MySQL 5.7 Aborted Connection - Got an error reading communication packets

[kyluke]

Issue description

The connection to MySQL should open. However, opening this connection in Golang, results in the error (Got an error reading communication packets). Opening the MySQL connection from the cli works.

Tried:

• Increasing the wait_time
• Increasing the connection_time
• Increasing the max packet size

Example code

func open_mysql(Host *string, Username *string, Password *string, Database *string, parameters string) *sql.DB {
	open, err := sql.Open("mysql", *Username+":"+*Password+"@tcp("+*Host+")/"+*Database+parameters)

	if err != nil {
		log.Printf("%s\n", err)
	}
	return open
}

Error log

[Note] Aborted connection 13086 to db: '<redacted>' user: '<redacted>' host: '<redacted but not localhost, outside network connection>' (Got an error reading communication packets)

Configuration

Driver version (or git SHA):
latest pull from go get -u github.com/go-sql-driver/mysql as of today.

Go version:
go version go1.7.5 darwin/amd64
AND
go version go1.8 darwin/amd64

Server version:
Server version: 5.7.17-0ubuntu0.16.04.1 (Ubuntu)

Server OS:
Ubuntu 16.04.1

[kyluke]

Tested it with go version go1.7.3 darwin/amd64

Still fails.

[methane]

What is "error log"? Is it MySQL server's error log?
If so, would you try increase log verbosity and paste logs before the line?
What log.Printf("%s\n", err) shows?

[kyluke]

[Note] Aborted connection 13086 to db: '<redacted>' user: '<redacted>' host: '<redacted but not localhost, outside network connection>' (Got an error reading communication packets)

Is from /var/log/mysql/error.log
I'll try with a more verbose output.

The curious thing is, log.Printf("%s\n", err) doesn't report any errors.

[methane]

Actually, sql.Open() doesn't create any connection.
sql.Exec("SELECT 1+1") may create connection (and make error).

[kyluke]

I've tried to increase the verbosity of the MySQL logs using

SET GLOBAL log_warnings=3;

and have also tried to print out any errors from the sql query directly using

stmt, queryErr := db.Query(sqlQuery.String())
log.Printf("error: %s\n", queryErr.Error())
log.Printf("stmt error: %s\n", stmt.Err())

But no luck yet. Running the SQL query (which I unfortunately cannot share here) within the mysql cli client, works 100%.

[kyluke]

Any ideas? This has totally broken our binaries. They cannot connect to a MySQL database, whether it's local nor remote.

I've tried different versions of MySQL and different versions of golang (1.7.3 upwards).

I've also built this on a linux machine with a fresh installed copy of github.com/go-sql-driver/mysql with no positive result.

Any pointers that you guys may have to fix this are much appreciated.

[julienschmidt]

Got an error reading communication packets suggests that something went wrong while MySQL was waiting for a packet. You could use Wireshark or tcpdump to further inspect what exactly is going e.g. after which packet it aborts

[methane]

What "but no lock yet" means?
MySQL server doesn't log anything when increased log level?

[kyluke]

@methane switching log level from 2 to 3 didn't yield any more information.

@julienschmidt I'll try that now and see if I can get anywhere with that.

[methane]

I've tried different versions of MySQL and different versions of golang (1.7.3 upwards).

Do you mean same problem happened on MySQL 5.6 too?

Your report lacks detail information about "what you tried and what you got."

Many users uses this with MySQL 5.7. You is the only person reporting issue.
This issue is very likely caused by your environment. Please report more complete information.

[kyluke]

@methane Will do.

[kyluke]

Problem resolved.

I'm not sure how though. Recompiled the code a bunch of times with certain sections commented out. Then pushed versions with specific lines uncommented again until I found the culprit. Unfortunately, I uncommented everything one by one and it ended up working. No changes to the code.

Really annoying. Thank you guys for your input and your help. @julienschmidt your idea to monitor tcpdumps was incredibly useful, thanks.

[faisalburhanudin]

I know this is old issue, but when I search this problem, this issue appear in search result
In my case, the problem appear because I forgot to close connection.

so just don't forget to close your connection db.Close()

[deddu]

I've been having the exact same problem. Code works with mysql 5.6 and fails with 5.7.
Even more curiously, in msyql5.7 a select x,y from points limit 10 works. but with larger limits it fails with the Got an error reading communication packets.
I've attempted changing the mysqld config parameter max_allowed_packet as I expected that to be related but without success.