how to debug mysql has gone?

Question

I have a virtual machine(Ubuntu 12.04, MySQL 5.5) running under VMware and is dedicated to host a mysql server. I connect to this server on internal IP.

I'm trying to find out why I get mysql server has gone error. One my windows machines apache it stops because of this issue. I have been trying to fine tune my mysql my.cnf with the following parameters but did not bring the desired result.

# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
 bind-address           = 0.0.0.0
#
# * Fine Tuning
#
wait_timeout = 180
key_buffer              = 384M
max_allowed_packet      = 64M
thread_stack            = 192K
thread_cache_size       = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover         = BACKUP
max_connections        = 500
table_cache            = 64
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit       = 1M
query_cache_size        = 32M

how to debug this issue what is missing from configuration to avoid this error?

Answer 1

this is a very generic, annoying error.

you can try to up your timeouts on the mysql server side (not only wait-timeout, but connect-timeout as well).... how long are your queries running when you run them manually on mysql shell? longer than your timeouts? thats a problem.

it could be on the application side, such as, if you are using php, if the code hits max_execution_time [sic], then you may see this error.

also, the mysql variable, max_packet [sic], will cause this error, and commonly occurs on importing mysqldumps.

lastly, if you have iptables rate limiting for tcp/3306 (or whatever mysql is listening on), you may see this as a result of dropped packets.

in short, try upping all limits/timeouts, both and mysql side and application side, one at a time, and repeat until fixed.