Write Custom Log Entries

On this page

About this Task

Steps
Results

You can write custom log entries from your MongoDB Shell scripts. Custom log entries help with debugging, error handling, and alert you when the script performs specific functions.

About this Task

MongoDB Shell supports the following methods for custom log entries:

log.debug()
log.error()
log.fatal()
log.info()
log.warn()

Steps

Create a script that writes a custom log entry

The following script inserts documents into the movies collection and writes a custom info log entry. If the script errors, it writes a custom error log entry instead.

// connect-and-insert-with-log-entry.js
try {
   db = connect( 'mongodb://localhost/myDatabase' );
   db.movies.insertMany( [
      {
         title: 'Titanic',
         year: 1997,
         genres: [ 'Drama', 'Romance' ]
      },
      {
         title: 'Spirited Away',
         year: 2001,
         genres: [ 'Animation', 'Adventure', 'Family' ]
      },
      {
         title: 'Casablanca',
         genres: [ 'Drama', 'Romance', 'War' ]
      }
   ] )
   log.info('InsertData: Inserted 3 movies');
} catch (error) {
   log.error('Insert failed', { error: error.message });
}

Save the script as connect-and-insert-with-log-entry.js.

Run the script

To run the connect-and-insert-with-log-entry.js script, use mongosh to connect to your deployment and run the following command within MongoDB Shell:

load("connect-and-insert-with-log-entry.js")

Alternatively, you can run the script programmatically by using the --file option when you start mongosh:

mongosh --file connect-and-insert-with-log-entry.js

Results

The custom log entry appears in the logs for your session:

{"t":{"$date":"2025-02-25T18:04:01.690Z"},"s":"I","c":"MONGOSH-SCRIPTS","id":1000000054,"ctx":"custom-log","msg":"InsertData: Inserted 3 movies"}

For more information about log sessions and how to retrieve log messages, see View Shell Logs.

To verify that the script inserted the documents, query the movies collection:

use myDatabase
db.movies.find()

Output:

[
   {
      _id: ObjectId('67bde8c2a527c6b1341979f2'),
      title: 'Titanic',
      year: 1997,
      genres: [ 'Drama', 'Romance' ]
   },
   {
      _id: ObjectId('67bde8c2a527c6b1341979f3'),
      title: 'Spirited Away',
      year: 2001,
      genres: [ 'Animation', 'Adventure', 'Family' ]
   },
   {
      _id: ObjectId('67bde8c2a527c6b1341979f4'),
      title: 'Casablanca',
      genres: [ 'Drama', 'Romance', 'War' ]
   }
]

Back

Specify Log Location

Retention