Enable slow logs not working

Hi, I have referred Elastic search guide for enabling slow logs

PUT /_cluster/settings
"transient" : {
"logger.index.search.slowlog" : "DEBUG",
"logger.index.indexing.slowlog" : "WARN"

PUT /my_index/_settings
"index.search.slowlog.threshold.query.warn" : "10s",
"index.search.slowlog.threshold.fetch.debug": "500ms",
"index.indexing.slowlog.threshold.index.info": "5s"

But all the logs are empty. any pointers , i tried to set the threshold level to ms also, in that case was unable to see the logs

Maybe there is nothing running that slow?
What if you set it all to 0, does it log then?

Did you solve this problem?