The OpenTelemetry project announced its roadmap for its metrics specification. The roadmap includes a stable metrics API/SDK, metrics data model and protocol, and compatibility with Prometheus.
The OpenTelemetry project arose from the merging of two other projects - OpenCensus and OpenTracing - in 2019. The OpenTracing project used to provide APIs and instrumentation for distributed tracing, while the OpenCensus project allowed the same plus metrics collection. Before they merged, both projects had interface implementations and integration support with major monitoring vendors as well as common metrics collection backends. The stated aims of the OpenTelemetry metrics roadmap are to be able to connect metrics to other signals, provide a migration path for OpenCensus users to migrate to OpenTelemetry, and provide compatibility with industry-accepted standards like Prometheus and StatsD. Reiley Yang, one of the project contributors, recently wrote about the roadmap. It’s worth noting that OpenTelemetry reached v1.0 of their specification recently.
The OpenTelemetry specification defines different kinds of "signals" including tracing, metrics, baggage, and logs. The v1.0 specification announced a stable API and a stable SDK for tracing. Co-creator of OpenTelemetry and OpenCensus Morgan McLean had commented last year after the tracing specification reached release candidate status that "we (the project team) will apply the focus that we’ve had on tracing to the metrics specification".
Following up on that, this roadmap announces a plan for a similar goal for the metrics API/SDK, data model, and protocol. A stable set of Metrics APIs is expected to reach feature freeze by the end of September 2021. This work along with support for Prometheus metrics is being done in close collaboration with the Prometheus team.
Together, these efforts reflect the parallel streams for the project’s metrics related work. The group working on Prometheus metrics support has a list of common Prometheus features on their list like service discovery, support for the "up" metric, and labelling incoming samples in the OpenTelemetry Collector. The Collector is "a vendor-agnostic implementation on how to receive, process and export telemetry data". It does this by supporting multiple telemetry data protocols and a "pipeline" approach to receiving, sending, and transforming that data. The Prometheus support is expected to be done by the end of May 2021.
An exporter in this context is a process which is responsible for sending the metrics data to backend systems. Exporters are available for metrics, traces, and logs. As of this writing, the core distribution of the OpenTelemetry collector has metric exporters for OpenCensus, OTLP (gRPC and HTTP), and Prometheus. OTLP is the OpenTelemetry Protocol that describes the protocol for encoding, transport, and delivery of telemetry data between sources, middlemen like collectors, and backends. It is currently in beta. There is an additional repository of collectors with vendor specific exporters.
OpenTelemetry is currently a CNCF sandbox project.