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control_plane: let reconciler avoid bumping generation when changing config

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John Spray
2024-02-27 11:50:04 +00:00
parent ee558cb77b
commit 24b01c1652
1 changed files with 37 additions and 6 deletions
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43
control_plane/attachment_service/src/reconciler.rs
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@@ -440,15 +440,46 @@ impl Reconciler {
// Nothing to do
tracing::info!(%node_id, "Observed configuration already correct.")
}
_ => {
observed => {
// In all cases other than a matching observed configuration, we will
// reconcile this location. This includes locations with different configurations, as well
// as locations with unknown (None) observed state.
self.generation = self
.persistence
.increment_generation(self.tenant_shard_id, node_id)
.await?;
wanted_conf.generation = self.generation.into();
// The general case is to increment the generation. However, there are cases
// where this is not necessary:
// - if we are only updating the TenantConf part of the location
// - if we are only changing the attachment mode (e.g. going to attachedmulti or attachedstale)
// and the location was already in the correct generation
let increment_generation = match observed {
None => true,
Some(ObservedStateLocation { conf: None }) => true,
Some(ObservedStateLocation {
conf: Some(observed),
}) => {
// If mode and generation are the same, it follows that only the configuration has changed
let config_update = observed.generation == wanted_conf.generation
&& observed.mode == wanted_conf.mode;
// Usually the short-lived attachment modes (multi and stale) are only used
// in the case of [`Self::live_migrate`], but it is simple to handle them correctly
// here too. Locations are allowed to go Single->Stale and Multi->Single within the same generation.
let mode_transition = observed.generation == wanted_conf.generation
&& ((observed.mode == LocationConfigMode::AttachedSingle
&& wanted_conf.mode == LocationConfigMode::AttachedStale)
|| (observed.mode == LocationConfigMode::AttachedMulti
&& wanted_conf.mode == LocationConfigMode::AttachedSingle));
!(config_update || mode_transition)
}
};
if increment_generation {
self.generation = self
.persistence
.increment_generation(self.tenant_shard_id, node_id)
.await?;
wanted_conf.generation = self.generation.into();
}
tracing::info!(%node_id, "Observed configuration requires update.");
self.location_config(node_id, wanted_conf, None).await?;
self.compute_notify().await?;