try code:load_file if loading with code:ensure_loaded fails

[hmmr]

code:ensure_loaded fails if our code server is in embedded mode, causing riak_cs to fail to configure riak with a custom backend storage:

     [{add_paths,
          ["/home/hmmr/X/titokyo/g/riak_cs/dev/dev1/riak-cs/lib/riak_cs-3.0.0pre3+build.3435.ref2aaece2f/ebin"]},
      {storage_backend,riak_cs_kv_multi_backend},
      ...

Loading the module with code:load_file/1 actually makes it happen.

[martinsumner]

Another Riak user raised the issue of code in additional paths not working in riak_kv >= 3.0 (e.g. map/reduce functions), and returning {error, embedded} instead.

As part of the switch to OTP 20 with 3.0, the switch was made to relx - and this changes the default mode from interactive to embedded:

https://github.com/erlware/relx/blob/master/priv/templates/extended_bin#L923-L924

So it appears the root cause here is we're now running embedded. But this wasn't a deliberate change. So perhaps the best answer, to solve this and other dynamic code loading issues, is to switch back to interactive.

For packaged deployments - I think we could do this by setting the CODE_LOADING_MODE in the riak script https://github.com/basho/riak/blob/develop-3.0/rel/files/riak. This wouldn't work though when running direct from make rel and make devrel.

Are there any objections to switching back to interactive mode? @martincox

[martinsumner]

See basho/riak#1077

This changes the default back to interactive by using a pre_start script (as with changing the max log size). This seems better than changing rel/fiiles/riak.

[hmmr]

As far as #1077 fixes the loading regression, I'm totally fine with the proposed change to interactive mode.

[hmmr]

Closing as basho/riak#1077 has been merged.