S3 output plugin "upload_worker_count" logs

I've realized I don't see the detailed s3 log in console when running logstash for kafka input and s3 output. Also I've configured the S3 output plugin to run with multiple workers, how could I make sure the 5 workers are all running as in /tmp/logstash/ I only see one file being created at a time even after configuring this parameter.

	s3 {
		bucket => "logstash-test-bucket"
		prefix => "logstash_test1/%%{}{+YYYY}/%%{}{+MM}/%%{}{+dd}/%%{}{+HH}"
		server_side_encryption => true
		server_side_encryption_algorithm => "aws:kms"
		size_file => 26214400
		time_file => 5
		codec => "json"
		upload_workers_count => 5
		upload_queue_size => 10
		upload_multipart_threshold => 5242880
		encoding => "gzip"