Chaostoolkit-lib

Added

- Raise the `chaoslib.exceptions.InterruptExecution` on `SIGTERM`
- New exception `chaoslib.exceptions.ExperimentExitedException` that can only
be injected into blocking background activities when we received the SIGUSR2
signal
- We now inject `chaoslib.exceptions.ExperimentExitedException` into blocking
background activities when we received the SIGUSR2 signal. This is relying
on https://docs.python.org/3/c-api/init.html#c.PyThreadState_SetAsyncExc
There is much we can to interrupt blocking calls and the limit is now reached
because we have no control over any call that is out of the Python VM (just
calling `time.sleep()` will get you in that situation). This is a constraint
we have to live in and this extension authors must keep this in mind when
they create their blocking calls. [185][185]

Added

- SIGTERM signal is now listened for. This triggers the interruption mechanism
of the experiment.

Added

- Add two functions to programmatically exit the experiment as soon as feasible
by the Python VM [185][185]:
* `chaoslib.exit.exit_gracefully`: terminates but abides to the rollback strategy
* `chaoslib.exit.exit_ungracefully`: terminates but bypasses rollbacks entirely
and does not wait for background actions/probes still running
This should mostly be useful to have a harsh way to interrupt an execution
and is therefore an advanced concept with undesirable side effects (though
Chaos Toolkit tries to do as right as it can).

CAVEAT: Only works on Unix/Linux systems implementing SIGUSR1/SIGUSR2 signals

[185]: https://github.com/chaostoolkit/chaostoolkit-lib/issues/185


Changed

- Fix [chaostoolkit192][chaostoolkit192] to make sure a failing hypothesis
prevents the method to be executed.

[chaostoolkit192]: https://github.com/chaostoolkit/chaostoolkit/issues/192

Changed

- Ensure the method is always executed, even when no steady-state was provided
in the experiment.

Added

- Steady-state hypothesos runtime strategies can be now set to determine if the
the hypothesis is executed before/after the method as usual (default behavior)
or continuously throughout the method too. You can also make it applied
before or after only, or even only during the method. [191][191]

[191]: https://github.com/chaostoolkit/chaostoolkit/pull/191

Changed

- Always pass all secrets to control hookpoints [187][187]
- Massive refactor of the `run_experiment` function so that it raises now events
of where it is during the execution so that external plugins to the Chaos
Toolkit can react and impact the run. This goes beyond mere controls and
is advanced usage. Still, this is a public interface. [178][178]
In theory, this is an internal change only and the `run_experiment` function
has not changed its API. However, this may have deep impact if you already
depended on its internals.

[187]: https://github.com/chaostoolkit/chaostoolkit/issues/187
[178]: https://github.com/chaostoolkit/chaostoolkit-lib/issues/178

Added

- Added ways to override configuration and secrets from var files or passed to
the chaostoolkit cli [chaostoolkit175][].

Changed

- Always ensure the [status][statuses] in the journal is one of
the specified value, with a default to `"completed"`.

[statuses]: https://docs.chaostoolkit.org/reference/api/journal/#required-properties

[chaostoolkit175]: https://github.com/chaostoolkit/chaostoolkit/issues/175