Intermittent error - sql: driver does not support non-default isolation level

[derekperkins]

Issue description

We're pushing on average ~5k QPS and we see intermittent spurts of errors when we try to begin a transaction. We've seen this error happen a few hundred thousand times over the last 24 hours. It will appear and then resolve itself typically within an hour if we don't catch it first. It is happening across multiple handlers, and we still have millions of transactions starting within that same hour. We are also able to successfully use other isolation levels most of the time.

It feels like there is either a race condition somewhere or there is another transient error happening that is triggering the wrong error value. I can't reliably reproduce it, but it has been happening for a few weeks on multiple versions of the driver.

The issue began when we started explicitly passing in sql.TxOptions. We mitigated the problem by sending in nil when we're using REPEATABLE READ, since that is the driver default and accounts for > 99% of our transaction volume.

I'm not super familiar with the stdlib <-> driver interaction, but I'm happy to help debug where I can help. Thanks for a great driver!

Example code

tx, err := db.BeginTx(c, &sql.TxOptions{
	Isolation: sql.LevelRepeatableRead,
})

Error log

sql: driver does not support non-default isolation level

Configuration

Driver version (or git SHA):
9181e3a
fade210

Go version: run go version in your console
1.9.2

Server version: E.g. MySQL 5.6, MariaDB 10.0.20
5.7.20

Server OS: E.g. Debian 8.1 (Jessie), Windows 10
Debian 8.9

cc @kardianos @josephbergevin

[kardianos]

This driver needs to implement https://godoc.org/database/sql/driver#ConnBeginTx to support non-default isolation levels.

[derekperkins]

@kardianos That is supported by this library and it works most of the time. This issue is regarding an intermittent error when using the isolation options.

[kardianos]

Can you test with Go1.10? A beta will probably be cut today or tomorrow. Or test from Go master?

I really don't know why or how that could happen intermittently.

[kardianos]

If you can't test Go1.10, you could also just vendor the "database/sql/..." packages and it will override the stdlib packages.

[derekperkins]

Yeah, we can run some tests with the new database/sql code, whether through vendoring or testing the beta release. I'm pretty confident that we also have encountered, golang/go#22976, so we're motivated to get those changes ASAP.

[kardianos]

Hmm, also, do you have a canary running with the race detector on?

[derekperkins]

No, but I could try that and hope that it triggers.

[jmalloc]

I'm getting this error as well, but consistently. It looks like the requisite database/sql/driver.ConnBeginTx() method is only implemented when building with Go 1.8?

[methane]

@jmalloc Of course. BeginTx is new API from Go 1.8.
Consistent error is your setup problem, and not relating to this issue.

[methane]

@derekperkins
By grepping, your error message comes from here.
https://github.com/golang/go/blob/b9dca1b165fad8d8ad8fcd47cfa7bf0d5ae60c63/src/database/sql/ctxutil.go#L113

Would you add this log line before the line?

log.Printf("%T: %+v", ci, ci)

[dcormier]

When I add that logging, I get this:

