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I have a database setup with chained replication:

+-----------+       +-----------------+       +----------+
| A: master |  <--  | B: slave/master |  <--  | C: slave |
+-----------+       +-----------------+       +----------+

So A is the master of B and it is itself a master of C.

Now the C lost track of B and I need to synchronize it back. Copying the whole database would be very inconvenient, as it's about 100GB in size and C is connected over WAN.

Normally I'd use pt-table-sync, but I'm not sure if it's safe to run it on B, which is a slave itself. The man page isn't very clear about such scenarios, it just mentions that replication should be always done on the master, but here I have two.

So I'd like to ask: What are the options I could use?

  • Is it possible and safe to use pt-table-sync, either on B, or somehow on A, telling it to make checksums on C instead of B?
  • Are there some other, efficient options, how to synchronize C with B?
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