if pushUrls are not provided, data will be persisted by aws-exec and this function will poll until process completion, pulling log data as it is available and invoking logDataCallback, then returning the exit code.

if pushUrls were provided to Exec(), you can use Tail() to follow the output and return the exit code.

reasonably upper bound to write to s3 from 128mb lambda.

s3 keys to pull data from.

s3 presigned put urls.