Flesh out status report from reconfigurator rendezvous RPW (#7401)

Example output from `omicron-dev run-all` (so no meaningful rows, but
just checking the field formatting and omdb deserialization):

```
task: "blueprint_rendezvous"
  configured period: every 5m
  currently executing: no
  last completed activation: iter 5, triggered by a dependent task completing
    started at 2025-01-24T21:07:40.740Z (222s ago) and ran for 68ms
    target blueprint:     72d199ef-d6bd-4895-8858-006f3ed212ad
    inventory collection: 7dfbf99c-3613-498c-a871-cfb9b2945abe
    debug_dataset rendezvous counts:
        num_inserted:           0
        num_already_exist:      0
        num_not_in_inventory:   0
        num_tombstoned:         0
        num_already_tombstoned: 0
    crucible_dataset rendezvous counts:
        num_inserted:         0
        num_already_exist:    0
        num_not_in_inventory: 0
```

Closes #7392.

dev-tools/omdb/src/bin/omdb/nexus.rs

@@ -1128,6 +1128,27 @@ fn print_task_blueprint_rendezvous(details: &serde_json::Value) {
                 "    inventory collection: {}",
                 status.inventory_collection_id
             );
+            println!("    debug_dataset rendezvous counts:");
+            println!(
+                "        num_inserted:           {}",
+                status.stats.debug_dataset.num_inserted
+            );
+            println!(
+                "        num_already_exist:      {}",
+                status.stats.debug_dataset.num_already_exist
+            );
+            println!(
+                "        num_not_in_inventory:   {}",
+                status.stats.debug_dataset.num_not_in_inventory
+            );
+            println!(
+                "        num_tombstoned:         {}",
+                status.stats.debug_dataset.num_tombstoned
+            );
+            println!(
+                "        num_already_tombstoned: {}",
+                status.stats.debug_dataset.num_already_tombstoned
+            );
             println!("    crucible_dataset rendezvous counts:");
             println!(
                 "        num_inserted:         {}",

nexus/reconfigurator/rendezvous/src/debug_dataset.rs

@@ -10,6 +10,7 @@ use nexus_db_queries::db::model::RendezvousDebugDataset;
 use nexus_db_queries::db::DataStore;
 use nexus_types::deployment::BlueprintDatasetConfig;
 use nexus_types::deployment::BlueprintDatasetDisposition;
+use nexus_types::internal_api::background::DebugDatasetsRendezvousStats;
 use omicron_common::api::internal::shared::DatasetKind;
 use omicron_uuid_kinds::BlueprintUuid;
 use omicron_uuid_kinds::DatasetUuid;
@@ -23,7 +24,7 @@ pub(crate) async fn reconcile_debug_datasets(
     blueprint_id: BlueprintUuid,
     blueprint_datasets: impl Iterator<Item = &BlueprintDatasetConfig>,
     inventory_datasets: &BTreeSet<DatasetUuid>,
-) -> anyhow::Result<()> {
+) -> anyhow::Result<DebugDatasetsRendezvousStats> {
     // We expect basically all executions of this task to do nothing: we're
     // activated periodically, and only do work when a dataset has been
     // newly-added or newly-expunged.
@@ -39,27 +40,42 @@ pub(crate) async fn reconcile_debug_datasets(
         .map(|d| (d.id(), d))
         .collect::<BTreeMap<_, _>>();
 
