This is the home of the Holochain Rust libraries, being rewritten from Go into Rust, and extended.
Code Status: Rust version is currently Pre-Alpha. Not for production use. The code has not yet undergone a security audit. We expect to destructively restructure code APIs and data chains until Beta. Prototype go version was unveiled at our first hackathon (March 2017), with go version Alpha 0 released October 2017. Alpha 1 was released May 2018. We expect a developer pre-release of this Rust re-write in mid October 2018.
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holochain-rust repository implements a number of distinct yet overlapping aspects of the Holochain framework.
- A library for the core Holochain functionality for defining and running DNA instances: core
- A library and syntax for use in Rust based development of Zomes within DNAs, called Holochain Development Kit: hdk-rust
- A library for managing instances and connecting them to interfaces: container_api
- A Rust based container that uses the container_api: container
- A nodejs based container for running tests: container
- A command line developer tool: hc
- A sample application that we use to demonstrate the current functionality and drive development: app-spec
Let's elaborate on these three aspects.
The core folder contains the code that implements the core functionality of Holochain. It is the aspect that takes in an application DNA, and an agent, and securely runs peer-to-peer applications by exposing the API functions to Zomes. It draws on other top level definitions and functions such as dna, cas_implementations, agent, and core_types.
Holochain applications have been designed to consist at the low-level of WebAssembly (WASM) running in a virtual machine environment. However, most languages will be easiest to use with some stub code to connect into the WASM runtime environment, because of some constraints with WASM. That is the main reason why a "Developer Kit" for a language exists. It is a library, and a syntax, for writing Zome code in that language.
hdk-rust is a solid reference implementation of this, that enables Zomes to be written in the Rust language (the same, somewhat confusingly, as Holochain Core).
Within this repository, some aspects cross over between
hdk-rust, such as core_types, since they get stored into WASM memory in
core, and then loaded from WASM memory, within
hdk-rust. Related, wasm_utils is used on both sides to actually perform the storing, and loading, of values into and from WASM memory.
Other HDKs and language options
Any language that compiles to WASM and can serialize/deserialize JSON data can be available as an option for programmers to write Holochain applications.
We expect many more languages to be added by the community, and there is even an article on how to write a kit for a new language.
These gave us the experience from which we abstracted the container_api crate which specifies and implements a standard way for building containers, including specifying the various interfaces that might be available for executing calls on a particular DNA, i.e. websockets, HTTP, Unix domain sockets, carrier pigeon network, etc...
If you need to implement your own container, container_api should provide you with the needed types and functions to do so easily.
To implement a container in a C based language, the core_api_c_binding [NEEDS UPDATING] code could be used, such as HoloSqape does.
The container crate uses the container_api to implement an executable which is intended to become the main, highly configurable and GUI less container implementation that can be run as a background system service. Currently the Rust Container
The nodejs_container directory implements a node package that creates a container that wraps the Holochain core Rust implementation so we can access it from node. This is crucial especially for creating a test-driven development environment for developing Holochain DNA. The
hc command-line tool relies on it to run tests.
HC Command-line developer tool.
The cmd crate implements our command line developer tool which allows you to create DNA scaffold, run tests, and finally package your DNA for running in a containter. For more details see the crate README.
Documentation: The Book on Holochain
There is a work-in-progress book of documentation being written about
holochain-rust. See the published version at the associated GitHub Pages for this repo, https://developer.holochain.org/guide/latest. See instructions for how to contribute to the book at doc/holochain_101/src/how_to_contribute.md.
Installation & Usage
Important: for installation of the tools with which you can build Holochain applications, you will want to instead proceed to the instructions on the quick start installation guide.
The following instructions are for developing Holochain Core or the HDK itself
There are two approaches to building and testing Holochain, using
make or using
Make (ubuntu and macOS only)
If you are running on ubuntu or macOS, and you have
make installed, you can do local development by simply typing:
make which will:
- install (or update to) the correct version of rust
- build all the rust libraries from the source code in this repository.
- build and install the command-line tools.
We also use docker. The
docker folder contains scripts to build and run docker images.
If you have
nix-shell then feel free to use our
shell.tools.nix are split to mirror the versioning behaviour in the makefile.
Not everything in the Makefile is implemented in nix, and a lot of things don't need to be. Notably the cross-platform and defensive installation of dependencies is not included.
