Unicode

The Prometheus Java client library allows all Unicode characters, that can be encoded as UTF-8.

At scrape time, some characters are replaced based on the encoding header according to the Escaping scheme.

For example, if you use the underscores escaping scheme, dots in metric and label names are replaced with underscores, so that the metric name http.server.duration becomes http_server_duration.

Prometheus servers that do not support Unicode at all will not pass the encoding header, and the Prometheus Java client library will replace dots, as well as any character that is not in the legacy character set (a-zA-Z0-9_:), with underscores by default.

When escaping=allow-utf-8 is passed, add valid UTF-8 characters to the metric and label names without replacing them. This allows you to use dots in metric and label names, as well as other UTF-8 characters, without any replacements.

When using the Pushgateway, Unicode support has to be enabled explicitly by setting io.prometheus.exporter.pushgateway.escapingScheme to allow-utf-8 in the Pushgateway configuration file - see Pushgateway configuration