+    let mut stats = DebugDatasetsRendezvousStats::default();
+
     for dataset in blueprint_datasets.filter(|d| d.kind == DatasetKind::Debug) {
         match dataset.disposition {
             BlueprintDatasetDisposition::InService => {
                 // Only attempt to insert this dataset if it has shown up in
                 // inventory (required for correctness) and isn't already
                 // present in the db (performance optimization only). Inserting
                 // an already-present row is a no-op, so it's safe to skip.
-                if inventory_datasets.contains(&dataset.id)
-                    && !existing_db_datasets.contains_key(&dataset.id)
-                {
+                if existing_db_datasets.contains_key(&dataset.id) {
+                    stats.num_already_exist += 1;
+                } else if !inventory_datasets.contains(&dataset.id) {
+                    stats.num_not_in_inventory += 1;
+                } else {
                     let db_dataset = RendezvousDebugDataset::new(
                         dataset.id,
                         dataset.pool.id(),
                         blueprint_id,
                     );
-                    datastore
+                    let did_insert = datastore
                         .debug_dataset_insert_if_not_exists(opctx, db_dataset)
                         .await
                         .with_context(|| {
                             format!("failed to insert dataset {}", dataset.id)
-                        })?;
+                        })?
+                        .is_some();
+
+                    if did_insert {
+                        stats.num_inserted += 1;
+                    } else {
+                        // This means we hit the TOCTOU race mentioned above:
+                        // when we queried the DB this row didn't exist, but
+                        // another Nexus must have beat us to actually inserting
+                        // it.
+                        stats.num_already_exist += 1;
+                    }
                 }
             }
             BlueprintDatasetDisposition::Expunged => {
@@ -81,7 +97,9 @@ pub(crate) async fn reconcile_debug_datasets(
                     .get(&dataset.id)
                     .map(|d| d.is_tombstoned())
                     .unwrap_or(false);
-                if !already_tombstoned {
+                if already_tombstoned {
+                    stats.num_already_tombstoned += 1;
+                } else {
                     if datastore
                         .debug_dataset_tombstone(
                             opctx,
@@ -96,17 +114,23 @@ pub(crate) async fn reconcile_debug_datasets(
                             )
                         })?
                     {
+                        stats.num_tombstoned += 1;
                         info!(
                             opctx.log, "tombstoned expunged dataset";
                             "dataset_id" => %dataset.id,
                         );
+                    } else {
+                        // Similar TOCTOU race lost as above; this dataset was
+                        // either already tombstoned by another racing Nexus, or
+                        // has been hard deleted.
+                        stats.num_already_tombstoned += 1;
                     }
                 }
             }
         }
     }
 
-    Ok(())
+    Ok(stats)
 }
 
 #[cfg(test)]
@@ -213,15 +237,15 @@ mod tests {
         ))| {
             let blueprint_id = BlueprintUuid::new_v4();
 
-            let datastore_datasets = runtime.block_on(async {
+            let (result_stats, datastore_datasets) = runtime.block_on(async {
                 let (blueprint_datasets, inventory_datasets) = proptest_do_prep(
                     opctx,
                     datastore,
                     blueprint_id,
                     &prep,
                 ).await;
 
-                reconcile_debug_datasets(
+                let result_stats = reconcile_debug_datasets(
                     opctx,
                     datastore,
                     blueprint_id,
@@ -231,15 +255,19 @@ mod tests {
                 .await
                 .expect("reconciled debug dataset");
 
-                 datastore
+                 let datastore_datasets = datastore
                     .debug_dataset_list_all_batched(opctx)
                     .await
                     .unwrap()
                     .into_iter()
                     .map(|d| (d.id(), d))
-                    .collect::<BTreeMap<_, _>>()
+                    .collect::<BTreeMap<_, _>>();
+
+                 (result_stats, datastore_datasets)
             });
 
+            let mut expected_stats = DebugDatasetsRendezvousStats::default();
+
             for (id, prep) in prep {
                 let id: DatasetUuid = u32_to_id(id);
 
@@ -252,6 +280,32 @@ mod tests {
                     prep.disposition == ArbitraryDisposition::InService;
                 let in_inventory = prep.in_inventory;
 
