Implement pt-table-checksum --dry-run.

[Agustín]

It would be nice to have --dry-run in pt-table-checksum, also, as a means of being able to see to what slaves the tool will connect to, for debugging purposes. I tried with --explain, but it won't connect to the slaves in this way.

Comparing to pt-table-sync --dry-run:

$ pt-table-sync --dry-run --replicate percona.checksums h=127.0.0.1,P=23389,u=root,p=msandbox
# NOTE: --dry-run does not show if data needs to be synced because it
# does not access, compare or sync data. --dry-run only shows
# the work that would be done.
# Syncing via replication P=23390,h=127.0.0.1,p=...,u=root in dry-run mode, without accessing or comparing data
# DELETE REPLACE INSERT UPDATE ALGORITHM START END EXIT DATABASE.TABLE
# 0 0 0 0 Chunk 18:11:39 18:11:39 0 test.t1
# Syncing via replication P=23391,h=127.0.0.1,p=...,u=root in dry-run mode, without accessing or comparing data
# DELETE REPLACE INSERT UPDATE ALGORITHM START END EXIT DATABASE.TABLE

This would be useful if we wanted to check this, without actually generating load in the servers (or network traffic due to replicated statements).

Thanks,
Agustín.

[Frank Cizmich (frank-cizmich)]

Hi Agustín,

It's a fair request.
Meanwhile, if you want to check which slaves the tool is connecting to without generating load on the server or the network you can try running in debug mode while ignoring all the databases via the ignore-databases-regex option:

e.g:

PTDEBUG=1 pt-table-checksum --ignore-databases-regex='.' <dns>

Notice the regex is a single period, which matches all possible database names.

Cheers!
;-)

[Agustín (agustin-gallego)]

Awesome! That worked ok as a workaround. Thanks Frank.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-826