backporting raft_register_state_cb and making compatible with canonical/raft v0.18.1

[listout]

canonical/raft@6535161 adds a callback function raft_register_state_cb. In gentoo we ship dqlite which is dependent on cowsql/raft and it's failing with build error

rc/server.c: error: implicit declaration of function raft_register_state_cb

Refer: https://bugs.gentoo.org/925012

[freeekanayaka]

TL;DR: starting from the next dqlite release this won't a be a problem anymore since the whole canonical/raftsource code will be moved directly inside the canonical/dqlite repository, and built together in a single shared library.

See this comment canonical/dqlite#549 (comment) and this PR canonical/dqlite#568.

Note that dqlite 1.16.0 works fine with canonical/cowsql. The only non-compatible release is dqlite 1.16.2. Would it be fine for you/gentoo to just to wait for dqlite 1.16.3 and stick with 1.16.0 fow now? It doesn't make much sense to fix this issue which is effectively going away soon.

[juippis]

That sounds good, will do that.

[freeekanayaka]

That sounds good, will do that.

https://github.com/canonical/dqlite/releases/tag/v1.16.3

you can now build dqlite with --enable-build-raft.