diff options
Diffstat (limited to 'sql')
| -rw-r--r-- | sql/slave.cc | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/sql/slave.cc b/sql/slave.cc index ed16c3361c6..e737febdd8a 100644 --- a/sql/slave.cc +++ b/sql/slave.cc @@ -2065,8 +2065,21 @@ int show_master_info(THD* thd, MASTER_INFO* mi) - mi->rli.last_master_timestamp) - mi->clock_diff_with_master; /* - Apparently on some systems tmp can be <0 (which is still a - mistery). This confuses users, so we don't go below 0. + Apparently on some systems tmp can be <0. Here are possible reasons + related to MySQL: + - the master is itself a slave of another master whose time is ahead. + - somebody used an explicit SET TIMESTAMP on the master. + Possible reason related to granularity-to-second of time functions + (nothing to do with MySQL), which can explain a value of -1: + assume the master's and slave's time are perfectly synchronized, and + that at slave's connection time, when the master's timestamp is read, + it is at the very end of second 1, and (a very short time later) when + the slave's timestamp is read it is at the very beginning of second + 2. Then the recorded value for master is 1 and the recorded value for + slave is 2. At SHOW SLAVE STATUS time, assume that the difference + between timestamp of slave and rli->last_master_timestamp is 0 + (i.e. they are in the same second), then we get 0-(2-1)=-1 as a result. + This confuses users, so we don't go below 0. */ protocol->store((longlong)(max(0, tmp))); } |