HTTP Instrumentation

SyntropyLog does not ship a built-in HTTP client or getHttp(). You keep using your own client (e.g. Axios) and add request interceptors that inject the correlation ID from the context manager. That way, outbound requests carry the same correlation ID as your logs.

Overview

• No getHttp() — Use your existing HTTP client.
• Correlation via interceptors — In the request interceptor, set the correlation ID header using getContextManager().getCorrelationId() and getCorrelationIdHeaderName().
• Logging — Log requests/responses yourself with syntropyLog.getLogger() (e.g. LoggerName.axios if you use a central logger config) inside the same context so the correlation ID is included.

Basic pattern: Axios interceptors

After initializing SyntropyLog and once ready has fired, get the context manager and attach an Axios request interceptor so every outbound request gets the correlation ID header.

import axios from 'axios';
import { syntropyLog } from 'syntropylog';

// After syntropyLog is ready:
const contextManager = syntropyLog.getContextManager();
const axiosInstance = axios.create({ baseURL: 'https://api.example.com' });

axiosInstance.interceptors.request.use((config) => {
  const headerName = contextManager.getCorrelationIdHeaderName();
  const correlationId = contextManager.getCorrelationId();
  if (correlationId) {
    config.headers[headerName] = correlationId;
  }
  return config;
});

All requests made with axiosInstance will now include the correlation ID (e.g. x-correlation-id) in the headers. Downstream services can read it and use it in their logs.

Optional: response and error logging

You can add response/error interceptors and log with the same logger so everything stays in the same correlation context. Use debug for successful responses (to avoid noise) and info or error for failures:

const logger = syntropyLog.getLogger('http');

axiosInstance.interceptors.response.use(
  (response) => {
    logger.debug('HTTP response', {
      method: response.config.method,
      url: response.config.url,
      status: response.status,
    });
    return response;
  },
  (error) => {
    logger.error('HTTP request failed', {
      method: error.config?.method,
      url: error.config?.url,
      status: error.response?.status,
      message: error.message,
    });
    return Promise.reject(error);
  }
);

Running each request in its own context

For incoming HTTP (e.g. Express), run each request inside contextManager.run() and optionally set the correlation ID from the incoming header:

const contextManager = syntropyLog.getContextManager();
const headerName = contextManager.getCorrelationIdHeaderName();

app.use((req, res, next) => {
  const incomingId = req.headers[headerName] as string | undefined;
  contextManager.run(async () => {
    if (incomingId) contextManager.setCorrelationId(incomingId);
    // ... set userId, requestId, etc. from req ...
    next();
  });
});

Then the Axios interceptor above will send that same correlation ID (or a new one if none was provided) on outbound calls.

Full runnable example in the repo

The doc above shows the pattern; for a complete runnable app (server + withContext + Axios instance and interceptors), use the examples in the repo:

• 10-basic-http-correlation — Correlation ID in headers and context.
• 11-axios-interceptors — Axios request/response interceptors with SyntropyLog context.

Summary

What you need	How
Correlation on outbound HTTP	Axios (or other) request interceptor that sets contextManager.getCorrelationIdHeaderName() → contextManager.getCorrelationId().
Correlation on incoming HTTP	Run each request in contextManager.run() and optionally set correlation ID from request headers.
Request/response logging	Use syntropyLog.getLogger() in interceptors or in your handlers; no built-in HTTP logger.

No getHttp(), http.instances, or adapters are required in the core library; your HTTP client stays the single source of truth.