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scylladb/gms
Pavel Emelyanov ac60d8afca gossiper: Enable features and register enabler from outside
It's a bit hairy. The maybe_enable_features() is called from two places
-- the feature_enabler upon notifications from gossiper and directory by
gossiper from wait_for_gossip_to_settle().

The _latter_ is called only when the wait_for_gossip_to_settle() is
called for the first time because of the _gossip_settled checks in it.
For the first time this method is called by storage_service when it
tries to join the ring (next it's called from main, but that's not of
interest here).

Next, despite feature_enabler is registered early -- when gossiper
instance is constructed by sharded<gossiper>::start() -- it checks for
the _gossip_settled to be true to take any actions.

Considering both -- calling maybe_enable_features() _and_ registering
enabler after storage_service's call to wait_for_gossip_to_settle()
doesn't break the code logic, but make further patching possible. In
particular, the feature_enabler will move to feature_service not to
pollute gossiper code with anything that's not gossiping.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
2023-04-25 16:42:17 +03:00
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