How to decease bulk queue size?

Elastic Stack Elasticsearch
1

I find some of nodes were running into max bulk queue. But after I stop all my rsyslog/logstash process, the bulk queue size didn't decease. Some other nodes would even increase its bulk queue size!

I try to get hot_threads of such node, got only two lucene segment merge thread. (old indices)

2

Are you sure you are looking at the number of entries in the queue or are
you looking at the number of threads spun up to handle bulk? Have a look
at
http://www.elastic.co/guide/en/elasticsearch/reference/1.x/modules-threadpool.html
for more on these queues.