From d7db26d9c6f09fec3fec6991e4a9cd7f90128465 Mon Sep 17 00:00:00 2001
From: David Pacheco <dap@oxidecomputer.com>
Date: Mon, 26 Feb 2024 11:54:31 -0800
Subject: [PATCH] trigger inventory collection after blueprint execution
 (#5130)

---
 .../src/app/background/blueprint_execution.rs | 11 +++-
 nexus/src/app/background/init.rs              | 56 +++++++++++--------
 2 files changed, 42 insertions(+), 25 deletions(-)

diff --git a/nexus/src/app/background/blueprint_execution.rs b/nexus/src/app/background/blueprint_execution.rs
index 373f023288..4ba60ab566 100644
--- a/nexus/src/app/background/blueprint_execution.rs
+++ b/nexus/src/app/background/blueprint_execution.rs
@@ -20,6 +20,7 @@ pub struct BlueprintExecutor {
     datastore: Arc<DataStore>,
     rx_blueprint: watch::Receiver<Option<Arc<(BlueprintTarget, Blueprint)>>>,
     nexus_label: String,
+    tx: watch::Sender<usize>,
 }
 
 impl BlueprintExecutor {
@@ -30,7 +31,12 @@ impl BlueprintExecutor {
         >,
         nexus_label: String,
     ) -> BlueprintExecutor {
-        BlueprintExecutor { datastore, rx_blueprint, nexus_label }
+        let (tx, _) = watch::channel(0);
+        BlueprintExecutor { datastore, rx_blueprint, nexus_label, tx }
+    }
+
+    pub fn watcher(&self) -> watch::Receiver<usize> {
+        self.tx.subscribe()
     }
 }
 
@@ -71,6 +77,9 @@ impl BackgroundTask for BlueprintExecutor {
             )
             .await;
 
+            // Trigger anybody waiting for this to finish.
+            self.tx.send_modify(|count| *count = *count + 1);
+
             // Return the result as a `serde_json::Value`
             match result {
                 Ok(()) => json!({}),
diff --git a/nexus/src/app/background/init.rs b/nexus/src/app/background/init.rs
index 846051a068..9ba30bab64 100644
--- a/nexus/src/app/background/init.rs
+++ b/nexus/src/app/background/init.rs
@@ -170,30 +170,6 @@ impl BackgroundTasks {
             )
         };
 
-        // Background task: inventory collector
-        let task_inventory_collection = {
-            let collector = inventory_collection::InventoryCollector::new(
-                datastore.clone(),
-                resolver,
-                &nexus_id.to_string(),
-                config.inventory.nkeep,
-                config.inventory.disable,
-            );
-            let task = driver.register(
-                String::from("inventory_collection"),
-                String::from(
-                    "collects hardware and software inventory data from the \
-                    whole system",
-                ),
-                config.inventory.period_secs,
-                Box::new(collector),
-                opctx.child(BTreeMap::new()),
-                vec![],
-            );
-
-            task
-        };
-
         // Background task: phantom disk detection
         let task_phantom_disks = {
             let detector =
@@ -230,6 +206,7 @@ impl BackgroundTasks {
             rx_blueprint.clone(),
             nexus_id.to_string(),
         );
+        let rx_blueprint_exec = blueprint_executor.watcher();
         let task_blueprint_executor = driver.register(
             String::from("blueprint_executor"),
             String::from("Executes the target blueprint"),
@@ -239,6 +216,37 @@ impl BackgroundTasks {
             vec![Box::new(rx_blueprint)],
         );
 
+        // Background task: inventory collector
+        //
+        // This currently depends on the "output" of the blueprint executor in
+        // order to automatically trigger inventory collection whenever the
+        // blueprint executor runs.  In the limit, this could become a problem
+        // because the blueprint executor might also depend indirectly on the
+        // inventory collector.  In that case, we may need to do something more
+        // complicated.  But for now, this works.
+        let task_inventory_collection = {
+            let collector = inventory_collection::InventoryCollector::new(
+                datastore.clone(),
+                resolver,
+                &nexus_id.to_string(),
+                config.inventory.nkeep,
+                config.inventory.disable,
+            );
+            let task = driver.register(
+                String::from("inventory_collection"),
+                String::from(
+                    "collects hardware and software inventory data from the \
+                    whole system",
+                ),
+                config.inventory.period_secs,
+                Box::new(collector),
+                opctx.child(BTreeMap::new()),
+                vec![Box::new(rx_blueprint_exec)],
+            );
+
+            task
+        };
+
         let task_service_zone_nat_tracker = {
             driver.register(
                 "service_zone_nat_tracker".to_string(),