# Streaming

## Stream JSON Lines

To stream JSON Lines, declare the return type and use `yield` to return the data.

```python
@app.get("/items/stream")
async def stream_items() -> AsyncIterable[Item]:
    for item in items:
        yield item
```

## Server-Sent Events (SSE)

To stream Server-Sent Events, use `response_class=EventSourceResponse` and `yield` items from the endpoint.

     */
    LlmChatResponse chat(LlmChatRequest request);

    /**
     * Performs a streaming chat completion request.
     * The callback is invoked for each chunk of the response.
     *
     * @param request the chat request containing messages and parameters
     * @param callback the callback to receive streaming chunks
     * @throws LlmException if an error occurs during the request
     */

 * governing permissions and limitations under the License.
 */
package org.codelibs.fess.llm;

/**
 * Callback interface for receiving streaming chat responses from LLM.
 */
@FunctionalInterface
public interface LlmStreamCallback {

    /**
     * Called for each chunk of the streaming response.
     *
     * @param chunk the text chunk from the LLM response
     * @param done true if this is the final chunk
     */

"""
Test that async streaming endpoints can be cancelled without hanging.

Ref: https://github.com/fastapi/fastapi/issues/14680
"""

from collections.abc import AsyncIterable

import anyio
import pytest
from fastapi import FastAPI
from fastapi.responses import StreamingResponse

pytestmark = [
    pytest.mark.anyio,
    pytest.mark.filterwarnings("ignore::pytest.PytestUnraisableExceptionWarning"),
]


app = FastAPI()

For more details about the extension, refer to the README on the [GitHub repository](https://github.com/fastapi/fastapi-vscode).

## Setup and Installation { #setup-and-installation }

 * governing permissions and limitations under the License.
 */
package org.codelibs.fess.chat;

/**
 * Callback interface for receiving notifications about chat processing phases.
 * Used for SSE streaming to notify clients about the current processing state.
 */
public interface ChatPhaseCallback {

    /** Phase name for intent detection */
    String PHASE_INTENT = "intent";

     * For files larger than {@value #MAX_BUF_SIZE} bytes (10MB), an
     * {@link IORuntimeException} will be thrown to prevent OutOfMemoryError.
     * For large files, use streaming APIs instead.
     * </p>
     *
     * @param file
     *            The file. Must not be {@literal null}.
     * @return A byte array containing the contents of the file.

SSE is a standard for streaming data from the server to the client over HTTP.

Each event is a small text block with "fields" like `data`, `event`, `id`, and `retry`, separated by blank lines.

It looks like this:

```
data: {"name": "Portal Gun", "price": 999.99}

data: {"name": "Plumbus", "price": 32.99}

```

# Custom Response Classes - File, HTML, Redirect, Streaming, etc.

There are several custom response classes you can use to create an instance and return them directly from your *path operations*.

Read more about it in the [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).

You can import them directly from `fastapi.responses`:

```python
from fastapi.responses import (
    FileResponse,

{* ../../docs_src/stream_data/tutorial001_py310.py ln[26:29] hl[27] *}

### No Annotation { #no-annotation }

You don't really need to declare the return type annotation for streaming binary data.

As FastAPI will not try to convert the data to JSON with Pydantic or serialize it in any way, in this case, the type annotation is only for your editor and tools to use, it won't be used by FastAPI.