[jsdl-wg] Question on jsdl:HostName element

[Michel Drescher]

Andreas,

thanks for the answer.

I appreciate that the solution sketched below has its pros. But, 
unfortunately, this overloads the semantics of the id attribute and, 
frankly, I am not happy with this.

This attribute is in JSDL (and other specs) consistently used as an 
identifier to a particular element for _referencing_ purposes, and not 
for declarative purposes such as describing a uniform path to the home 
directory of a user, a particular spool directory etc. The fact that 
the identifier _can_ carry a very similar value to that is another 
story (and an often used technique).

Cheers,
Michel


On 1 Mar 2005, at 1:37, Andreas Savva wrote:

> Michel
>
> I've done most of the writeup for the filesystem section so I'll have 
> a first go at this.
>
> My intention in writing the  filesystem section was to address the 
> case you raise with option (a) (with some extra support to pass the 
> value of the mountpoint  to the job via an environment variable 
> present during execution, see daft 0.9.2).  If the consensus is to try 
> and formalize this more then I would suggest defining the meaning of a 
> small set of values for the filesystem  "id"; the meaning of ids such 
> as "HOME", "TMP" etc. The filesystem id is already tied into other 
> JSDL constructs (e.g., DataStaging) so this approach would be a 
> natural one.
>
> Andreas
>
> Michel Drescher wrote:
>
>>     From:       Michel.Drescher at uk.fujitsu.com
>>     Subject:     Various questions sourcing from external
>>     Date:     28 February 2005 14:06:02 GMT
>>     To:       jsdl
>>
>> Dear JSDL wranglers,
>>
>> I got assigned to relay the following question to the JSDL working 
>> group:
>>
>> 1) jsdl:FileSystem
>> A very popular use case for this element is to mount the user's home 
>> directory to the execution environment.
>> How do I do that using JSDL?
>>
>> Solution a) - "Magic interpreter"
>> The JSDL snippet would be
>>    <jsdl:FileSystem id="Home">
>>       <jsdl:Description>foo</jsdl:Description>
>>    <jsdl:FileSystem>
>> and the genie interpreter would recognise the id attribute to mount 
>> the execution user's home dir.
>> JDSL goes "Genie in the bottle", if I may say so. ;-)
>>
>> Solution b) - Platform specific incarnation
>> The JSDL snippet would be
>>    <jsdl:FileSystem id="Home">
>>       <jsdl:Description>foo</jsdl:Description>
>>       <jsdl:MountPoint>/home/mdrescher</jsdl:MountPoint>
>>    <jsdl:FileSystem>
>> This solution lacks abstraction since I cannot resubmit that very job 
>> to another site where my home directory is mounted to another path 
>> (i.e. /users/drescher).
>> Brokering this job is also hardly possible even if I try to mess 
>> around with an incredibly large set of jsdl:Profile elements (to 
>> match all possible mount points for home directories).
>>
>> Solution b) - adding "abstractable" directories to jsdl:FileSystemType
>> The JSDL snippet would be
>>    <jsdl:FileSystem id="Home">
>>       <jsdl:Description>foo</jsdl:Description>
>>       <jsdl:FileSystemType>home</jsdl:FileSystemType>
>>    <jsdl:FileSystem>
>> This way, JSDL would introduce the "home directory" syntactically. 
>> The downside is that $HOME is not a filesystem. But, then, is "tmp" 
>> always a different filesystem?
>>
>> Solution c) - Allowing globbing in jsdl:MountPoint
>> The JSDL snippet could be
>>    <jsdl:FileSystem id="Home">
>>       <jsdl:Description>foo</jsdl:Description>
>>       <jsdl:MountPoint>{$HOME}</jsdl:FileSystemType>
>>    <jsdl:FileSystem>
>>    or something similar
>> This mechanism would introduce the well-known globbing mechanisms 
>> from PERL or the shells like tcsh, bash etc.
>>
>> Solution d) - A revised jsdl:FileSystem element
>> I don't have any idea yet to propose, but personally, I think JSDL 
>> would benefit from an abstraction of file systems (like UNICORE or 
>> Globus provide).
>>
>> Any thoughts?
>>
>>
>>
>> Cheers,
>> Michel
>>