Surprisingly enough, by doing small cirurgical changes in the existing
EMQX control scripts, we are able to get it running with Elixir and
with existing functionalities (`console`, `remote_console`, `start`,
`stop`, `ctl`, `foreground`, `eval`).
While declaring `emqx_conf` as an application dependency of
`emqx_resource` worked for releases, it messed up the startup
relationship during tests. Since only removing `emqx_conf` from the
`applications` key in `emqx_resource` breaks the list of apps that
need to be rebooted on config changes (since `emqx_conf` is not on any
apps dependencies list, it was not being added to the final
topologically sorted list), we now always add it as a vertex to ensure
its presence there. This (apparently) makes the rebar3 release, the
mix release and test runs behave normally.
Adding hocon to emqx solves the issue, since other offending apps
depend on emqx. The warnings were that it was not able to find info
on the `hocon_schema` behaviour.
Example:
```
Callback info about the hocon_schema behaviour is not available
```
In order for us to reuse most of the functionalities implemented in
`bin/eqmx` also in the Elixir release script, common variable and
function definitions are extracted in separated bash files that can be
sourced by both Rebar and Elixir release scripts.
By treating the apps in the umbrella as dependencies to be managed and
built by rebar3, we can simplify the maintenance of the release, at
the cost of increased build times: using Mix as before, it could track
changed files better than using rebar. But the complexity and
possibility of discrepancies make it using rebar much more compelling.
Since Mix does not support hot upgrades out of the box, it does not
create a `RELEASES` file by default. Here, we introduce functionality
similar to what `relx` does in order for that file to be generated.
fdc8d7237e/src/rlx_assemble.erl (L928-L948)
The `RELEASES` file, in its turn, is required for `nodetool` to work
properly, and `nodetool` is required for us to generate several
required config files using `hocon`. Since the `start{_clean}.boot`
file used by the files generated by Elixir must be explicitly defined
in the `RELEASE_LIB` `boot_var`, we apply a small patch in the
existing `nodetool` in order to inject that required parameter when
calling the escript.
This commit enables a minimal working build of EMQX release using
Mix. However, to properly start the release, several configuration
steps are still missing. A `mix_release.sh` script does a few hacks
to get the release built with Mix to start properly, by first assuming
that `make emqx` has been run prior to the release, ran once to
generate the `app.*.config` files, and then it copies that and some
other files to the expected places.
Also, `emqx_telemetry` hangs the start procedure because it thinks
it's in an official release and tries to make a request. We disable
it temporarily via config just to get a working build for now.
