ExpressPayments Ruby Library

The ExpressPayments Ruby library provides convenient access to the ExpressPayments API from applications written in the Ruby language. It includes a pre-defined set of classes for API resources that initialize themselves dynamically from API responses which makes it compatible with a wide range of versions of the ExpressPayments API.

The library also provides other features. For example:

• Easy configuration path for fast setup and use.
• Helpers for pagination.
• Built-in mechanisms for the serialization of parameters according to the expectations of ExpressPayments' API.

See the Ruby API docs.

See video demonstrations covering how to use the library.

You don't need this source code unless you want to modify the gem. If you just want to use the package, just run:

gem install expresspayments

If you want to build the gem from source:

gem build expresspayments.gemspec

• Ruby 2.3+.

If you are installing via bundler, you should be sure to use the https rubygems source in your Gemfile, as any gems fetched over http could potentially be compromised in transit and alter the code of gems fetched securely over https:

source 'https://rubygems.org'

gem 'rails'
gem 'expresspayments'

The library needs to be configured with your account's secret key which is available in your ExpressPayments Dashboard. Set ExpressPayments.api_key to its value:

require 'expresspayments'
ExpressPayments.api_key = 'sk_test_...'

# list customers
ExpressPayments::Customer.list()

# retrieve single customer
ExpressPayments::Customer.retrieve('cus_123456789')

For apps that need to use multiple keys during the lifetime of a process, like one that uses ExpressPayments Connect, it's also possible to set a per-request key and/or account:

require "expresspayments"

ExpressPayments::Customer.list(
  {},
  {
    api_key: 'sk_test_...',
    ep_account: 'acct_...',
    ep_version: '2023-11-01',
  }
)

ExpressPayments::Customer.retrieve(
  'cus_123456789',
  {
    api_key: 'sk_test_...',
    ep_account: 'acct_...',
    ep_version: '2023-11-01',
  }
)

ExpressPayments::Customer.retrieve(
  {
    id: 'cus_123456789',
    expand: %w(balance_transaction)
  },
  {
    ep_version: '2023-11-01',
    api_key: 'sk_test_...',
  }
)

ExpressPayments::Customer.capture(
  'cus_123456789',
  {},
  {
    ep_version: '2023-11-01',
    api_key: 'sk_test_...',
  }
)

Keep in mind that there are different method signatures depending on the action:

• When operating on a collection (e.g. .list, .create) the method signature is method(params, opts).
• When operating on resource (e.g. .capture, .update) the method signature is method(id, params, opts).
• One exception is that retrieve, despite being an operation on a resource, has the signature retrieve(id, opts). In addition, it will accept a Hash for the id param but will extract the id key out and use the others as options.

Get access to response objects by initializing a client and using its request method:

client = ExpressPayments::ExpressPaymentsClient.new
customer, resp = client.request do
  ExpressPayments::Customer.retrieve('cus_123456789',)
end
puts resp.request_id

A proxy can be configured with ExpressPayments.proxy:

ExpressPayments.proxy = 'https://user:pass@example.com:1234'

By default, the library will use the API version pinned to the account making a request. This can be overridden with this global option:

ExpressPayments.api_version = '2023-11-01'

See versioning in the API reference for more information.

By default, the library will use its own internal bundle of known CA certificates, but it's possible to configure your own:

ExpressPayments.ca_bundle_path = 'path/to/ca/bundle'

You can enable automatic retries on requests that fail due to a transient problem by configuring the maximum number of retries:

ExpressPayments.max_network_retries = 2

Various errors can trigger a retry, like a connection error or a timeout, and also certain API responses like HTTP status 409 Conflict.

Idempotency keys are added to requests to guarantee that retries are safe.

Open, read and write timeouts are configurable:

ExpressPayments.open_timeout = 30 # in seconds
ExpressPayments.read_timeout = 80
ExpressPayments.write_timeout = 30 # only supported on Ruby 2.6+

Please take care to set conservative read timeouts. Some API requests can take some time, and a short timeout increases the likelihood of a problem within our servers.

The library can be configured to emit logging that will give you better insight into what it's doing. The info logging level is usually most appropriate for production use, but debug is also available for more verbosity.

