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Add sequence diagram for shim runtime v2

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Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>
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Maksym Pavlenko 2022-10-31 14:22:49 -07:00
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runtime/v2/README.md
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@ -17,6 +17,12 @@ This will be translated by containerd into a binary name for the shim.
`io.containerd.runc.v1` -> `containerd-shim-runc-v1`
Since 1.6 release, it's also possible to specify absolute runtime path:
```bash
> ctr run --runtime /usr/local/bin/containerd-shim-runc-v1
```
containerd keeps the `containerd-shim-*` prefix so that users can `ps aux | grep containerd-shim` to see running shims on their system.
## Shim Authoring
@ -173,6 +179,90 @@ The Runtime v2 supports an async event model. In order for the an upstream calle
| `runtime.TaskExitEventTopic` | MUST (follow `TaskExecStartedEventTopic`) | When an exec (other than the init exec) exits expected or unexpected |
| `runtime.TaskDeleteEventTopic` | SHOULD (follow `TaskExitEventTopic` or `TaskExecAddedEventTopic` if never started) | When an exec is removed from a shim |
### Flow
The following sequence diagram shows the flow of actions when `ctr run` command executed.
```mermaid
sequenceDiagram
participant ctr
participant containerd
participant shim
autonumber
ctr->>containerd: Create container
Note right of containerd: Save container metadata
containerd-->>ctr: Container ID
ctr->>containerd: Create task
%% Start shim
containerd-->shim: Prepare bundle
containerd->>shim: Execute binary: containerd-shim-runc-v1 start
shim->shim: Start TTRPC server
shim-->>containerd: Respond with address: unix://containerd/container.sock
containerd-->>shim: Create TTRPC client
%% Schedule task
Note right of containerd: Schedule new task
containerd->>shim: TaskService.CreateTaskRequest
shim-->>containerd: Task PID
containerd-->>ctr: Task ID
%% Start task
ctr->>containerd: Start task
containerd->>shim: TaskService.StartRequest
shim-->>containerd: OK
%% Wait task
ctr->>containerd: Wait task
containerd->>shim: TaskService.WaitRequest
Note right of shim: Block until task exits
shim-->>containerd: Exit status
containerd-->>ctr: OK
Note over ctr,shim: Other task requests (Kill, Pause, Resume, CloseIO, Exec, etc)
%% Kill signal
opt Kill task
ctr->>containerd: Kill task
containerd->>shim: TaskService.KillRequest
shim-->>containerd: OK
containerd-->>ctr: OK
end
%% Delete task
ctr->>containerd: Task Delete
containerd->>shim: TaskService.DeleteRequest
shim-->>containerd: Exit information
containerd->>shim: TaskService.ShutdownRequest
shim-->>containerd: OK
containerd-->shim: Close client
containerd->>shim: Execute binary: containerd-shim-runc-v1 delete
containerd-->shim: Delete bundle
containerd-->>ctr: Exit code
```
#### Logging
Shims may support pluggable logging via STDIO URIs.