Mysql – Replicating into a Percona XtraDB Cluster

it seems the binlog doesn't include the new inserts

I'm not sure whether you're saying the binlog actually doesn't include them, and you have confirmed this with mysqlbinlog, or that it "seems" like it doesn't, because they don't replicate.

PXC needs log_slave_updates turned on at the node serving as master to the asynchronous slave, otherwise, not everything will be written to the master's binary log. This is very different than an ordinary MySQL server as master, where log_slave_updates will do nothing at all (unless the master is actually a slave to another master).

If that's not it, remove replicate_do_db and binlog_do_db and all of their related options from your configuration and then remove them from your brain. They should never be added unless you know exactly how they work, in your sleep. The simplest and by far most reliable replication configuration is, and will always be, replicate everything, which is the default.

Forget about binlog_format on the slave. It makes absolutely no difference unless the slave, itself, has other, subtended slaves... and if the master is using ROW format, the slave will still log in ROW format if you do indeed have it configured with subtended slaves. Also, the slave's binlogs (not to be confused with the relay logs) will not log statements received from an upstream master unless log_slave_updates is enabled on the slave.

The same thing goes for innodb_flush_log_at_trx_commit. It does not impact actual replication. It's a setting the determines a tradeoff between ACID compliance and performance.

By its Nature in a Galera Cluster a DML statement is expected to run a bit slower than a DML statement on a normal MySQL node because the response time of the DML statements includes not only the commit time on the local node but also sending the the write-set (ws) to the Group and receiving back the GTID of the ws.

So the total response time is: query time + 2 x round-trip to the group.

A simple insert will run possibly within 1 ms. And the round-trip to the group is possibly about 400 - 600 us. So 5 instead of 3 minutes I am not surprised to see...

Now, what can we improve?

a) Reduce query time: Write performance is influenced by: innodb_buffer_pool_size (big enough to cache all data in memory), innodb_log_file_size (as bigger as better) and innodb_flush_log_at_trx_commit (0 or 2 are faster than 1). With your setting above you have not followed the Codership recommendation (innodb_flush_log_at_trx_commit=0).

b) Reduce number of round trips. When you batch your DML statements into transactions you have bigger but less write-sets which should cause less round trips. So your time spent in the network should become smaller.

c) Make your network faster. Use smallest possible network latency: dedicated network. 1 or 10 Gbit. Not much hardware in between (firewall, switches, routers, etc).

d) Parallelize your inserts?

Regards, Oli

PS: There are still some places free in our Galera Cluster trainings in 2 weeks!