我的 memcached (v1.5.13) 实例出现了问题。它启动正常，但几秒后就无响应了。我使用当前已更新的 arch-linux 机器，尝试从本地主机访问它，因此不存在防火墙/网络问题。
我尝试使用“官方的“工具，这是结果：
$ systemctl start memcached.service
$ ./mc_conn_tester.pl -s localhost -p 11211 -c 1000 --timeout 1
loop: (timeout: 1) (elapsed: 0.00663400) (conn: 0.00418401) (set: 0.00200486) (get: 0.00035810)
loop: (timeout: 1) (elapsed: 0.00163913) (conn: 0.00074816) (set: 0.00039697) (get: 0.00038695)
loop: (timeout: 1) (elapsed: 0.00193477) (conn: 0.00113797) (set: 0.00030398) (get: 0.00041795)
loop: (timeout: 1) (elapsed: 0.00166988) (conn: 0.00101185) (set: 0.00033712) (get: 0.00024605)
loop: (timeout: 1) (elapsed: 0.00124598) (conn: 0.00079703) (set: 0.00018406) (get: 0.00021100)
loop: (timeout: 1) (elapsed: 0.00123787) (conn: 0.00081491) (set: 0.00020504) (get: 0.00016499)
loop: (timeout: 1) (elapsed: 0.00171614) (conn: 0.00114703) (set: 0.00028014) (get: 0.00022793)
loop: (timeout: 1) (elapsed: 0.00115395) (conn: 0.00074410) (set: 0.00015283) (get: 0.00018811)
loop: (timeout: 1) (elapsed: 0.00132918) (conn: 0.00079608) (set: 0.00030398) (get: 0.00016999)
loop: (timeout: 1) (elapsed: 0.00126791) (conn: 0.00082994) (set: 0.00016093) (get: 0.00021601)
loop: (timeout: 1) (elapsed: 0.00120115) (conn: 0.00081515) (set: 0.00015998) (get: 0.00017190)
loop: (timeout: 1) (elapsed: 0.00153708) (conn: 0.00091696) (set: 0.00025797) (get: 0.00027800)
loop: (timeout: 1) (elapsed: 0.00208688) (conn: 0.00102091) (set: 0.00049210) (get: 0.00047183)
loop: (timeout: 1) (elapsed: 0.00124884) (conn: 0.00082898) (set: 0.00017500) (get: 0.00018001)
loop: (timeout: 1) (elapsed: 0.00228310) (conn: 0.00106001) (set: 0.00074816) (get: 0.00034499)
loop: (timeout: 1) (elapsed: 0.00214005) (conn: 0.00116301) (set: 0.00035381) (get: 0.00044703)
loop: (timeout: 1) (elapsed: 0.00207090) (conn: 0.00098491) (set: 0.00034094) (get: 0.00066209)
loop: (timeout: 1) (elapsed: 0.00130296) (conn: 0.00073791) (set: 0.00019097) (get: 0.00029707)
loop: (timeout: 1) (elapsed: 0.00242686) (conn: 0.00132298) (set: 0.00049806) (get: 0.00054789)
loop: (timeout: 1) (elapsed: 0.00280905) (conn: 0.00146294) (set: 0.00038409) (get: 0.00087500)
loop: (timeout: 1) (elapsed: 0.00151491) (conn: 0.00077105) (set: 0.00036383) (get: 0.00027919)
loop: (timeout: 1) (elapsed: 0.00125599) (conn: 0.00063396) (set: 0.00040388) (get: 0.00016403)
loop: (timeout: 1) (elapsed: 0.00157404) (conn: 0.00080013) (set: 0.00019789) (get: 0.00049305)
loop: (timeout: 1) (elapsed: 0.00114512) (conn: 0.00071216) (set: 0.00017500) (get: 0.00020289)
Fail: (timeout: 1) (elapsed: 1.00045800) (conn: 0.00885892) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00032616) (conn: 0.00062394) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00024891) (conn: 0.00064898) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00029612) (conn: 0.00111318) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00028920) (conn: 0.00076103) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00022006) (conn: 0.00080514) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00071883) (conn: 0.00067496) (set: 0.00000000) (get: 0.00000000)
Fail: (timeout: 1) (elapsed: 1.00066304) (conn: 0.00082493) (set: 0.00000000) (get: 0.00000000)
^CAverages: (conn: 0.03975320) (set: 0.00907159) (get: 0.00800204)
这是-vv每个 的输出Loop，此后 s 期间不会显示任何内容Fail。
<28 new auto-negotiating client connection
28: Client using the ascii protocol
<28 set foo 0 0 2
>28 STORED
<28 set foo 0 0 2
>28 STORED
<28 set foo 0 0 2
>28 STORED
<28 get foo
>28 sending key foo
>28 END
<28 get foo
>28 sending key foo
>28 END
<28 get foo
>28 sending key foo
>28 END
<28 get foo
>28 sending key foo
>28 END
<28 get foo
>28 sending key foo
>28 END
<28 get foo
>28 sending key foo
>28 END
<28 connection closed.
