The config package makes it easy to manage environment specific configuration values. For example, you might want to use distinct values for development, testing, and production environments.
You can install the config package from CRAN as follows:
install.packages("config")
Configurations are defined using a YAML text file and are read by default from a file named config.yml in the current working directory (or parent directories if no config file is found in the initially specified directory).
Configuration files include default values as well as values for arbitrary other named configurations, for example:
config.yml
default:
trials: 5
dataset: "data-sampled.csv"
production:
trials: 30
dataset: "data.csv"
To read configuration values you call the config::get
function, which
returns a list containing all of the values for the currently active
configuration:
config <- config::get()
config$trials
config$dataset
You can also read a single value from the configuration as follows:
config::get("trials")
config::get("dataset")
The get
function takes an optional config
argument which determines
which configuration to read values from (the “default” configuration is
used if none is specified).
You can specify which configuration is currently active by setting the
R_CONFIG_ACTIVE
environment variable. The R_CONFIG_ACTIVE
variable
is typically set within a site-wide Renviron
or Rprofile
(see R
Startup
for details on these files).
# set the active configuration globally via Renviron.site or Rprofile.site
Sys.setenv(R_CONFIG_ACTIVE = "production")
# read configuration value (will return 30 from the "production" config)
config::get("trials")
You can check whether a particular configuration is active using the
config::is_active
function:
config::is_active("production")
The default
configuration provides a set of values to use when no
named configuration is active. Other configurations automatically
inherit all default
values so need only define values specialized for
that configuration. For example, in this configuration the production
configuration doesn’t specify a value for trials
so it will be read
from the default
configuration:
config.yml
default:
trials: 5
dataset: "data-sampled.csv"
production:
dataset: "data.csv"
All configurations automatically inherit from the “default”
configuration. Configurations can also inherit from one or more other
named configurations. For example, in this file the production
configuration inherits from the test
configuration:
config.yml
default:
trials: 5
dataset: "data-sampled.csv"
test:
trials: 30
dataset: "data-test.csv"
production:
inherits: test
dataset: "data.csv"
By default configuration data is read from a file named config.yml within the current working directory (or parent directories if no config file is found in the initially specified directory).
You can use the file
argument of config::get
to read from an
alternate location. For example:
config <- config::get(file = "conf/config.yml")
If you don’t want to ever scan parent directories for configuration
files then you can specify use_parent = FALSE
:
config <- config::get(file = "conf/config.yml", use_parent = FALSE)
You can execute R code within configuration files by prefacing values
with !expr
. This could be useful in the case where you want to base
configuration values on environment variables, R options, or even other
config files. For example:
default:
cores: 2
debug: true
server: "localhost:5555"
production:
cores: !expr getOption("mc.cores")
debug: !expr Sys.getenv("ENABLE_DEBUG") == "1"
server: !expr config::get("server", file = "/etc/server-config.yml")