Service never stop

I am using Amazon Linux 2015, Logstash 1.5.1 and this configuration file.

```
input {
zeromq {
address => "tcp://127.0.0.1:8006"
mode => "client"
topology => "pubsub"
}
}
filter {
json {
source => "message"
target => "message"
}
date {
match => ["_timestamp", "UNIX_MS"]
remove_field => ["_timestamp"]
}
mutate {
merge => ["tags", "[_tags]"]
remove_field => "[_tags]"
}
geoip {
source => "[_origin]"
target => "_geoip"
}
useragent {
source => "[_userAgent]"
target => "_parsedUserAgent"
}
}
output {
if [_organization] and [_organization][slug] =~ /.+/ and [_api] and [_api][id] {
elasticsearch {
index => "events-%{[_organization][slug]}-%{[_api][id]}-%{+YYYYMMdd}"
document_type => "events"
template_name => "logstash"
manage_template => false
cluster => "elasticsearch_felipe"
}

if [_clientApplication] and [_clientApplication][id] {
http {
http_method => "put"
url => "http://localhost:9200/events-%{[_organization][slug]}-%{[_api][id]}-%{+YYYYMMdd}/_alias/events-by-client-app-%{[_organization][slug]}-%{[_clientApplication][id]}-%{+YYYYMMdd}"
message => '{ "filter" : { "term" : { "_clientApplication.id" : "%{[_clientApplication][id]}" } } }'
format => "message"
content_type => "application/json"
workers => 2
}

}
}
}
```

When I try to stop logstash service sometimes it never dies and sometimes I have this error
https://github.com/logstash-plugins/logstash-input-zeromq/issues/5