# `Obscura.Phoenix.ChannelLogger`
[🔗](https://github.com/hfiguera/obscura/blob/v0.2.0/lib/obscura/phoenix/channel_logger.ex#L1)

Privacy-safe logging for Phoenix channel joins and incoming events.

This opt-in telemetry handler replaces the channel portion of Phoenix's
default logger after `config :phoenix, :logger, false` disables it. Raw topics
and event names are never logged. Applications declare safe topic patterns
and event names at startup; unmatched values are rendered as filtered labels.
Oversized topics are filtered before content validation. Join and
incoming-event parameters are omitted by default.

    children = [
      {Obscura.Phoenix.ChannelLogger,
       topic_patterns: ["room:*", "system"],
       events: ["new_message", "typing"]}
    ]

A bounded redacted parameter copy can be enabled independently for joins and
incoming events:

    {Obscura.Phoenix.ChannelLogger,
     topic_patterns: ["room:*"],
     events: ["new_message"],
     join_params: {:redact, entities: [:email, :phone]},
     handle_in_params: {:redact, entities: [:email, :phone]}}

Applications can opt in to include one validated UUID-valued socket assign
as Logger metadata, allowing related channel events to be correlated.
Invalid or missing values are omitted:

    {Obscura.Phoenix.ChannelLogger,
     topic_patterns: ["room:*"],
     events: ["new_message"],
     correlation: {:socket_assign, :chat_id, :uuid}}

This metadata supports log correlation; it does not create spans, propagate
trace context, or provide distributed tracing. Logger-reserved and oversized
assign names, plus names containing high-confidence PII recognized by the
`:fast` profile, are rejected at startup.

Phoenix's join telemetry contains the socket from before `join/3` runs.
Consequently, a correlation assign must already exist before `join/3` to
appear on the join record. An assign added by `join/3` is available to later
handled-event records.

Only the dependency-light `:fast` profile is accepted in this synchronous
path. Parameter text above the fixed 4 KiB realtime analysis budget is logged
as `[FILTERED]` without running PII recognition. Structs and tuple-bearing
terms, including keyword lists, also fail closed without protocol dispatch.
Apart from an explicitly configured correlation assign, the handler never
inspects socket assigns, private application data, identifiers, references,
or callback results.

Configured topic and event labels containing control or directional
formatting codepoints are rejected. Allowed event labels are emitted from
owned startup configuration rather than client-frame binaries.

# `child_spec`

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `start_link`

```elixir
@spec start_link(keyword()) :: GenServer.on_start()
```

Starts the Phoenix channel telemetry handler.

---

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