mariadb Error Reading Communication Packets - php

Question

I have a problem. When I split my MariaDB from main server to another server (my database server is running MariaDB docker from latest tag) I got an error:
Got an error writing communication packets
i have 2 server the one is a webserver (no db) the other is a ubuntu 20.04 with 4gig ram and 4 core(2gh per core)
The port is open and my PING is less than 1ms.
I tried with a basic WP site DB and the connection is OK, there was no problem, but my database is about 1GB and I guess this made this problem.
I also try to connect over private network (192.168.100.25) instead of public IP, but the problem is same.
Here is my MariaDB log
Aborted connection 3 to db: 'wpdb' user: 'root' host: 'myip' (Got an error reading communication packets)
Aborted connection 5 to db: 'wpdb' user: 'root' host: 'myip' (Got an error writing communication packets)
I also edited MariaDB config:
increased max_allowed_packet to 1GB
increased net_buffer_length to 1000000
but nothing changes!
here is mariadb variable :
https://pastebin.ubuntu.com/p/yHFRh7CnVC/
SHOW GLOBAL STATUS:
https://pastebin.pl/view/b3db2b91
show process list:
8,root,31.56.66.249:60612,,Query,0,starting,SHOW FULL PROCESSLIST,0
ulimit on server root:
ubuntu#rangoabzar:~$ ulimit -a
ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 15608
max locked memory (kbytes, -l) 65536
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 15608
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
ulimit in docker container:
root#63aa95764534:/# ulimit -a
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 15608
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1048576
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) unlimited
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
iostat
htop

Answer 1

I got this same error by doing a query that returned multiple rows, then processing those rows using rows.Next() (in Golang), and exiting early because of an unrelated error without calling rows.Close(). The confusing part was that it worked the first few times, but eventually failed, indicating some resource (connections?) was being used up.
I was able to take advantage of Golang's defer statement, and just do
defer rows.Close()
before ever calling rows.Next(), but calling rows.Close() before every early exit from the rows.Next() loop works as well.