<div align="center">
<img src="assets/logo.svg" alt="Oura" width="500">
<hr />
<h2 align="center" style="border-bottom: none">The tail of Cardano</h2>
<img alt="GitHub" src="https://img.shields.io/github/license/txpipe/oura" />
<img alt="Crates.io" src="https://img.shields.io/crates/v/oura" />
<img alt="GitHub Workflow Status" src="https://img.shields.io/github/workflow/status/txpipe/oura/Validate" />
<hr/>
</div>
## Introduction
We have tools to "explore" the Cardano blockchain, which are useful when you know what you're looking for. We argue that there's a different, complementary use-case which is to "observe" the blockchain and react to particular event patterns.
_Oura_ is a rust-native implementation of a pipeline that connects to the tip of a Cardano node through a combination of _Ouroboros_ mini-protocol (using either a unix socket or tcp bearer), filters the events that match a particular pattern and then submits a succint, self-contained payload to pluggable observers called "sinks".
Check our [documentation](https://txpipe.github.io/oura) for detailed information on how to start working with _Oura_.
## Etymology
The name of the tool is inspired by the `tail` command available in unix-like systems which is used to display the tail end of a text file or piped data. Cardano's consensus procotol name, _Ouroboros_, is a reference to the ancient symbol depicting a serpent or dragon eating its own tail, which means "tail eating". "Oura" is the ancient greek word for "tail".
## Terminal Output Demo
In this terminal recording we get to see a few mins of live output from a testnet node connected to the terminal sink.
[watch full asciicast](https://asciinema.org/a/453455)
## Under the Hood
All the heavy lifting required to communicate with the Cardano node is done by the [Pallas](https://github.com/txpipe/pallas) library, which provides an implementation of the Ouroboros multiplixer and a few of the required mini-protocol state-machines (ChainSync and LocalState in particular).
The data pipeline makes heavy use (maybe a bit too much) of multi-threading and mpsc channels provided by Rust's `std::sync` library.
## Use Cases
### CLI to Watch Live Transactions
You can run `oura watch <socket>` to print TX data into the terminal from the tip of a local or remote node. It can be useful as a debugging tool for developers or if you're just curious to see whats going on in the network (for example, to see airdrops as they happen or oracles posting new information).
### As a Bridge to Other Persistence Mechanisms
Similar to the well-known db-sync tool provided by IOHK, _Oura_ can be used as a daemon to follow a node and output the data into a different data storage techonology more suited for your final use-case. The main difference with db-sync is that _Oura_ was designed for easy integration with data-streaming pipelines instead of relational databases.
Given its small memory / cpu footprint, _Oura_ can be deployed side-by-side with your Cardano node even in resource-constrained environments, such as Raspberry PIs.
### As a Trigger of Custom Actions
_Oura_ running in `daemon` mode can be configured to use custom filters to pinpoint particular transaction patterns and trigger actions whenever it finds a match. For example: send an email when a particular policy / asset combination appears in a transaction; call an AWS Lambda function when a wallet delegates to a particular pool; send a http-call to a webhook each time a metadata key appears in the TX payload;
### As a Library for Custom Scenarios
If the available out-of-the-box features don't satisfiy your particular use-case, _Oura_ can be used a library in your Rust project to setup tailor-made pipelines. Each component (sources, filters, sinks, etc) in _Oura_ aims at being self-contained and reusable. For example, custom filters and sinks can be built while reusing the existing sources.
## Features
- Sources
- [x] chain-sync full-block (node-to-client)
- [ ] chain-sync headers-only (node-to-node)
- [x] chain-sync + block-fetch (node-to-node)
- [ ] shared file system
- Sinks
- [x] Kafka topic
- [ ] Redis streams
- [ ] AWS SQS queue
- [ ] AWS Lambda call
- [ ] GCP PubSub
- [ ] webhook (http post)
- [x] terminal (append-only, tail-like)
- [ ] TUI
- Filters
- [ ] by event type (block, tx, mint, cert, etc)
- [ ] by block property (size, tx count)
- [ ] by tx property (fee, has native script, has plutus script, etc)
- [ ] by utxo property (address, asset, amount range)
- Enrichment
- [ ] policy info from metadata service
- [ ] input tx info from Blockfrost api
- [ ] address translation from ADAHandle