最近，在实操zipkin,jaeger,opencensus,opentracing,opentelemetry等。
opentelemetry将Observability提到了重要页面，
并进行了讲解，我以为是提纲性的说法了。
=============================
The term observability stems from the discipline of control theory and refers to how well a system can be understood on the basis of the telemetry that it produces.
In software, observability typically refers to telemetry produced by services and is divided into three major verticals:
- Tracing, aka distributed tracing, provides insight into the full lifecycles, aka traces, of requests to the system, allowing you to pinpoint failures and performance issues.
- Metrics provide quantitative information about processes running inside the system, including counters, gauges, and histograms.
- Logging provides insight into application-specific messages emitted by processes.
These verticals are tightly interconnected. Metrics can be used to pinpoint, for example, a subset of misbehaving traces. Logsassociated with those traces could help to find the root cause of this behavior. And then new metrics can be configured, based on this discovery, to catch this issue earlier next time.
OpenTelemetry is an effort to combine all three verticals into a single set of system components and language-specific telemetry libraries. It is meant to replace both the OpenTracing project, which focused exclusively on tracing, and the OpenCensus project, which focused on tracing and metrics.
OpenTelemetry will not initially support logging, though we aim to incorporate this over time.