pt-table-checksum with slaves using non-standard ports

Trying to run pt-table-checksum to detect slave drift in MySQL replication. My slaves are not using the standard TCP listening port however, and so when I run the tool I get an error:

Cannot connect to P=3306,h=,p=...

It still checksums the master's tables, but without being able to connect to the slaves it's not very useful. I can't figure out how to specify alternate ports for the slaves when running the command. My current command looks like

pt-table-checksum -h  -P 3388 -p

The issue is that the replicas don't report their ports to the master. By default pt-table-checksum tries to connect by filling unknowns with defaults; if the unknowns aren't using defaults, this will fail. In this case, there are two options:

1) Use the --recursion-method option to change from inspecting SHOW PROCESSLIST to inspecting SHOW SLAVE HOSTS, and configure slaves to report their host. I don't recommend this.

2) I recommend, instead, that you use --recursion-method=dsn and create a table full of DSN (data source name) instructions that tell the tool how to connect to each replica. If this table is foo.bar, then you will use --recursion-method=dsn=D=foo,t=bar.

This is only available in the 2.0 series of the toolkit, but you should be using that anyway, because pt-table-checksum is hugely improved in 2.0.

StackExchange Database Administrators Q#11988, answer score: 3