There are a few options for enabling it:

1. Set the environment variable EP_LOG to the value debug or info:

   $ export EP_LOG=info

2. Set ExpressPayments.log_level:

   ExpressPayments.log_level = ExpressPayments::LEVEL_INFO

The library has various hooks that user code can tie into by passing a block to ExpressPayments::Instrumentation.subscribe to be notified about specific events.

Invoked when an HTTP request starts. Receives RequestBeginEvent with the following properties:

• method: HTTP method. (Symbol)
• path: Request path. (String)
• user_data: A hash on which users can set arbitrary data, and which will be passed through to request_end invocations. This could be used, for example, to assign unique IDs to each request, and it'd work even if many requests are running in parallel. All subscribers share the same object for any particular request, so they must be careful to use unique keys that will not conflict with other subscribers. (Hash)

Invoked when an HTTP request finishes, regardless of whether it terminated with a success or error. Receives RequestEndEvent with the following properties:

• duration: Request duration in seconds. (Float)
• http_status: HTTP response code (Integer) if available, or nil in case of a lower level network error.
• method: HTTP method. (Symbol)
• num_retries: The number of retries. (Integer)
• path: Request path. (String)
• user_data: A hash on which users may have set arbitrary data in request_begin. See above for more information. (Hash)
• request_id: HTTP request identifier. (String)
• response_header: The response headers. (Hash)
• response_body = The response body. (String)
• request_header = The request headers. (Hash)
• request_body = The request body. (String)

For example:

ExpressPayments::Instrumentation.subscribe(:request_end) do |request_event|
  # Filter out high-cardinality ids from `path`
  path_parts = request_event.path.split("/").drop(2)
  resource = path_parts.map { |part| part.match?(/\A[a-z_]+\z/) ? part : ":id" }.join("/")

  tags = {
    method: request_event.method,
    resource: resource,
    code: request_event.http_status,
    retries: request_event.num_retries
  }
  StatsD.distribution('ep_request', request_event.duration, tags: tags)
end

If you're writing a plugin that uses the library, we'd appreciate it if you identified using #set_app_info:

ExpressPayments.set_app_info('MyAwesomePlugin', version: '1.2.34', url: 'https://myawesomeplugin.info')

This information is passed along when the library makes calls to the ExpressPayments API.

By default, the library sends request latency telemetry to ExpressPayments. These numbers help ExpressPayments improve the overall latency of its API for all users.

You can disable this behavior if you prefer:

ExpressPayments.enable_telemetry = false

ExpressPayments has features in the beta phase that can be accessed via the beta version of this package. We would love for you to try these and share feedback with us before these features reach the stable phase. To install a beta version use gem install with the exact version you'd like to use:

gem install expresspayments -v 7.1.0.pre.beta.2

Note There can be breaking changes between beta versions. Therefore we recommend pinning the package version to a specific beta version in your Gemfile. This way you can install the same version each time without breaking changes unless you are intentionally looking for the latest beta version.

We highly recommend keeping an eye on when the beta feature you are interested in goes from beta to stable so that you can move from using a beta version of the SDK to the stable version.

If your beta feature requires a EP-Version header to be sent, use the ExpressPayments.api_version field to set it:

ExpressPayments.api_version += "; feature_beta=v3"

New features and bug fixes are released on the latest major version of the ExpressPayments Ruby library. If you are on an older major version, we recommend that you upgrade to the latest in order to use the new features and bug fixes including those for security vulnerabilities. Older major versions of the package will continue to be available for use, but will not be receiving any updates.

The test suite depends on expresspayments-mock, so make sure to fetch and run it from a background terminal (expresspayments-mock's README also contains instructions for installing via Homebrew and other methods):

go get -u github.com/expresspayments/expresspayments-mock
expresspayments-mock

Run all tests:

bundle exec rake test

Run a single test suite:

bundle exec ruby -Ilib/ test/expresspayments/util_test.rb

Run a single test:

bundle exec ruby -Ilib/ test/expresspayments/util_test.rb -n /should.convert.names.to.symbols/

Run the linter:

bundle exec rake rubocop

Update bundled CA certificates from the Mozilla cURL release:

bundle exec rake update_certs

Update the bundled expresspayments-mock by editing the version number found in .travis.yml.