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d48f04f25e
The check was added to support migration from schema tables format v2
to v3. It was needed to handle the rolling upgrade from 2.x to 3.x
scylla version. Old nodes wouldn't recognize new schema mutations, so
the pull handler in v3 was changed to ignore requests from v2 nodes based
on their advertised SCHEMA_TABLES_VERSION gossip state.
This started to cause problems after 3b1ff90 (get rid of the seed
concept). The bootstrapping node sometimes would hang during boot
unable to reach schema agreement.
It's relevant that gossip exchanges about new nodes are unidirectional
(refs #2862).
It's also relevant that pulls are edge-triggered only (refs #7426).
If the bootstrapping node (A) is listed as a seed in one of the
existing node's (B) configuration then node A can be contacted before
it contacts node B. Node A may then send schema pull request to node B
before it learns about node A, and node B will assume it's an old node
and give an empty response. As a result, node A will end up with an
old schema.
The fix is to drop the check so that pull handler always responds with
the schema. We don't support upgrades from nodes using v2 schema
tables format anymore so this should be safe.
Fixes #7396
Tests:
- manual (ccm)
- unit (dev)
Message-Id: <1602612578-21258-1-git-send-email-tgrabiec@scylladb.com>