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 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: schema and configuration files can be either in the JSON format or in the newer JSON5 format, so comments are welcome
• Configuration file additional types support: custom file type support can be used for the configuration file

Install

npm install convict

Usage

An example config.js file:

var convict = require('convict');

convict.addFormat(require('convict-format-with-validator').ipaddress);

// Define a schema
var config = convict({
  env: {
    doc: 'The application 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: 8080,
    env: 'PORT',
    arg: 'port'
  },
  db: {
    host: {
      doc: 'Database host name/IP',
      format: '*',
      default: 'server1.dev.test'
    },
    name: {
      doc: 'Database name',
      format: String,
      default: 'users'
    }
  },
  admins: {
    doc: 'Users with write access, or null to grant full access without login.',
    format: Array,
    nullable: true,
    default: null
  }
});

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

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

module.exports = config;

An example server.js file leveraging the config.js file above:

var http = require('http');
var config = 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(config.get('port'), config.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: Command-line arguments must be supplied with a double-hyphen prefix (e.g. --arg). Single-hypen prefixes (e.g. -a) are not supported at this time.

The Schema

A configuration module, with its deep nested schema, could look like this:

config.js:

var config = convict({
  db: {
    name: {
      format: String,
      default: ''
    },
    synchro: {
      active: {
        format: 'Boolean',
        default: false
      },
      remote_url: {
        format: 'url',
        default: 'http://localhost:8080/'
      }
    }
  },
  secret: {
    doc: 'Secret used for session cookies and CSRF tokens',
    format: '*',
    default: '',
    sensitive: true
  }
});

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

Each setting in the schema has the following 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. An environment variable may not be mapped to more than one setting.
• 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 config.getSchemaString() and have it displayed in the output.
• Sensitive values and secrets: If sensitive is set to true, this value will be masked to "[Sensitive]" when config.toString() is called. This helps avoid disclosing secret keys when printing configuration at application start for debugging purposes.
• Null values: If nullable is set to true, the value counts as valid not only if it matches the specified format, but also when it is null.

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. Most of them are self-explanatory:

• * - any value is valid
• int
• port
• windows_named_pipe
• port_or_windows_named_pipe
• nat - positive integer (natural number)

You can find other format here.

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

If nullable is set to true, null will be a valid value as well.

Custom format checking

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

For example:

var config = convict({
  key: {
    doc: 'API key',
    format: function check (val) {
      if (!/^[a-fA-F0-9]{64}$/.test(val)) {
        throw new Error('must be a 64 character hex key')
      }
    },
    default: '3cec609c9bc601c047af917a544645c50caf8cd606806b4e0a23312441014deb'
  },
  name: {
    doc: 'user name',
    format: function check (val) {
      if (typeof val.first_name !== 'string') {
        throw new TypeError(`first name '${val.first_name}' is not a string`);
      }
      if (typeof val.last_name !== 'string') {
        throw new TypeError(`last name '${val.last_name}' is not a string`);
      }
    },
    default: {
      first_name: 'John',
      last_name: 'Doe'
    }
  }
});

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

The coerce function is optional.

Custom format for array items

You can specify a custom format checking for array items:

convict.addFormat({
  name: 'source-array',
  validate: function(sources, schema) {
    if (!Array.isArray(sources)) {
      throw new Error('must be of type Array');
    }

    for (source of sources) {
      convict(schema.children).load(source).validate();
    }
  }
});

convict.addFormat(require('convict-format-with-validator').url);

const schema = {
  sources: {
    doc: 'A collection of data sources.',
    format: 'source-array',
    default: [],

    children: {
      type: {
        doc: 'The source type',
        format: ['git', 'hg', 'svn'],
        default: null
      },
      url: {
        doc: 'The source URL',
        format: 'url',
        default: null
      }
    }
  }
};

convict(schema).load({
  'sources': [
    {
      'type': 'git',
      'url': 'https://github.com/mozilla/node-convict.git'
    },
    {
      'type': 'git',
      'url': 'https://github.com/github/hub.git'
    }
  ]
}).validate();

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.

Precedence order

When merging configuration values from different sources, Convict follows precedence rules. The order, from lowest to highest, for config.loadFile(file) and config.load(json) is:

1. Default value
2. File or json set in function argument
3. Environment variables (only used when env property is set in schema)
4. Command line arguments (only used when arg property is set in schema)

This order means that if schema defines parameter to be taken from an environment variable and environment variable is set then you cannot override it with config.loadFile(file) or config.load(json).

process.env.PORT = 8080; // environment variable is set
const config = convict({
  port: {
    default: 3000,
    env: 'PORT'
  }
});
config.load({ port: 9000 });
console.log(config.get('port')); // still 8080 from env

Overriding Environment variables and Command line arguments

Convict allows to override Environment variables and Command line arguments. It can be helpful for testing purposes.

