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283d7d52c8
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>
42 lines
1.6 KiB
Markdown
42 lines
1.6 KiB
Markdown
# History
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## Kata 1.x architecture
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In the old [Kata 1.x architecture](https://github.com/kata-containers/documentation/blob/master/design/architecture.md),
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the Kata [runtime](README.md#runtime) was an executable called `kata-runtime`.
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The container manager called this executable multiple times when
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creating each container. Each time the runtime was called a different
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OCI command-line verb was provided. This architecture was simple, but
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not well suited to creating VM based containers due to the issue of
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handling state between calls. Additionally, the architecture suffered
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from performance issues related to continually having to spawn new
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instances of the runtime binary, and
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[Kata shim](https://github.com/kata-containers/shim) and
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[Kata proxy](https://github.com/kata-containers/proxy) processes for systems
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that did not provide VSOCK.
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## Kata 2.x architecture
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See the ["shimv2"](README.md#shim-v2-architecture) section of the
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architecture document.
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## Architectural comparison
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| Kata version | Kata Runtime process calls | Kata shim processes | Kata proxy processes (if no VSOCK) |
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| 1.x | multiple per container | 1 per container connection | 1 |
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| 2.x | 1 per VM (hosting any number of containers) | 0 | 0 |
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> **Notes:**
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>
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> - A single VM can host one or more containers.
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>
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> - The "Kata shim processes" column refers to the old
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> [Kata shim](https://github.com/kata-containers/shim) (`kata-shim` binary),
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> *not* the new shimv2 runtime instance (`containerd-shim-kata-v2` binary).
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The diagram below shows how the original architecture was simplified
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with the advent of shimv2.
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