#tower #batch

tower-fallback

A Tower service combinator that sends requests to a first service, then retries processing on a second fallback service if the first service errors

8 releases

0.2.41-beta.7 Nov 7, 2023
0.2.41-beta.6 Oct 17, 2023
0.2.41-beta.5 Sep 2, 2023
0.2.41-beta.4 Jul 22, 2023
0.0.0-placeholder.0 Apr 18, 2023

#106 in Asynchronous

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176 downloads per month
Used in 4 crates (via zebra-consensus)

MIT/Apache

11KB
197 lines

Zebra logotype


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Contents

About

Zebra is the Zcash Foundation's independent, consensus-compatible implementation of a Zcash node.

Zebra's network stack is interoperable with zcashd, and Zebra implements all the features required to reach Zcash network consensus, including the validation of all the consensus rules for the NU5 network upgrade. Here are some benefits of Zebra.

Zebra validates blocks and transactions, but needs extra software to generate them:

  • To generate transactions, run Zebra with lightwalletd.
  • To generate blocks, use a mining pool or miner with Zebra's mining JSON-RPCs. Currently Zebra can only send mining rewards to a single fixed address. To distribute rewards, use mining software that creates its own distribution transactions, a light wallet or the zcashd wallet.

Please join us on Discord if you'd like to find out more or get involved!

Getting Started

You can run Zebra using our Docker image or you can build it manually. Please see the System Requirements section in the Zebra book for system requirements.

Docker

This command will run our latest release, and sync it to the tip:

docker run zfnd/zebra:latest

For more information, read our Docker documentation.

Building Zebra

Building Zebra requires Rust, libclang, pkg-config, and a C++ compiler.

Zebra is tested with the latest stable Rust version. Earlier versions are not supported or tested. Any Zebra release can start depending on new features in the latest stable Rust.

Every few weeks, we release a new Zebra version.

Below are quick summaries for installing the dependencies on your machine.

General instructions for installing dependencies

  1. Install cargo and rustc.

  2. Install Zebra's build dependencies:

    • libclang is a library that might have different names depending on your package manager. Typical names are libclang, libclang-dev, llvm, or llvm-dev.
    • clang or another C++ compiler: g++ (all platforms) or Xcode (macOS).
    • pkg-config

Dependencies on Arch

sudo pacman -S rust clang pkgconf

Note that the package clang includes libclang as well as the C++ compiler.

Once the dependencies are in place, you can build and install Zebra:

cargo install --locked zebrad

You can start Zebra by

zebrad start

See the Installing Zebra and Running Zebra sections in the book for more details.

Optional Configs & Features

Configuring Progress Bars

Configure tracing.progress_bar in your zebrad.toml to show key metrics in the terminal using progress bars. When progress bars are active, Zebra automatically sends logs to a file.

There is a known issue where progress bar estimates become extremely large.

In future releases, the progress_bar = "summary" config will show a few key metrics, and the "detailed" config will show all available metrics. Please let us know which metrics are important to you!

Configuring Mining

Zebra can be configured for mining by passing a MINER_ADDRESS and port mapping to Docker. See the mining support docs for more details.

Custom Build Features

You can also build Zebra with additional Cargo features:

You can combine multiple features by listing them as parameters of the --features flag:

cargo install --features="<feature1> <feature2> ..." ...

Our full list of experimental and developer features is in the API documentation.

Some debugging and monitoring features are disabled in release builds to increase performance.

Known Issues

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

Future Work

We will continue to add new features as part of future network upgrades, and in response to community feedback.

Documentation

The Zebra website 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. It also renders internal documentation for private APIs on the main branch.

docs.rs renders API documentation for the external API of the latest releases of our crates.

User support

For bug reports please open a bug report ticket in the Zebra repository.

Alternatively by chat, Join the Zcash Foundation Discord Server and find the #zebra-support channel.

Security

Zebra has a responsible disclosure policy, 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 and LICENSE-MIT.

Some Zebra crates are distributed under the MIT license only, because some of their code was originally from MIT-licensed projects. See each crate's directory for details.


lib.rs:

A service combinator that sends requests to a first service, then retries processing on a second fallback service if the first service errors.

Fallback designs have a number of downsides but may be useful in some cases. For instance, when using batch verification, the Fallback wrapper can be used to fall back to individual verification of each item when a batch fails to verify.

TODO: compare with similar code in linkerd.

Dependencies

~1.1–1.7MB
~32K SLoC