When creating a config object pass an object with two optional properties as the 2nd parameter:

• env: Object - this object will be used instead of process.env
• args: Array<string> - this array will be used instead of process.argv

var config = convict({
  // configuration schema
}, {
  env: {
    // Environment variables
  },
  args: [
    // Command line arguments
  ]
});

Configuration file additional types support

Convict is able to parse files with custom file types during loadFile. For this specify the corresponding parsers with the associated file extensions.

convict.addParser({ extension: 'toml', parse: toml.parse });
convict.addParser({ extension: ['yml', 'yaml'], parse: yaml.load });
convict.addParser([
  { extension: 'json', parse: JSON.parse },
  { extension: 'json5', parse: json5.parse },
  { extension: ['yml', 'yaml'], parse: yaml.load },
  { extension: 'toml', parse: toml.parse }
]);

const config = convict({ ... });
config.loadFile('config.toml');

If no supported extension is detected, loadFile will fallback to using the default json parser.

Allow comments in JSON files

If you want to allow comments in your JSON file, use JSON5.

convict.addParser({extension: 'json', parse: require('json5').parse});

API

var config = convict(schema[, opts])

convict() takes a schema object or a path to a schema JSON file and returns a convict configuration object.

opts: Optional object:

• opts.env: Override process.env if specified using an object {'NODE_ENV': 'production'}.
• opts.args: Override process.argv if specified using an array ['--argname', 'value'] or a string --argname value.

The configuration object has an API for getting and setting values, described below.

var config = convict({
  env: {
    doc: 'The application environment.',
    format: ['production', 'development', 'test'],
    default: 'development',
    env: 'NODE_ENV'
  },
  log_file_path: {
    'doc': 'Log file path',
    'format': String,
    'default': '/tmp/app.log'
  }
});

// or
config = convict('/some/path/to/a/config-schema.json');

convict.addParser(parser or parserArray)

Adds new parsers for custom file extensions

convict.addFormat(format) or convict.addFormat(name, validate, coerce)

Adds a new custom format, format being an object, see example below.

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);
  }
});

convict.addFormats(formats)

Adds new custom formats, formats being an object whose keys are the new custom format names, see example below.

convict.addFormats({
  prime: {
    validate: function(val) {
      function isPrime(n) {
        if (n <= 1) return false; // zero and one are not prime
        for (let i=2; i*i <= n; i++) {
          if (n % i === 0) return false;
        }
        return true;
      }
      if (!isPrime(val)) throw new Error('must be a prime number');
    },
    coerce: function(val) {
      return parseInt(val, 10);
    }
  },
  'hex-string': {
    validate: function(val) {
      if (/^[0-9a-fA-F]+$/.test(val)) {
        throw new Error('must be a hexadecimal string');
      }
    }
  }
});

config.get(name)

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

config.get('db.host');

// or
config.get('db').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.reset(name)

Resets a property to its default value as defined in the schema. E.g.:

config.reset('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. "db.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"

If you call config.load or config.loadFile after config.set then value provided by config.set will be overridden in case of conflict.

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 fileArray)

Loads and merges one or multiple JSON configuration files into config. E.g.:

config.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
config.loadFile(process.env.CONFIG_FILES.split(','));

config.validate([options])

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

allowed option

1. warn: If set to warn (that is {allowed: 'warn'} is passed), any properties specified in config files that are not declared in the schema will print a warning. This is the default behavior.

2. strict: If set to strict (that is {allowed: 'strict'} is passed), any properties specified in config files that are not declared in the schema will throw errors. This is to ensure that the schema and the config files are in sync.

3. output : You can replace the default output console.log by your own output function. You can use debug module like this:

     output: require('debug')('convict:validate:error')

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, with sensitive values masked. Sensitive values are masked even if they aren't set, to avoid revealing any information.

config.getSchema()

Exports the schema as JSON.

config.getSchemaString()

Exports the schema as a JSON string.

config.getArgs()

The array of process arguments (not including the launcher and application file arguments). Defaults to process.argv unless an override is specified using the args key of the second (options) argument of the convict function.

config.getEnv()

The map of environment variables. Defaults to process.env unless an override is specified using the env key of the second argument (options) argument of the convict function.

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.

Migrating

• Migrating from Convict 5 to 6