On 1/22/09 4:12 AM, Gerhardus Geldenhuis wrote:
> I have found this very usefull, however I do not understand the
> difference between HOSTS and HOSTFILTER. It would be great if you
> could explain it from another angle
I'll give it another try. Consider this concrete example. Suppose your
script defines three servers, A, B, and C. And it defines a task, "foo",
that (by default) wants to run on A and B, but not C. Like this:
role :app, "A", "B"
role :web, "C"
task :foo, :roles => :app do
run "echo hello"
end
Now, if you do "cap foo", it will run the echo command on both A and B.
If you do "cap HOSTS=C foo", it will run the echo command on C,
regardless of the :roles parameter to the task.
If you do "cap HOSTFILTER=C foo", it will not run the echo command at
all, because the intersection of (A B) and (C) is an empty set. (There
are no hosts in foo's host list that match C.)
If you do "cap HOSTFILTER=A foo", it will run the echo command on only
A, because (A B) intersected with (A) is (A).
Lastly, if you do "cap HOSTFILTER=A,B,C foo", it will run the echo
command on A and B (but not C), because (A B) intersected with (A B C)
is (A B).
To summarize: HOSTS completely overrides the hosts or roles declaration
of the task, and forces everything to run against the specified host(s).
The HOSTFILTER, on the other hand, simply filters the existing hosts
against the given list, choosing only those servers that are already in
the tasks server list.
Hope that's clearer,
Jamis
>
> Regards
>
> On Jan 21, 5:03 pm, Jamis Buck <[email protected]> wrote:
>> Try the HOSTS environment variable:
>>
>> cap HOSTS=app2.example.com production deploy
>>
>> Note that doing this will treat app2 as being in every role, not just
>> whichever role(s) it happens to be declared in.
>>
>> If what you want is to do a regular deploy, but only act on app2, and
>> only as app2 is declared in your recipe file, you can use the HOSTFILTER
>> variable instead:
>>
>> cap HOSTFILTER=app2.example.com production deploy
>>
>> Sorry if the distinction isn't clear there. Let me know if you need more
>> clarification as to the difference between HOSTS and HOSTFILTER.
>>
>> - Jamis
>>
>> On 1/21/09 9:54 AM, Pete Hodgson wrote:
>>
>>> Hi Folks,
>>> I have a system in production that has several servers in serveral
>>> roles. I would like to test a new app server by deploying to that
>>> specific server, without having to redeploy to every server in
>>> production. Is there a way to ask Capistrano to deploy to a specific
>>> server? Ideally I'd like to be able to run something like cap
>>> SERVER=app2.example.com ROLE=app production deploy if I just wanted to
>>> deploy to app2.example.com.
>>> I original posted this question on Stack Overflow a few days back [1]
>>> and got a few answers, but neither solution seemed to work for me.
>>> Hope it's not bad form to now post here.
>>> Cheers,
>>> Pete
>>> [1]http://stackoverflow.com/questions/429816/how-to-deploy-to-a-single-s...
> >
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