Re: Multiple transactions on multiple packages with rpm

[Jeff Johnson <n3npq nc rr com>]

Rafael Angel Garcia Leiva wrote:

> Dear all,
>
> We are developing a new toolsuite for the automated installation, 
> configuration and management of clusters and farms running Linux (see 
> http://quattor.org for more information). The Quattor information model is 
> based on the distinction between the "desired state" and the "actual state" 
> of nodes. 
>  

Nod. Directly figguring the delta between starting and ending manifests 
is the best approach.

> Regarding to software packages, we have a Software Package Management Agent  
> that reads a configuration file with the target packages, compares it with  
> the currently installed packages, computes the necessary  
> install/deinstall/upgrade operations, and invokes the packager with the right  
> operation transaction set.
>
> The problem is that the current version of rpm can not handle multiple 
> operations on multiple packages in a single transaction. Just imagine that 
> you want to install 'foo' and 'bar' RPMs replacing another RPM called 
> 'foobar'. How can I order the operations respecting dependencies, validate, 
> and execute the complete operation in one go? This is currently not possible 
> in RPM (an 'rpm -e --test foobar' followed by 'rpm -i --test foo bar' does 
> evidently not work).
>  

As you have seen, there is no way to mix added and erased packages on 
the CLI even
though rpmlib will handle mixed added/erased transactions.

I immediately ask why you are trying to design around execing /bin/rpm. 
I suspect
that you can/will do better linking rpmlib directly. Alternatively, 
rpm-python is
an easier (i.e. more flexible, easier to change) implementation than Yet 
Another
Executable.

I'll be happy to help with either rpmlib or rpm-python programming if 
you want. There's also nothing
wrong with a new executable in C either ;-)

> What we have done to solve this problem is to develop a new software packager 
> (called rpmt) built on top of rpmlib to handle those lists of transactions 
> (if you are interested, you can download the source code from 
> http://datagrid.in2p3.fr/cvsweb/edg-quattor/rpmt-4.2.1)
>
> As we have seen, rpmlib is ready to handle such lists of transactions. It is 
> possible to use rpmtsAddInstallElement() and rpmtsAddEraseElement() within 
> the same transaction set. So, it seems that it would be not very difficult to 
> extend rpm to handle lists of transactions. We really do not understand why 
> it is not possible to do with rpm something like:
>
> rpm -U package_1.rpm -e package_2
>  

The reason for *not* permitting multiple options factored this way is 
architectural, and has to
do with popt aliases. The problem quickly becomes scoping multiple other 
options correctly,
and that's much much harder to get right.

> We would like to know if you think it is interesting to extend rpm in this 
> direction, or if you have plans to do so. Even, we offer ourselves to provide 
> a patch to rpm implementing the new functionality, if it is necessary.
>  

When I get around to permitting mixed upgrade/erase on the CLI, the 
syntax will be
    rpm ... -- +package_1.rpm -package_2
and it won't maytter whether you invoke with major mode --install, 
--upgrade, --erase.

That avoids many architectural problems, and sidesteps the problem of 
factoring multiple
options on a per-package basis.

Meanwhile, add an RFE at http://bugzilla.redhat.com and attach rpmt.c 
(or supply a pointer)
please, and I'll be happy to take a look at what you are trying to do.

73 de Jeff