# Kata API Design
To fulfill the [Kata design requirements](kata-design-requirements.md), and based on the discussion on [Virtcontainers API extensions](https://docs.google.com/presentation/d/1dbGrD1h9cpuqAPooiEgtiwWDGCYhVPdatq7owsKHDEQ), the Kata runtime library features the following APIs:
-  Sandbox based top API
-  Storage and network hotplug API
-  Plugin frameworks for external proprietary Kata runtime extensions
-  Built-in shim and proxy types and capabilities

## Sandbox Based API
### Sandbox Management API

|Name|Description|
|---|---|
|`CreateSandbox(SandboxConfig)`| Create and start a sandbox, and return the sandbox structure.|
|`FetchSandbox(ID)`| Connect to an existing sandbox and return the sandbox structure.|
|`ListSandboxes()`| List all existing sandboxes with status. |

### Sandbox Operation API

|Name|Description|
|---|---|
|`sandbox.Pause()`| Pause the sandbox.|
|`sandbox.Resume()`| Resume the paused sandbox.|
|`sandbox.Release()`| Release a sandbox data structure, close connections to the agent, and quit any goroutines associated with the sandbox. Mostly used for daemon restart.|
|`sandbox.Delete()`| Destroy the sandbox and remove all persistent metadata.|
|`sandbox.Status()`| Get the status of the sandbox and containers.|
|`sandbox.Monitor()`| Return a context handler for caller to monitor sandbox callbacks such as error termination.|
|`sandbox.CreateContainer()`| Create new container in the sandbox.|
|`sandbox.DeleteContainer()`| Delete a container from the sandbox.|
|`sandbox.StartContainer()`| Start a container in the sandbox.|
|`sandbox.StatusContainer()`| Get the status of a container in the sandbox.|
|`sandbox.EnterContainer()`| Run a new process in a container.|
|`sandbox.WaitProcess()`| Wait on a process to terminate.|
### Sandbox Hotplug API
|Name|Description|
|---|---|
|`sandbox.AddDevice()`| Add new storage device to the sandbox.|
|`sandbox.AddInterface()`| Add new NIC to the sandbox.|
|`sandbox.RemoveInterface()`| Remove a NIC from the sandbox.|
|`sandbox.ListInterfaces()`| List all NICs and their configurations in the sandbox.|
|`sandbox.UpdateRoutes()`| Update the sandbox route table (e.g. for portmapping support).|
|`sandbox.ListRoutes()`| List the sandbox route table.|

### Sandbox Relay API
|Name|Description|
|---|---|
|`sandbox.WinsizeProcess(containerID, processID, Height, Width)`|Relay TTY resize request to a process.|
|`sandbox.SignalProcess(containerID, processID, signalID, signalALL)`| Relay a signal to a process or all processes in a container.|
|`sandbox.IOStream(containerID, processID)`| Relay a process stdio. Return stdin/stdout/stderr pipes to the process stdin/stdout/stderr streams.|

## Plugin framework for external proprietary Kata runtime extensions
### Hypervisor plugin

TBD.
### Metadata storage plugin
The metadata storage plugin controls where sandbox metadata is saved.
All metadata storage plugins must implement the following API:

|Name|Description|
|---|---|
|`storage.Save(key, value)`| Save a record.|
|`storage.Load(key)`| Load a record.|
|`storage.Delete(key)`| Delete a record.|

Built-in implementations include:
   -  Filesystem storage
   -  LevelDB storage

### VM Factory plugin
The VM factory plugin controls how a sandbox factory creates new VMs.
All VM factory plugins must implement following API:

|Name|Description|
|---|---|
|`VMFactory.NewVM(HypervisorConfig)`|Create a new VM based on `HypervisorConfig`.|

Built-in implementations include:

|Name|Description|
|---|---|
|`CreateNew()`| Create brand new VM based on `HypervisorConfig`.|
|`CreateFromTemplate()`| Create new VM from template.|
|`CreateFromCache()`| Create new VM from VM caches.|

### Sandbox Creation Plugin Workflow
![Sandbox Creation Plugin Workflow](https://raw.githubusercontent.com/bergwolf/raw-contents/master/kata/Kata-sandbox-creation.png "Sandbox Creation Plugin Workflow")

### Sandbox Connection Plugin Workflow
![Sandbox Connection Plugin Workflow](https://raw.githubusercontent.com/bergwolf/raw-contents/master/kata/Sandbox-Connection.png "Sandbox Connection Plugin Workflow")

## Built-in Shim and Proxy Types and Capabilities
### Built-in shim/proxy sandbox configurations
-  Supported shim configurations:

|Name|Description|
|---|---|
|`noopshim`|Do not start any shim process.|
|`ccshim`| Start the cc-shim binary.|
|`katashim`| Start the `kata-shim` binary.|
|`katashimbuiltin`|No standalone shim process but shim functionality APIs are exported.|
-  Supported proxy configurations:

|Name|Description|
|---|---|
|`noopProxy`| a dummy proxy implementation of the proxy interface, only used for testing purpose.|
|`noProxy`|generic implementation for any case where no actual proxy is needed.|
|`ccProxy`|run `ccProxy` to proxy between runtime and agent.|
|`kataProxy`|run `kata-proxy` to translate Yamux connections between runtime and Kata agent. |
|`kataProxyBuiltin`| no standalone proxy process and connect to Kata agent with internal Yamux translation.|

### Built-in Shim Capability
Built-in shim capability is implemented by removing standalone shim process, and
supporting the shim related APIs.

### Built-in Proxy Capability
Built-in proxy capability is achieved by removing standalone proxy process, and
connecting to Kata agent with a custom gRPC dialer that is internal Yamux translation.
The behavior is enabled when proxy is configured as `kataProxyBuiltin`.