eth-tracker/README.md

# eth-tracker

![GitHub Tag](https://img.shields.io/github/v/tag/grassrootseconomics/eth-tracker)

A fast and lightweight tracker designed to monitor EVM blockchains for live and historical transaction events, including reverted transactions. It filters these events and publishes them to NATS for further processing.

It applies deduplication at the NATS level, making it safe to run in a distributed fashion.

Note: To run it against an L2/EVM chain, you will need to manually add a replace directive in the `go.mod` file pointing to the EVM chain's `*geth` compatible source code. This will allow the tracker to process transaction types other than Ethereum's `0x0, 0x1 and 0x2`.

## Getting Started

A `Makefile` is also provided to build the required binaries to run eth-tracker.

### Bootstrap Cache

An optional binary, `eth-tracker-cache-bootstrap`, is included to build the Redis cache with all relevant Grassroots Economics smart contract and user addresses to allow filtering on very busy smart contracts e.g. cUSD.

The cache will auto-update based on any additions/removals from all indexes.

### Prerequisites

* Git
* Docker
* NATS server
* Redis server
* Access to a Celo RPC node

See [docker-compose.yaml](dev/docker-compose.yaml) for an example on how to run and deploy a single instance.

### 1. Build the Docker image

We provide pre-built images for `linux/amd64`. See the packages tab on Github.

If you are on any other platform:

```bash
git clone https://github.com/grassrootseconomics/eth-tracker.git
cd eth-tracker
docker buildx build --build-arg BUILD=$(git rev-parse --short HEAD) --tag eth-tracker:$(git rev-parse --short HEAD) --tag eth-tracker:latest .
docker images
```

### 2. Run NATS and Redis

For an example, see `dev/docker-compose.yaml`.
### 3. Update config values

See `.env.example` on how to override default values defined in `config.toml` using env variables. Alternatively, mount your own config.toml either during build time or Docker runtime.

```bash
# Override only specific config values
nano .env.example
mv .env.example .env
```

Refer to [`config.toml`](config.toml) to understand different config value settings.


### 4. Run the tracker

```bash
cd dev
docker compose up
```

## Processing NATS messages

### JSON structure

```js
{
    "block": Number,
    "contractAddress": String,
    "success": Boolean,
    "timetamp" Number,
    "transactionHash": String,
    "transactionType": String,
    "payload": Object
}
```

### Monitoring with NATS CLI

Install NATS CLI from [here](https://github.com/nats-io/natscli?tab=readme-ov-file#installation).

```bash
nats subscribe "TRACKER.*"
```

### DB File

A `tracker_db` file is created on the first run. This keeps track of all blocks missed by the processor to attempt a retry later on. This file should not be deleted if you want to maintain resume support for historical tracking across restarts.

## License

[AGPL-3.0](LICENSE).