升级 Discourse 后出现了一个奇怪的问题。
cd /var/discourse
./launcher enter app
cd /shared/log/rails
tail -f production.log
会一直输出以下内容：
Job exception: MISCONF Redis is configured to save RDB snapshots, but it is currently not able to persist on disk. Commands that may modify the data set are disabled, because this instance is configured to report errors during writes if RDB snapshotting fails (stop-writes-on-bgsave-error option). Please check the Redis logs for details about the RDB error.
Error connecting to Redis on localhost:6379 (Redis::TimeoutError)
unicorn.stderr.log 中充满了：
E, [2022-03-01T20:45:20.703541 #65] ERROR -- : reaped #<Process::Status: pid 30842 exit 1> worker=unknown
Detected dead worker 30842, restarting...
Failed to report error: Error connecting to Redis on localhost:6379 (Redis::TimeoutError) 3 Job exception: Error connecting to Redis on localhost:6379 (Redis::TimeoutError)
MISCONF Redis is configured to save RDB snapshots, but it is currently not able to persist on disk. Commands that may modify the data set are disabled, because this instance is configured to report errors during writes if RDB snapshotting fails (stop-writes-on-bgsave-error option). Please check the Redis logs for details about the RDB error.
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/redis-4.1.3/lib/redis/client.rb:126:in `call'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/redis-4.1.3/lib/redis.rb:538:in `block in del'
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/redis-4.1.3/lib/redis.rb:52:in `block in synchronize'
...
显然，这似乎是 Redis 的问题，我怀疑它被某种方式杀死了，但在 Docker 镜像之外的内核日志中似乎没有显示，然而在 Docker 镜像内部，我看到：
$ df -h
Filesystem Size Used Avail Use% Mounted on
overlay 157G 53G 97G 36% /
tmpfs 64M 0 64M 0% /dev
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
shm 512M 0 512M 0% /dev/shm
/dev/sda 157G 53G 97G 36% /shared
tmpfs 3.9G 0 3.9G 0% /proc/acpi
tmpfs 3.9G 0 3.9G 0% /proc/scsi
tmpfs 3.9G 0 3.9G 0% /sys/firmware
$ free
total used free shared buff/cache available
Mem: 8167420 3248628 794816 8596 4123976 4634504
Swap: 524284 268 524016
看起来不太好，但似乎也不是很糟糕。
回到宿主机系统 htop 显示：
有什么调试/解决此问题的步骤吗？