That is brilliant clear, thanks. Basically defining a task with a role safeguards you against using the task on a server where it would'nt make any sense.
I have been thinking of tasks as a bit more abstract. For me copy files to a apache server is a generic task but specific to webservers. However my server list is not static and might change 3 times a day and I have found it strange to include my server lists as part of my capistrano program. I guess you can import an external file that contains a list of servers and dynamically build your role members. It boils down to how you use capistrano. Regards On Jan 22, 4:14 pm, Jamis Buck <[email protected]> wrote: > 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... --~--~---------~--~----~------------~-------~--~----~ To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/capistrano -~----------~----~----~----~------~----~------~--~---
