[klntsky]

Arion is a Nix wrapper tool for docker-compose. Nix is handy for use as a template language. It is actually closer to a general-purpose language than to a template engine, so I guess what you want can be implemented manually, since it only requires config file generation.

Arion docs: https://docs.hercules-ci.com/arion/

Nix language: https://nixos.wiki/wiki/Nix_Expression_Language

[pxc]

In Arion, dependencies between services are still implicit, as at the end of the day what you're doing is generating a docker-compose.yml file.

There are other tools that model things more like the OP is thinking, though! With Disnix, you have an explicit service model where you declare those dependencies.

See: https://hydra.nixos.org/build/203347995/download/2/manual/ or maybe Sander's blog posts on it

[Randomdevops]

Yes!

I haven't quite wrapped my head around Nix yet, but https://hydra.nixos.org/build/203347995/download/2/manual/#e...

  ### Databases
  zipcodes = {
    name = "zipcodes"; 
    pkg = customPkgs.zipcodes; 
    dependsOn = {};
    type = "mysql-database";
  };
  ...

  ### Web services

  ZipcodeService = { 
    name = "ZipcodeService"; 
    pkg = customPkgs.ZipcodeService; 
    dependsOn = { 
      inherit zipcodes;
    };
    type = "tomcat-webapplication"; 
  };
  ...

And then in the ZipcodeService you can access your dependency attributes https://hydra.nixos.org/build/203347995/download/2/manual/#e...

  contextXML = ''
    <Context>
      <Resource name="jdbc/ZipcodeDB" auth="Container" type="javax.sql.DataSource"
                maxActivate="100" maxIdle="30" maxWait="10000"
                username="${zipcodes.target.container.mysqlUsername}" password="${zipcodes.target.container.mysqlPassword}"   driverClassName="com.mysql.jdbc.Driver"
                url="jdbc:mysql://${zipcodes.target.properties.hostname}:${toString  (zipcodes.target.container.mysqlPort)}/${zipcodes.name}?autoReconnect=true" />
    </Context> 3
  '';

Still wondering if the 'zipcodes.target.properties.hostname' is a fixed schema that could be validated or if it is just a map...

So yeah it looks like I'm searching for what they describe as a 'services-model' where as docker compose is what they describe as a 'deployment model'...

Their idea of always doing a new deployment and leaving the old versions running, so you can always do a rollback is interesting.