convict

What is convict?

Convict is a configuration management tool for Node.js applications. It allows you to define a schema for your configuration files, validate them, and load them from various sources such as JSON files, environment variables, or command-line arguments.

What are convict's main functionalities?

Define a Configuration Schema

This feature allows you to define a schema for your configuration. The schema can include various types of data such as strings, numbers, and arrays. You can also specify default values and environment variables.

const convict = require('convict');

const config = convict({
  env: {
    doc: 'The application environment.',
    format: ['production', 'development', 'test'],
    default: 'development',
    env: 'NODE_ENV'
  },
  port: {
    doc: 'The port to bind.',
    format: 'port',
    default: 8080,
    env: 'PORT'
  }
});

console.log(config.get('env'));

Load Configuration from Multiple Sources

Convict allows you to load configuration from multiple sources such as JSON files, environment variables, and command-line arguments. This makes it easy to manage configuration in different environments.

const convict = require('convict');

const config = convict({
  env: {
    doc: 'The application environment.',
    format: ['production', 'development', 'test'],
    default: 'development',
    env: 'NODE_ENV'
  },
  port: {
    doc: 'The port to bind.',
    format: 'port',
    default: 8080,
    env: 'PORT'
  }
});

config.loadFile('./config.json');
config.load({ port: 3000 });

console.log(config.get('port'));

Validate Configuration

Convict can validate your configuration against the schema you defined. This ensures that your configuration is correct and helps prevent runtime errors.

const convict = require('convict');

const config = convict({
  env: {
    doc: 'The application environment.',
    format: ['production', 'development', 'test'],
    default: 'development',
    env: 'NODE_ENV'
  },
  port: {
    doc: 'The port to bind.',
    format: 'port',
    default: 8080,
    env: 'PORT'
  }
});

config.validate({ allowed: 'strict' });

console.log('Configuration is valid');

Other packages similar to convict

config

The 'config' package is another popular configuration management tool for Node.js. It allows you to define configuration files for different environments and load them based on the current environment. Unlike Convict, it does not provide schema validation out of the box.

dotenv

The 'dotenv' package is a simple module that loads environment variables from a .env file into process.env. It is more lightweight compared to Convict and does not provide schema validation or support for multiple configuration sources.

nconf

The 'nconf' package is a hierarchical configuration manager for Node.js. It allows you to load configuration from multiple sources and provides a flexible way to manage configuration. However, it does not provide schema validation like Convict.

README

Node-convict

Convict expands on the standard pattern of configuring node.js applications in a way that is more robust and accessible to collaborators, who may have less interest in digging through imperative code in order to inspect or modify settings. By introducing a configuration schema, convict gives project collaborators more context on each setting and enables validation and early failures for when configuration goes wrong.

Features

• Loading and merging: configurations are loaded from disk or inline and merged
• Nested structure: keys and values can be organized in a tree structure
• Environmental variables: values can be derived from environmental variables
• Command-line arguments: values can also be derived from command-line arguments
• Validation: configurations are validated against your schema (presence checking, type checking, custom checking), generating an error report with all errors that are found
• Comments allowed: Configuration and schema files can be either be in the JSON format or in the newer JSON5 format, so comments are welcome

Install

npm install convict

Example:

An example config.js:

var convict = require('convict');

// Define a schema
var conf = convict({
  env: {
    doc: "The applicaton environment.",
    format: ["production", "development", "test"],
    default: "development",
    env: "NODE_ENV"
  },
  ip: {
    doc: "The IP address to bind.",
    format: "ipaddress",
    default: "127.0.0.1",
    env: "IP_ADDRESS",
  },
  port: {
    doc: "The port to bind.",
    format: "port",
    default: 0,
    env: "PORT"
  }
});

// Load environment dependent configuration
var env = conf.get('env');
conf.loadFile('./config/' + env + '.json');

// Perform validation
conf.validate({strict: true});

module.exports = conf;

Usage

Example server.js:

var http = require('http');
var conf = require('./config.js');

var server = http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});

// Consume
server.listen(conf.get('port'), conf.get('ip'), function(x) {
  var addy = server.address();
  console.log('running on http://' + addy.address + ":" + addy.port);
});

To launch your example server, and set a port:

node ./server.js --port 8080

Note: arguments must be supplied with the double-hyphen --arg. (Single hypen's are not supported at this time.)

