Re: second version of proposed patch for delayed replication (Bug#28760)

Hi Kay.

What's the master_delay global variable for? Here's how I see it used, with "grep".

+uint32 master_delay= 0;
+  mi->delay= master_delay;
+  /* added value of master_delay */
+          init_intvar_from_file(&delay, &mi->file, master_delay))
+extern uint32 master_delay;

Perhaps it's the first step in something you're planning to submit?

Since the patch came with no test, I took the time to create one. Here's my first try of a test file.

I welcome ideas for new tests or implementations of the ideas at the end. I want to prove that there are no bugs or unexpected behavior in adding this feature. Help!

> source include/master-slave.inc;
> disable_warnings;
> sync_slave_with_master;
> reset master;
> enable_warnings;
>
>
> ##
> #
> # First test: Create a table, delay the slave, insert into the
> master, and die
> # if the slave presents that data before the delay has elapsed.
> #
> ##
>
> # This is an arbitrary value. Smaller means that the test could
> yeild false
> # passing results. Larger means unnecessary delay in the tests.
> let $delay=5;
> ###
>
> # Create work table
> connection master;
> drop table if exists delay_test;
> create table delay_test ( c1 int );
> select count(*) as c from delay_test;
> insert into delay_test values (1);
>
> # Wait until the table is replicated. (Just being paranoid.)
> connection slave;
> let $t = 0;
> let $time_remaining = 60;
>
> disable_result_log;
> error 0,ER_NO_SUCH_TABLE;
> select count(*) as c from delay_test;
> enable_result_log;
> while ($mysql_errno == 1146)
> {
> if (!$time_remaining)
> {
> echo $t, $time_remaining;
> exit;
> die "Table DDL replication took more than a minute! $i";
> }
>
> sleep 1;
> inc $t;
> dec $time_remaining;
>
> disable_result_log;
> error 0,ER_NO_SUCH_TABLE;
> select count(*) as c from delay_test;
> enable_result_log;
> }
> delete from delay_test;
>
> # While we're connected to the slave, verify that we can't change
> the value
> # without shutting it down.
> error ER_SLAVE_MUST_STOP;
> eval change master to master_delay=$delay;
>
> # Actually change the delay value.
> stop slave;
> eval change master to master_delay=$delay;
> start slave;
>
> # Insert values into the master.
> connection master;
> delete from delay_test;
> insert into delay_test values (1);
> insert into delay_test values (2);
> insert into delay_test values (3);
> insert into delay_test values (4);
>
> connection slave;
> let $elapsed = 0;
> let $row_count = 0;
> let $time_remaining = 60;
>
> # Assert that there is nothing in the table yet.
> select c1 from delay_test order by c1;
>
> # Time how long it takes to arrive in the table.
> while (!$row_count)
> {
> sleep 1;
> let $row_count = query_get_value("select count(*) as c from
> delay_test", c, 1);
> inc $elapsed;
> dec $time_remaining;
>
> if (!$time_remaining)
> {
> echo $row_count, $t, $time_remaining;
> exit;
> die "Replication delay test got out of hand. Aborting.";
> }
> }
> select c1 from delay_test order by c1;
>
> # If the elapsed time is shorter than the delay, then the delay
> didn't work.
> if (`select $elapsed < $delay`)
> {
> echo $row_count, $t, $time_remaining;
> echo "Failed! Statement showed up on master before delay had
> elapsed.";
> }
>
> # Clean up.
> stop slave;
> connection slave;
> eval change master to master_delay=0;
> start slave;
> connection master;
> drop table delay_test;
>
> ##
>
>
> # Other tests that may be a good idea: Prove that one can:
> # - Delay, stop the master, after delay elapsed start the master.
> # - Delay, reduce the delay.
> # - Delay, increase the delay.
> # - Delay, remove the delay.
> # - Replicate in a circle with a delay on one node.
> # - Replicate in a circle with a delay on both nodes.

• chad

--
Chad Miller, Software Developer                         chad@mysql.com
MySQL Inc., www.mysql.com
Orlando, Florida, USA                                13-20z,  UTC-0400
Office: +1 408 213 6740                         sip:6740@sip.mysql.com

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