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Tools Overview#

Tools are used to execute steps in a job. Each step indicates what tools should be used to its execution. It can be a shell to execute commands, other programs, or a git tool for cloning Git repository. A step can have several fields with values defined that are required by a tool or are optional.

A tool communicates with Kraken agent using specific protocol. Thanks to this it is possible to write your own custom tools.

There are several ways a tool can get in interaction with Kraken server via Kraken agent. Tools can be:

  • do nothing, just do its job and that's it
  • return list of all available test cases (eg. pytest tool); this allows pre-storing all test case results as not run initially and also splitting execution of test cases to several jobs
  • report continuously test results (eg. pytest tool)
  • report continuously issues (eg. pylint tool)
  • report stored artifacts (eg. artifacts tool)

More about particular tools can be found in Workflow Schema chapter, in Tools section.

Custom Tools#

Tools can be written in Python. It is possible to write them in other languages but for Python there is already a framework that makes some actions easier.

Protocol Overview#

There is defined a protocol between Kraken agent and a tool. It works differently depending on the direction. Generally an agent invokes one of predefined commands of a tool and then a tool responds to the agent via an HTTP connection using JSON as a response format.

The commands expected by Kraken agent:

  • get_commands - it should return list of commands exposed by a tool; this command must be provided by every tool
  • collect_tests - it returns list of available tests according to specification provided by step definition; optional
  • run - it should just execute a step; optional
  • run_tests - it executes tests according to specification provided by step definition and report results live, progresively, one by one if possible; optional
  • run_analysis - it should perform an analysis and report issues live, progresively, one by one if possible

One of run* commands must be provided by a tool.

Tool Framework#

Handling of commands and sending reponses are quite automated by a Python tool framework. The framework required defining one of run* functions and collect_tests function if wanted.

Example of Simple Tool#

import os
from . import utils
def run(step, **kwargs):
cmd = step['cmd']
cwd = step.get('cwd', None)
timeout = int(step.get('timeout', 60))
ret = utils.execute(cmd, cwd=cwd, timeout=timeout)
if ret != 0:
return ret, 'cmd exited with non-zero retcode: %s' % ret
return 0, ''

This is a simplified implementation of shell tool. It just executes a cmd command provided in a step. It uses also optional cwd and timeout parameters provided in a step.

Tool framework provides several helper modules. One of them is utils that offers an execute function. To use it impot the module:

from . import utils

A run functions must return an exit code (0 means all is ok) and a message that in case of an error describes the error (otherwise it returns '' empty string).

Example of Testing Tool#

import random
def collect_tests(step):
# return list of available tests
tests = ['', 'test.bbb', 'test.ccc']
return tests
def run_tests(step, report_result=None):
# Now the step contains list of tests reported
# by collect_tests function. If there is no collect_tests
# function then the run_tests function should determine
# on its own scope of tests based of step definition.
tests = step['tests']
for test in tests:
cmd = 'command to execute a test'
# status should indicate test result: 0 - not run, 1 - passed, 2 - failed,
# 3 - error, 4 - disabled/skip, 5 - unsupported
result = dict(cmd=cmd, test=test, status=random.choice([0, 1, 2, 3, 4, 5]))
# report_result is a callback provided by Kraken tool framework that sends back
# the test result to the server
return 0, ''

The tool has hardcoded list of tests to execute regardless of step definition. Generally collect_tests function should return list of tests based of step definition. Then the run_tests function receives list of tests in step definition and then it "executes" them one by one, and then reports them using report_result callback from Kraken tool framework.