What is Assembly Execution Progress?
Transloadit Assembly Execution Progress estimates an Assembly’s completion in real time for Assemblies that opt in with the emit_execution_progress parameter. Percentages are calculated from the Assembly’s Steps and may describe overall execution or an individual file.
How Assembly Execution Progress works
Execution progress aggregates how far scheduled work has advanced across a graph whose branches may differ greatly in cost. The displayed value is derived from Step and file activity rather than from a simple wall-clock countdown, so it may advance unevenly, and parallel branches can make it appear to pause while a costly operation runs. Progress is not emitted for URL Transform Assemblies. Overall progress summarizes the job, whereas file-level progress can expose a slow or blocked item. Interfaces consume the estimate for feedback while status data remains the authority on completion.
Key facts
- A late transcoding Step can account for much more real time than an earlier metadata Step, so equal percentage increments do not imply equal remaining durations.
- Progress events are emitted only when the Assembly’s parameters set
emit_execution_progressto true, and they are delivered over the realtime connection; polling the Assembly Status document alone will not surface these percentages. - A Step that is still executing reports capped progress (95%) because finishing work such as metadata extraction and result storage remains. Confirm completion only from terminal Assembly status; a failed or canceled branch is not a successful 100%.
When Assembly Execution Progress matters
Enable emit_execution_progress and listen for the progress events on the realtime connection when users need feedback during long processing jobs; the percentages arrive as streamed events rather than as a field in the polled Assembly Status. Treat the percentage as an estimate rather than elapsed time, because Steps can have unequal or unpredictable durations.