Statistics

    • Downstream: Downstream statistics relate to incoming connections/requests. They are emitted by listeners, the HTTP connection manager, the TCP proxy filter, etc.

    • Server: Server statistics describe how the Envoy server instance is working. Statistics like server uptime or amount of allocated memory are categorized here.

    As of the v2 API, Envoy has the ability to support custom, pluggable sinks. A few standard sink implementations are included in Envoy. Some sinks also support emitting statistics with tags/dimensions.

    Within Envoy and throughout the documentation, statistics are identified by a canonical string representation. The dynamic portions of these strings are stripped to become tags. Users can configure this behavior via .

    Envoy emits three types of values as statistics:

    • Gauges: Unsigned integers that both increase and decrease. E.g., currently active requests.

    Internally, counters and gauges are batched and periodically flushed to improve performance. Histograms are written as they are received. Note: what were previously referred to as timers have become histograms as the only difference between the two representations was the units.