OpenTracing

Elastic APM RUM agent provides an implementation for the OpenTracing API. The ElasticApmTracer translates OpenTracing API calls to Elastic APM, which allows the reuse of existing instrumentation.

The first span of a service will be converted to an Elastic APM Transaction, and subsequent spans are mapped to Elastic APM Span.

In order to use OpenTracing API with Elastic APM, you need to first create a Tracer:

const { init: initApm, createTracer } = require('@elastic/apm-rum/dist/bundles/elastic-apm-opentracing.umd.js')
const elasticApm = initApm({
    // ...
})
const elasticTracer = createTracer(elasticApm)

At this point you can either use elasticTracer directly, or register it as a global tracer:

const opentracing = require('opentracing-javascript')
opentracing.initGlobalTracer(elasticTracer);

// ...

const tracer = opentracing.globalTracer();

Please refer to opentracing-javascript documentation for more detail on OpenTracing API.

Elastic APM defines some tags which are not included in the OpenTracing specification, but are relevant in the context of Elastic APM.

• type - sets the type of the transaction or span, e.g. "page-load", or "ext.http". If type is not specified, custom would be set instead.

The following tags are relevant only to the root spans, which are translated to Elastic APM transactions. These tags appear in the "User" tab on the transaction details page in the Elastic APM app.

• user.id - sets the user id
• user.email - sets the user email
• user.username - sets the user name

Some of the OpenTracing features are not fully supported by Elastic APM RUM agent.

Currently, the only carrier formats supported are FORMAT_HTTP_HEADERS and FORMAT_TEXT_MAP. FORMAT_BINARY is not supported.

Currently, the Elastic APM Tracer supports REFERENCE_CHILD_OF references. However, only the first REFERENCE_CHILD_OF reference is recorded and the rest are ignored. Other references, e.g. follows_from, are currently not supported.

The Span.setBaggageItem method is not supported. Baggage items are silently dropped.

Only Error logging is supported. Logging an Error on the OpenTracing span will create an Elastic APM Error.