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Inspect logs

Logs are messages you can add to your test script to help you debug tests.

Log methods

You can use the following logging methods:

• console.log()
• console.info()
• console.warn()
• console.error()
• console.debug()
  • Only shown when running k6 with the -v/--verbose flag.

To view all the logs for a test run, click the Logs tab. Depending on the method you’re using, a green, yellow, or red marking is displayed next to each log.

You can select a log message to expand it and see more details such as:

• instance_id
• level
• lz (load zone)
• source
• test_run_id

You can also filter the list by using:

• Filter: Filter by text in the log message.
• Level: Choose from the different level options.
  • Info: console.log and console.info.
  • Debug: console.debug.
  • Warning: console.warning.
  • Error: console.error.
• Load zone: Choose from the different load zones used in the test run.

Limitations

Grafana Cloud k6 has a limit of 10 messages per second for log lines. If you exceed this limit, k6 shows a warning with the number of discarded log lines.

While logs can help you debug a script or test results, they shouldn’t replace k6 API functions. It’s often an anti-pattern to use logs in the following ways:

• Track a condition status. Instead, use Checks to assert conditions.
• Track a variable value during the test execution. Instead, use the Trend metric.

You should also not rely on logging to interpret or analyze the performance of your system.