zebra/README.md

![Zebra logotype](https://zfnd.org/wp-content/uploads/2022/03/zebra-logotype.png)

---

[![CI Docker](https://github.com/ZcashFoundation/zebra/actions/workflows/continous-integration-docker.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/continous-integration-docker.yml) [![CI OSes](https://github.com/ZcashFoundation/zebra/actions/workflows/continous-integration-os.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/continous-integration-os.yml) [![Continuous Delivery](https://github.com/ZcashFoundation/zebra/actions/workflows/continous-delivery.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/continous-delivery.yml) [![Coverage](https://github.com/ZcashFoundation/zebra/actions/workflows/coverage.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/coverage.yml) [![codecov](https://codecov.io/gh/ZcashFoundation/zebra/branch/main/graph/badge.svg)](https://codecov.io/gh/ZcashFoundation/zebra) [![Build docs](https://github.com/ZcashFoundation/zebra/actions/workflows/docs.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/docs.yml) [![Build lightwalletd](https://github.com/ZcashFoundation/zebra/actions/workflows/zcash-lightwalletd.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/zcash-lightwalletd.yml) [![Build Zcash Params](https://github.com/ZcashFoundation/zebra/actions/workflows/zcash-params.yml/badge.svg)](https://github.com/ZcashFoundation/zebra/actions/workflows/zcash-params.yml)

![License](https://img.shields.io/badge/license-MIT%2FApache--2.0-blue.svg)

## Contents

- [Contents](#contents)
- [About](#about)
  - [Using Zebra](#using-zebra)
- [Release Candidates](#release-candidates)
- [Getting Started](#getting-started)
  - [Build Instructions](#build-instructions)
  - [Configuring JSON-RPC for lightwalletd](#configuring-json-rpc-for-lightwalletd)
  - [Optional Features](#optional-features)
  - [System Requirements](#system-requirements)
    - [Memory Troubleshooting](#memory-troubleshooting)
    - [macOS Test Troubleshooting](#macos-test-troubleshooting)
  - [Network Ports and Data Usage](#network-ports-and-data-usage)
    - [Network Troubleshooting](#network-troubleshooting)
  - [Disk Usage](#disk-usage)
    - [Disk Troubleshooting](#disk-troubleshooting)
- [Known Issues](#known-issues)
- [Future Work](#future-work)
- [Documentation](#documentation)
- [Security](#security)
- [License](#license)

## About

[Zebra](https://zebra.zfnd.org/) is the Zcash Foundation's independent,
consensus-compatible implementation of a Zcash node, currently under
development. It can be used to join the Zcash peer-to-peer network, which helps
keeping Zcash working by validating and broadcasting transactions, and maintaining
the Zcash blockchain state in a distributed manner.

[Zcash](https://doc.zebra.zfnd.org/zebrad/index.html#about-zcash)
is a cryptocurrency designed to preserve the user's privacy.
If you just want to send and receive Zcash then you don't need to use Zebra
directly. You can download a Zcash wallet application which will handle that
for you.

Please [join us on Discord](https://discord.gg/na6QZNd) if you'd
like to find out more or get involved!

### Using Zebra

You would want to run Zebra if you want to contribute to the
Zcash network: the more nodes are run, the more reliable the network will be
in terms of speed and resistance to denial of service attacks, for example.

Zebra aims to be
[faster, more secure, and more easily extensible](https://doc.zebra.zfnd.org/zebrad/index.html#zebra-advantages)
than other Zcash implementations.

## Release Candidates

Every few weeks, we release a [new Zebra version](https://github.com/ZcashFoundation/zebra/releases).

Zebra's network stack is interoperable with `zcashd`,
and Zebra implements all the features required to reach Zcash network consensus.

Zebra also supports the [`lightwalletd` backend JSON-RPCs](https://github.com/ZcashFoundation/zebra#configuring-json-rpc-for-lightwalletd).

Currently, Zebra validates all of the Zcash consensus rules for the NU5 network upgrade.

## Getting Started

You can run Zebra using our Docker image.
This command will run our latest release, and sync it to the tip:

<!-- TODO: replace with `docker run zfnd/zebra` when we release 1.0.0 -->

```sh
docker run zfnd/zebra:1.0.0-rc.0
```

You can also [enable Zebra's RPC port](https://github.com/ZcashFoundation/zebra#configuring-json-rpc-for-lightwalletd) and [configure other features](https://zebra.zfnd.org/user/run.html).

### Build Instructions

If you want to build `zebrad` yourself, you'll need [Rust](https://www.rust-lang.org/tools/install), [libclang](https://clang.llvm.org/get_started.html), a C++ compiler, and some other dependencies.

To run `zebrad`, follow the instructions to compile `zebrad`
for your platform:

1. Install [`cargo` and `rustc`](https://www.rust-lang.org/tools/install).
   - Zebra is tested with the latest `stable` Rust version.
     Earlier versions are not supported or tested.
     Any Zebra release can remove support for older Rust versions, without any notice.
     (Rust 1.59 and earlier are definitely not supported, due to missing features.)
2. Install Zebra's build dependencies:
   - **libclang:** the `libclang`, `libclang-dev`, `llvm`, or `llvm-dev` packages, depending on your package manager
   - **clang** or another C++ compiler: `g++`, `Xcode`, or `MSVC`
3. Run `cargo install --locked --git https://github.com/ZcashFoundation/zebra --tag v1.0.0-rc.0 zebrad`
4. Run `zebrad start` (see [Running Zebra](https://zebra.zfnd.org/user/run.html) for more information)

For more detailed instructions, refer to the [documentation](https://zebra.zfnd.org/user/install.html).

