S3 input plugin

I want to send log of ELB to s3 bucket. ELB logs of different service will be in different directory of my main log bucket. When I tried to put that in my input s3 conf, I am not getting any log
Here is my s3 input conf file:
input {
s3 {
bucket => "production-logs"
region => "us-east-1"
prefix => "elb/"
type => "elb"
sincedb_path => "log_sincedb"

But If I set a name of filepath as prefix then I can view the log in Kibana. (example: elb/production-XXXX/AWSLogs/XXXXXX/elasticloadbalancing/us-east-1/2016/02/24/). But I want to send log from all subdirectory of my bucket

do you have logstash on debug mode (it should show what it is doing on s3)? It could be taking a long time to recursively list all the files from all the directories.