Reference

SDK Reference.

CheckUpstream SDKs instrument your application to capture outbound HTTP telemetry. They auto-detect calls to supported services and report latency, status codes, and error rates. Two SDKs are GA — Node.js and Browser. Seven more languages are in private beta and ship the same configuration surface.

Quickstart.

Pick the SDK that matches your runtime. Both GA SDKs use the same init({ sdkKey }) shape.

npm install @checkupstream/sdk

import { checkupstream } from "@checkupstream/sdk";

checkupstream.init({
  sdkKey: "cup_sdk_your_key",
});

// Your existing fetch calls are now instrumented
const response = await fetch("https://api.stripe.com/v1/charges");
// → Telemetry event: { host: "api.stripe.com", endpoint: "/v1/charges", status: 200, latency_ms: 142 }

process.on("SIGTERM", async () => {
  await checkupstream.shutdown();
  process.exit(0);
});

Other languages — private beta.

Seven additional SDKs are functionally complete but haven't been validated against production traffic yet. Email us with your stack and we'll reply within one business day with an SDK Key, a setup walkthrough, and direct access to the engineer who wrote the SDK. First three production deployments per language get founder-level support.

• PythonBeta
  Django · FastAPI · Flaskrequests · httpx · urllib3
  Request access→
• GoBeta
  net/http · Gin · Echo · Fiber · Chihttp.Transport wrapper
  Request access→
• RustBeta
  Axum · Actix-web · Rocketreqwest::Client wrapper
  Request access→
• RubyBeta
  Rails · Sinatra · HanamiNet::HTTP
  Request access→
• PHPBeta
  Laravel · Symfony · SlimGuzzle middleware
  Request access→
• JavaBeta
  Spring Boot · Quarkus · Micronautinstrumented HttpClient wrapper
  Request access→
• .NETBeta
  ASP.NET Core · MVC · Minimal APIDelegatingHandler via IHttpClientFactory
  Request access→

Configuration.

All SDKs share the same configuration surface. Field names use the idiomatic casing for each language (e.g. sdkKey in JS, sdk_key in Python, SDKKey in Go).

Telemetry events.

Each intercepted request generates a telemetry event. Events are batched and sent as a TelemetryBatch.

Auto-detected services.

All SDKs automatically recognise outbound requests to these domains. Subdomain matching is supported (e.g. us-east-1.s3.amazonaws.com resolves to AWS S3).

Common patterns.

Restrict to specific services

Pass a services array to track only a subset. Requests to other hosts pass through unchanged.

checkupstream.init({
  sdkKey: "cup_sdk_your_key",
  services: ["stripe", "openai"],
});

Disable in tests

Tie the SDK to your environment so unit tests don't ping the ingest endpoint.

checkupstream.init({
  sdkKey: "cup_sdk_test_key",
  enabled: process.env.NODE_ENV === "production",
});