[question] Is `service_discovery_postgres` application started first?

[toraritte]

rebar.config's relx section starts with

{relx, [{release, {service_discovery, {git, long}},
         [service_discovery_postgres,
          service_discovery,
          service_discovery_http,
          service_discovery_grpc,
          recon]},

and the Releases chapter states that

When constructing the boot script a stable sort on all applications based on their dependencies is done to decide the order to start them. However, when the dependency order is not specific enough to make a decision, the order defined in the list is kept. Each of service_discovery_postgres, service_discovery_http and service_discovery_grpc depend on service_discovery, resulting in the latter being the first to start. The next one will then be service_discovery_postgres because it is listed first.

So the startup/boot order will be (1) service_discovery, (2) service_discovery_postgres, (3) service_discovery_http, (4) service_discovery_grpc and not (1) service_discovery_postgres, (2) service_discovery, (3) service_discovery_http, (4) service_discovery_grpc , or did I completely misunderstood that paragraph?

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service_discovery_storage is not listed because it is a library (i.e., collection of modules without any processes), right? So if it would be an external library it would simply go to the deps section in rebar.config?

Thanks in advance!

[tsloughter]

Correct, the startup will be service_discovery first.

service_discovery_storage has to be listed in the .app.src of service_discovery_postgres, but yes, if it was an external library it would also have to be listed as a dep in rebar.config.

[toraritte]

Thank you, especially for the .app.src bit!

Note to self:

• https://www.rebar3.org/docs/basic-usage#adding-dependencies