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MDEV-14014 Multi-Slave Replication Fail: bogus data in log event

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MDEV-7257 made a dump thread to read from binlog concurrently with
writers as long as the read bytes are below a water-mark
(MYSQL_BIN_LOG::binlog_end_pos). However it appeared to be possible a
dump thread reader reach out for bytes past the water mark through a
feature of IO_CACHE that fills in the internal buffer and while doing
so it could read what the reader is not supposed to see (the bytes
above MYSQL_BIN_LOG::binlog_end_pos).

The issue is fixed with constraining the IO_CACHE buffer fill to respect
the watermark.

An added unit test proves reading from file is bound to an external
parameter
passed to {IO_CACHE::end_of_file} cache member.
This commit is contained in:
Andrei Elkin 2018-03-18 21:01:41 +02:00 committed by Sergei Golubchik
parent 52a25d7b67
commit 00ccff48af
2 changed files with 37 additions and 1 deletions
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1
sql/sql_repl.cc
View File

@ -2538,6 +2538,7 @@ static int send_events(binlog_send_info *info, IO_CACHE* log, LOG_INFO* linfo,
linfo->pos= my_b_tell(log);
info->last_pos= my_b_tell(log);
log->end_of_file= end_pos;
while (linfo->pos < end_pos)
{
if (should_stop(info))

37
unittest/sql/mf_iocache-t.cc
View File

@ -253,10 +253,43 @@ void mdev10259()
}
void mdev14014()
{
int res;
uchar buf_o[200];
uchar buf_i[200];
memset(buf_i, 0, sizeof( buf_i));
memset(buf_o, FILL, sizeof(buf_o));
diag("MDEV-14014 Dump thread reads past last 'officially' written byte");
init_io_cache_encryption();
res= open_cached_file(&info, 0, 0, CACHE_SIZE, 0);
ok(res == 0, "open_cached_file" INFO_TAIL);
res= my_b_write(&info, buf_o, sizeof(buf_o));
ok(res == 0, "buffer is written" INFO_TAIL);
res= my_b_flush_io_cache(&info, 1);
ok(res == 0, "flush" INFO_TAIL);
res= reinit_io_cache(&info, READ_CACHE, 0, 0, 0);
ok(res == 0, "reinit READ_CACHE" INFO_TAIL);
info.end_of_file= 100;
res= my_b_read(&info, buf_i, sizeof(buf_i));
ok(res == 1 && buf_i[100] == 0 && buf_i[200-1] == 0,
"short read leaves buf_i[100..200-1] == 0");
close_cached_file(&info);
}
int main(int argc __attribute__((unused)),char *argv[])
{
MY_INIT(argv[0]);
plan(46);
plan(51);
/* temp files with and without encryption */
encrypt_tmp_files= 1;
@ -272,6 +305,8 @@ int main(int argc __attribute__((unused)),char *argv[])
mdev10259();
encrypt_tmp_files= 0;
mdev14014();
my_end(0);
return exit_status();
}