I was greeted with this error in PHP log where redis is being used.
PHP message: RedisException: MISCONF Redis is configured to save RDB snapshots, but it's currently unable to persist to 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.
Upon checking redis log file, `/var/log/redis/redis-server.log`, I found this warning
WARNING Memory overcommit must be enabled! Without it, a background save or replication may fail under low memory condition. Being disabled, it can can also cause failures without low memory condition, see https://github.com/jemalloc/jemalloc/issues/1328. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
Solution
I did as what it asking me to
Edit /etc/sysctl.conf
$ sudo nano /etc/sysctl.conf
Paste this line at the very end
vm.overcommit_memory = 1
Apply the change
$ sudo sysctl -p