pt-online-schema-change will proceed even if no slaves are connectable, rendering throttling useless

Reported by rcoli on 2012-12-19
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Percona Toolkit
Undecided
Unassigned

Bug Description

1) run pt-osc with a user who has permissions to the master but not the slaves
2) notice many errors like : print STDERR "Cannot connect to ", $dp->as_string($dsn), "\n"
3) even if 100% of slaves fail, pt-online-schema-change proceeds with the ALTER, but is unable to monitor any slave lag. this would appear to render any lag-based throttling irrelevant
4) users typically expect throttling to work when it is enabled by default

I suggest making it FATAL when you can discover slaves but are unable to monitor a single one, and require that the user set --recursion-method=none if they want this behavior. Many people might have a good reason to ignore one of a list of slaves, but I think it is more rare for someone to want to ignore ALL of them.

tags: added: privs pt-online-schema-change
Changed in percona-toolkit:
status: New → Triaged
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