OpenCensus

OpenCensus is an open-source framework designed to collect and export telemetry data from cloud-native applications. It provides observational capabilities including distributed tracing and metrics collection, with a unified API across multiple programming languages. Engineers instrument code with spans and metrics, and export data to backends such as Jaeger, Zipkin, Prometheus, Stackdriver, and others. The architecture consisted of an API, a language-specific SDK, and exporters, plus a community-maintained set of libraries for many languages.

OpenCensus began as an effort by Google and other contributors to standardize instrumentation across services and stacks. It aimed to be pluggable and portable, allowing instrumentation to be independent of backend choice and language. The project matured across languages including Go, Java, C++, Python, and JavaScript, among others.

In 2019-2020, OpenCensus merged with OpenTracing to form OpenTelemetry, an Cloud Native Computing Foundation project that continues the work of both systems. OpenCensus components remain in OpenTelemetry as the API surface, SDKs, instrumentations, and exporters, with a focus on unifying traces and metrics under a single framework. OpenCensus is considered a forerunner in modern cloud telemetry and influenced standardization within the broader observability ecosystem.