Configuration

This guide will help you to know the most important configuration options for SPV Wallet.

Order of resolving configuration

The configuration is resolved in the following priority

1. Environment variables - the environment variables are prefixed with SPVWALLET_ and are in uppercase. They have the highest priority when resolving the configuration.

2. Configuration file - the configuration file is resolved next. The default configuration file is config.yaml in the working directory. You can also specify custom configuration file path using C flag in the command line.

3. If you don't specify the configuration file and environment variables, the default configuration will be used - it's resolved in defaults.go file in the config package. Default configuration from defaults.go is the same as the configuration from config.example.yaml.

Configuration File

We store the configuration in a file called config.example.yaml in the root of the project. You can copy this file to config.yaml and modify it to your needs.

The most important configuration options are:

auth:
  # xpub used for admin api authentication
  admin_key: xpub661MyMwAqRbcFgfmdkPgE2m5UjHXu9dj124DbaGLSjaqVESTWfCD4VuNmEbVPkbYLCkykwVZvmA8Pbf8884TQr1FgdG2nPoHR8aB36YdDQh
  # ...
  # other auth options
cache:
  # cache engine - freecache/redis
  engine: freecache
  # ...
  # other cache options
db:
  datastore:
  # enable datastore debug mode
  debug: false
  # datastore engine - sqlite/postgresql/mysql/mongodb (experimental)
  engine: sqlite
  # in this section you can define details about your database
  # ...
arc:
  url: https://arc.taal.com
  token: mainnet_06770f425eb00298839a24a49cbdc02c
  # deployment id used annotating api calls in XDeployment-ID header - this value will be randomly generated if not set
  _deployment_id: spv-wallet-deployment-id
  callback:
    enabled: false
    host: https://example.com
    # token to authenticate callback calls - default callback token will be generated from the Admin Key
    _token: 44a82509
# custom fee unit used for calculating fees (if not set, a unit from ARC policy will be used)
_custom_fee_unit:
  satoshis: 1
  bytes: 1000
  
block_headers_service:
  auth_token: mQZQ6WmxURxWz5ch
  # URL used to communicate with Block Headers Service (BHS)
  url: http://localhost:8080
  
paymail:
  beef:
    use_beef: true
  domains:
    - localhost

# Prometheus metrics configuration
metrics:
  enabled: false

Going throught highlighted options:

• The auth section contains the admin_key which is used for admin api authentication. This key is used to authenticate the admin api calls.

• The cache section contains the engine option which can be set to freecache or redis. The freecache is the default option.

• The db section contains the datastore section which contains the engine option which can be set to sqlite or postgresql. The sqlite is the default option. You can also define details about your database in this section.

• The arc section contains:

  • the url and token which are used for getting and broadcasting transactions.

  • the callback section which is used to receive notifications about broadcasted transactions from ARC.

  • the deployment_id option is used to define the deployment id used annotating api calls in XDeployment-ID header. This value will be randomly generated if not set.

• The custom_fee_unit option is used for transaction fee calculation. The fee_unit option is used as the fee value if custom_fee_unit is configured.

• The block_headers_service section contains the auth_token and url options used to communicate with Block Headers Service to make SPV.

Callback is an Arc feature that allows the wallet to receive notifications about broadcasted transactions. It is useful because it limits the need for polling the node for transaction status.

• The paymail section contains the domains option which is used to define the list of domains.

• The beef section with the use_beef option is used to enable or disable beef paymail capability support.

You can read more about the SPV and BEEF in the SPV and BEEF section.

• The metrics section allows to enable or disable Prometheus metrics.

Environment Variables

You can also set the configuration options using environment variables. The environment variables are prefixed with SPVWALLET_ and are in uppercase. For example, the auth.admin_key can be set using the SPVWALLET_AUTH_ADMIN_KEY environment variable.