Client distribution proposal

This proposal has been superceded but is retained for reference.

Please see here

Proposal

Enable the coordinated update of middleware clients (ie the glite-WN) on sites via a central service run by operations. This would require the MB to endorse the use of a VO for this purpose and would of course require the cooperation of the sites in the scheme.

Advantages

There are two main advantages;

• Reduced deployment delays (an update could theoretically be propagated everywhere within hours).
• Fast rollback in case of problems (not currently possible).

Mechanism

The mechanism used is the same as the experiments use to install their software on sites today; installation on a shared area and publishing of availability via the InfoSys.

Use case

A user selects, via their jdl, the specific version of the middleware clients that they want to use. If they specify nothing, they will get the native version installed on the WN (as now). If they specify 'DEFAULT', then they will always get the project endorsed best version. 'DEFAULT' can be redefined centrally to enable rollback.

Requirements

A script, called a1_env.sh, must be preinstalled on the WNs. This script ensures that the correct environment is set up for the job, and has been part of the release for a while.

A VO which operations can use to install the middleware must be identified. There are a number of possibilities;

• ops - this has the advantage of being available across WLCG, but software installation is not explicitly in the mandate.
• dteam - probably more appropriate, but EGEE only.
• VO - we provide a mechanism where each VO can do this themselves.

Concerns

Use of middleware on a shared filesystem can have performance problems.

Sites are reluctant to allow a 3rd party to install middleware. The middleware will be generally available to all jobs (unlike the experiment case where only one VO can access the installation). A model where sites can subscribe to this scheme could be considered.

Further Information

https://twiki.cern.ch/twiki/bin/view/LCG/WnTarOnSiteUsage