A Dataflow job starts, processes a few elements, then fails with errors tied to a specific DoFn in the monitoring UI. What is the most likely cause?

When a Dataflow job starts and processes some elements before failing with errors tied to a specific DoFn, it strongly indicates that the worker code within that DoFn encountered an issue during execution. This usually manifests as an unhandled exception (e.g., NullPointerException, IndexOutOfBoundsException, or a custom application-level error) that causes the worker to crash or report a failure. Job validation errors would typically prevent the job from starting at all. Graph or pipeline construction issues would also likely cause failures before any elements are processed, often during the pipeline submission phase. Insufficient permissions might prevent the job from starting, accessing resources, or writing output, but wouldn't usually manifest as a failure within a specific DoFn after initial processing has begun.