[erlang-questions] Appup & Relup possible failures

Rob Stephenson <>
Tue Mar 20 23:10:24 CET 2012


Hi,

Our company has built an application using Erlang and we would like to
support continuous deployment (
http://wiki.smartfrog.org/wiki/display/sf/Pattern+-+Continuous+Deployment) for
this application.  We're considering using the OTP appup and relup code
updating features.  We've reviewed the OTP documentation for release
handling, and it mentions that upgrading or downgrading can fail under
certain circumstances, but does not mention what those circumstances are.
 Can anyone shed any light on this?

>From http://www.erlang.org/doc/design_principles/release_handling.html
Section 11.1

"If the installation fails, the system may be rebooted. The old release
version is then automatically used. "

We've found information on other websites indicating that circular
dependencies will cause application upgrade failures, but without a lot of
details.  Of the following use cases, which should be expected to work?

   - Circular dependencies between functional code modules
   - Circular dependencies between a functional code module and a residence
   module (a module that hosts the message loop of an application)
   - Circular dependencies between residence modules in the same node
   - Circular dependencies between residence modules in different nodes

Is there a definitive list of what cases the application upgrade can fail?

Thanks,
Rob Stephenson
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