Continuum.Snapshot (continuum v0.5.0)

Compacted history prefix for long-running workflows.

A snapshot does not capture a BEAM continuation. Workflow code still runs from the top; the snapshot only replaces an old prefix of raw journal events with compacted steps that validate the requested effect and return the previously journaled result.

Summary

Types

step()

t()

Functions

compact(run_id, version_hash, events, opts \\ [])

Compact a contiguous event list into snapshot steps.

decode(binary)

Decode a stored snapshot payload.

encode(snapshot)

Encode a snapshot for storage.

encoded_size(snapshot)

Return the encoded size in bytes.

format_version()

Current snapshot payload format version.

Types

step()

@type step() :: %{
  effect_type: atom(),
  command_id: term(),
  shape: term(),
  result: term(),
  advance_by: pos_integer()
}

t()

@type t() :: %Continuum.Snapshot{
  run_id: binary(),
  steps_by_seq: %{required(non_neg_integer()) => step()},
  taken_at: DateTime.t(),
  through_seq: non_neg_integer(),
  version_hash: binary()
}

Functions

compact(run_id, version_hash, events, opts \\ [])

@spec compact(binary(), binary(), [map()], keyword()) ::
  {:ok, t()} | {:skip, term()} | {:error, term()}

Compact a contiguous event list into snapshot steps.

Pass :base to extend an existing compatible snapshot. If the event list ends with a pending scheduled/awaited event, the compacted snapshot stops at the last complete step instead of covering the incomplete tail.

decode(binary)

@spec decode(binary()) :: t()

Decode a stored snapshot payload.

encode(snapshot)

@spec encode(t()) :: binary()

Encode a snapshot for storage.

encoded_size(snapshot)

@spec encoded_size(t()) :: non_neg_integer()

Return the encoded size in bytes.

format_version()

@spec format_version() :: pos_integer()

Current snapshot payload format version.