During my review queue time I had the opportunity to review the new hpcc charm. The hpcc charm deploys an instance of HPCC (High Performance Computing Cluster) Community Edition that is a Big Data platform alternate to Hadoop. http://hpccsystems.com/products-and-services/products/community-edition
The charm is available in the personal name space here: http://manage.jujucharms.com/~xwang2713/precise/hpcc First and most importantly the hpcc charm deploys according to the readme file! I had to increase the memory constraints on the HP-cloud to 4GB per machine (juju set-constraints mem=4GB) so all the services had enough memory to start up. After that I was able to cluster by adding units of hpcc. In the end the charm was unable to pass review because some of the configuration options were immutable, meaning the values did not change after the charm was created. When I changed some configuration values, they were not acted upon by the charm and that breaks the Juju user experience. When a user changes a configuration value they expect the charm to act upon those changes. I bring this up so future charm authors know to avoid immutable configuration when creating a charm. There are exceptions to every rule, but immutable configuration are only in extreme cases of data integrity where there are no other options. A good way to avoid immutable configuration is to have the configuration options are processed by the config-changed hook. We did not have very good documentation about immutable configuration so I opened a pull request against the Juju docs with more detail about this problem. The change was merged and will show up on the Best Practices page when the documentation processing completes. https://juju.ubuntu.com/docs/authors-charm-best-practice.html - Matt Bruzek <matthew.bru...@canonical.com>
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