Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.6
Description
If a semi-sync primary has multiple semi-sync slaves, the primary seems to only listen for ACKs on one replica at a time. If the focused slave fails to reply, but another one does reply, the transaction will still time-out and semi-sync will switch off. See the following MTR snippets:
When server_2 delays its ACK (using debug with "+d,simulate_delay_semisync_slave_reply") but server_3 sends its ACK, the transaction times out and semi-sync turns off
--source include/have_debug.inc
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# binlog_format independent
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--source include/have_binlog_format_statement.inc
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--let $rpl_topology= 1->2,1->3
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--source include/rpl_init.inc
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--connection server_1
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set global rpl_semi_sync_master_enabled= 1;
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set global rpl_semi_sync_master_timeout= 500; # a slave will be delayed 800 milliseconds to force the timeout
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--connection server_2
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--source include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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set global debug_dbug="+d,simulate_delay_semisync_slave_reply";
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--source include/start_slave.inc
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--connection server_3
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--source include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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--source include/start_slave.inc
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--connection server_1
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--echo # Ensure semi-sync is working for both connected replicas
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--let $status_var_value= 2
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--let $status_var= rpl_semi_sync_master_clients
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--source include/wait_for_status_var.inc
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--echo #
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--echo # Semi-sync status starts ON
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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--connection server_1
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create table t1 (a int);
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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--connection server_1
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insert into t1 values (1);
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--echo #
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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--echo #
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--echo # Cleanup
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--source include/rpl_end.inc
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--echo # End of test
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And result:
include/rpl_init.inc [topology=1->2,1->3]
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connection server_1;
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set global rpl_semi_sync_master_enabled= 1;
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set global rpl_semi_sync_master_timeout= 500;
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connection server_2;
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include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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set global debug_dbug="+d,simulate_delay_semisync_slave_reply";
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include/start_slave.inc
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connection server_3;
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include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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include/start_slave.inc
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connection server_1;
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# Ensure semi-sync is working for both connected replicas
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#
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# Semi-sync status starts ON
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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Variable_name Value
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Rpl_semi_sync_master_status ON
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connection server_1;
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create table t1 (a int);
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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Variable_name Value
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Rpl_semi_sync_master_status OFF
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connection server_1;
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insert into t1 values (1);
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#
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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Variable_name Value
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Rpl_semi_sync_master_status OFF
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#
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# Cleanup
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include/rpl_end.inc
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# End of test
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But vice-versa, if server_2 ACKS but server_3 times-out, the primary sees the ACK and no timeout occurs
--source include/have_debug.inc
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# binlog_format independent
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--source include/have_binlog_format_statement.inc
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--let $rpl_topology= 1->2,1->3
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--source include/rpl_init.inc
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--connection server_1
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set global rpl_semi_sync_master_enabled= 1;
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set global rpl_semi_sync_master_timeout= 500; # a slave will be delayed 800 milliseconds to force the timeout
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--connection server_2
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--source include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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--source include/start_slave.inc
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--connection server_3
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--source include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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set global debug_dbug="+d,simulate_delay_semisync_slave_reply";
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--source include/start_slave.inc
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--connection server_1
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--echo # Ensure semi-sync is working for both connected replicas
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--let $status_var_value= 2
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--let $status_var= rpl_semi_sync_master_clients
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--source include/wait_for_status_var.inc
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--echo #
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--echo # Semi-sync status starts ON
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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--connection server_1
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create table t1 (a int);
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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--connection server_1
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insert into t1 values (1);
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--echo #
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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--echo #
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--echo # Cleanup
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--source include/rpl_end.inc
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--echo # End of test
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With result:
include/rpl_init.inc [topology=1->2,1->3]
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connection server_1;
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set global rpl_semi_sync_master_enabled= 1;
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set global rpl_semi_sync_master_timeout= 500;
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connection server_2;
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include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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include/start_slave.inc
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connection server_3;
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include/stop_slave.inc
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set global rpl_semi_sync_slave_enabled= 1;
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set global debug_dbug="+d,simulate_delay_semisync_slave_reply";
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include/start_slave.inc
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connection server_1;
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# Ensure semi-sync is working for both connected replicas
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#
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# Semi-sync status starts ON
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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Variable_name Value
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Rpl_semi_sync_master_status ON
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connection server_1;
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create table t1 (a int);
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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Variable_name Value
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Rpl_semi_sync_master_status ON
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connection server_1;
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insert into t1 values (1);
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#
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SHOW STATUS LIKE 'rpl_semi_sync_master_status';
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Variable_name Value
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Rpl_semi_sync_master_status ON
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#
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# Cleanup
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include/rpl_end.inc
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# End of test
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Attachments
Issue Links
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- Closed
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