Names

OpenTelemetry naming conventions are different from Prometheus naming conventions. The mapping from OpenTelemetry metric names to Prometheus metric names is well defined in OpenTelemetry’s Prometheus and OpenMetrics Compatibility spec, and the OpenTelemetryExporter implements that specification.

The goal is, if you set up a pipeline as illustrated below, you will see the same metric names in the Prometheus server as if you had exposed Prometheus metrics directly.

The main steps when converting OpenTelemetry metric names to Prometheus metric names are:

• Escape illegal characters as described in Unicode support
• If the metric has a unit, append the unit to the metric name, like _seconds.
• If the metric type has a suffix, append it, like _total for counters.

OpenTelemetry defines not only a line protocol, but also semantic conventions, i.e. standardized metric and label names. For example, OpenTelemetry’s Semantic Conventions for HTTP Metrics say that if you instrument an HTTP server with OpenTelemetry, you must have a histogram named http.server.duration.

Most names defined in semantic conventions use dots. Dots in metric and label names are now supported in the Prometheus Java client library as described in Unicode support.