what is the best solutions to mysql connection timeout?

问题

I am writing a small web app in Go, which uses mysql to store data.

I got intermittent mysql error if the web sever didn't get any request after some amount of time(> 8 hours):

[mysql] 2017/02/08 16:31:56 packets.go:33: unexpected EOF
[mysql] 2017/02/08 16:31:56 packets.go:130: write tcp 127.0.0.1:49188->127.0.0.1:3306: write: broken pipe

I found some related discussion on github(issue 529, issue 257 and issue 446). From what I understand, mysql db would close the connection if timeout is reached.

I tried to set SetMaxOpenConns to 9 and SetMaxIdleConns to 0 as some people recommended. However, this threw exception immediately. (But if I set SetMaxIdleConns larger than 0, there was no immediate exception thrown)

I also tried to set SetConnMaxLifetime to 5 mins. This threw exception too after 5 mins.

Now I am trying the code below:

db.SetConnMaxLifetime(0)
db.SetMaxOpenConns(10)
db.SetMaxIdleConns(5)

It has been running for 20 mins. It's still too early to tell. (UPDATE: this doesn't work either)

Here is configuration:

• driver: go-sql-driver V1.3.
• go version: go1.7.1 darwin/amd64
• mysql: latest from docker hub
• rkt version: 1.18
• CoreOS: 1284.0.0

回答1:

Perhaps you can start a heartbeat Goroutine to avoid timeout.

回答2:

1. you can check your mysql time_wait variable:

   mysql> show global variables like 'wait_timeout':
   +---------------+-------+
   | Variable_name | Value |
   +---------------+-------+
   | wait_timeout  | 300   |
   +---------------+-------+
   1 row in set (0.00 sec)
   

2. then use db.SetConnMaxLifetime(120*time.Second), which mean when db connection is idle over than 120s, sql.db will reopen or get a new connection from db pool by db.Open. If you not set connection max life time, you maybe use a closed connection and got the error.

3. watching the mysql process list，mysql> show processlist;，if connection sleep over than 300s，it's recycled by mysql:

   mysql> show processlist;
   +-------+-----------------+------------------+-------------+---------+---------+------------------------+------------------+
   | Id    | User            | Host             | db          | Command | Time    | State                  | Info             |
   +-------+-----------------+------------------+-------------+---------+---------+------------------------+------------------+
   |     4 | event_scheduler | localhost        | NULL        | Daemon  | 1363480 | Waiting on empty queue | NULL             |
   | 26539 | root            | 172.17.0.1:48732 | NULL        | Query   |       0 | starting               | show processlist |
   | 26575 | auditcenter     | 172.17.0.1:51714 | obs_gb_test | Sleep   |      51 |                        | NULL             |
   +-------+-----------------+------------------+-------------+---------+---------+------------------------+------------------+
   3 rows in set (0.00 sec)
   

4. SetMaxOpenConns and SetMaxIdleConns is used for setting connection resource, see enter link description here

来源：https://stackoverflow.com/questions/42127441/what-is-the-best-solutions-to-mysql-connection-timeout