Murano exception handling

Current exception handling in murano project differs from the way all OpenStack projects handle their exception. Murano have very small list of its own exceptions and use webob or general exceptions everywhere instead of store all needed exceptions in one place.

Problem description

  • Murano is OpenStack project and should follow community practices.
  • Using murano specific exceptions can make debugging easier.
  • Now we have 3 different places where exceptions are stored: murano.packages.exceptions, murano.dsl.exceptions, murano.common.exception depends on part of murano which throws the exception.

Proposed change

It’s planned to create 2 new basic exceptions in murano.common.exceptions which will be parents for others. First one will be general exception and the second one will be exception for HTTP requests. Exceptions in murano.packages.exceptions should have general MuranoException as a parent. Exceptions in murano.dsl.exceptions should be kept as is since dsl is mostly separate part of murano.

These exceptions will be replaced with exceptions inherited from MuranoHTTPException:

  • webob.exc.HTTPBadRequest
  • webob.exc.HTTPInternalServerError
  • webob.exc.HTTPForbidden
  • webob.exc.HTTPUnsupportedMediaType
  • webob.exc.HTTPUnauthorized
  • webob.exc.HTTPForbidden
  • webob.exc.HTTPConflict
  • webob.exc.HTTPClientError

These exceptions will be replaced with exceptions inherited from MuranoException:

  • ValueError
  • Exception
  • RuntimeError
  • NotImplementedError
  • SyntaxError
  • TypeError
  • NameError

All custom exceptions which defined in murano should be moved to one of the general exceptions files.


Keep everything as it is.

Data model impact


REST API impact


Versioning impact


Other end user impact

End users will see new murano specific exceptions.

Deployer impact


Developer impact


Murano-dashboard / Horizon impact

New exceptions should be introduced and handled in horizon.



Primary assignee:

Work Items

  • Create new exception in murano-api, change exception handling where it will be needed
  • Create new exception in packages, change exception handling where it will be needed
  • Handle new exceptions in python-muranoclient
  • Handle new exception in murano-dashboard




This change need a huge refactoring for unit and functional tests.

Documentation Impact