Conferer
what, why and a bit of how
VERY UNSTABLE DON’T USE IN PRODUCTION JUST YET
Conferer is a library that defines ways to get configuration for your Haskell
application and the libraries it uses, which is at heart string keys which map
to other strings.
To get this map we use Providers
which define a way to get a key (eg.
db.username
) that may or may not exist, we then use a list of providers for
getting the value for that key (position on the list defines priority). This
allows adding new providers easily (for example a dhall file provider,
a git repo or a etcd database)
The other side of this is that we have the FromConfig
which gets some value
from a Config
at a certain key possibly using only keys under some namespacing
key
Example (not implemented)
Let’s say I want to configure warp. Let’s say we wrote this program.
main = do
-- by default gets cli parameters, envvars and json file
config <- getDefaultConfigFor "awesomeapp"
warpConfig :: Warp.Settings <- getKey "warp" config
Warp.runSettings warpConfig myApp
Now I need to chage the port of the app, I can change it by either:
- Setting cli params like
./myApp -Cwarp.port=5555
- Setting an environment variable called
AWESOMEAPP_WARP_PORT=5555
- In a json file you can have
{"warp": {"port": 5555}}
And you may also get that value from different configuration providers like
redis or etc or whichever you may need.
Utilities
There are as well some utilities to change providers:
Conferer.Provider.Namespace
: All keys must be namespaced and the namespace
is striped for lookup
Conferer.Provider.Mapped
: Using a map key to maybe key you can change the
name of a key or even hiding some key
Conferer.Provider.Simple
: Get keys from a hardcoded map key to string
Future maybe things
- Interpolate keys with other keys:
{a: "db", b: "${a}_thing"}
, getting b
will give "db_thing"
(maybe)
- A LOT of providers
- A LOT of
FromConfig
implementations
- Docs