Lockfile location

[Luigi Paioro]

Dear All,

this is the first of a couple of e-mails where I'd like to submit at 
your evaluation two proposals of small backward compatible 
changes/improvements in SAMP protocol (which is still at the first REC 
since almost one year).

On September 2009 (more or less) we discussed about a possible 
alternative mechanism for a client to reach a Hub respect the present one:

http://www.ivoa.net/forum/apps-samp/0909/0368.htm

Mark suggested that the lockfile location could be searched as the value 
of an environment variable if it exists, otherwise falling back to the 
<home>/.samp file as now.

Following this suggestion I proposed the environment variable having a 
name an a value as specified in this EBNF:

name     ::= "SAMP_HUB" ;

value    ::= std | ? any other profile dependent string ? ;
std      ::= "std:", endpoint ;
endpoint ::= lockfile | params ;
lockfile ::= "lockfile=", ? any valid file path ? ;
params   ::= secret, ",", url ;
secret   ::= "secret=", ? any string ? ;
url      ::= "url=", ? any valid URL ? ;


Examples:

SAMP_HUB = \
"std:secret=75fb6691223bb6e6,url=http://127.0.0.1:42866/xmlrpc"

or

SAMP_HUB = \
"std:lockfile=/home/luigi/.samp-1/samp-hub-12019-1"


the "std:" prefix specifies that the endpoint refers to a Standard 
Profile hub... in principle the environment mechanism can be used with 
other profiles as well, thus a prefix which specifies the profile type 
might be useful.

I think that introducing something like the proposal above would be 
simple, backward compatible and rather useful. I would really appreciate 
any comment or opinion on this issue.

Thanks in advance.

   Luigi



-- 

Luigi Paioro

INAF - IASF Milano
Via Bassini 15, I-20133 Milano, Italy

Phone  (+39) 02 23 699 470
Fax    (+39) 02 26 660 17
Site   http://cosmos.iasf-milano.inaf.it/luigi/