The Schema

A configuration module could look like this:

config.js:

var config = module.exports = convict({
  env: {
    doc: "The application environment.",
    format: ["production", "development", "test"],
    default: "development",
    env: "NODE_ENV",
    arg: "node-env",
  }
});

config.loadFile(['./prod.json', './config.json']);

Each setting in the schema has four possible properties, each aiding in convict's goal of being more robust and collaborator friendly.

• Type information: the format property specifies either a built-in convict format (ipaddress, port, int, etc.), or it can be a function to check a custom format. During validation, if a format check fails it will be added to the error report.
• Default values: Every setting must have a default value.
• Environmental variables: If the variable specified by env has a value, it will overwrite the setting's default value.
• Command-line arguments: If the command-line argument specified by arg is supplied, it will overwrite the setting's default value or the value derived from env.
• Documentation: The doc property is pretty self-explanatory. The nice part about having it in the schema rather than as a comment is that we can call conf.toSchemaString() and have it displayed in the output.

Nested configuration settings are also supported:

var config = convict({
  server: {
    ip: {
      doc: "IP address to bind",
      format: 'ipaddress',
      default: '0.0.0.0'
    },
    port: {
      doc: "port to bind",
      format: 'port',
      default: 8080
    }
  },
  database: {
    host: {
      doc: "Database host name/IP",
      format: String,
      default: 'testing'
    },
    name: {
      doc: "Database name",
      format: String,
      default: 'users'
    }
  }
});

Note: Search for the word "nested" throughout this documentation to find out more about nested configuration settings.

Validation

In order to help detect misconfigurations, convict allows you to define a format for each setting. By default, convict checks if the value of the property has the same type (according to Object.prototype.toString.call) as the default value specified in the schema. You can define a custom format checking function in the schema by setting the format property.

convict provides several predefined formats for validation that you can use (using node-validator and moment.js). Most of them are self-explanatory:

• * - any value is valid
• int
• port
• url
• email
• ipaddress - IPv4 and IPv6 addresses
• duration - milliseconds or a human readable string (e.g. 3000, "5 days")
• timestamp - Unix timestamps or date strings recognized by moment.js
• nat - positive integer (natural number)

If format is set to one of the built-in JavaScript constructors, Object, Array, String, Number, or Boolean, validation will use Object.prototype.toString.call to check that the setting is the proper type.

Custom format checking

You can specify a custom format checking method on a property basis.

For example:

var conf = convict({
  key: {
    doc: "API key",
    format: function check (val) {
      if (!/^[a-fA-F0-9]{64}$/.test(val)) {
        throw new Error('must be a 64 character hex key')
      }
    },
    default: '3cec609c9bc601c047af917a544645c50caf8cd606806b4e0a23312441014deb'
  }
});

Or, you can use convict.addFormat() to register a custom format checking method that can be reused for many different properties:

convict.addFormat({
  name: 'float-percent',
  validate: function(val) {
    if (val !== 0 && (!val || val > 1 || val < 0)) {
      throw new Error('must be a float between 0 and 1, inclusive');
    }
  },
  coerce: function(val) {
    return parseFloat(val, 10);
  }
});

var conf = convict({
  space_used: {
    format: 'float-percent',
    default: 0.5
  },
  success_rate: {
    format: 'float-percent',
    default: 60.0
  }
});

The coerce function is optional.

Coercion

Convict will automatically coerce environmental variables from strings to their proper types when importing them. For instance, values with the format int, nat, port, or Number will become numbers after a straight forward parseInt or parseFloat. duration and timestamp are also parse and converted into numbers, though they utilize moment.js for date parsing.

