fix(venom): user executors performance issues

[alexGNX]

This is a fix about performance issues we encountered running testsuites with many User Defined Executors (UDE). Issue 826 was opened regarding this problem.

UDEs

Previous behavior

• Each time a test step uses an UDE, every UDE YAML definition files are parsed and interpolated 2 times, due to multiple calls to:

func (v *Venom) registerUserExecutors

• All UDEs are loaded at the moment an UDE is executed. This causes confusing behaviors: e. g. if you have 2 UDEs in the lib folder (let's call them createUser and createProduct), but createUser.yaml is not valid YAML. When running a test suite that only uses the createProduct UDE, you get the following error message:

$ venom run mytestsuite.yml
executor "createProduct" is not implemented

even though createProduct is valid. This occurs because the parsing of createUserfailed (even if it is not used in the test suite).

• No UDE duplication check, i. e. you have 2 UDEs with the same name in 2 separate files you get no error.
• if you set the libDirconfiguration option to the same value as the default one (lib/), each file of the directory will be loaded 2 times at each call of registerUserExecutors()
• There are nearly no logs regarding UDEs when they fail, which make debugging them extremely tedious. They are not included in the tests reports either.

New behaviour

• All UDEs are loaded during the parsing step (pre-run). During this step we check that the keys executor and steps are present, we load the raw file in memory and we perform a duplication check:

$ venom run mytestsuite.yml

unable to register user executors: unable to register user executor "createUser" from file "lib/createUser.yml": executor "createUser" already exists (from file "lib/createUser copy.yml")

• the interpolation and parsing of the UDE is performed only when the UDE is called
• when an UDE fails, we output the interpolated file to make debugging easy, e. g.:

 venom run headers.yml 
 • test maps behavior (headers.yml)
        • headers-UDE FAIL
                • headers
                  Testcase "headers", step #0-0: 1 error(s) decoding:

* 'Headers' expected a map, got 'string' (headers.yml:10)
                  Testcase "headers UDE", step #0-0: executor "headers" failed - raw interpolated:
executor: headers
input:
  headers: {}
steps:
- type: http
  method: GET
  url: https://httpbin.org/headers
  headers: "{{ .input.header }}"
  assertions:
    - result.statuscode ShouldEqual 200
    - result.bodyjson.headers.Host ShouldEqual "httpbin.org"
    - result.bodyjson.headers.Foo ShouldEqual "bar"
  vars:
    hdrs:
      from: result.bodyjson.headers
output:
  systemout: "{{.hdrs}}" (headers.yml:22)
Writing file out/test_results_headers.xml
final status: FAIL

Improvement measurement

I tested this fix on a collection of test suites totalling around 700 test cases and 120 UDEs, with some of them layered (UDE calling another UDE). Runtime has been divided by a factor of 3 (from around 35min down to around 12min)

Additional performance enhancement

• Optimize the way the exec executor reads stdout and stderr. For exemple when loading a file into a variable with exec:

- name: getFile
  steps:
  - type: exec
    script: cat dat/bigfile.json
    vars:
      content:
        from: result.systemout

With 100k lines in the file, this test step used to take more than a minute. This lowers it down to only a couple ms.

• use maps.Clone() to clone a map