If you have a nix friendly system, this is probably the fastest way to develop and test.
nix-shell shell.core.nix --run "hc-wasm-build && hc-test"
Note that there are also make commands for running the tests of just core, or the command-line line tools or app_spec separately:
make test_cmd make test_holochain make test_app_spec make build_nodejs_container
There is a linter/formatter enforcing code style.
Compilation warnings are NOT OK in shared/production level code.
Warnings have a nasty habit of piling up over time. This makes your code increasingly unpleasant for other people to work with.
CI MUST fail or pass, there is no use in the ever noisier "maybe" status.
If you are facing a warning locally you can try:
- Fixing it
#[allow(***)]inline to surgically override a once-off issue
- Proposing a global
allowfor a specific rule
- this is an extreme action to take
- this should only be considered if it can be shown that:
- the issue is common (e.g. dozens of
- disabling it won't cause issues/mess to pile up elsewhere
- the wider Rust community won't find our codebase harder to work with
- the issue is common (e.g. dozens of
If you don't know the best approach, please ask for help!
It is NOT OK to disable
deny for warnings globally at the CI or makefile/nix level.
You can allow warnings locally during development by setting the
RUSTFLAGS environment variable.
CI configuration changes
Please also be aware that extending/changing the CI configuration can be very time consuming. Seemingly minor changes can have large downstream impact.
Some notable things to watch out for:
- Adding changes that cause the Travis cache to be dropped on every run
- Changing the compiler/lint rules that are shared by many people
- Changing versions of crates/libs that also impact downstream crates/repos
- Changing the nightly version of Rust used
- Adding/removing tools or external libs
The change may not be immediately apparent to you. The change may break the development environment on a different operating system, e.g. Windows.
At the same time, we do not want to catastrophise and stifle innovation or legitimate upgrades.
If you have a proposal to improve our CI config, that is great!
Please open a dedicated branch for the change in isolation so we can discuss the proposal together.
Please broadcast the proposal in chat to maximise visibility and the opportunity for everyone to respond.
It is NOT OK to change the behaviour of tests/CI in otherwise unrelated PRs. SOMETIMES it MAY be OK to change CI in a related PR, e.g. adding a new lib that your code requires. DO expect that a change like this will probably attract additional scrutiny during the PR review process, which is unfortunate but important.
Use your best judgement and respect that other people, across all timezones, rely on this repository remaining a productive working environment 24/7/365.
Updating the CI Environment
The continuous integration (CI) suite executes the same
. docker/run-test command that developers are encouraged to run.
What happens if I need to change that environment? E.g. what if I need a new system library dependency installed?
- Step 1 - Add the dependency to
RUN apt-get update && apt-get install --yes\ # ... snip ... my-new-lib-here
- Step 2 - Build it
- Step 3 - Test it out
- Step 4 - Wait a minute! The CI environment is still using the old Dockerfile!
If your changes do not break the current environment, you can submit a separate Pull Request first, and once it is merged, the CI environment should be up-to-date for your code change Pull Request.
Otherwise, you will need to speak to an admin who can force merge your full changes after testing locally.
Building for Android
Note there is an article written on how to build Holochain for Android, read it here.
Holochain is an open source project. We welcome all sorts of participation and are actively working on increasing surface area to accept it. Please see our contributing guidelines for our general practices and protocols on participating in the community.
App Spec Driven Development
In adding significant changes and new features to Holochain, we follow a specific test-driven development protocol:
- Start by creating a branch in this repository and modifying the example app in the app_spec directory to demonstrates an actual implementation of the use of the new feature, including tests that would pass if the feature were actually implemented.
- Create a pull request on that branch for the development team to talk about and discuss the suggested change. The PR triggers Continuous Integration tests which will initially fail.
- Do any development necessary in core or hdk crates of this repo to actually implement the feature demonstrated in
- Finally, when the feature is fully implemented, the CI tests should turn green and the branch can be merged.
In this way
app_spec works as a living specification with example app to build against.
Some helpful links:
Current Throughput graph:
Copyright (C) 2018, Holochain Trust
This program is free software: you can redistribute it and/or modify it under the terms of the license p rovided in the LICENSE file (GPLv3). This program is distributed in the hope that it will be useful, bu t WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Note: We are considering other 'looser' licensing options (like MIT license) but at this stage are using GPL while we're getting the matter sorted out. See this article for some of our thinking on licensing for distributed application frameworks.