Memcached hangs after "END" when getting stats - memcached

Question

enter code hereI have memcached installed on a Microsoft Azure ubuntu 18.04 server. First we tried installing it in a docker container, but we removed that and installed it using sudo apt-get install memcached libmemcached-tools -y. The configuration is the default one. When I run echo stats | nc 127.0.0.1 11211 it prints out the stats as normal finishing with END, like this
deploy#xyz-api-01:~$ echo stats | nc 127.0.0.1 11211
STAT pid 65896
STAT uptime 6847
STAT time 1584992459
STAT version 1.5.6 Ubuntu
STAT libevent 2.1.8-stable
STAT pointer_size 64
STAT rusage_user 0.597944
STAT rusage_system 0.768785
STAT max_connections 1024
STAT curr_connections 1
STAT total_connections 7
STAT rejected_connections 0
STAT connection_structures 2
STAT reserved_fds 20
STAT cmd_get 1
STAT cmd_set 0
STAT cmd_flush 0
STAT cmd_touch 0
STAT get_hits 0
STAT get_misses 1
STAT get_expired 0
STAT get_flushed 0
STAT delete_misses 0
STAT delete_hits 0
STAT incr_misses 0
STAT incr_hits 0
STAT decr_misses 0
STAT decr_hits 0
STAT cas_misses 0
STAT cas_hits 0
STAT cas_badval 0
STAT touch_hits 0
STAT touch_misses 0
STAT auth_cmds 0
STAT auth_errors 0
STAT bytes_read 64
STAT bytes_written 9509
STAT limit_maxbytes 67108864
STAT accepting_conns 1
STAT listen_disabled_num 0
STAT time_in_listen_disabled_us 0
STAT threads 4
STAT conn_yields 0
STAT hash_power_level 16
STAT hash_bytes 524288
STAT hash_is_expanding 0
STAT slab_reassign_rescues 0
STAT slab_reassign_chunk_rescues 0
STAT slab_reassign_evictions_nomem 0
STAT slab_reassign_inline_reclaim 0
STAT slab_reassign_busy_items 0
STAT slab_reassign_busy_deletes 0
STAT slab_reassign_running 0
STAT slabs_moved 0
STAT lru_crawler_running 0
STAT lru_crawler_starts 3825
STAT lru_maintainer_juggles 6891
STAT malloc_fails 0
STAT log_worker_dropped 0
STAT log_worker_written 0
STAT log_watcher_skipped 0
STAT log_watcher_sent 0
STAT bytes 0
STAT curr_items 0
STAT total_items 0
STAT slab_global_page_pool 0
STAT expired_unfetched 0
STAT evicted_unfetched 0
STAT evicted_active 0
STAT evictions 0
STAT reclaimed 0
STAT crawler_reclaimed 0
STAT crawler_items_checked 0
STAT lrutail_reflocked 0
STAT moves_to_cold 0
STAT moves_to_warm 0
STAT moves_within_lru 0
STAT direct_reclaims 0
STAT lru_bumps_dropped 0
END
At that point it hangs though, as if it was waiting for something, but typing commands doesn't do anything. It sits there until I type CTRL+C. We had exctly the same issue when it was running in a docker container, which is why we tried installing it directly in the server in case it was an issue with the container. Our application which uses memcached also times out when trying to connect to memcached, so I don't think it's just a terminal problem.
Googling has not found any posts about this specific problem, most people who have issues with memcached hanging find that it hangs for a while and then eventually returns. I've never seen this behaviour before, and I can't find anything in configuration or anywhere that would explain this. I'd appreciate if anyone knows of something that might cause this or some configuration that I need to check.

Answer 1

nc essentially connects and listens, and it won't stop listening until you tell it not to. So CTRL+C, or if you want to force it to timeout after a second:
echo stats | nc -w 1 127.0.0.1 11211
There is nothing wrong happening here. It's about how nc works.
https://www.tutorialspoint.com/unix_commands/nc.htm

Answer 2

You need to send an quit command, for example:
printf "stats\nquit\n" | nc 127.0.0.1 11211