Creating OTP Applications

In the wider Erlang community, it is very common to see applications that run one or more gen_servers (or other server behaviours) managed by a supervision tree (with the appropriate restart strategy defined). The LFE rebar3 plugin provides the ability to generate OTP gen_server applications with the server managed in a supervision tree.

To create an LFE/OTP application:

rebar3 new lfe-app otp-lfe

===> Writing otp-lfe/README.md
===> Writing otp-lfe/LICENSE
===> Writing otp-lfe/rebar.config
===> Writing otp-lfe/.gitignore
===> Writing otp-lfe/src/otp-lfe.lfe
===> Writing otp-lfe/src/otp-lfe-app.lfe
===> Writing otp-lfe/src/otp-lfe-sup.lfe
===> Writing otp-lfe/src/otp-lfe.app.src

We can use the plugin's REPL command to demonstrate usage.

Start the REPL:

cd otp-lfe
rebar3 lfe repl

Start the app:

lfe> (application:ensure_all_started 'otp-lfe)
#(ok (otp-lfe))

Make sure the supervisor is running:

lfe> (erlang:whereis 'otp-lfe-sup)
#Pid<0.205.0>

Make an API call to the gen_server:

lfe> (otp-lfe:echo "testing the supervised gen_server ...")
"testing the supervised gen_server ..."