# Async Hybrid Streaming Example
This example demonstrates using `allow_sync_streaming_callbacks=True` to enable hybrid streaming mode with AsyncPipeline and legacy sync-only components.
## Overview
This example shows how to use an **AsyncPipeline** with **OpenAIGenerator** (a legacy component that only supports synchronous streaming callbacks) by enabling hybrid mode with `allow_sync_streaming_callbacks=True`.
## The Problem
Some Haystack components like `OpenAIGenerator` only support **synchronous** streaming callbacks and don't have `run_async()` support. When you try to use them with `async_streaming_generator` in an AsyncPipeline, you'll get an error:
```text
ValueError: Component 'llm' of type 'OpenAIGenerator' seems to not support async streaming callbacks
```
## The Solution
Set `allow_sync_streaming_callbacks=True` to enable **hybrid mode**:
```python
async_streaming_generator(
pipeline=self.pipeline,
pipeline_run_args={...},
allow_sync_streaming_callbacks=True # ✅ Enables hybrid mode
)
```
### What Hybrid Mode Does
When `allow_sync_streaming_callbacks=True`, the system automatically detects components with sync-only streaming callbacks (e.g., `OpenAIGenerator`) and enables hybrid mode to bridge them to work in async context. If all components support async, no bridging is applied (pure async mode).
## When to Use This
**Use `allow_sync_streaming_callbacks=True` when:**
- Working with **legacy components** like `OpenAIGenerator` that don't have async equivalents
- Deploying **YAML pipelines** where you don't control which components are used
- **Migrating** from sync to async pipelines gradually
- Using **third-party components** without async support
**For new code, prefer:**
- Using async-compatible components (e.g., `OpenAIChatGenerator` instead of `OpenAIGenerator`)
- Default strict mode (`allow_sync_streaming_callbacks=False`) to ensure proper async components
## Usage
### Deploy with Hayhooks
```bash
# Set your OpenAI API key
export OPENAI_API_KEY=your_api_key_here
# Deploy the pipeline
hayhooks deploy examples/pipeline_wrappers/async_hybrid_streaming
# Test it via OpenAI-compatible API
curl -X POST http://localhost:1416/v1/chat/completions \
-H "Content-Type: application/json" \
-d '{
"model": "async_hybrid_streaming",
"messages": [{"role": "user", "content": "What is machine learning?"}],
"stream": true
}'
```
## Performance
Hybrid mode might have a minimal overhead (~1-2 microseconds per streaming chunk for sync components). This is negligible compared to network latency and LLM generation time.
## Related Documentation
- [Hybrid Streaming Concept](https://deepset-ai.github.io/hayhooks/concepts/pipeline-wrapper/#hybrid-streaming-mixing-async-and-sync-components)
- [Async Operations](https://deepset-ai.github.io/hayhooks/examples/async-operations/)
- [Pipeline Wrapper Guide](https://deepset-ai.github.io/hayhooks/concepts/pipeline-wrapper/)
