Newbie, working through https://www.elastic.co/guide/en/logstash/5.6/working-with-plugins.html
The output for bin/logstash-plugin list includes:
logstash-input-beats
logstash-input-couchdb_changes
logstash-input-dead_letter_queue
logstash-input-elasticsearch
logstash-input-exec
logstash-input-file
logstash-input-ganglia
logstash-input-gelf
logstash-input-generator
logstash-input-graphite
logstash-input-heartbeat
logstash-input-http
logstash-input-http_poller
logstash-input-imap
logstash-input-irc
logstash-input-jdbc
logstash-input-kafka
logstash-input-log4j
logstash-input-lumberjack
logstash-input-pipe
logstash-input-rabbitmq
logstash-input-redis
logstash-input-s3
logstash-input-snmptrap
logstash-input-sqs
logstash-input-stdin
logstash-input-syslog
logstash-input-tcp
logstash-input-twitter
logstash-input-udp
logstash-input-unix
logstash-input-xmpp
while the entire output for bin/logstash-plugin list --group input is
logstash-input-beats
logstash-input-couchdb_changes
logstash-input-elasticsearch
logstash-input-exec
logstash-input-file
logstash-input-ganglia
logstash-input-gelf
logstash-input-generator
logstash-input-graphite
logstash-input-heartbeat
logstash-input-http
logstash-input-http_poller
logstash-input-imap
logstash-input-irc
logstash-input-jdbc
logstash-input-log4j
logstash-input-lumberjack
logstash-input-pipe
logstash-input-rabbitmq
logstash-input-redis
logstash-input-s3
logstash-input-snmptrap
logstash-input-sqs
logstash-input-stdin
logstash-input-syslog
logstash-input-tcp
logstash-input-twitter
logstash-input-udp
logstash-input-unix
logstash-input-xmpp
Why are logstash-input-dead_letter_queue and logstash-input-kafka missing from the group-filtered list?