Overview of LocalStack logging and error reporting

LocalStack supports logging output and error reporting through the localstack CLI or a Docker/Docker Compose based setup. LocalStack’s logging setup allows you to:

  • Discover errors in your code during development & testing.
  • Get visibility into how and why your API calls are failing.
  • Figure out unexpected errors such as Lambda timeouts and more!

With LocalStack logging, you can easily retrieve additional detail around errors using various configuration variables to specify the verbosity and the log level.

Log Level

You can explicitly set a log level via two configuration variables: DEBUG and LS_LOG. You can configure them while starting the LocalStack container, either with the CLI or a Docker/Docker-Compose setup.

DEBUG can be either 0 or 1 (0 is the default). With DEBUG, you can print more verbose logs, useful for troubleshooting issues. With DEBUG=1, errors inside LocalStack are reported to the client in full, and these stack traces can help you better triage your issues.

LS_LOG supports the following values:

  • trace
  • trace-internal
  • debug
  • info
  • warn
  • error
  • warning

The LS_LOG affects the log handlers level directly. If LS_LOG is configured as trace or trace-internal, it will automatically set DEBUG=1. To retrieve the debug information, it is recommended to set DEBUG=1. While configuring LS_LOG as trace or trace-internal, the LocalStack container will report the same log format but append the request and response objects and the HTTP headers to the log line.

Error reporting

AWS requests are logged uniformly in the INFO log level (set by default or when DEBUG=0). The shape is AWS <service>.<operation> => <http-status> (<error type>). Requests to HTTP endpoints are logged in a similar way.

2022-07-12T10:12:03.250  INFO --- [   asgi_gw_0] localstack.request.aws     : AWS s3.PutObject => 404 (NoSuchBucket)
2022-07-12T10:12:11.295  INFO --- [   asgi_gw_0] localstack.request.aws     : AWS s3.CreateBucket => 200
2022-07-12T10:12:13.159  INFO --- [   asgi_gw_1] localstack.request.aws     : AWS s3.PutObject => 200
2022-07-12T10:12:28.761  INFO --- [   asgi_gw_0] localstack.request.http    : GET /_localstack/health => 200

Log inspection

You can inspect the logs of the LocalStack container using the localstack CLI or your Docker/Docker Compose setup. With the localstack CLI, you can run the following command to inspect the logs of the LocalStack container:

$ localstack logs

With Docker/Docker-Compose, you can run docker ps to get the container ID of the LocalStack container and then run docker logs <container-id> to inspect the logs.

To view the logs via a user interface, you can use the following options: