New protocol stage during JOIN: IPROTO_JOIN_META, IPROTO_JOIN_SNAPSHOT #2276
Description
Product: Tarantool
Since: 2.10.0-beta1
Root document: https://www.tarantool.io/en/doc/latest/dev_guide/internals/box_protocol/#box-protocol-join
SME: @ sergepetrenko
Details
A new stage is added to the stream of JOIN rows coming from master.
The stage is marked with a bodyless row with type
IPROTO_JOIN_META = 71
Once all the rows from the stage are sent out, the JOIN continues as
before (as a stream of snapshot rows). The end of META stage is marked
with a row of type IPROTO_JOIN_SNAPSHOT = 72
The stage contains the rows that are necessary for instance
initialization (current Raft term, current state of synchronous
transaction queue), but do not belong to any system space.
Requested by @sergepetrenko in tarantool/tarantool@f1c2127.
Related to #2275