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docs: Split history out of arch doc

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Move the historical details out of the architecture doc
and into a separate file.

Partially fixes: #3246.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
This commit is contained in:
James O. D. Hunt 2021-12-15 18:03:55 +00:00
parent 6f9efb4043
commit 283d7d52c8
2 changed files with 45 additions and 36 deletions
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40
docs/design/architecture/README.md
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@ -39,22 +39,10 @@ Kata Containers provides a ["shimv2"](#shim-v2-architecture) compatible runtime.
The Kata Containers runtime is shim v2 ("shimv2") compatible. This
section explains what this means.
### History
In the old [Kata 1.x architecture](https://github.com/kata-containers/documentation/blob/master/design/architecture.md),
the Kata [runtime](#runtime) was an executable called `kata-runtime`.
The container manager called this executable multiple times when
creating each container. Each time the runtime was called a different
OCI command-line verb was provided. This architecture was simple, but
not well suited to creating VM based containers due to the issue of
handling state between calls. Additionally, the architecture suffered
from performance issues related to continually having to spawn new
instances of the runtime binary, and
[Kata shim](https://github.com/kata-containers/shim) and
[Kata proxy](https://github.com/kata-containers/proxy) processes for systems
that did not provide VSOCK.
### An improved architecture
> **Note:**
>
> For a comparison with the Kata 1.x architecture, see
> [the architectural history document](history.md).
The
[containerd runtime shimv2 architecture](https://github.com/containerd/containerd/tree/main/runtime/v2)
@ -86,26 +74,6 @@ launch both Pod and OCI compatible containers with a single
alone `kata-proxy` process is required, even if VSOCK is not
available.
### Architectural comparison
| Kata version | Kata Runtime process calls | Kata shim processes | Kata proxy processes (if no VSOCK) |
|-|-|-|-|
| 1.x | multiple per container | 1 per container connection | 1 |
| 2.x | 1 per VM (hosting any number of containers) | 0 | 0 |
> **Notes:**
>
> - A single VM can host one or more containers.
>
> - The "Kata shim processes" column refers to the old
> [Kata shim](https://github.com/kata-containers/shim) (`kata-shim` binary),
> *not* the new shimv2 runtime instance (`containerd-shim-kata-v2` binary).
The diagram below shows how the original architecture was simplified
with the advent of shimv2.
![Kubernetes integration with shimv2](../arch-images/shimv2.svg)
## Root filesystem
This document uses the term _rootfs_ to refer to a root filesystem

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docs/design/architecture/history.md Normal file
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@ -0,0 +1,41 @@
# History
## Kata 1.x architecture
In the old [Kata 1.x architecture](https://github.com/kata-containers/documentation/blob/master/design/architecture.md),
the Kata [runtime](README.md#runtime) was an executable called `kata-runtime`.
The container manager called this executable multiple times when
creating each container. Each time the runtime was called a different
OCI command-line verb was provided. This architecture was simple, but
not well suited to creating VM based containers due to the issue of
handling state between calls. Additionally, the architecture suffered
from performance issues related to continually having to spawn new
instances of the runtime binary, and
[Kata shim](https://github.com/kata-containers/shim) and
[Kata proxy](https://github.com/kata-containers/proxy) processes for systems
that did not provide VSOCK.
## Kata 2.x architecture
See the ["shimv2"](README.md#shim-v2-architecture) section of the
architecture document.
## Architectural comparison
| Kata version | Kata Runtime process calls | Kata shim processes | Kata proxy processes (if no VSOCK) |
|-|-|-|-|
| 1.x | multiple per container | 1 per container connection | 1 |
| 2.x | 1 per VM (hosting any number of containers) | 0 | 0 |
> **Notes:**
>
> - A single VM can host one or more containers.
>
> - The "Kata shim processes" column refers to the old
> [Kata shim](https://github.com/kata-containers/shim) (`kata-shim` binary),
> *not* the new shimv2 runtime instance (`containerd-shim-kata-v2` binary).
The diagram below shows how the original architecture was simplified
with the advent of shimv2.
![Kubernetes integration with shimv2](../arch-images/shimv2.svg)