From 4835ca8c91a03b8ae5f1e99caf761d29d498f1cc Mon Sep 17 00:00:00 2001
From: damocles <damocles@hyperhive.local>
Date: Sat, 1 Aug 2026 14:54:47 +0200
Subject: [PATCH] hive-c0re: list_descendants reads cached container snapshot
 instead of live systemctl calls

---
 .../src/socket_server/lifecycle_handlers.rs   | 37 +++++++++++++------
 hive-c0re/src/socket_server/mod.rs            |  2 +-
 2 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/hive-c0re/src/socket_server/lifecycle_handlers.rs b/hive-c0re/src/socket_server/lifecycle_handlers.rs
index 997558e0..92a9312f 100644
--- a/hive-c0re/src/socket_server/lifecycle_handlers.rs
+++ b/hive-c0re/src/socket_server/lifecycle_handlers.rs
@@ -158,7 +158,7 @@ pub(super) fn handle_update(coord: &Arc<Coordinator>, agent: &str, name: &str) -
 
 /// `ListDescendants` — every topological descendant of `agent` with
 /// its running/stopped state, parents before children.
-pub(super) async fn handle_list_descendants(agent: &str) -> Response {
+pub(super) async fn handle_list_descendants(coord: &Arc<Coordinator>, agent: &str) -> Response {
     tracing::debug!(%agent, "agent: list descendants");
     // Walk the full topology and collect every descendant.
     let topo = crate::topology::read();
@@ -169,16 +169,29 @@ pub(super) async fn handle_list_descendants(agent: &str) -> Response {
         .collect();
     // Parents before children, then alpha within each tier.
     crate::auto_update::topology_sort(&mut names, &topo);
-    // Query each container's actual systemd unit state (same source
-    // `container_view::build_all` uses for the dashboard). `nixos-container
-    // list` — what this used to key off of via a "known containers" set —
-    // reports every *registered* container, stopped and ghost-registered
-    // (machined still holds the name after a crashed/killed process) ones
-    // included, so membership there is not the same thing as "running".
-    let mut containers = Vec::with_capacity(names.len());
-    for name in names {
-        let running = crate::lifecycle::is_running(&name).await;
-        containers.push(hive_sh4re::ContainerInfo { name, running });
-    }
+    // Read from the coordinator's cached container snapshot instead of
+    // live-querying each container's systemd unit state — the same
+    // `containers_snapshot()` the dashboard's `/api/state` cold-load path
+    // already uses, kept fresh by `rescan_containers_and_emit()` on every
+    // mutation plus the crash-watcher's periodic poll. Avoids N
+    // `systemctl is-active` subprocess spawns per `list_containers` call;
+    // per mara, daemons should do the expensive work themselves and serve
+    // clients a cheap cached read.
+    let snapshot = coord.containers_snapshot().await;
+    let running_by_name: std::collections::HashMap<&str, bool> = snapshot
+        .iter()
+        .map(|v| (v.name.as_str(), v.running))
+        .collect();
+    let containers = names
+        .into_iter()
+        .map(|name| {
+            // A descendant absent from the snapshot (not yet scanned since
+            // its own registration, e.g. mid-spawn) reads as not running
+            // rather than erroring — matches the old membership-check's
+            // default-false behavior for an unknown name.
+            let running = running_by_name.get(name.as_str()).copied().unwrap_or(false);
+            hive_sh4re::ContainerInfo { name, running }
+        })
+        .collect();
     Response::Containers { containers }
 }
diff --git a/hive-c0re/src/socket_server/mod.rs b/hive-c0re/src/socket_server/mod.rs
index e9cfc3d0..c2f65173 100644
--- a/hive-c0re/src/socket_server/mod.rs
+++ b/hive-c0re/src/socket_server/mod.rs
@@ -574,7 +574,7 @@ async fn dispatch(req: &Request, agent: &str, coord: &Arc<Coordinator>) -> Respo
         Request::Restart { name } => handle_restart(coord, agent, name).await,
         Request::Kill { name } => handle_kill(coord, agent, name).await,
         Request::Update { name } => handle_update(coord, agent, name),
-        Request::ListDescendants => handle_list_descendants(agent).await,
+        Request::ListDescendants => handle_list_descendants(coord, agent).await,
         Request::RequestInitConfig { name, description } => {
             handle_request_init_config(coord, agent, name, description.clone())
         }