otterscan/README.md

# Otterscan

An open-source, fast, local, laptop-friendly Ethereum block explorer.

## What?

This is an Ethereum block explorer designed to be run locally with an archive node companion, more specifically, with [Erigon](https://github.com/ledgerwatch/erigon).

This approach brings many advantages, as follows.

### Privacy

You are querying your own node, so you are not sending your IP address or queries to an external third-party node.

### Fast

Since you are querying your local archive node, everything is fast, no network roundtrips are necessary.

### Actually, very fast

This software was designed to be a companion of Erigon, a blazingly fast archive node.

### Really, it is even faster

The standard web3 jsonrpc methods are quite verbose and generic requiring many calls to gather many pieces of information at client side.

We've implemented some custom methods at rpcdaemon level, less information is needed to be json-marshalled and transmitted over network.

## Why?

Current offerings are either closed source or lack many features the most famous Ethereum block explorer has, or simply have high requirements like having an archive node + additional indexers.

Otterscan requires only a patched Erigon installation + running Otterscan itself (a simple React app), which makes it a laptop-friendly block explorer.

## Why the name?

3 reasons:

- It is heavily based on Erigon, whose mascot is an otter (Erigon, the otter), think about an otter scanning your transactions inside blocks.
- It is an homage to the most famous and used ethereum block explorer.
- The author loves wordplays and bad puns.

## It looks familiar...

The UI was intentionally made very similar to the most popular Ethereum block explorer so users do not strugle trying to find where the information is.

However, you will see that we made many UI improvements.

## Install instructions

This software is currently available as compile-only form.

It depends heavily on a working Erigon installation with Otterscan patches applied, so let's begin with it first.

### Install Erigon

You will need an Erigon installation with Otterscan patches. Since setting up an Erigon environment itself can take some work, make sure to follow their instructions and have a working archive node before continuing.

My personal experience: at the moment of this writing (~block 12,700,000), setting up an archive node takes over 5-6 days and ~1.3 TB of SSD.

They have weekly stable releases, make sure you are running on of them, not development ones.

### Install Otterscan patches on top of Erigon

Add our forked Erigon git tree as an additional remote and checkout the corresponding branch.

```
git remote add otterscan git@github.com:wmitsuda/erigon.git
```

Checkout the branch corresponding to the Erigon's stable tag you are using, or the `otterscan-develop` branch to the current development branch (be sure to check from which tag it is branched from to be sure it is a compatible branch).

```
git checkout otterscan-develop
```

Build the patched `rpcdaemon` binary.

```
make rpcdaemon
```

Run it paying attention to enable the `erigon`, `ots`, `eth` apis to whatever cli options you are using to start `rpcdaemon`.

`ots` stands for Otterscan and it is the namespace we use for our own custom APIs.

```
./build/bin/rpcdaemon --http.api "eth,erigon,ots,<your-other-apis>" --private.api.addr 127.0.0.1:9090 --chaindata <erigon-chaindata-dir> --http.corsdomain "*"
```

Be sure to include both `--private.api.addr` and `--chaindata` parameter so you run it in dual mode, otherwise the performance will be much worse.

Also pay attention to the `--http.corsdomain` parameter, CORS is required for the browser to call the node directly.

Now you should have an Erigon node with Otterscan jsonrpc APIs enabled, running in dual mode with CORS enabled.

### Clone Otterscan repository and build the project

Make sure you have a working node 12/npm installation.

Clone Otterscan repo and its submodules. For now, only the default `develop` branch is available (it is alpha...).

```
git clone --recurse-submodules git@github.com:wmitsuda/otterscan.git
cd otterscan
npm install
npm run build
```

### Run it from the source

First, as brief explanation about the app:

- The app itself is a simple React app which will be run locally and communicates with your Erigon node.
- The app makes use of two sources of external databases for cosmetic reasons:
  - Token icons come from the trustwallet public assets repository.
  - Method names come from the 4bytes database.
- These 2 repositories were cloned as submodules and are made available to the app through separate http services. They are accessed at browser level and are optional, if the service is down the result will be broken icons and default 4bytes method selectors instead of human-readable names.

These instructions are subjected to changes in future for the sake of simplification.

Open a new terminal and start the 4bytes method decoding service:

```
npm run serve-4bytes
```

Open another terminal and start the trustwallet assets service:

```
npm run serve-trustwallet-assets
```

In another terminal start the Otterscan app:

```
npm run serve
```

Otterscan should now be running at http://localhost:5000/.

You can make sure it is working correctly if the homepage is able to show the latest block/timestamp your Erigon node is at just bellow the search button.

## Kudos

To the [Geth](https://geth.ethereum.org/) team whose code Erigon is based on.

To the [Erigon](https://github.com/ledgerwatch/erigon) team that made possible for regular humans to run an archive node in a retail laptop. Also, they have been very helpful explaining Erigon's internals which made possible the modifications Otterscan requires.

To the [mdbx](https://github.com/erthink/libmdbx) team which is the blazingly fast database that empowers Erigon.

To [Trust Wallet](https://github.com/trustwallet/assets) who sponsor and make available their icons under a permissive license.

To the owners of the [4bytes repository](https://github.com/ethereum-lists/4bytes) that we import and use to translate and method selector to human-friendly strings.

## Future

Erigon keeps evolving at a fast pace, with weekly releases, sometimes with (necessary) breaking changes.

This project intends to keep following their progress and mantaining compatibility as the availability of the author permits.

Erigon itself is alpha, so I consider this software is also in alpha state, however it is pretty usable.

Also there is room for many improvements that are not possible in the current centralized, closed source block explorer offerings and the author of this software would like to have.