Just for fun, I'm designing a few web applications using a microservices architecture. I'm trying to determine the best way to do configuration management, and I'm worried that my approach for configuration may have some enormous pitfalls and/or something better exists.

To frame the problem, let's say I have an authentication service written in c++, an identity service written in rust, an analytics services written in haskell, some middletier written in scala, and a frontend written in javascript. There would also be the corresponding identity DB, auth DB, analytics DB, (maybe a redis cache for sessions), etc... I'm deploying all of these apps using docker swarm.

Whenever one of these apps is deployed, it necessarily has to discover all the other applications. Since I use docker swarm, discovery isn't an issue as long all the nodes share the requisite overlay network.

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> However, each application still needs the upstream services host\_addr, maybe a port, the credentials for some DB or sealed service, etc...
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I know docker has `secrets` which enable apps to read the configuration from the container, but I would then need to write some configuration parser in each language for each service. This seems messy.

What I would rather do is have a `configuration service`, which maintains knowledge about how to configure all other services. So, each application would start with some RPC call designed to get the configuration for the application at runtime. Something like

```
int main() {
    AppConfig cfg = configClient.getConfiguration("APP_NAME");
    // do application things... and pass around cfg
    return 0;
}

```

The AppConfig would be defined in an IDL, so the class would be instantly available and language agnostic.

This seems like a good solution, but maybe I'm really missing the point here. Even at scale, tens of thousands of nodes can be served easily by a few configuration services, so I don't forsee any scaling issues. Again, it's just a hobby project, but I like thinking about the "what-if" scenarios :)

How are configuration schemes handled in microservices architecture? Does this seem like a reasonable approach? What do the major players like Facebook, Google, LinkedIn, AWS, etc... do?