Krustlet v0.7.0 is mainly an SDK focused release. The biggest under the hood change was the update of our underlying task runtime (Tokio) to its first stable release. There are also a few more small SDK feature adds. We have also switched out the logging implementation so that it can eventually be used to pass tracing data to another service. Lastly, this release marks the official move of the wasmCloud Provider to its own repo! For more details on what isn't implemented yet, see the Known Issues section.

Because this is pre-release software, there are no backwards compatibility guarantees for the Rust API or functionality. However, we will do our best to document any breaking changes in future releases.

Caveats

Please note that this is NOT production-ready software, but it is in a usable state. The WASI standard and wasmtime are still under heavy development, and because of this there are key features (like networking) that are missing; these will appear in the future. However, there is networking support available in the wasmCloud provider.

Notable Features/Changes

• The wasmCloud provider is no longer released with the Krustlet artifacts. Its code and artifacts are now hosted over at https://github.com/wasmCloud/krustlet-wasmcloud-provider to facilitate better collaboration and maintenance with the wasmCloud maintainers.
• Krator now supports admission webhooks
• Logging has been switched to the tracing crate. We will be instrumenting more of our code over the next release
• You can now add pod conditions using the StatusBuilder

Breaking changes

• All Krustlet project crates (oci-distribution, kubelet, and krator) are now using the Tokio 1.X runtime. This means it will be a breaking change for SDK consumers that are using tokio 0.2 or 0.3 in their code

Known Issues/Missing Features

• Kubernetes networking support. See the "What's next?" section for more information
• Unsupported workloads (such as those dropped automatically onto a node like kube-proxy) can enter an error loop. This is more of a nuisance that will cause some logging noise, but not impact the running of Krustlet. If you have any ideas or feedback, please check out #167
• Modifying a bare pod's image is not implemented. Nothing will error, but Krustlet will not restart the "container"
• TLS bootstrapping does not auto-renew certificates when they are close to expiry

What's next?

Our next anticipated version is 1.0.0-alpha.1 (although we will cut a 0.7.1 if necessary). As we move to 1.0 our focus will be on fixing all outstanding bugs and polishing up the CSI support. We also are hoping to streamline the installation and deployment process as much as possible.

After many discussions, we have also decided that CNI and 100% native Kubernetes network support will not be part of the 1.0 release. Networking implementations vary wildly between different Krustlet providers and it would be difficult and unwise to try and define a common abstraction at this time. For example, wasmCloud connects using a system called a "lattice" which can consist of an arbitrary graph of connected hosts. Whereas the CRI provider relies on the CNI spec implementations built in to many Kubernetes distros. However, what we will have is basic host port (and probably node port) support for each of the Wasm based providers. Any provider will be in charge of creating their own networking implementation tailored to the needs of their provider. Our hope is that once we have several different networking examples from various providers, it will be easier to add in a common abstraction at this time. Waiting on that information would only introduce additional delay for releasing Krustlet as an otherwise stable and production-ready (though still bleeding edge) project.

Thanks

We want to express a huge thanks to all of those in the community who contributed to this release. There have been quite a few bug fix contributions from the community that have been very helpful. We appreciate your efforts in making this project a success.

Contributors to 0.7

• @kflansburg
• @itowlson
• @bacongobbler
• @thomastaylor312
• @jiayihu
• @vasu1124
• @matsbror
• @kesselborn
• @lfrancke
• @siegfriedweber
• @yanganto

Installation

Download Krustlet 0.7.0:

• checksum file
• Linux amd64
• MacOS amd64
• Windows 64-bit

Check out our installation docs for information on how to install Krustlet.