Dne 1.4.2016 v 16:00 Cleber Rosa napsal(a):
MOTIVATION
==========
The idea of adding hooks to be run by Avocado before and after tests is
general enough, and may be used by the community in unpredictable ways.
And that is good.
For this team, the initial motivation was to be able to bring back an
Autotest feature that some of our users are missing: the ability to set
the system-wide "kernel core pattern" configuration for tests.
Having a pre-test hook would allow "/proc/sys/kernel/core_pattern" to be
read, saved and modified to point to the test results directory. Having
a post-test hook would allow "/proc/sys/kernel/core_pattern" to be
reverted back to its original state.
Other currently core features such as sysinfo collection, could be
re-implemented as pre/post test hooks.
GENERAL DESIGN POINTS
=====================
These are the most important design decisions to be acknowledged or
questioned. Please reply with either ACK or your questions/suggestions.
1) Hooks are implemented as plugin classes, based on a given defined
interface, in the same way current "CLICmd" and "CLI" interfaces allow
plugin writers to extend Avocado and give it new commands and command
line options.
I'd prefer "pluginizing" the whole "runner" instead of custom pre and
post classes. What am I talking about:
The CLICmd and CLI allows one to add several methods + "run" method
which is executed to do the action. It makes sense for CLI, but IMO it
does not suit this case.
Instead we can create plugin interface which allows to do things on
certain occasions (hooks), one of them `start_test` and `stop_test`.
It's similar to `ResultsProxy`, `LoaderProxy`, ....
They both can achieve the same, the main reason is convenience:
The CLI-like:
+ clearly defines the interface
+ adds itself by publishing itself into the correct namespace
- for pre+post plugins requires double plugin initialization
- to reuse information from pre-hook in post-hook one needs to store the
state inside the results.
The *Proxy-like:
+ defines the interface
+ adds itself by publishing itself into the correct namespace
+ pre+post plugins are initialized just once (pure pre-plugins define
only `pre_test` hook, post-plugins only `post_test` hook...)
+ the state is preserved throughout the execution, so one can store the
details inside `self`.
+ is easily extensible of another hooks related to this
Details in
https://github.com/avocado-framework/avocado/pull/1106#discussion_r58193746
2) The hooks are executed by the *runner*, and not by the test process.
The goal is not interfere with the test itself. The pre and post code
that runs before and after the test should not *directly* change the
test behavior and outcome. Of course, the test environment can be
changed in a way (say having packages removed) that a test may fail
because of hook actions.
ACK
3) Test execution time should not be changed by pre and post hooks. If a
pre-test hook takes "n" seconds to run, "n" should not be added to the
test run time.
ACK
4) Job run time: right now, Avocado times a Job based on the sum of
individual test run times. With pre and post test hooks, this can be
very different from job "wall clock" times. My instinct is to change
that, so that a Job run time is the job "wall clock" time. I'm unsure if
we should add yet another time measure, that is, the sum of individual
test run time. This is also bound to be broken when parallel run of
tests is implemented.
I'm fine with either "real time" `time.time - start`, or with the
"user+sys time" `sum(test.time for test in job.tests)` (so sum of all
test times). I don't think we should do anything smart in here as it
might be misleading.
time stress -c 8 -t 10
stress: info: [23182] dispatching hogs: 8 cpu, 0 io, 0 vm, 0 hdd
stress: info: [23182] successful run completed in 10s
real 0m10.001s
user 1m19.005s
sys 0m0.003s
5) The pre test hook is given the test "early status". Information such
as the test tagged name, the fact that it has not yet started to run and
the test results directory are all part of the early status.
Does it means the test execution would wait for the pre-job hooks
completion? It's logical, but currently it requires bi-directional
communication with the runner (not after the Test/runner cleanup).
Anyway yes, the pre-job should get the early status with all benefits
and drawbacks. Users are responsible to understand them.
6) Because of point #5, the test is instantiated on the test process,
its early state is sent, but the test execution itself is held until the
runner finishes running the pre-test hooks.
OMG, I should first read and then think... For now, yes, but once we
move the test workflow from test to runner (as proposed in the
https://trello.com/c/W58vhyHR/539-bug-some-avocado-test-methods-and-atributes-are-public
).
PS: The pre and post test hooks are acctually also mentioned in that card...
7) The post test hook is given the last test status, which is also used
by the runner to identify test success, failure, etc.
Yep
Thanks,
- Cleber.
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