Patching Workflows

Continuum.patched?/1 is for small, backward-compatible changes that should take effect for new executions without moving old in-flight runs onto a new branch mid-replay.

def run(input) do
  if Continuum.patched?(:add_fraud_check_v2) do
    activity FraudCheck.v2(input)
  else
    activity FraudCheck.v1(input)
  end
end

Inside a workflow, patched?/1 is journaled. The first live execution at that source location writes a patched event with value: true; later replays use the journaled value. Histories recorded before the patch line existed return false without consuming the next old event, so they stay on the old branch.

Outside a workflow process, patched?/1 returns false.

When To Use It

Use patched?/1 when the old and new branches can both remain in the same workflow module until affected runs drain.

Prefer a new workflow version when the shape of the workflow state changes substantially, when you remove or reorder existing effects, or when you cannot keep both branches loaded.

Prefer a normal deploy with no patch marker only when there are no active runs that can replay through the edited code.

Operational Discipline

Patch markers are durable decisions. Once some runs have journaled true and older runs are still taking the false branch, removing either branch is a compatibility decision. Keep the marker and both branches until you know the old histories have completed or been cancelled.

Content-addressed workflow versioning protects runs from being dispatched into the wrong entrypoint, but it does not remove the need to keep code for old patch branches while old histories reference them.

Telemetry

Continuum emits [:continuum, :patched, :hit] with the patch name and value.