ETV

Ethereum Transaction Verifier

This project is a simple Elixir Umbrella Application that checks if a certain Ethereum transaction has enough "confirmations". If it does, it marks it "Complete", otherwise it's marked "Pending".

Setup

Following dependencies are required:

• Erlang 20+
• Elixir 1.6+
• Postgres

Compile Application and Assets:

$ mix do deps.get, compile
$ mix do ecto.create, ecto.migrate
$ cd apps/etv_web/assets && npm install

Start the Server:

$ mix phx.server

Structure

The Application is organized into 4 sub-apps, each handling a specific responsibility. They are:

ETV.Data

This sub-app is responsible for persisting data to the database via Ecto. It exposes a simple API via the Data.Transaction module to read/write transactions. It also handles validation of the transaction hashes, ensuring only correct values are specified. (We could also easily replace the implementation to use a simple GenServer, Mnesia, or another DB).

• Umbrella Dependencies: None
• Elixir Packages: Ecto and Helper modules

ETV.Network

This app is responsible for connecting to external APIs to fetch information about Ethereum Transactions, and exposes just one ETV.Network.tx_info method. Underneath, it uses the API provided by Ethplorer, but that can be easily swapped by another 3rd-party by specifying another adapter.

You can specify a custom API Key by passing a API_KEY_ETHPLORER environment variable (defaults to freekey which has server-side rate-limits).

• Umbrella Dependencies: None
• Elixir Packages: HTTPoison, Jason

ETV.Tracker

The Tracker has it's own Application Supervision Tree, which continuously checks for unconfirmed Transactions in the DB (via the Data app). If there are any unconfirmed transactions, it fetches latest information about it (via the Network app) and updates their status if it has changed.

The time period currently specified is 10 seconds, but you can change the value in the Tracker.AutoUpdater module.

• Umbrella Dependencies: ETV.Data, ETV.Network
• Elixir Packages: None

ETV.Web

The last one is a Phoenix application, that spawns a web-server and handles incoming requests. It simply interacts with the ETV.Data app to insert new or display existing transactions.

• Umbrella Dependencies: ETV.Data
• Elixir Packages: Phoenix

Tests

The app consists of a very modest test suite. You can run them with mix:

$ MIX_ENV=test mix do ecto.create, ecto.migrate
$ mix test

As to not hit the actual Ethplorer Web API, Bypass is used to test against the expected behaviour (in the ETV.Network application).

License

The code is available as open source under the terms of the MIT License.