Dear Mark and Nicolas,
Thank you for your reply. Dashes used to be illegal in class names, but as
of 3.0.5p1 that is no longer the case. I found this out yesterday:
cf-promise -v
listed both "lax-it-web01-prod01" and "lax_it_web01_prod01"; so I tried using
the "lax-it-web01-prod01" class and it worked fine!
Nicolas, I really like your rewrite, thank you and well done, sir.
It gets rid of the
'expression ="any";' which did not contribute to making my intention clear,
and fits well with the idea that roles are senior to hostnames.
classes: "webserver" or => {"lax_it_web01_prod01",
"lax_it_web02_prod01" };
classes: "nagios" or => {"lax_it_web01_prod01" };
classes: "postgress" or => {"lax_it_db01_prod01" };
classes: "zenoss" or => {"lax_it_db01_prod01" };
classes: "provisioning" or => {"lax_it_admin01_prod01" };
Let's take this a step further.
Let's say I want to add a new server. to an existing role. I have a
provisioning role
that can create new server instances non-interactively (so suitable
for automation) with
cloud API command line tools. I want cfengine on the provisioning
server it to notice
there is a server in the role list that has not yet been provisioned,
and to provision
it.
You could not accomplish that with the above class promises. So
let's try a list:
vars: "server_list" slist => {
"lax-it-web01-prod01",
"lax-it-web02-prod01", # web02 is the new server
"lax-it-db01-prod01",
"lax-it-admin01-prod01",
}
How would cfengine know which servers have already been provisioned
and which ones
need to be created?
(Maybe every time it creates a server, it also touches a file on the
local filesystem or
makes an entry in a host inventory database. But that's part of what
I am trying to figure
out, how to implement a host inventory database in Cfengine, or if
it's better to interface
with an external one.)
Just to let you know where I am going with this - the next step would
be to say "I should
have 2 web servers and 1 db server and 1 admin server, and I don't
care about the
hostnames" (I don't, actually, I care about the roles and the
service.) But I want to work
out the provisioning question first before I look at abstracting the
host names.
Some clouds assign hostnames dynamically.
Please let me know your thoughts about handling host/role inventory.
Truly,
Aleksey
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