diff options
| author | unknown <guilhem@mysql.com> | 2003-12-04 15:30:14 +0100 |
|---|---|---|
| committer | unknown <guilhem@mysql.com> | 2003-12-04 15:30:14 +0100 |
| commit | 8479e5a379044acad53baa8f9b7a8cd9266c582a (patch) | |
| tree | ebe7a79e0ce5811215ea0ef2a0b0c25db2c1e5b4 /sql/slave.cc | |
| parent | e8fc6d460c379bbb7b5b4b75e9919ea226a62a43 (diff) | |
| download | mariadb-git-8479e5a379044acad53baa8f9b7a8cd9266c582a.tar.gz | |
Fix for BUG#2011 "rare race condition producing "binlog has bad magic number" error in slave".
The problem was that when the slave SQL thread reads a hot relay log (hot = the one being written to by the
slave I/O thread), it must have the LOCK_log. It already took it for read_log_event(), but needs
it also for check_binlog_magic().
This should fix all recently reported failures of the rpl_max_relay_size test in 4.1 and 5.0
(though the bug exists since 4.0, it showed up first in 5.0).
sql/slave.cc:
Fix for BUG#2011 "rare race condition producing "binlog has bad magic number" error in slave".
The problem was that when the slave SQL thread reads a hot relay log (hot = the one being written to by the
slave I/O thread), it must have the LOCK_log. It already took it for read_log_event(), but needs
it also for check_binlog_magic().
Diffstat (limited to 'sql/slave.cc')
| -rw-r--r-- | sql/slave.cc | 31 |
1 files changed, 26 insertions, 5 deletions
diff --git a/sql/slave.cc b/sql/slave.cc index 6816d968007..5bc31fd6a21 100644 --- a/sql/slave.cc +++ b/sql/slave.cc @@ -3497,8 +3497,20 @@ rli->relay_log_pos=%s rli->pending=%lu", sizeof(rli->relay_log_name)-1); flush_relay_log_info(rli); } - - // next log is hot + + /* + Now we want to open this next log. To know if it's a hot log (the one + being written by the I/O thread now) or a cold log, we can use + is_active(); if it is hot, we use the I/O cache; if it's cold we open + the file normally. But if is_active() reports that the log is hot, this + may change between the test and the consequence of the test. So we may + open the I/O cache whereas the log is now cold, which is nonsense. + To guard against this, we need to have LOCK_log. + */ + + DBUG_PRINT("info",("hot_log: %d",hot_log)); + if (!hot_log) /* if hot_log, we already have this mutex */ + pthread_mutex_lock(log_lock); if (rli->relay_log.is_active(rli->linfo.log_file_name)) { #ifdef EXTRA_DEBUG @@ -3511,15 +3523,24 @@ rli->relay_log_pos=%s rli->pending=%lu", /* Read pointer has to be at the start since we are the only - reader + reader. + 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). */ if (check_binlog_magic(cur_log,&errmsg)) + { + if (!hot_log) pthread_mutex_unlock(log_lock); goto err; + } + if (!hot_log) pthread_mutex_unlock(log_lock); continue; } + if (!hot_log) pthread_mutex_unlock(log_lock); /* - if we get here, the log was not hot, so we will have to - open it ourselves + if we get here, the log was not hot, so we will have to open it + ourselves. We are sure that the log is still not hot now (a log can get + from hot to cold, but not from cold to hot). No need for LOCK_log. */ #ifdef EXTRA_DEBUG sql_print_error("next log '%s' is not active", |