Open Stack

Excerpts from corvus's message of 2018-03-28 13:21:38 -0700:
> Hi,
> 
> I've proposed a change to devstack which slightly alters the
> LIBS_FROM_GIT behavior.  This shouldn't be a significant change for
> those using legacy devstack jobs (but you may want to be aware of it).
> It is more significant for new-style devstack jobs.
> 
> The change is at https://review.openstack.org/549252
> 
> In summary, when this change lands, new-style devstack jobs should no
> longer need to set LIBS_FROM_GIT explicitly.  Existing legacy jobs
> should be unaffected (but there is a change to the verification process
> performed by devstack).
> 
> 
> Currently devstack expects the contents of LIBS_FROM_GIT to be
> exclusively a list of python packages which, obviously, should be
> installed from git and not pypi.  It is used for two purposes:
> determining whether an individual package should be installed from git,
> and verifying that a package was installed from git.
> 
> In the old devstack-gate system, we prepared many of the common git
> repos, whether they were used or not.  So LIBS_FROM_GIT was created to
> indicate that in some cases devstack should ignore those repos and
> install from pypi instead.  In other words, its original purpose was
> purely as a method of selecting whether a devstack-gate prepared repo
> should be used or ignored.
> 
> In Zuul v3, we have a good way to indicate whether a job is going to use
> a repo or not -- add it to "required-projects".  Considering that, the
> LIBS_FROM_GIT variable is redundant.  So my patch causes it to be
> automatically generated based on the contents of required-projects.
> This means that job authors don't need to list every required repository
> twice.
> 
> However, a naïve implementation of that runs afoul of the second use of
> LIBS_FROM_GIT -- verifying that python packages are installed from git.
> 
> This usage was added later, after a typographical error ("-" vs "_" in a
> python package name) in a constraints file caused us not to install a
> package from git.  Now devstack verifies that every package in
> LIBS_FROM_GIT is installed.  However, Zuul doesn't know that devstack,
> tempest, and other packages aren't installed.  So adding them
> automatically to LIBS_FROM_GIT will cause devstack to fail.
> 
> My change modifies this verification to only check that packages
> mentioned in LIBS_FROM_GIT that devstack tried to install were actually
> installed.  I realize that stated as such this sounds tautological,
> however, this check is still valid -- it would have caught the original
> error that prompted the check in the first case.
> 
> What the revised check will no longer handle is a typo in a legacy job.
> If someone enters a typo into LIBS_FROM_GIT, it will no longer fail.
> However, I think the risk is worthwhile -- particularly since it is in
> service of a system which eliminates the opportunity to introduce such
> an error in the first place.
> 
> To see the result in action, take a look at this change which, in only a
> few lines, implements what was a significantly more complex undertaking
> in Zuul v2:
> 
> https://review.openstack.org/548331
> 
> Finally, a note on the automatic generation of LIBS_FROM_GIT -- if, for
> some reason, you require a new-style devstack job to manually set
> LIBS_FROM_GIT, that will still work.  Simply define the variable as
> normal, and the module which generates the devstack config will bypass
> automatic generation if the variable is already set.
> 
> -Jim
> 

How does this apply to uses of devstack outside of zuul, such as in a
local development environment?

Doug