MySQL Bugs: #85215: Broken connection will be enqueued into the idle pool which may cause problems

Bug #85215	Broken connection will be enqueued into the idle pool which may cause problems
Submitted:	28 Feb 2017 3:25	Modified:	29 Sep 19:19
Reporter:	Yenan Wang	Email Updates:
Status:	Verified	Impact on me:	None
Category:	Connector / NET	Severity:	S2 (Serious)
Version:	6.9.9 and below	OS:	Windows
Assigned to:	Assigned Account	CPU Architecture:	Any
Tags:	broken connection, charset issue

Description:
According to the source code of connector/net,after Driver class created a new connection but before doing the Configuration operation or the operation have not been done completely,for example,the charset have not been set correctly,if an error occured this time(such as network issue,etc),an exception will be catched by the caller and when the caller invoking the Close method to close this broken imcompleted connection,it will be enqueued into the idle pool instead of being destroyed,or if the caller invoking the Dispose method,though it won't be enqueued into the idle pool,may lead to the connection leaking issue.

How to repeat:
Throw an exception manually after Drvier created the driver but before doing Configuration operation to emulate the network issue，a broken connection will be enqueued into the idle pool.

Suggested fix:
Driver creating and configuring should be atom operation like connector/J.

Hello Yenan Wang,

Thank you for the bug report.
Could you please provide repeatable test case(exact steps/sample project, sample connection details etc. - please make it as private if you prefer) to confirm this issue at our end?

Thanks,
Chiranjeevi.

Dummy code to repeat the situation.

Attachment: Program.cs (text/plain), 1.53 KiB.

Modify source code of MySql.Data to emulate the network issue.

Attachment: emulate_network_issue.png (image/png, text), 33.73 KiB.

I uploaded some dummy code to repeat the situation,but have to modify the source code of MySql.Data at first to emulate the network issue which may cause the problem.

Verified.

Posted by developer:
 
The report is valid. The problematic control flow is still present.

- OpenInternal marks the connection as open before driver.Configure(...) runs: [MySqlConnection.cs (line 781)].
- A configuration failure is outside the preceding try/catch, so it propagates while the driver remains attached.
- A caller’s Dispose/Close then calls CloseFully, which returns any open pooled driver to the pool: [MySqlConnection.cs (line 1022)].
- ReleaseConnection only rejects expired/clearing connections; it does not verify that initialization/configuration completed successfully before enqueueing it idle: [MySqlPool.cs (line 330)].

That exactly supports the report’s scenario: a network failure during server-property or charset configuration can leave a partially configured/broken connection in the idle pool, contaminating a later checkout. The async path has the same ordering at [MySqlConnection.cs (line 910)].