Open source monitoring system Prometheus has hit version 2.27, with the new release providing service discovery and security features, while also giving the tool what every dev’s looking for: a dark mode.

Users are therefore able to switch between the default light UI, a dark one, or an auto setting, which then uses the preferences set in the browser to decide how to present Prometheus. A smaller UI enhancement can also be found in the time range as additional range step sizes of 16 and 26 weeks should give teams a bit more flexibility when checking system behaviour.

Prometheus 2.27 has been fitted with service discovery features for AWS Lightsail and Docker (for scenarios that don’t use Docker Swarm) and allows for use of OAuth 2.0 anywhere an HTTP client is used. A new experimental feature adds exemplar remote write capabilities to the system, though this currently needs explicit activation.

Promtool has meanwhile learned to retroactively evaluate rules, so that new recording rule expressions can be evaluated against old Prometheus data. The result can then be used to create interim dashboards that allow full range querying without too much configuration work until there is new data available. 

Teams working with small Prometheus instances will be happy to learn that v2.27 now allows them to control the maximal chunk size of blocks in the time series database (TSDB) by using the –storage.tsdb.max-block-chunk-segment-size flag. 

Bug fixes that made it into the release include tweaks to have TSDB not panic when very large records are written to the WAL or mmaped memory is referenced after the file is closed. Details are available in the project’s repository.

The Prometheus team recently also updated its blackbox exporter, a tool to probe endpoints, to version 0.19. The new version is the first to include experimental OAuth2 support when probing HTTP and comes with TLS and basic authentication enabled. The exporter now also knows how to decompress HTTP responses which should make it easier to use in certain scenarios, and sports a health endpoint and a metric for unknown probes.

Last week, the Prometheus project announced a Prometheus Conformance Programme to foster interoperability and innovation. It currently offers compliance tests for three components and awaits formal approval by the Cloud Native Computing Foundation’s Governing Board, since Prometheus is part of the foundation’s portfolio.