### Configuring JSON-RPC for lightwalletd

To use `zebrad` as a `lightwalletd` backend, give it this `~/.config/zebrad.toml`:

```toml
[rpc]
# listen for RPC queries on localhost
listen_addr = '127.0.0.1:8232'

# automatically use multiple CPU threads
parallel_cpu_threads = 0
```

**WARNING:** This config allows multiple Zebra instances to share the same RPC port.
See the [RPC config documentation](https://doc.zebra.zfnd.org/zebra_rpc/config/struct.Config.html) for details.

### Optional Features

For performance reasons, some debugging and monitoring features are disabled in release builds.

You can [enable these features](https://doc.zebra.zfnd.org/zebrad/index.html#zebra-feature-flags) using:

```sh
cargo install --features=<name> ...
```

### System Requirements

The recommended requirements for compiling and running `zebrad` are:

- 4 CPU cores
- 16 GB RAM
- 300 GB available disk space for building binaries and storing cached chain state
- 100 Mbps network connection, with 300 GB of uploads and downloads per month

We continuously test that our builds and tests pass on:

The _latest_ [GitHub Runners](https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources) for:

- macOS
- Ubuntu

Docker:

- Debian Bullseye

Zebra's tests can take over an hour, depending on your machine.
We're working on making them faster.

`zebrad` might build and run fine on smaller and slower systems - we haven't
tested its exact limits yet.

For more detailed requirements, refer to the [documentation](https://zebra.zfnd.org/user/requirements.html).

#### Memory Troubleshooting

If Zebra's build runs out of RAM, try setting:
`export CARGO_BUILD_JOBS=2`

If Zebra's tests timeout or run out of RAM, try running:
`cargo test -- --test-threads=2`

(cargo uses all the processor cores on your machine by default.)

#### macOS Test Troubleshooting

Some of Zebra's tests deliberately cause errors that make Zebra panic.
macOS records these panics as crash reports.

If you are seeing "Crash Reporter" dialogs during Zebra tests,
you can disable them using this Terminal.app command:

```sh
defaults write com.apple.CrashReporter DialogType none
```

### Network Ports and Data Usage

By default, Zebra uses the following inbound TCP listener ports:

- 8233 on Mainnet
- 18233 on Testnet

Zebra needs some peers which have a round-trip latency of 2 seconds or less.
If this is a problem for you, please
[open a ticket.](https://github.com/ZcashFoundation/zebra/issues/new/choose)

`zebrad`'s typical mainnet network usage is:

- Initial sync: 100 GB download, we expect the initial download to grow to hundreds of gigabytes over time
- Ongoing updates: 10 MB - 10 GB upload and download per day, depending on user-created transaction size and peer requests

Zebra performs an initial sync every time its internal database version changes,
so some version upgrades might require a full download of the whole chain.

For more detailed information, refer to the [documentation](https://zebra.zfnd.org/user/run.html).

#### Network Troubleshooting

Some of Zebra's tests download Zcash blocks, so they might be unreliable depending on your network connection.
You can set `ZEBRA_SKIP_NETWORK_TESTS=1` to skip the network tests.

Zebra may be unreliable on Testnet, and under less-than-perfect network conditions.
See our [roadmap](#future-work) for details.

### Disk Usage

Zebra uses around 200 GB of space for cached mainnet data, and 10 GB of space for cached testnet data.
We expect disk usage to grow over time, so we recommend reserving at least 300 GB for mainnet nodes.

Zebra's database cleans up outdated data periodically, and when Zebra is shut down and restarted.

#### Disk Troubleshooting

Zebra's state commits changes using RocksDB database transactions.

If you forcibly terminate Zebra, or it panics,
any incomplete changes will be rolled back the next time it starts.

So Zebra's state should always be valid, unless your OS or disk hardware is corrupting data.

## Known Issues

There are a few bugs in Zebra that we're still working on fixing:

- Zebra falsely estimates that it's close to the tip when the network connection goes down [#4649](https://github.com/ZcashFoundation/zebra/issues/4649)

  - One of the consequences of this issue is that Zebra might add unwanted load
    to other peers when the connection goes back up. This load will last only
    for a short period of time because Zebra will quickly find out that it's
    still not close to the tip.

- If Zebra fails downloading the Zcash parameters, use [the Zcash parameters download script](https://github.com/zcash/zcash/blob/master/zcutil/fetch-params.sh) instead. This script might be needed on macOS, even with Rust stable.
- No Windows support [#3801](https://github.com/ZcashFoundation/zebra/issues/3801)
  - We used to test with Windows Server 2019, but not anymore; see issue for details
  
- Experimental Tor support is disabled until [`arti-client` upgrades to `x25519-dalek` 2.0.0 or later](https://github.com/ZcashFoundation/zebra/issues/5492)
  - This happens due to a Rust dependency conflict, which can only be resolved by changing the dependencies of `x25519-dalek`

## Future Work

Performance and Reliability:

- Reliable syncing under poor network conditions
- Additional batch verification
- Performance tuning

Currently, the following features are out of scope:

- Optional Zcash network protocol messages
- Consensus rules removed before Canopy activation (Zebra checkpoints on Canopy activation)

## Documentation

The [Zebra website](https://zebra.zfnd.org/) contains user documentation, such
as how to run or configure Zebra, set up metrics integrations, etc., as well as
developer documentation, such as design documents. We also render [API
documentation](https://doc.zebra.zfnd.org) for the external API of our crates,
as well as [internal documentation](https://doc-internal.zebra.zfnd.org) for
private APIs.

## Security

Zebra has a [responsible disclosure policy](https://github.com/ZcashFoundation/zebra/blob/main/SECURITY.md), which we encourage security researchers to follow.

## License

Zebra is distributed under the terms of both the MIT license
and the Apache License (Version 2.0).

See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT).