Wait & resume

Some Workflow nodes pause execution until something external happens — a communication event (email opened, link clicked), a human approval in Slack, or a timer expiring. While paused, the Job status is set to WAITING and the full execution state is saved so the run can resume exactly where it left off.

How execution is paused

When a node enters a WAITING state:

1. The execution engine serialises the current execution context into a ResumeWorkflowSnapshot record. The snapshot id is the trackingId propagated through the run.

2. A CommWaitPool record is created to track what the run is waiting for:

   Field	What it records
   internalCorrelationId	Unique identifier linking this wait slot to the expected event
   communicationType	The channel being waited on (e.g. email, WhatsApp)
   event	The specific event to wait for (e.g. email opened, link clicked)
   expiresAt	When the wait times out
   alreadyExecuted	Set to true once the event arrives to prevent duplicate resumes
   trackingId / jobId	Links back to the paused Job
   nodeId / workflowId	The exact node and Workflow to resume

3. The Job's status is updated to WAITING and execution halts. No process or thread is held open while waiting.

How execution resumes

When the awaited event arrives:

1. EzFlow matches the incoming event to the CommWaitPool entry via internalCorrelationId.
2. The CommWaitPool record is marked alreadyExecuted = true to prevent double-resume.
3. The ResumeWorkflowSnapshot is loaded by trackingId.
4. The orchestrator rehydrates the snapshot and continues the DAG from the waiting node, injecting the event result as input.
5. When the run completes, the Job's status is updated to COMPLETED (or a failure status).

Nodes that use wait & resume

WAIT_FOR_EVENT

WAIT_FOR_EVENT pauses until a communication tracking event arrives or a timeout elapses. Configure the event type (e.g. email opened) and a timeout duration. The node outputs result: true when the event arrives in time, or result: false when the timer expires first.

SLACK_APPROVAL

SLACK_APPROVAL posts an Approve / Reject message to a Slack channel and pauses until a team member clicks one of the buttons. When the Workflow resumes it outputs approved (boolean), approvedBy, approvedAt, and status ("approved" or "rejected"). A timeoutMinutes setting caps how long the Workflow waits.

Timeout behaviour

When the expiresAt time on the CommWaitPool record passes without the awaited event arriving, EzFlow resumes the Workflow with the timeout outcome — result: false for WAIT_FOR_EVENT, or the equivalent rejection path for SLACK_APPROVAL.

Related

• WAIT_FOR_EVENT — waits for a communication event or timer
• SLACK_APPROVAL — waits for a human approval in Slack
• Run history — find WAITING Jobs and inspect their state
• Executions & Jobs — overview of Job statuses and the execution lifecycle