Backend correlation

You do not need to follow the steps in this document to use Instana's website monitoring. The steps describe how to improve or enable backend correlation, such as to support backend correlation for older web browsers or to support backend correlation across origins. Most of the backend correlations are automatic. See the following steps to extend the backend correlation coverage. These steps are optional. You can follow them in-order, when you identify a missing backend correlation.

Instana can establish a link between backend and website activity when the backend activity is traced. As a prerequisite of correlation, you need to enable the collection of backend data, also known as tracing. To enable tracing, see Tracing in Instana.

Instana website monitoring script supports the following kinds of backend correlation technology:

• Instana tracing
• W3C trace context

If you want to continue to learn more about the backend correlation process, you must have a good understanding of the concept of origins. The Instana FAQ article explains what you need to know about origins to understand the following steps:

The correlation of XMLHttpRequest and fetch API usages work reliably for all same-origin calls. Due to the same-origin policy and Cross-origin, the automatic HTTP call backend correlation is not possible.

To unlock backend correlation when multiple origins are involved, the cross-origin resource sharing (CORS) is used. CORS is a mechanism that establishes controlled exceptions to the same-origin policy security mechanism. To address the same-origin policy-imposed restrictions, see the following screenshot that describes what is required.

Backend traces and website page loads, that is, the retrieval of the initial HTML files, are automatically backend correlated for web browsers that support Server-Timing. By manually exposing the trace ID of the initial page load to the JavaScript agent, it is possible to enable backend correlation for all web browsers. To enable backend correlation, you need to do the following steps:

1. Retrieve the trace ID on the backend side.
2. Render the trace ID into Instana's JavaScript snippet

// via plain Java Servlet request object (standard API)
// http://docs.oracle.com/javaee/6/api/javax/servlet/ServletRequest.html
servletRequest.getAttribute("X-INSTANA-T")

// via the  $_SERVER superglobal array (standard API)
// http://php.net/manual/en/reserved.variables.server.php
$_SERVER["X-INSTANA-T"]

// via plain Node.js HTTP request objects (standard API)
// https://nodejs.org/api/http.html#http_class_http_incomingmessage
req.headers['x-instana-t']

// via express.js request objects
// https://expressjs.com/en/4x/api.html#req.get
req.get('x-instana-t')

// For ASP.NET WebForms
HttpContext.Current.Items["X-INSTANA-T"]

// For ASP.NET MVC Applications
Context.ApplicationInstance.Context.Items["X-INSTANA-T"]

::Instana.tracer.context &&
  ::Instana::Util.id_to_header(::Instana.tracer.context.trace_id)

# Synchronous (Django, Flask etc..)
from instana.singletons import tracer

from instana.singletons import async_tracer as tracer

tracer.active_span and tracer.active_span.context.trace_id

import instana "github.com/instana/go-sensor"

span := opentracing.StartSpan("MySpanName)
spanContext := span.Context().(instana.SpanContext)
traceId := instana.FormatID(spanContext.TraceID)

<script>
  (function(i,s,o,g,r,a,m){i['InstanaEumObject']=r;i[r]=i[r]||function(){
  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
  })(window,document,'script','https://eum.instana.io/eum.min.js','ineum');

  // API calls as generated by the Instana user interface

  ineum('traceId', '*TraceID*');
</script>

Backend correlation for resources or assets, such as images, JavaScript, and CSS files, is automatic for:

• Web browsers that support Server-Timing.
• Resources or assets that are served from the same origin as the HTML document.

To unlock backend correlation when multiple origins are involved, use the Timing-Allow-Origin response header. This header instructs the timing allow check to expose the data to JavaScript and to the Instana JavaScript agent.

To unlock backend correlation capabilities for the resources that are retrieved from origins different from the origin of the HTML document, see the following screenshot:

If the backend server is OpenTelemetry compatible, you can extend the Instana JavaScript snippet with a call to the ineum('enableW3CHeaders', true); API. If the server embeds the traceparent metadata to the HTML page, the Instana JavaScript agent can parse the content for parent-id and use it as backendTraceId for the pageLoad beacon.

With XMLHttpRequest or fetch call, traceparent and tracestate are generated and added to original HTTP headers. tracestate is used as backendTraceId for the xhr beacon that is sent to the Instana backend.