Per-shard atomic write version counters for WATCH/EXEC support.
When writes bypass the Shard GenServer (quorum durability path), the Shard's
internal write_version field is not updated. This module provides a shared
atomic counter per shard that can be incremented by any process -- the Router
(quorum bypass), the Shard GenServer (async path), or the StateMachine.
The counters are stored in a single :counters reference held in
:persistent_term, giving ~5ns read/increment with zero contention on
different shard indices.
Usage
# During application boot (called once):
WriteVersion.init(4)
# Increment after a successful write:
WriteVersion.increment(shard_index)
# Read the current version for WATCH:
WriteVersion.get(shard_index)Summary
Functions
Returns the current write version for shard_index.
Returns the current write version using instance ctx.
Atomically increments the write version for shard_index.
Atomically increments the write version using instance ctx.
Initializes the per-shard write version counters.
Functions
@spec get(non_neg_integer()) :: non_neg_integer()
Returns the current write version for shard_index.
@spec get(FerricStore.Instance.t(), non_neg_integer()) :: non_neg_integer()
Returns the current write version using instance ctx.
@spec increment(non_neg_integer()) :: :ok
Atomically increments the write version for shard_index.
Returns :ok. The shard_index is 0-based but :counters uses 1-based
indices, so we add 1 internally.
@spec increment(FerricStore.Instance.t(), non_neg_integer()) :: :ok
Atomically increments the write version using instance ctx.
@spec init(pos_integer()) :: :ok
Initializes the per-shard write version counters.
Must be called once during application startup before any writes occur.
shard_count determines the number of independent counters.