[Bug 1832105] Re: ceph-mgr dashboard incompatible with cython >= 0.29 (disco)

[James Page]

@hcoin

I don't think anyone is recommending the solution to this bug is to use
an unreleased development version of Ubuntu which by its nature has not
been through full testing.  That's just a part of the process - to be
able to update a released version of Ubuntu we have to evidence that the
same software bug has been fixed in the development release; otherwise
when users upgrade to the new release, they regress the fix to this
issue.

You'll note activity on this bug - its moving forward and we will
provide stable release updates for the fixes into 19.04 (Disco) which
*is* the solution to this bug.

If you encounter separate issues please feel free to raise new bugs
against the ceph package.

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https://bugs.launchpad.net/bugs/1832105

Title:
  ceph-mgr dashboard incompatible with cython >= 0.29 (disco)

Status in ceph package in Ubuntu:
  Fix Released
Status in ceph source package in Disco:
  In Progress
Status in ceph source package in Eoan:
  Fix Released

Bug description:
  [Impact]
  The ceph-mgr daemon is unable to load additional module due to a new check in cython >= 0.29.  This limits the function of the manager.

  
  [Test Case]
  Deploy ceph
  Check /var/log/ceph/ceph-mgr.`hostname`.log
  Errors about loading rados module in subprocesses will be seen.

  [Regression Potential]
  The fix from upstream actually just works around this issue by overriding the check that cython does; the code works in a subprocess when loaded multiple times.  Regression potential low; cython may produce a longer term fix which means we can drop this patch.

  [Original Bug Report]
  If Ubuntu is really committed to ceph as I think I've been reading:  Notice the ceph dashboard went entirely broken in a major regression of the disco upgrade.  It won't load at all in 13.2.4+dfsg1-0ubuntu2.

  The detail is ceph-mgr (and lots of ceph) relied on a non-feature in
  cython that went away in cython v29, to do with sub-interpreters.  The
  ceph folks responded with a hack/workaround to avoid the bug being
  noticed, and a requirement of the package for an earlier version of
  cython.  This was done some weeks and months ago.  Actually fixing the
  problem is a major project the ceph maintainers are struggling to
  engage, perhaps waiting for later versions of cython to provide a
  different way forward.

  However, as of today, on disco ths error message remains:

  Module 'dashboard' has failed dependency: Interpreter change detected
  - this module can only be loaded into one interpreter per process.

  The ceph primary development platform is Debian, on which the
  workaround has been available for some time.

  However in our ubuntu case, a major feature of a core packge (web
  health/monitoring/config interface of  a distributed file system), was
  allowed to both ship broken and remain so for a long time, even
  through today.

  I urge quick attention to the necessary backports.
  https://github.com/ceph/ceph/pull/25585
  http://tracker.ceph.com/issues/38788
  http://tracker.ceph.com/issues/37472

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