Comment 1 for bug 1532969

The guest with pxc5.6/pxb2.3 is failing during prepare. The failure manifests as an authentication failure during SST (Snapshot State Transfer). This process is currently setup to use xtrabackup. One workaround would be to switch to using rsync. This has been tested to work but has one drawback - the source DB has to be in read only mode during SST - this is likely not an issue during a create operation but could be an issue during cluster-grow.

Issues/possible solutions with SST using xtrabackup

1. The core issue with using pxb2.3 for SST is because Percona changed the process to pass in the mysql password using the env var "MYSQL_PWD". Historically, they were just passing the password on the backup command (innobackupex) command line. The problem is that the guest stores its mysql credentials (os_admin) in the my.cnf file, in a [client] section. This overrides the use of MYSQL_PWD and causes the authentication failure above. (Clearly, percona didn't test this scenario or expect anyone to do this). This issue can be corrected by moving the [client] section settings from the file under /etc/mysql/conf.d into ~/.my.cnf. I tested this and it will make pxc startup the cluster.

2. We need to switch to using sst method "xtrabackup-v2". This is recommended by Percona when using this combination (and if you don't do it, you just get a different failure). To set this, we just need to change templates/pxc/cluster.config.template:
               wsrep_sst_method=xtrabackup-v2

3. pxb2.3 seems to want to connect to an unknown socket when it gets "localhost" for the host. Fix is to put "host=127.0.0.1" in [client] section.