#At file:///home/lsoares/Workspace/bzr/work/bugfixing/push/mysql-5.1-bugteam/ based on revid:luis.soares@stripped
3524 Luis Soares 2010-10-06 [merge]
BUG 55263: automerged bzr bundle from bug report.
=== modified file 'sql/rpl_rli.h'
--- a/sql/rpl_rli.h 2009-12-14 16:32:22 +0000
+++ b/sql/rpl_rli.h 2010-09-24 09:44:53 +0000
@@ -94,6 +94,16 @@ public:
+ Pointer that either points at relay_log.get_log_file() or
+ &rli->cache_buf, depending on whether the log is hot or there was
+ the need to open a cold relay_log.
+ IO_CACHE used when opening cold relay logs.
/* The following variables are safe to read any time */
=== modified file 'sql/slave.cc'
--- a/sql/slave.cc 2010-07-20 18:07:36 +0000
+++ b/sql/slave.cc 2010-09-24 09:44:53 +0000
@@ -4349,12 +4349,66 @@ static Log_event* next_event(Relay_log_i
DBUG_ASSERT(rli->cur_log_fd == -1);
- Read pointer has to be at the start since we are the only
- We must keep the LOCK_log to read the 4 first bytes, as this is a hot
- log (same as when we call read_log_event() above: for a hot log we
- take the mutex).
+ When the SQL thread is [stopped and] (re)started the
+ following may happen:
+ 1. Log was hot at stop time and remains hot at restart
+ SQL thread reads again from hot_log (SQL thread was
+ reading from the active log when it was stopped and the
+ very same log is still active on SQL thread restart).
+ In this case, my_b_seek is performed on cur_log, while
+ cur_log points to relay_log.get_log_file();
+ 2. Log was hot at stop time but got cold before restart
+ The log was hot when SQL thread stopped, but it is not
+ anymore when the SQL thread restarts.
+ In this case, the SQL thread reopens the log, using
+ cache_buf, ie, cur_log points to &cache_buf, and thence
+ its coordinates are reset.
+ 3. Log was already cold at stop time
+ The log was not hot when the SQL thread stopped, and, of
+ course, it will not be hot when it restarts.
+ In this case, the SQL thread opens the cold log again,
+ using cache_buf, ie, cur_log points to &cache_buf, and
+ thence its coordinates are reset.
+ 4. Log was hot at stop time, DBA changes to previous cold
+ log and restarts SQL thread
+ The log was hot when the SQL thread was stopped, but the
+ user changed the coordinates of the SQL thread to
+ restart from a previous cold log.
+ In this case, at start time, cur_log points to a cold
+ log, opened using &cache_buf as cache, and coordinates
+ are reset. However, as it moves on to the next logs, it
+ will eventually reach the hot log. If the hot log is the
+ same at the time the SQL thread was stopped, then
+ coordinates were not reset - the cur_log will point to
+ relay_log.get_log_file(), and not a freshly opened
+ IO_CACHE through cache_buf. For this reason we need to
+ deploy a my_b_seek before calling check_binlog_magic at
+ this point of the code (see: BUG#55263 for more
+ - We must keep the LOCK_log to read the 4 first bytes, as
+ this is a hot log (same as when we call read_log_event()
+ above: for a hot log we take the mutex).
+ - Because of scenario #4 above, we need to have a
+ my_b_seek here. Otherwise, we might hit the assertion
+ inside check_binlog_magic.
+ my_b_seek(cur_log, (my_off_t) 0);
if (!hot_log) pthread_mutex_unlock(log_lock);
Attachment: [text/bzr-bundle] firstname.lastname@example.org
|• bzr commit into mysql-5.1-bugteam branch (luis.soares:3524) ||Luis Soares||6 Oct|