sse-streaming（sse 流媒体）

sse-streaming

Handle SSE streaming implementation, debugging, and reconnection for pplx-sdk.

When to use

Use this skill when implementing, debugging, or extending SSE streaming functionality for the Perplexity API.

Instructions

SSE Protocol Format

The Perplexity API uses standard SSE format:

event: query_progress
data: {"status": "searching", "progress": 0.5}

event: answer_chunk
data: {"text": "partial token", "backend_uuid": "uuid-here"}

event: final_response
data: {"text": "complete answer", "cursor": "cursor-value", "backend_uuid": "uuid-here"}

: [end]

Parsing Rules

1. Read line-by-line from streaming response
2. Skip lines starting with : (comments) — except check for [end] marker
3. Parse event: <type> lines → set current event type
4. Parse data: <json> lines → json.loads() into payload
5. Empty line → emit event (type + accumulated data), reset buffers
6. Stop on [end] marker

Event Types

Stream Lifecycle

for chunk in transport.stream(query="...", context_uuid="..."):
    if chunk.type == "answer_chunk":
        print(chunk.text, end="", flush=True)  # Incremental display
    elif chunk.type == "final_response":
        entry = Entry(...)  # Build complete entry
        break

Reconnection with Cursor

When a stream disconnects, resume using the cursor from the last final_response:

cursor = last_chunk.data.get("cursor")
backend_uuid = last_chunk.backend_uuid

payload["cursor"] = cursor
payload["resume_entry_uuids"] = [backend_uuid]

Retry with Exponential Backoff

from pplx_sdk.shared.retry import RetryConfig

config = RetryConfig(
    max_retries=3,
    initial_backoff_ms=1000,   # 1s, 2s, 4s
    max_backoff_ms=30000,
    backoff_multiplier=2.0,
    jitter=True,               # ±25% randomization
)

Common Pitfalls

• Don't parse non-JSON data lines: Wrap json.loads() in try/except
• Handle empty streams: Raise StreamingError if no events received
• Buffer multi-line data: Some data: fields span multiple lines; accumulate until empty line
• Respect [end] marker: Always check for [end] in comment lines to stop iteration