [Override Logger](./custom-logger/page.mdx) guide.

The Medusa application registers the `Logger` class in the Medusa container and each module's container as `logger`. 

---

## How to Log a Message

Resolve the `logger` using the Medusa container to log a message in your resource.

For example, create the file `src/jobs/log-message.ts` with the following content:

export const highlights = [
  ["7", "resolve", "Resolve the `Logger` class."],
  ["9", "info", "Log a message of level `info`."]
]

```ts title="src/jobs/log-message.ts" highlights={highlights}
import { MedusaContainer } from "@medusajs/framework/types"
import { ContainerRegistrationKeys } from "@medusajs/framework/utils"

export default async function myCustomJob(
  container: MedusaContainer
) {
  const logger = container.resolve(ContainerRegistrationKeys.LOGGER)

  logger.info("I'm using the logger!")
}

export const config = {
  name: "test-logger",
  // execute every minute
  schedule: "* * * * *",
}
```

This creates a scheduled job that resolves the `logger` from the Medusa container and uses it to log a message.

### Test the Scheduled Job

To test out the above scheduled job, start the Medusa application:

```bash npm2yarn
npm run dev
```

After a minute, you'll see the following message as part of the logged messages:

```text
info:    I'm using the logger!
```

---

## Log Levels

The `Logger` class has the following methods:

- `info`: The message is logged with level `info`.
- `warn`: The message is logged with level `warn`.
- `error`: The message is logged with level `error`.
- `debug`: The message is logged with level `debug`.

Each of these methods accepts a string parameter to log in the terminal with the associated level.

---

## Logging Configurations

### Log Level

The available log levels, from lowest to highest levels, are:

1. `silly`
2. `debug`
3. `verbose`
4. `http` (default, meaning only HTTP requests are logged)
5. `info`
6. `warn`
7. `error`

You can change that by setting the `LOG_LEVEL` environment variable to the minimum level you want to be logged.

For example:

```bash
LOG_LEVEL=error
```

This logs `error` messages only.

<Note title="Important">

The environment variable must be set as a system environment variable and not in `.env`.

</Note>

### Save Logs in a File

Aside from showing the logs in the terminal, you can save the logs in a file by setting the `LOG_FILE` environment variable to the path of the file relative to the Medusa server’s root directory.

For example:

```bash
LOG_FILE=all.log
```

Your logs are now saved in the `all.log` file at the root of your Medusa application.

<Note title="Important">

The environment variable must be set as a system environment variable and not in `.env`.

</Note>

---

## Show Log with Progress

The `Logger` class has an `activity` method used to log a message of level `info`. If the Medusa application is running in a development environment, a spinner starts to show the activity's progress.

For example:

```ts title="src/jobs/log-message.ts"
import { MedusaContainer } from "@medusajs/framework/types"
import { ContainerRegistrationKeys } from "@medusajs/framework/utils"

export default async function myCustomJob(
  container: MedusaContainer
) {
  const logger = container.resolve(ContainerRegistrationKeys.LOGGER)

  const activityId = logger.activity("First log message")

  logger.progress(activityId, `Second log message`)

  logger.success(activityId, "Last log message")
}
```

The `activity` method returns the ID of the started activity. This ID can then be passed to one of the following methods of the `Logger` class:

- `progress`: Log a message of level `info` that indicates progress within that same activity.
- `success`: Log a message of level `info` that indicates that the activity has succeeded. This also ends the associated activity.
- `failure`: Log a message of level `error` that indicates that the activity has failed. This also ends the associated activity.

<Note>

If you configured the `LOG_LEVEL` environment variable to a level higher than those associated with the above methods, their messages won’t be logged.

</Note>