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chore(*) document metric name prefixing differences betweeen SDK hosts
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casimiro authored and thibaultcha committed Sep 19, 2024
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# Proxy-Wasm Host Differences

Listed here are noteworthy internal discrepancies (implementation differences)
between ngx_wasm_module and other Proxy-Wasm host implementations.

## Table of Contents

- [Metrics Prefixing](#metrics-prefixing)

## Metrics Prefixing

- Envoy internally prefixes metric names with `wasmcustom.*` and only exposes
this prefix in the output of the `/metrics` endpoint.
- For internal implementation reasons, ngx_wasm_module prefixes metric names
with `pw.[filter_name].*`, where `filter_name` is the name of the filter
that defined the metric. Only the ngx_wasm_module FFI library may expose the
existence of this prefix.

Proxy-Wasm SDK users need not worry as metric names are never exposed through
the SDK in the first place.

[Back to TOC](#table-of-contents)

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