The second argument to coerce is the config object, this can be used to implement placeholders and other advanced functionality:

convict.addFormat({
  name: "placeholder",
  validate: function(val) {
    /* validate proper path here */
  },
  coerce: function(val, config) {
    return val.replace(/\$\{([\w\.]+)}/g, function(v,m) { return config.get(m); });
  }
});

var conf = convict({
  env: {
    format: ['production', 'development'],
    default: 'development',
    env: 'NODE_ENV',
    doc: 'The environment that we\'re running in.'
  },
  configPath: {
    format: 'placeholder',
    default: '/path/to/config',
    doc: 'Path to configuration files.'
  },
  config: {
    format: 'placeholder',
    default: '${configPath}/${env}.json',
    doc: 'Path to configuration file.'
  }
});

conf.get('config'); /* "/path/to/config/development.json" */

Precendence order

When merging configuration values from different sources, Convict follows precedence rules. The order, from lowest to highest, is:

1. Default value
2. File (config.loadFile())
3. Environment variables
4. Command line arguments
5. Set and load calls (config.set() and config.load())

API

var config = convict(schema)

convict() takes a schema object or a path to a schema file and returns a convict configuration object. The configuration object has an API for getting and setting values, described below.

config.addFormat(format)

Adds a new custom format.

config.addFormats(format1, format2, ...)

Adds new custom formats.

config.get(name)

Returns the current value of the name property. name can use dot notation to reference nested values. E.g.:

config.get('database.host');

// or
config.get('database').host;

config.default(name)

Returns the default value of the name property. name can use dot notation to reference nested values. E.g.:

config.default('server.port');

config.has(name)

Returns true if the property name is defined, or false otherwise. E.g.:

if (config.has('some.property')) {
  // Do something
}

config.set(name, value)

Sets the value of name to value. name can use dot notation to reference nested values, e.g. "database.port". If objects in the chain don't yet exist, they will be initialized to empty objects. E.g.:

config.set('property.that.may.not.exist.yet', 'some value');
config.get('property.that.may.not.exist.yet');
// Returns "some value"

config.load(object)

Loads and merges a JavaScript object into config. E.g.:

config.load({
  "env": "test",
  "ip": "127.0.0.1",
  "port": 80
});

config.loadFile(file or [file1, file2, ...])

Loads and merges one or multiple JSON configuration files into config. JSON files are loaded using cjson, so they can contain comments. E.g.:

conf.loadFile('./config/' + conf.get('env') + '.json');

Or, loading multiple files at once:

// CONFIG_FILES=/path/to/production.json,/path/to/secrets.json,/path/to/sitespecific.json
conf.loadFile(process.env.CONFIG_FILES.split(','));

config.validate([options])

Validates config against the schema used to initialize it. All errors are collected and thrown at once.

Options: At the moment strict is the only available option.

If the strict option is passed (that is {strict: true} is passed), any properties specified in config files that are not declared in the schema will result in errors. This is to ensure that the schema and the config files are in sync. By default the strict mode is set to false.

config.getProperties()

Exports all the properties (that is the keys and their current values) as JSON.

config.toString()

Exports all the properties (that is the keys and their current values) as a JSON string.

config.getSchema()

Exports the schema as JSON.

config.getSchemaString()

Exports the schema as a JSON string.

FAQ

How can I define a configuration property as "required" without providing a default value?

The philosophy was to have production values be the default values. Usually you only want to change defaults for deploy or instance (in aws speak) specific tweaks. However, you can set a default value to null and if your format doesn't accept null it will throw an error.

How can I use convict in a (browserify-based) browser context?

Thanks to browserify, convict can be used for web applications too. To do so,

• Use brfs to ensure the fs.loadFileSync schema-loading calls are inlined at build time rather than resolved at runtime (in Gulp, add .transform(brfs) to your browserify pipe).
• To support "loading configuration from a http://foo.bar/some.json URL", build a thin wrapper around convict using your favorite http package (e.g. superagent). Typically, in the success callback, call convict's load() on the body of the response.

Contributing

Read the Contributing doc.