Execution abstraction layer for high-level system scripts.
xal is a Python library which provides an high-level API to interact with system resources (files, commands, …) and low-level execution via third-parties (stdlib, Fabric, Salt, …).
The concept is you open a session in system, then you run commands within the session:
- session is specific, it holds the execution context, it knows the low-level implementation.
- commands use a generic API. You could run the same commands in another session.
“xal” is the acronym of “eXecution Abstraction Layer”.
Let’s initialize a session on local system:
>>> import xal >>> local_session = xal.LocalSession()
In this session, we can manage files:
>>> path = local_session.path('hello-xal.txt') >>> path.exists() False >>> written = path.open('w').write(u'Hello world!') >>> path.exists() True >>> print path.open().read() Hello world! >>> path.unlink() >>> path.exists() False
We can also execute sh commands:
>>> result = local_session.sh.run(u"echo 'Goodbye!'") >>> print result.stdout Goodbye! <BLANKLINE>
Now let’s make a function that does the same. It takes the session as input argument:
>>> def hello(session): ... path = session.path('hello-xal.txt') ... path.open('w').write(u"Hello world!") ... print path.open().read() ... path.unlink() ... print session.sh.run(u"echo 'Goodbye!'").stdout
Of course, we can run it in local session:
>>> hello(local_session) Hello world! Goodbye! <BLANKLINE>
What’s nice is that we can reuse the same function in another session. Let’s create a remote SSH session using Fabric…
>>> remote_session = xal.FabricSession(host='localhost')
… then just run the same function with this remote session:
>>> hello(remote_session) Hello world! Goodbye! <BLANKLINE>
xal ideas are:
- Python users (including sysadmins and devops) have a consistent and unified API to write scripts that perform operations on system.
- such scripts are portable, i.e. they can be executed in various environments. Whatever the operating system, whatever the protocol to connect to and communicate with the system…
- Python community can share libraries that are compatible with tools such as Fabric, zc.buildout, Salt, Ansible…
- it is easier to switch from one tool to another: reconfigure the session, don’t change the scripts. Develop scripts locally, test them remotely via Fabric, distribute them using Salt… or vice-versa.
Today: xal is a proof-of-concept. It focuses on sample implementation of basic features such as managing files and directories, or executing sh commands. The idea is that, as a Python user, you can give it a try and, if you like it, use it for simple tasks.
Tomorrow, depending on feedback from community, xal may improve or be deprecated. As xal’s author, I would like the following things to happen:
- increased stability and performances for current features.
- more execution contexts (i.e. sessions): Salt, Fabric as sudoer, …
- more resources: users, system packages, …
- better API, preferrably built as PEPs. Just as xal’s proof of concept tries to mimic pathlib, there could be a PEP related to every resource. Sh commands (a.k.a. replacement for subprocess) are an epic example.
As xal’s author, I can’t do it alone. If you’d like to help:
- provide feedback. Do you like xal? What do you dislike in xal? Your feedback matters!
- join the project on Github.
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