OpenStack Rust

Welcome to the OpenStack<->Rust project.

As a programming language Rust is getting more and more traction in the low level programming. It has very unique programming safety features what makes it a very good fit in a complex world of OpenStack. As a compiled language it is also a very good fit for the CLI tools allowing users to escape the python dependency issues. In the containerization era placing a small size binary is so much easier.

Current focus of the project is at introducing Rust as a programming language into the ecosystem of OpenStack user facing tooling and provides SDK as well as CLI.

Design principles

After long time maintaining OpenStack client facing tools it became clear that it cannot continue the same way as before. OpenStack services are very different and are not behaving similar to each other. There were multiple attempts to standardize APIs across services, but it didn't worked. Then there were attempts to try to standardize services on the SDK level. This is partially working, but require a very high implementation effort and permanent maintenance. Reverse-engineering service API by looking at the API-REF documentation is very time consuming. A huge issue is also that API-REF is being a human-written document that very often diverges from the code what leads to the issues when covering those resources in SDK/CLI. Tracking the API evolving is another aspect of the maintenance effort.

As a solution a completely different approach has been chosen to reduce maintenance effort while at the same time guaranteeing that API bindings match to what service is supporting in reality. Instead of human reading the API-REF written by another human who maybe was involved in the implementation of the feature OpenAPI specs is being chosen as a source of truth. Since such specs were also not existing and multiple attempts to introduce OpenAPI in OpenStack failed the process was restarted again. Currently there is a lot of work happening in OpenStack to produce specs for majority of the services. Main component responsible for that is codegenerator. Apart of inspecting source code of the selected OpenStack services it is also capable of generating of the tools in this repository.

There is of course a set of the framework code, but the REST API wrapping and commands implementation is fully generated.

At the end of the day it means that there is no need to touch the generated code at all. Once resources available in the OpenAPI spec of the service are being initially integrated into the subprojects here they become maintained by the generator. New features added into the resource by the service would be automatically updated once OpenAPI spec is being updated.

Generating code from the OpenAPI has another logical consequence: generated code is providing the same features as the API itself. So if API is doing thing not very logical the SDK/CLI will do it in the same way. Previously it was always landing on the shoulders of SDK/CLI maintainers to try to cope with it. Now if API is bad - API author is to blame.

• Code being automatically generated from OpenAPI specs of the service APIs.
• Unix philosophy: "do one thing well". Every resource/command coverage tries to focus only on the exact API. Combination of API calls is not in scope of the generated code. "Simple is better then complex" (The Zen of Python).
• SDK/CLI bindings are wrapping the API with no additional guessing or normalization.
• User is in full control of input and output. Microversion X.Y has a concrete body schema and with no faulty merges between different versions.

Components

• openstack_sdk - SDK
• openstack_cli - The new and shiny CLI for OpenStack
• structable_derive - Helper crate for having Output in some way similar to old OpenStackClient
• xtask - Workflow helper
• doc - Project documentation

Trying out

Any software is created to be used.

Install binary

It is possible to install compiled version from the GitHub releases. It comes with a dedicated installer and can be retrieved with the following command:

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/gtema/openstack/releases/latest/download/openstack_cli-installer.sh | sh

Build locally

Alternatively it is possible to compile project from sources. Since the project is a pure Rust it requires having a Rust compile suite.

cargo b

Run

Once the binary is available just start playing with it. If you already have your clouds.yaml config file from python-openstackclient you are free to go:

osc --help
osc --os-cloud devstack compute flavor list

Functional testing

SDK and CLI are coming with a set of basic functional tests.

To trigger functional tests invoke:

OS_CLOUD=devstack cargo t --test functional

Benchmarks

Rust is known to deliver nearly maximum possible performance being only marginally slower compared to C. The table below presents time comparison between python-openstackclient (isolated virtual environment) and osc on the Intel i5-5250 (2 cores) on a reference public cloud (not local devstack) and token caching enabled. Benchmarking is performed using hyperfine tool.

Note: Performance results depend heavily on the time spent waiting for the API response. High amount of long API requests causes smaller performance difference.

Support

The project is a private initiative. If you find it useful or just want to support it please consider GitHub sponsoring. Pull Requests, Issues or other form of support are of course welcome as well.