MySQL Bugs: #106737: Wrong SE called to ack clone application if >1 SE

Bug #106737	Wrong SE called to ack clone application if >1 SE
Submitted:	15 Mar 2022 11:52	Modified:	20 Apr 2023 7:35
Reporter:	Laurynas Biveinis (OCA)	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Clone Plugin	Severity:	S4 (Feature request)
Version:	8.0.28-8.0.32	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	Clone

Description:
If more than one clone-supporting SE is available, acknowledging clone application will send a remote command to the server with the SE locator with index zero, even if it's an incorrect one.

Part of the stacktrace:

  * frame #0: 0x0000000112412cf1 mysql_clone.so`myclone::Client::remote_command(this=0x0000700006064610, com=COM_ACK, use_aux=true) at clone_client.cc:1155:14
    frame #1: 0x00000001124163ad mysql_clone.so`myclone::Client_Cbk::buffer_cbk(this=0x0000600002634120, from_buffer=0x0000000000000000, buf_len=46) at clone_client.cc:1709:22
    frame #2: 0x00000001025c1572 mysqld`Clone_Handle::ack_state_metadata(this=0x000000011520ee20, task=0x000000011520ef58, callback=0x0000600002634120, state_desc=0x0000700006063ca8) at clone0apply.cc:636:24
    frame #3: 0x00000001025c1378 mysqld`Clone_Handle::apply_state_metadata(this=0x000000011520ee20, task=0x000000011520ef58, callback=0x0000600002634120) at clone0apply.cc:594:11
    frame #4: 0x00000001025c2fb8 mysqld`Clone_Handle::apply(this=0x000000011520ee20, thd=0x000000011504c400, task_id=0, callback=0x0000600002634120) at clone0apply.cc:1059:13
    frame #5: 0x0000000102569547 mysqld`innodb_clone_apply(hton=0x0000000111506800, thd=0x000000011504c400, loc="", loc_len=34, task_id=0, in_err=0, cbk=0x0000600002634120) at clone0api.cc:821:20
    frame #6: 0x0000000112415d39 mysql_clone.so`myclone::Client::set_descriptor(this=0x0000700006064610, buffer="", length=46) at clone_client.cc:1626:9

Suppose that at frame #6, loc_index == 1, and the InnoDB locator is there. But, Client::remote_command (frame #0) will call prepare_command_buffer which will call serialize_ack_cmd, which will use the following loc:

 auto loc = &m_share->m_storage_vec[m_conn_aux.m_cur_index];
 
where m_conn_aux.m_cur_index == 0, as it was never set to anything else in this code path.

How to repeat:
Code analysis due to not having a 2nd clone-supporting SE

Suggested fix:
Client::set_descriptor should have

clone_callback->set_loc_index(loc_index);

before clone_apply call to set m_conn_aux.m_cur_index to the correct value.

Hi Mr. Biveinis,

Thank you for your feature request.

We agree that this is a valid feature request that would improve our server functionality. We also agree that it would not require major rewrite of the existing code.

Verified as a feature request.

This report has been now accepted as a valid feature request.

Bug 106737 fix for 8.0.30 (*) I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it.

Contribution: bug106737.patch (application/octet-stream, text), 1.09 KiB.

Hi Laurynas,

Thank you for your contribution .....

The patch applies to 8.0.31 too, MTR clone suite passes cleanly.

Thank you, Mr. Biveinis,

We checked and you are quite correct.

Applies cleanly on 8.0.32 and does not regress MTR

Thanks a lot, Laurynas.

Applies cleanly on 8.0.33 and does not regress MTR

Again, thanks a lot, Laurynas ........