Hi Christian,
First, do note you can always fall back to Fabric 1 for a while if Fabric 2
isn't yet up to snuff for your particular use case. We're still feeling out
some of the APIs in terms of ease of use. Unfortunately, Group is one of
those - it's real basic right now.
I just looked and there's no great way to set global connect_kwargs in such
an object, without creating your own Connections to hand to its alternate
constructor 'from_connections()':
```
hosts = ['switch1', 'switch2', 'switch3']
connections = [Connection(host=host, user='user',
connect_kwargs={'password': 'pw'}) for host in hosts]
switch_group = group.SerialGroup.from_connections(connections)
@task
def inventory(c):
switch_group.run('show chassis hardware')
```
That's not the end of the world, but it's not ideal, so I just made
https://github.com/fabric/fabric/issues/1831 and then (since I was thinking
about it and it was very easy for once) implemented it. It'll be out in the
next feature release!
The rest of your issues are more high level, so here's a bit of a wall of
text (sorry!):
Version 2 is much less implicit/magic than v1 – all objects need to fit
together in obvious, Pythonic ways (such as being handed to one another in
constructors or method calls). For example, context managers don't change
any object besides the one that they yield, so trying to do things to
switch_group inside a context manager about some other Connection object
won't do anything. (This is as opposed to e.g. 'with settings()' in v1,
which I assume you were thinking of; it, like the rest of that API, is all
about magically twiddling data behind the scenes.)
Connections can't be created without some 'host' argument, which I think is
triggering your TypeError. This ought to be in its __init__ docs, FWIW :)
See the code example above; you either need to make your Group from
explicitly-created Connections, where a host arg is being given, or (after
the next release) you can tell the Group's constructor about connect_kwargs.
Depending on your use case, there's a CLI flag that may replace your
getpass code:
http://docs.fabfile.org/en/2.2/cli.html#cmdoption-prompt-for-login-password
Which brings us to that context argument in the task signature: that's how
`fab` explicitly transmits CLI and config info to your tasks, including the
connection password. However, this introduces some ordering problems with
your code - you need to pass that context's config into your Group or
Connections.
Should be easily solved by moving away from module-level code exec (which
is honestly an antipattern anyways). Based on my above snippet:
```
hosts = ['switch1', 'switch2', 'switch3']
def make_group(c):
connections = [
Connection(host=host, user='user', config=c.config)
for host in hosts
]
return group.SerialGroup.from_connections(connections)
@task
def inventory(c):
switch_group = make_group(c)
switch_group.run('show chassis hardware')
```
Or, after 2.3 comes out, you could arguably nix make_group() again, though
hopefully you can see the various opportunities for refactoring, given that
everything is explicit:
```
hosts = ['switch1', 'switch2', 'switch3']
@task
def inventory(c):
switch_group = SerialGroup(*hosts, config=c.config)
switch_group.run('show chassis hardware')
```
Finally: if you're thinking "ok, but it'd be so nice to just plop my switch
hostnames and the fact that I want password prompting all the time, into a
config file and call it done": that sort of thing is definitely in the
pipeline! As I said up top, we're still hashing out a lot of the
'convenience' angles here, even though the core APIs are mostly in good
shape.
Hope that all helps,
Jeff
On Mon, Jul 23, 2018 at 3:45 PM, Christian MacNevin <cmacne...@nvidia.com>
wrote:
> Hi all,
>
> I’m new to Fabric 2, though in the past I’d used 1 a lot. I can find docs
> on using SerialGroup, but only with run directly. I’m using interactive
> mode authentication, so it seems like I need to gather a password (that’s
> fine, I’m doing it via getpass) and also pass kwargs into Connection. I
> have a large list of hosts, and also was planning to use @task decorators.
>
>
>
> What I have right now is a muddle between the two which obviously won’t
> work, but I can’t figure out how to glue the three
> concepts of having a defined group, a task which can be specified from the
> cli, and an interactive user/pass sequence together.
>
>
>
>
>
> import getpass
>
> from fabric import Connection, group
>
> from invoke import task
>
>
>
> switch_group = group.SerialGroup(switch1', 'switch2', 'switch3')
>
>
>
> pw = getpass.getpass("Password for netuser?")
>
>
>
> @task
>
> def inventory(c): ß This is purely here because tasks will error out
> if a kwarg ‘Context(..?)’ isn’t specified
>
> with Connection(user = 'user', connect_kwargs = {'password' : pw }) as
> c:
>
> switch_group.run('show chassis hardware')
>
>
>
> It’s failing out with ’TypeError: __init__() takes at least 2 arguments (3
> given)’
>
>
>
>
>
> _______________________________________________
> Fab-user mailing list
> Fab-user@nongnu.org
> https://lists.nongnu.org/mailman/listinfo/fab-user
>
>
--
Jeff Forcier
Unix sysadmin; Python engineer
http://bitprophet.org
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