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# Writable Operation

An operation which enables a remote worker to write data to the local worker.

To create the operation, a set of local [`Descriptor`](/dynamo/dev/additional-resources/nixl-connect-api/descriptor) objects must be provided which reference memory intended to receive data from a remote worker.
Once created, the memory referenced by the provided descriptors becomes immediately writable by a remote worker with the necessary metadata.
The NIXL metadata ([RdmaMetadata](/dynamo/dev/additional-resources/nixl-connect-api/rdma-metadata)) required to access the memory referenced by the provided descriptors is accessible via the operations `.metadata()` method.
Once acquired, the metadata needs to be provided to a remote worker via a secondary channel, most likely HTTP or TCP+NATS.

Disposal of the object will instruct the NIXL subsystem to cancel the operation,
therefore the operation should be awaited until completed unless cancellation is intended.
Cancellation is handled asynchronously.


## Example Usage

```python
    async def recv_data(
      self,
      local_tensor: torch.Tensor
    ) -> None:
      descriptor = dynamo.nixl_connect.Descriptor(local_tensor)

      with await self.connector.create_writable(descriptor) as write_op:
        op_metadata = write_op.metadata()

        # Send the metadata to the remote worker via sideband communication.
        await self.request_remote_data(op_metadata)
        # Wait the remote worker to complete its write operation to local_tensor.
        # AKA receive data from remote worker.
        await write_op.wait_for_completion()
```


## Methods

### `metadata`

```python
def metadata(self) -> RdmaMetadata:
```

Generates and returns the NIXL metadata ([RdmaMetadata](/dynamo/dev/additional-resources/nixl-connect-api/rdma-metadata)) required for a remote worker to write to the operation.
Once acquired, the metadata needs to be provided to a remote worker via a secondary channel, most likely HTTP or TCP+NATS.

### `wait_for_completion`

```python
async def wait_for_completion(self) -> None:
```

Blocks the caller until the operation has received a completion signal from a remote worker.


## Properties

### `status`

```python
@property
def status(self) -> OperationStatus:
```

Returns [`OperationStatus`](/dynamo/dev/additional-resources/nixl-connect-api/operation-status) which provides the current state (aka. status) of the operation.


## Related Classes

  - [Connector](/dynamo/dev/additional-resources/nixl-connect-api/connector)
  - [Descriptor](/dynamo/dev/additional-resources/nixl-connect-api/descriptor)
  - [Device](/dynamo/dev/additional-resources/nixl-connect-api/device)
  - [OperationStatus](/dynamo/dev/additional-resources/nixl-connect-api/operation-status)
  - [RdmaMetadata](/dynamo/dev/additional-resources/nixl-connect-api/rdma-metadata)
  - [ReadOperation](/dynamo/dev/additional-resources/nixl-connect-api/read-operation)
  - [ReadableOperation](/dynamo/dev/additional-resources/nixl-connect-api/readable-operation)
  - [WriteOperation](/dynamo/dev/additional-resources/nixl-connect-api/write-operation)