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21d5d4e15c
The function `gms::version_generator::get_next_version()` can only be called from shard 0 as it uses a global, unsynchronized counter to issue versions. Notably, the function is used as a default argument for the constructor of `gms::versioned_value` which is used from shorthand constructors such as `versioned_value::cache_hitrates`, `versioned_value::schema` etc. The `cache_hitrate_calculator` service runs a periodic job which updates the `CACHE_HITRATES` application state in the local gossiper state. Each time the job is scheduled, it runs on the next shard (it goes through shards in a round-robin fashion). The job uses the `versioned_value::cache_hitrates` shorthand to create a `versioned_value`, therefore risking a data race if it is not currently executing on shard 0. Fix the race by constructing the versioned value on shard 0.