jstverify-tracing

Python distributed tracing SDK for JstVerify application mapping. Auto-instruments your backend to produce trace spans that connect with the JstVerify JavaScript SDK, giving you a full frontend-to-backend service map.

Installation

pip install jstverify-tracing

With framework extras:

pip install jstverify-tracing[flask]
pip install jstverify-tracing[django]
pip install jstverify-tracing[fastapi]

Quick Start

1. Initialize (once at startup)

import jstverify_tracing

jstverify_tracing.init(
    api_key="your-sdk-key",
    service_name="my-backend",
)

The endpoint defaults to the production ingestion URL (https://sdkapi.jstverify.com/v1/tracing/spans). Override for dev environments:

jstverify_tracing.init(
    api_key="your-sdk-key",
    endpoint="https://sdkapi.dev.jstverify.com/v1/tracing/spans",
    service_name="my-backend",
)

2. Add Framework Middleware

Flask:

from jstverify_tracing.integrations.flask import JstVerifyTracingMiddleware
JstVerifyTracingMiddleware(app)

Django (settings.py):

MIDDLEWARE = [
    "jstverify_tracing.integrations.django.JstVerifyTracingMiddleware",
    ...
]

FastAPI:

from jstverify_tracing.integrations.fastapi import JstVerifyTracingMiddleware
app.add_middleware(JstVerifyTracingMiddleware)

AWS Lambda (API Gateway):

from jstverify_tracing.integrations.awslambda import JstVerifyTracingMiddleware

@JstVerifyTracingMiddleware
def lambda_handler(event, context):
    return {"statusCode": 200, "body": "ok"}

Flask / Django on AWS Lambda (via apig_wsgi, Mangum, etc.):

When running a framework app on Lambda, use the framework middleware above for tracing — but you must also call jstverify_tracing.flush() at the end of each invocation. The framework middleware buffers spans for a background flush thread, but Lambda freezes the process between invocations so that thread never runs.

# handler.py (Flask + apig_wsgi example)
from apig_wsgi import make_lambda_handler
from app import app
import jstverify_tracing

_apig_handler = make_lambda_handler(app)

def handler(event, context):
    try:
        return _apig_handler(event, context)
    finally:
        jstverify_tracing.flush()

# handler.py (Django + Mangum example)
from mangum import Mangum
from myapp.asgi import application
import jstverify_tracing

_mangum_handler = Mangum(application, lifespan="off")

def handler(event, context):
    try:
        return _mangum_handler(event, context)
    finally:
        jstverify_tracing.flush()

Note: The @JstVerifyTracingMiddleware Lambda decorator (below) handles flushing automatically — this manual flush is only needed when using framework middleware on Lambda.

AWS AppSync Lambda Resolver:

from jstverify_tracing.integrations.appsync import JstVerifyAppSyncMiddleware

@JstVerifyAppSyncMiddleware
def handler(event, context):
    return [{"id": "1", "name": "Alice"}]

The AppSync middleware extracts trace context from event["request"]["headers"] and derives the operation name from event["info"]["parentTypeName"] and event["info"]["fieldName"] (e.g. Query.listUsers). Only direct transport mode is supported — relay mode is not available for AppSync since GraphQL responses cannot carry custom HTTP headers.

3. Manual Instrumentation (optional)

from jstverify_tracing import trace, trace_span

@trace("process-payment")
def process_payment(order_id):
    ...

def handle_order(order_id):
    with trace_span("validate-order") as span:
        ...
        span.set_status(200)
    with trace_span("charge-card") as span:
        ...
        span.set_http_metadata(method="POST", url="/payments/charge", status_code=201)

4. Custom Attributes

Attach custom key-value metadata to any span. Values are coerced to strings.

Via @trace decorator:

@trace("process-payment", attributes={"env": "prod", "retries": 3})
def process_payment(order_id):
    ...

Via SpanHandle.set_attribute():

with trace_span("validate-order") as span:
    span.set_attribute("orderId", order_id)
    span.set_attribute("itemCount", len(items))
    ...

When both options and handle set the same key, the handle value wins.

5. DynamoDB Tracing

The patch_requests=True option only patches the requests HTTP library. AWS SDK calls via boto3 use urllib3 directly, so DynamoDB, S3, and SQS operations are not auto-traced.

Use the trace_dynamodb() helper to wrap individual DynamoDB operations:

from jstverify_tracing import trace_dynamodb

# Instead of: table.get_item(Key={"UserID": "123"})
result = trace_dynamodb("GetItem", table, Key={"UserID": "123"})

# Works with any DynamoDB operation
result = trace_dynamodb("Query", table, KeyConditionExpression="pk = :pk",
                        ExpressionAttributeValues={":pk": org_id})
result = trace_dynamodb("PutItem", table, Item={"UserID": "456", "name": "Alice"})

Each call creates a child span with the operation name (e.g. DynamoDB.GetItem) and the table name in metadata.

6. Shutdown

jstverify_tracing.shutdown()

Shutdown is also registered via atexit automatically.

Configuration Options

How It Works

Direct Mode (default)

1. The middleware reads X-JstVerify-Trace-Id and X-JstVerify-Parent-Span-Id headers from incoming requests (injected by the JS SDK).
2. A root span is created for each request, with nested child spans for @trace decorated functions and trace_span context managers.
3. Outgoing requests library calls are automatically instrumented — trace headers are injected so downstream services can continue the trace.
4. Spans are buffered in a thread-safe queue and flushed to the JstVerify API in batches by a background daemon thread.

Relay Mode

For backends without outbound internet access (private VPC, strict firewalls), relay mode encodes spans into the X-JstVerify-Spans response header. The JstVerify JS SDK reads this header and relays the spans to the ingestion API on behalf of the backend.

jstverify_tracing.init(
    api_key="your-sdk-key",
    service_name="my-backend",
    transport="relay",  # No endpoint needed
)

How it works:

1. Each request collects spans in a per-request buffer (async-safe via contextvars).
2. When the response is sent, all spans are base64url-encoded into the X-JstVerify-Spans header.
3. The JS SDK decodes the header and merges the spans into its own flush queue.

Limitations:

• ~20-30 spans per response max due to the 7500-byte header size limit.
• Only works for request-response flows — async background jobs have no response to carry spans.
• Cross-origin requests require the Access-Control-Expose-Headers header (set automatically by the middleware).

License

MIT