Debug Log

Goose can optionally and efficiently log arbitrary details, and specifics about requests and responses for debug purposes.

To enable, add the --debug-log <debug.log> command line option, where <debug.log> is either a relative or absolute path of the log file to create. Any existing file that may already exist will be overwritten.

If --debug-log <foo> is not specified at run time, nothing will be logged and there is no measurable overhead in your load test.

To write to the debug log, you must invoke log_debug from your load test task functions. The tag parameter allows you to record any arbitrary string: it can also identify where in the load test the log was generated, and/or why debug is being written, and/or other details such as the contents of a form the load test posts. Other paramters that can be included in the debug log are the complete Request that was made, as well as the Headers and Body of the Response.

(Known limitations in Reqwest prevent all headers from being recorded:

See examples/drupal_loadtest for an example of how you might invoke log_debug from a load test.

Request Failures

Calls to set_failure can be used to tell Goose that a request failed even though the server returned a successful status code, and will automatically invoke log_debug for you. See examples/drupal_loadtest and examples/umami for an example of how you might use set_failure to generate useful debug logs.

Log Format

By default, logs are written in JSON Lines format. For example:

{"body":"<!DOCTYPE html>\n<html>\n  <head>\n    <title>503 Backend fetch failed</title>\n  </head>\n  <body>\n    <h1>Error 503 Backend fetch failed</h1>\n    <p>Backend fetch failed</p>\n    <h3>Guru Meditation:</h3>\n    <p>XID: 1506620</p>\n    <hr>\n    <p>Varnish cache server</p>\n  </body>\n</html>\n","header":"{\"date\": \"Mon, 19 Jul 2021 09:21:58 GMT\", \"server\": \"Varnish\", \"content-type\": \"text/html; charset=utf-8\", \"retry-after\": \"5\", \"x-varnish\": \"1506619\", \"age\": \"0\", \"via\": \"1.1 varnish (Varnish/6.1)\", \"x-varnish-cache\": \"MISS\", \"x-varnish-cookie\": \"SESSd7e04cba6a8ba148c966860632ef3636=Z50aRHuIzSE5a54pOi-dK_wbxYMhsMwrG0s2WM2TS20\", \"content-length\": \"284\", \"connection\": \"keep-alive\"}","request":{"coordinated_omission_elapsed":0,"elapsed":9162,"error":"503 Service Unavailable: /node/1439","final_url":"http://apache/node/1439","name":"(Auth) comment form","raw":{"body":"","headers":[],"method":"Get","url":"http://apache/node/1439"},"redirected":false,"response_time":5,"status_code":503,"success":false,"update":false,"user":1,"user_cadence":0},"tag":"post_comment: no form_build_id found on node/1439"}

The --debug-format option can be used to log in csv, json (default), raw or pretty format. The raw format is Rust's debug output of the entire GooseDebug object.

Gaggle Mode

When operating in Gaggle-mode, the --debug-log option can only be enabled on the Worker processes, configuring Goose to spread out the overhead of writing logs.