FFX Config

FFX's configuration management allows you to configure your FFX code without recompiling. From a high level, configurations can be thought of as key-value map.

The configuration management code searches in several locations for the value associated with a key. The search is performed in the following order and returns the first value found:

  1. Runtime configuration (set by the command line)
  2. Environment variables
  3. Configuration files
  4. Heuristics (compiled methods that can guess from the environment)

Runtime Configuration

Configuration can be set at runtime when ffx is invoked. The top-level command accepts a configuration parameter:

$ fx ffx --config "config=runtime" ...

For example, run:

$ fx ffx --config "config-test=runtime" config get --name config-test

The runtime parameter takes the format of comma separated key-value pairs (“{key}={value},{key}={value},etc...”) because this is not strongly typed, any configurations set here will be assumed to be strings.

The daemon runs as its own process and currently the runtime configuration is not transferred from the CLI to the daemon if the daemon is started up. It's expected that if you want to configure the the daemon using the runtime configurations, the daemon command will be run manually:

$ fx ffx --config "config-test=runtime" daemon

Environment variables

Keys can be tied to environment variables as well. This is currently done at compile time.

Keys can be tied to any number of environment variables and the first environment variable that resolves to a value is used (in the order that they are given via the vector parameter).

Configuration Files

More to come.


Heuristic configurations use code that is executed at the time of query to resolve keys to values. This code is set at compile time.

Keys are associated with functions that must match the signature:

fn(key: &str) -> Option<Value>