Rheo.Event.Lineage (rheo v1.0.0)

Standard metadata keys for event lineage and provenance.

These live in Rheo.Event.metadata (string keys after persistence), not as top-level Event fields.

Key	Meaning
`correlation_id`	Shared id across a saga / request
`causation_id`	Id of the event or command that caused this one
`producer`	Producing service or component
`schema`	Payload schema name
`schema_version`	Schema version (string or number)

Example

iex> meta = Rheo.Event.Lineage.put(%{},
...>   correlation_id: "req-1",
...>   producer: "pricing",
...>   schema: "curve_update",
...>   schema_version: 1
...> )
iex> Rheo.Event.Lineage.get(meta, :correlation_id)
"req-1"

Summary

Functions

get(metadata, key)

Reads a lineage field from an event or metadata map.

keys()

Returns the list of standardized lineage metadata keys.

put(metadata \\ %{}, opts)

Builds a metadata map from lineage options.

Functions

get(metadata, key)

@spec get(Rheo.Event.t() | map(), atom()) :: term() | nil

Reads a lineage field from an event or metadata map.

Accepts atom or string keys on the source map.

Examples

iex> Rheo.Event.Lineage.get(%{"correlation_id" => "c1"}, :correlation_id)
"c1"

iex> event = %Rheo.Event{
...>   id: "e1",
...>   stream: "s",
...>   partition: 0,
...>   sequence: 1,
...>   timestamp: ~U[2026-01-15 12:00:00.000Z],
...>   payload: %{},
...>   metadata: %{producer: "api"}
...> }
iex> Rheo.Event.Lineage.get(event, :producer)
"api"

iex> Rheo.Event.Lineage.get(%{}, :schema)
nil

keys()

@spec keys() :: [atom()]

Returns the list of standardized lineage metadata keys.

Examples

iex> :correlation_id in Rheo.Event.Lineage.keys()
true

put(metadata \\ %{}, opts)

@spec put(map(), keyword()) :: map()

Builds a metadata map from lineage options.

Unknown keys are ignored. Values are kept as-is; backends stringify atom keys on append.

Arguments

metadata — existing map to merge into (default %{})
opts — keyword list; only keys in keys/0 are copied

Examples

iex> Rheo.Event.Lineage.put(correlation_id: "abc", ignored: true)
%{correlation_id: "abc"}

iex> Rheo.Event.Lineage.put(%{"x" => 1}, producer: "risk")
%{"x" => 1, producer: "risk"}