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Erik JohnstonandClaude Opus 4.8
2684275e1a
Previously a worker proxied a ReplicationPresenceSetState HTTP call to the presence writer on every sync request, which made the writer's load scale with the client sync rate and dominated its CPU on large deployments. Instead, carry presence over the existing USER_SYNC replication command: * UserSyncCommand gains a presence_state field. Workers edge-trigger it: a USER_SYNC is sent only when a device first starts syncing or changes the presence state it is syncing with, so a steady sync loop generates no presence traffic. The reconnect resync and an explicit REST set_state are handled so the writer's view stays correct. * The writer applies the state from USER_SYNC (factored into _apply_sync_state). Combined with the previous commit, a device is treated as active for as long as it stays in the syncing set, so it neither idles nor goes offline while syncing without the writer being told about every sync. * A new USER_SYNC_KEEPALIVE command lets a worker periodically remind the writer that its syncing users are still live, so a quiet worker isn't expired (which would otherwise mark all its users offline). * The sync-driven half of the relay throttle (#19941) is superseded: syncs no longer relay a set_state at all, so the throttle now only covers the per-user-action activity bumps. Its entries are reset whenever the device's state on the writer may have changed (an explicit set_state, a change of sync state, or the device stopping syncing), so a bump that may un-idle the device is always relayed immediately. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PRR4mYoQDuv2k1FwEyreL6