This implements the first edition of Connection Delegation, where
delegating connection establishment is initially single-threaded.
ansible_mitogen/strategy.py:
ansible_mitogen/plugins/connection/*:
Begin splitting connection.Connection into subclasses, exposing them
directly as "mitogen_ssh", "mitogen_local", etc. connection types.
This is far from removing strategy.py, but it's a tiny start.
ansible_mitogen/connection.py:
* config_from_play_context() and config_from_host_vars() build up a
huge dictionary containing either more or less PlayContext contents,
or our best attempt at reconstructing a host's connection config
from its hostvars, where that config is not the current
WorkerProcess target.
They both produce the same format with the same keys, allowing
remaining code to have a single input format.
These dicts contain fields named after how Ansible refers to them,
e.g. "sudo_exe".
* _config_from_via() parses a basic connection specification like
"username@inventory_name" into one of the aforementioned dicts.
* _stack_from_config() produces a list of dicts describing the order
in which (Mitogen) connections should be established, such that each
element is proxied via= the previous element. The dicts produced by
this function use Mitogen keyword arguments, the former di.
These dicts contain fields named after how Mitogen refers to them,
e.g. "sudo_path".
* Pass the stack to ContextService, which is responsible for actual
setup of the full chain.
ansible_mitogen/services.py:
Teach get() to walk the supplied stack, establishing each connection
in turn, creating refounts for it before continuing.
TODO: refcounting is broken in a variety of cases.
This commit only uses it for the target.get_file() helper, which is only
used for transferring modules. The next commit wires it into the
Connection.transfer_file() API, which is the method the copy module
uses.
This is a partial fix, there are still at least 2 cases needing covered:
- In-progress connections must have CallError or similar sent to any
waiters
- Once connection delegation exists, it is possible for other worker
processes to be active (and in any step in the process), trying to
communicate with a context that we know can no longer be communicated
with. The solution to that isn't clear yet.
Additionally ensure root has /bin/bash shell in both Docker images.
And by "compatible" I mean "terrible". This does not implement async job
timeouts, but I'm not going to bother, upstream async implementation is
so buggy and inconsistent it resists even having its behaviour captured
in tests.
Now Connection.close() *must* be called in the worker, to ensure the
reference count for a context drops correctly.
Remove 'discriminator' for now, I'm not using it for testing any more
and it complicated this code.
This code is a car crash, it needs rewritten again. Ideally some/most of
this behaviour could live on services.DeduplicatingService somehow, but
I couldn't come up with a sensible design.
Closes#105.
References #155.
mitogen/service.py:
Refactor services to support individually exposed methods with
different security policies for each method.
- @mitogen.service.expose() to expose a method and set its policy
- @mitogen.service.arg_spec() to validate input.
- Require basic service message format to be a tuple of
`(method, kwargs)`, where kwargs is always a dict.
- Update DeduplicatingService to match the new scheme.
ansible_mitogen/connection.py:
- Rename 'method' to 'method_name' to disambiguate it from the
service.call()'s method= argument.
ansible_mitogen/planner.py:
- Generate an ID for every job, sync or not, and fetch job results
from JobResultService rather than via the initiating function
call's return value.
- Planner subclasses now get to select whether their Runner should
run in a forked process. The base implementation requests this if
the 'mitogen_isolation_mode=fork' task variable is present.
ansible_mitogen/runner.py:
Teach runners to deliver their result via JobResultService executing
in their indirect parent mux process.
ansible_mitogen/plugins/actions/mitogen_async_status.py:
Split the implementation up into methods, and more compatibly
emulate Ansible's existing output.
ansible_mitogen/process.py:
Mux processes now host JobResultService.
ansible_mitogen/services.py:
Update existing services to the new mitogen.service scheme, and
implement JobResultService:
* listen() method for synchronous jobs. planner.invoke() registers a
Sender with the service prior to invoking the job, then sleeps
waiting for the service to write the job result to the
corresponding Receiver.
* Non-blocking get() method for implementing mitogen_async_status
action.
* Child-accessible push() method for delivering task results.
ansible_mitogen/target.py:
New helpers for spawning a virginal subprocess on startup, from
which asynchronous and mitogen_task_isolation=fork jobs are forked.
Necessary to avoid a task inheriting potentially
polluted/monkey-patched parent environment, since remaining jobs
continue to run in the original child process.
docs/ansible.rst:
Add/merge/remove some behaviours/risks.
tests/ansible/integration:
New tests for forking/async.
Before:
$ ANSIBLE_STRATEGY=mitogen ansible -i derp, derp -m setup
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: (''.join(bits)[-300:],)
derp | FAILED! => {
"msg": "Unexpected failure during module execution.",
"stdout": ""
}
After:
$ ANSIBLE_STRATEGY=mitogen ansible -i derp, derp -m setup
derp | UNREACHABLE! => {
"changed": false,
"msg": "EOF on stream; last 300 bytes received: 'ssh: Could not resolve hostname derp: nodename nor servname provided, or not known\\r\\n'",
"unreachable": true
}
Ansible's PluginLoader makes up bullshit when it imports a module
(mostly because it has to make up something), therefore we ended up with
duplicate copies of ansible_mitogen loaded: one under
ansible.plugins.*.mitogen, and one under the canonical namespace.
Which broke isinstance().
David Wilson