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Structured Logging

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Configure Structured JSON Logging

import structlog
from structlog.stdlib import BoundLogger
import logging

## Configure structlog
structlog.configure(
    processors=[
        structlog.contextvars.merge_contextvars,
        structlog.processors.add_log_level,
        structlog.processors.StackInfoRenderer(),
        structlog.dev.set_exc_info,
        structlog.processors.TimeStamper(fmt="iso"),
        structlog.processors.JSONRenderer()
    ],
    wrapper_class=BoundLogger,
    context_class=dict,
    logger_factory=structlog.stdlib.LoggerFactory(),
    cache_logger_on_first_use=True,
)

logger = structlog.get_logger()

## Usage
@app.post("/chat")
async def chat(query: str, user_id: str):
    logger.info(
        "Chat request received",
        user_id=user_id,
        query_length=len(query),
        endpoint="/chat"
    )

    try:
        response = await llm.ainvoke(query)

        logger.info(
            "LLM response generated",
            user_id=user_id,
            model="claude-sonnet-4-5-20250929",
            prompt_tokens=response.usage.prompt_tokens,
            completion_tokens=response.usage.completion_tokens,
            latency_ms=(time.time() - start_time) * 1000
        )

        return response

    except Exception as e:
        logger.error(
            "Chat request failed",
            user_id=user_id,
            error=str(e),
            error_type=type(e).__name__,
            exc_info=True
        )
        raise

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Correlation IDs

Track requests across services: 
from contextvars import ContextVar
import uuid

request_id_var: ContextVar[str] = ContextVar("request_id", default="")

@app.middleware("http")
async def add_correlation_id(request: Request, call_next):
    # Get or create correlation ID
    request_id = request.headers.get("X-Request-ID", str(uuid.uuid4()))
    request_id_var.set(request_id)

    # Add to structlog context
    structlog.contextvars.bind_contextvars(request_id=request_id)

    # Process request
    response = await call_next(request)

    # Add to response headers
    response.headers["X-Request-ID"] = request_id

    return response

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Next Steps

LangSmith Integration

Add LLM-specific observability

Distributed Tracing

Correlate logs with traces

Alerting

Set up log-based alerts

Back to Overview

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