背景
操作系统是 centos 6，RabbitMQ 3.8.1.
服务器突然无法连接，重启后查看/var/log/messages，报错日志如下：
epmd: erlang mapper daemon cant fork 2‘nd time Cannot allocate memory
epmd: erlang mapper daemon cant fork 2‘nd time Cannot allocate memory
epmd: erlang mapper daemon cant fork 2‘nd time Cannot allocate memory
epmd: erlang mapper daemon cant fork 2‘nd time Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
sshd[1121]: error: fork: Cannot allocate memory
使用locate erl_crash.dump找到崩溃日志 erl_crash.dump，使用 https://github.com/ferd/recon/edit/master/script/erl_crashdump_analyzer.sh 分析结果如下：
analyzing erl_crash.dump, generated on: Wed Apr 22 16:39:10 2020
Slogan: init terminating in do_boot ({error,{cannot_read_enabled_plugins_file,/etc/rabbitmq/enabled_plugins,eacces}})
Memory:
===
processes: 17 Mb
processes_used: 17 Mb
system: 16 Mb
atom: 0 Mb
atom_used: 0 Mb
binary: 0 Mb
code: 6 Mb
ets: 1 Mb
---
total: 34 Mb
Different message queue lengths (5 largest different):
===
89 0
Error logger queue length:
===
0
File descriptors open:
===
UDP: 0
TCP: 2
Files: 0
---
Total: 2
Number of processes:
===
89
Processes Heap+Stack memory sizes (words) used in the VM (5 largest different):
===
1 46422
1 10958
2 6772
2 4185
2 2586
Processes OldHeap memory sizes (words) used in the VM (5 largest different):
===
1 318187
1 75113
1 46422
1 10958
2 2586
Process States when crashing (sum):
===
1 CONNECTED
2 CONNECTED|BINARY_IO
2 CONNECTED|BINARY_IO|PORT_LOCK
1 Current Process Internal ACT_PRIO_NORMAL | USR_PRIO_NORMAL | PRQ_PRIO_NORMAL | ACTIVE | RUNNING | ACTIVE_SYS
1 Current Process Running
1 Internal ACT_PRIO_HIGH | USR_PRIO_HIGH | PRQ_PRIO_HIGH | OFF_HEAP_MSGQ
3 Internal ACT_PRIO_MAX | USR_PRIO_MAX | PRQ_PRIO_MAX
1 Internal ACT_PRIO_MAX | USR_PRIO_MAX | PRQ_PRIO_MAX | OFF_HEAP_MSGQ
1 Internal ACT_PRIO_MAX | USR_PRIO_MAX | PRQ_PRIO_NORMAL
76 Internal ACT_PRIO_NORMAL | USR_PRIO_NORMAL | PRQ_PRIO_NORMAL
1 Internal ACT_PRIO_NORMAL | USR_PRIO_NORMAL | PRQ_PRIO_NORMAL | ACTIVE | RUNNING | ACTIVE_SYS
6 Internal ACT_PRIO_NORMAL | USR_PRIO_NORMAL | PRQ_PRIO_NORMAL | OFF_HEAP_MSGQ
1 Running
88 Waiting
没排查出问题来，这台机器是8c32g的机器，按道理应该不该出现内存不足的问题。
后面开发说RabbitMQ不用了，服务停掉。。。问题消失了。