同样的情况也发生了memcached-tool，我重新启动后可以正常连接，但只能持续几秒钟：
$ systemctl restart memcached.service
$ memcached-tool 127.0.0.1:11211 stats
#127.0.0.1:11211 Field Value
accepting_conns 1
auth_cmds 0
auth_errors 0
bytes 0
bytes_read 14
bytes_written 1878
cas_badval 0
cas_hits 0
cas_misses 0
cmd_flush 0
cmd_get 0
cmd_set 0
cmd_touch 0
conn_yields 0
connection_structures 3
crawler_items_checked 0
crawler_reclaimed 0
curr_connections 2
curr_items 0
decr_hits 0
decr_misses 0
delete_hits 0
delete_misses 0
direct_reclaims 0
evicted_active 0
evicted_unfetched 0
evictions 0
expired_unfetched 0
get_expired 0
get_flushed 0
get_hits 0
get_misses 0
hash_bytes 524288
hash_is_expanding 0
hash_power_level 16
incr_hits 0
incr_misses 0
libevent 2.1.8-stable
limit_maxbytes 67108864
listen_disabled_num 0
log_watcher_sent 0
log_watcher_skipped 0
log_worker_dropped 0
log_worker_written 0
lru_bumps_dropped 0
lru_crawler_running 0
lru_crawler_starts 255
lru_maintainer_juggles 52
lrutail_reflocked 0
malloc_fails 0
max_connections 1024
moves_to_cold 0
moves_to_warm 0
moves_within_lru 0
pid 921
pointer_size 64
reclaimed 0
rejected_connections 0
reserved_fds 20
rusage_system 0.022412
rusage_user 0.014347
slab_global_page_pool 0
slab_reassign_busy_deletes 0
slab_reassign_busy_items 0
slab_reassign_chunk_rescues 0
slab_reassign_evictions_nomem 0
slab_reassign_inline_reclaim 0
slab_reassign_rescues 0
slab_reassign_running 0
slabs_moved 0
threads 4
time 1558023648
time_in_listen_disabled_us 0
total_connections 4
total_items 0
touch_hits 0
touch_misses 0
uptime 5
version 1.5.13
然后，当我重试时，它只是挂在那里等待：
$ memcached-tool 127.0.0.1:11211 stats
我彻底迷路了。
答案1
遇到了同样的问题。日志没有显示任何有用的信息。
就我而言，问题在于太多打开的客户端连接处于（未关闭）状态，因此无法建立新的连接。在客户端，这通常不会显示或记录（尽管这取决于客户端库）。
memcached-tool停止工作，因为到最后它也只是另一个 TCP 连接，试图获取统计数据。
您可以使用 netstat 检查当前客户端列表，例如：
netstat | grep memcached | grep ESTAB | wc -l
看看这个是否太高（默认最大是 1024 左右？）和/或客户是谁。