# `Sourced.Middleware.Telemetry`
[🔗](https://gitlab.com/dimakula/sourced/-/blob/0.2.0/lib/sourced/middleware/telemetry.ex#L1)

Wraps the pipeline in a `:telemetry.span/3`, one span per operation.

Emits `:start`, `:stop`, and `:exception` events under:

  * `[:sourced, :event_store, :append, _]`
  * `[:sourced, :event_store, :query, _]`
  * `[:sourced, :event_store, :subscribe, _]`
  * `[:sourced, :event_store, :notify, _]`

Start metadata carries `%{store: adapter_module}` plus the operation's inputs — `events`
for appends and notifications, `opts` for queries and subscribes. Stop metadata
adds `:outcome`, the operation's `result` (`{:ok, ...}` or `{:error, reason}`).

A `:notify` span covers delivering one batch of live events to one subscriber,
and is emitted from the adapter's process rather than a caller's.

This middleware normally sits near the top of the stack so its span covers the
work of the middleware below it — a domain middleware placed inside it means the
`:outcome` carries decoded events. See `Sourced.EventStore`.

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*Consult [api-reference.md](api-reference.md) for complete listing*