+                // Validate rendezvous output
+                match (in_db_before, in_service, in_inventory) {
+                    // "Not in database and expunged" is consistent with "hard
+                    // deleted", which we can't separate from "already
+                    // tombstoned".
+                    (false, false, _) => {
+                        expected_stats.num_already_tombstoned += 1;
+                    }
+                    // "In database and expunged" should result in tombstoning.
+                    (true, false, _) => {
+                        expected_stats.num_tombstoned += 1;
+                    }
+                    // In service but already existed
+                    (true, true, _) => {
+                        expected_stats.num_already_exist += 1;
+                    }
+                    // In service, not in db yet, but not in inventory
+                    (false, true, false) => {
+                        expected_stats.num_not_in_inventory += 1;
+                    }
+                    // In service, not in db yet, present in inventory
+                    (false, true, true) => {
+                        expected_stats.num_inserted += 1;
+                    }
+                }
+
                 // Validate database state
                 match (in_db_before, in_service, in_inventory) {
                     // Wasn't in DB, isn't in service: should still not be in db
@@ -298,6 +352,8 @@ mod tests {
                     }
                 }
             }
+
+            assert_eq!(result_stats, expected_stats);
         });
 
         runtime.block_on(db.terminate());

nexus/reconfigurator/rendezvous/src/lib.rs

@@ -30,7 +30,7 @@ pub async fn reconcile_blueprint_rendezvous_tables(
         .flat_map(|sled| sled.datasets.iter().flat_map(|d| d.id))
         .collect();
 
-    debug_dataset::reconcile_debug_datasets(
+    let debug_dataset = debug_dataset::reconcile_debug_datasets(
         opctx,
         datastore,
         blueprint.id,
@@ -51,7 +51,7 @@ pub async fn reconcile_blueprint_rendezvous_tables(
     )
     .await?;
 
-    Ok(BlueprintRendezvousStats { crucible_dataset })
+    Ok(BlueprintRendezvousStats { debug_dataset, crucible_dataset })
 }
 
 #[cfg(test)]

nexus/types/src/internal_api/background.rs

@@ -247,6 +247,7 @@ pub struct BlueprintRendezvousStatus {
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub struct BlueprintRendezvousStats {
+    pub debug_dataset: DebugDatasetsRendezvousStats,
     pub crucible_dataset: CrucibleDatasetsRendezvousStats,
 }
 
@@ -283,3 +284,53 @@ impl slog::KV for CrucibleDatasetsRendezvousStats {
         Ok(())
     }
 }
+
+#[derive(
+    Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize,
+)]
+pub struct DebugDatasetsRendezvousStats {
+    /// Number of new Debug datasets recorded.
+    ///
+    /// This is a count of in-service Debug datasets that were also present
+    /// in inventory and newly-inserted into `rendezvous_debug_dataset`.
+    pub num_inserted: usize,
+    /// Number of Debug datasets that would have been inserted, except
+    /// records for them already existed.
+    pub num_already_exist: usize,
+    /// Number of Debug datasets that the current blueprint says are
+    /// in-service, but we did not attempt to insert them because they're not
+    /// present in the latest inventory collection.
+    pub num_not_in_inventory: usize,
+    /// Number of Debug datasets that we tombstoned based on their disposition
+    /// in the current blueprint being expunged.
+    pub num_tombstoned: usize,
+    /// Number of Debug datasets that we would have tombstoned, except they were
+    /// already tombstoned or deleted.
+    pub num_already_tombstoned: usize,
+}
+
+impl slog::KV for DebugDatasetsRendezvousStats {
+    fn serialize(
+        &self,
+        _record: &slog::Record,
+        serializer: &mut dyn slog::Serializer,
+    ) -> slog::Result {
+        let Self {
+            num_inserted,
+            num_already_exist,
+            num_not_in_inventory,
+            num_tombstoned,
+            num_already_tombstoned,
+        } = *self;
+        serializer.emit_usize("num_inserted".into(), num_inserted)?;
+        serializer.emit_usize("num_already_exist".into(), num_already_exist)?;
+        serializer
+            .emit_usize("num_not_in_inventory".into(), num_not_in_inventory)?;
+        serializer.emit_usize("num_tombstoned".into(), num_tombstoned)?;
+        serializer.emit_usize(
+            "num_already_tombstoned".into(),
+            num_already_tombstoned,
+        )?;
+        Ok(())
+    }
+}