2018/03/21 12:47:37 *mysql.mysqlConn: &{buf:{buf:[5 0 0 0 25 3 0 0 0 3 100 101 102 20 104 101 114 109 101 115 95 116 101 115 116 95 52 55 100 55 48 97 53 101 2 97 107 8 97 112 105 95 107 101 121 115 2 105 100 2 105 100 12 63 0 11 0 0 0 3 35 66 0 0 0 78 0 0 3 3 100 101 102 20 104 101 114 109 101 115 95 116 101 115 116 95 52 55 100 55 48 97 53 101 2 97 107 8 97 112 105 95 107 101 121 115 13 97 112 105 95 99 108 105 101 110 116 95 105 100 13 97 112 105 95 99 108 105 101 110 116 95 105 100 12 63 0 11 0 0 0 3 41 80 0 0 0 66 0 0 4 3 100 101 102 20 104 101 114 109 101 115 95 116 101 115 116 95 52 55 100 55 48 97 53 101 2 97 107 8 97 112 105 95 107 101 121 115 7 97 112 105 95 107 101 121 7 97 112 105 95 107 101 121 12 45 0 144 0 0 0 253 1 16 0 0 0 74 0 0 5 3 100 101 102 20 104 101 114 109 101 115 95 116 101 115 116 95 52 55 100 55 48 97 53 101 2 97 107 8 97 112 105 95 107 101 121 115 11 100 101 115 99 114 105 112 116 105 111 110 11 100 101 115 99 114 105 112 116 105 111 110 12 45 0 0 8 0 0 253 1 16 0 0 0 72 0 0 6 3 100 101 102 20 104 101 114 109 101 115 95 116 101 115 116 95 52 55 100 55 48 97 53 101 2 97 107 8 97 112 105 95 107 101 121 115 10 99 114 101 97 116 101 100 95 97 116 10 99 114 101 97 116 101 100 95 97 116 12 63 0 23 0 0 0 7 129 4 3 0 0 72 0 0 7 3 100 101 102 20 104 101 114 109 101 115 95 116 101 115 116 95 52 55 100 55 48 97 53 101 2 97 107 8 97 112 105 95 107 101 121 115 10 100 101 108 101 116 101 100 95 97 116 10 100 101 108 101 116 101 100 95 97 116 12 63 0 23 0 0 0 7 128 0 3 0 0 5 0 0 8 254 0 0 1 0 112 0 0 9 0 128 2 0 0 0 2 0 0 0 36 57 50 51 99 48 52 53 49 45 50 100 50 55 45 49 49 101 56 45 57 48 56 98 45 48 50 52 50 97 99 49 50 48 48 48 52 52 84 101 115 116 68 101 108 97 121 68 101 102 101 114 114 101 100 69 109 97 105 108 47 112 97 114 97 108 108 101 108 47 100 101 108 97 121 95 100 101 102 101 114 114 101 100 95 101 109 97 105 108 11 226 7 3 21 16 47 41 112 231 7 0 5 0 0 10 254 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] nc:0xc4202dc110 idx:581 length:0 timeout:0} netConn:0xc4202dc110 affectedRows:1 insertId:2 cfg:0xc4202cc0c0 maxAllowedPacket:4194303 maxWriteSize:4194303 writeTimeout:0 flags:65535 status:1 sequence:1 parseTime:true strict:false}

I should note, in case others encounter this, that this was a package vendored with dep. It grabbed the latest release, v1.3 (commit a0583e0) from December 1, 2016.

I then added a constraint so dep would use master:

[[constraint]]
  name = "github.com/go-sql-driver/mysql"
  branch = "master"

After updating the dependencies, I no longer get sql: driver does not support non-default isolation level while trying to set the isolation level of a transaction with go1.10. Instead I get Error 1568: Transaction characteristics can't be changed while a transaction is in progress, but at least that's progress. I'm working on figuring out what's going on with that.

Perhaps it's time to tag a new release?

[methane]

@dcormier it's not relating this issue, completely.

[wayneashleyberry]

As far as I can tell, switching to the master branch has fixed this for me. So I'd also say it's time for a new release :)

 [[constraint]]
   name = "github.com/go-sql-driver/mysql"
-  version = "1.3.0"
+  branch = "master"

[rcgoodfellow]

I have the same experience as @wayneashleyberry. We first started to notice the error after moving to go 1.10. Changing the dependency to master works, but we would like to be back on a stable version as soon as possible.

Thanks!

[wayneashleyberry]

There's a tracking PR for the next release if anyone's interested.

#809

[derekperkins]

FWIW, we're still experiencing the issue with Go 1.11 and driver version 99ff426. I apologize that I haven't had the time to really dig in and debug it.

[derekperkins]

@methane @kardianos I just deployed a vendored copy of database/sql and am logging at the ctxutil error site. I'll report back if/when I have more information.