Start slave IO_THREAD in mysqldump output

[MikeG]

To immediately start queuing the master logs during a slave initialization from a master-data dump, it would be nice to optionally inject START SLAVE IO_THREAD after the CHANGE MASTER TO MASTER_LOG_FILE ...

This would presumably fail if the slave had not first had CHANGE MASTER TO MASTER_HOST, MASTER_USER, MASTER_PASSWORD but perhaps that is a feature since you then avoid having to manually extract the CHANGE from the dump file and worse forget to do so starting at the master's first available.

[m00dawg (tim-moocowproductions)]

It sounds like a good idea - I'm just trying to think of some of the edge cases. So far the worst case I can think of is queueing logs one might not use (such as when doing point-in-time-recovery). I think this should be a feature that must be enabled (ie not default) so at least people that turn it on should have an idea of what they are getting into?

[MikeG (mikegriffin)]

I said optionally.. :)

[Andrew Garner (muzazzi)]

I think this would be a better fit for some front-end script that assist with the restore (maybe a holland restore ... command). I don't think we should be messing with mysqldump's standard output at backup time at any rate.

For an example of how I might envision a restore script working you can see the holland_restore experiment for mysqldump I have here:

https://github.com/abg/holland_restore

I just implemented this basic idea:

$ mysqlrestore --start-slave-early < sakila.binlog.sql > sakila.binlog.io_thread.sql
…
$ diff -u sakila.binlog.sql sakila.binlog.io_thread.sql
--- sakila.binlog.sql 2011-04-19 21:31:59.000000000 -0400
+++ sakila.binlog.io_thread.sql 2011-04-19 21:41:10.000000000 -0400
@@ -20,6 +20,7 @@
--

CHANGE MASTER TO MASTER_LOG_FILE='bin-log.000001', MASTER_LOG_POS=106;
+START SLAVE IO_THREAD;

--
-- Table structure for table `actor`
$

[Andrew Garner (muzazzi)]

This has been open a while and I am going to reject this right now. I don't want holland to get into the business of modifying mysqldump output directly.