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Management of environment variables & dotenv files

Show me your .env file and I will tell you what issues your project has

Managing environment variables is not an easy task to do, especially with SOA or Microservices architecture. In some cases it may require additional abstraction layer to sucessfully address all challenges.

Let's go deeper into use cases.

Hierachy bellow represents not very complex stucture, but this will be enought to demonstrate key features. For demonstration purpose we can assume that project1 and project2 are stored in separate repositories. At the right side of component, you can see list of environment variables defined at component level (by default they should be stored inside .env.template file)

 /
 └ company
   └ department
     └ teamone
       ├ project1            [VERSION=20.6.0, HUB_HOST=localhost:12321]
       └ project2            [VERSION=20.7.0, HUB_HOST=localhost:32123]
         ├ dbs
         │ ├ mongo           [CONNECTION=localhost:27017]
         │ └ postgresql      [CONNECTION=localhost:5432]
         ├ msgbrs
         │ └ kafka           [BOOTSTRAP_SERVERS=localhost:29092]
         └ services          [HOST=myserver.io]
           ├ api             [PORT=9081]
           └ auth            [PORT=9082]

  • First obvious step is to collect all variables from project's root. If we execute next command from company/department/teamone/project1

    > tln dotenv --downstream=2

    the output will be (by default, it will be stored inside .env file)

      DBS_MONGO_CONNECTION=localhost:27017
  DBS_POSTGRESQL_CONNECTION=localhost:5432
  HUB_HOST=localhost:32123
  MSGBRS_KAFKA_BOOTSTRAP_SERVERS=localhost:29092
  SERVICES_API_PORT=9081
  SERVICES_AUTH_PORT=9082
  SERVICES_HOST=myserver.io
  VERSION=20.7.0

    As you can see, this is complete .env file and it can be used by k8s or docker-compose

  • When you need to debug specific component, you can collect environment variables not only from nested components, but also from parents. Run bellow command from company/department/teamone/project1/services/api

    > tln dotenv --upstream=2

     DBS_MONGO_CONNECTION=localhost:27017
 DBS_POSTGRESQL_CONNECTION=localhost:5432
 HUB_HOST=localhost:32123
 MSGBRS_KAFKA_BOOTSTRAP_SERVERS=localhost:29092
 PORT=9081
 SERVICES_AUTH_PORT=9082
 SERVICES_HOST=myserver.io
 VERSION=20.7.0

    The difference is that api component is used as an anchor and all other variables are constructed relative to it. Variable PORT was generated without any prefixes.

You can combine both options --upstream and --downstream to achieve any traversal scenario required by your use case.

Full command specification

tln dotenv [--upstream=<uint>] [--downstream=<uint>] [--input=<string>] [--output=<string>] [--prefix=<string>]
Option name Description Default
upstream Number of levels above current component 0
downstream Number of levels below current component 0
input Input template file name .env.template
output Output file name .env
prefix String which will be prepended to each variable name null