dependencies-tool

dependencies-tool is a command client utility that generates a dependency order (topological order) from dependency definition files.
It can be used to generate the order in which application needs to be deployed.

Dependency Definition Files

Dependency definition files are defined in YAML. Usually each application has a definition file in its directory. dependencies-tool discovers all definition files that are in a parent directory or in any subdirectory.

The name of the configuration files or their path suffix (subdir/deps.yaml) can be specified via a command line parameter.

Format

The YAML format of the configurations files is the following:

name: myapp
dependencies:
    prd: &prd
        billing-service: ~
        calc-service: { type: hard }
        letter-service: { type: soft }
    stg: 
      << : *prd
      auth-service: ~
    testing: ~

The file defines an app called myapp. myapp is part of the distribution prd, stg and testing. In the prd distribution it depends on the billing-service, calc-service and letter-service applications. The billing-service and calc-service are defined as hard dependencies. If the dependency type is omitted, it defaults to hard. The letter-service is a soft dependency, it must be deployed together with myapp but can be deployed before or after myapp. Hard dependencies can not contain loops, soft dependencies can. For the prd also the YAML anchor &prd is defined. The anchor is used to use the same dependencies in the stg distribution. The staging distribution defines additionally auth-service as a hard dependency. In the testing distribution myapp does not have any dependencies.

For all applications that are listed as dependencies, a dependency definition file must also exist. The applications must also have distribution entries in their dependencies dictionary, for which they were declared a dependency by myapp.

Examples

1. Give me an dependency-ordered list of applications for the distribution stg. Discover and parse dependency definitions file in /repo:

   dependencies-tool order /repo stg

2. Export all dependency information found in /repo to /tmp/export.deps:

   dependencies-tool export /repo /tmp/out.deps

3. Give me an dependency-ordered list for the application billing-service of the distribution prd, read the dependency information from /tmp/export.deps, output the list as JSON:

   dependencies-tool order --format json billing-service /tmp/export prd

4. Generate a DOT graph of the dependencies, that can be visualized with Graphviz:

   dependencies-tool order --format dot /repo stg