From 95689e3c99dedf386de873812718fa647d4f5048 Mon Sep 17 00:00:00 2001
From: Jan Eitzinger <jan@moebiusband.org>
Date: Wed, 28 Jan 2026 07:05:29 +0100
Subject: [PATCH] Add API endpoint for getUsedNodes

Needed by dynamic memory management for external ccms
---
 internal/api/api_test.go | 34 +++++++++++++++++++++++++
 internal/api/job.go      | 54 ++++++++++++++++++++++++++++++++++++++++
 internal/api/rest.go     |  5 ++--
 3 files changed, 91 insertions(+), 2 deletions(-)

diff --git a/internal/api/api_test.go b/internal/api/api_test.go
index 4a7fc07c..8cbf95d7 100644
--- a/internal/api/api_test.go
+++ b/internal/api/api_test.go
@@ -455,4 +455,38 @@ func TestRestApi(t *testing.T) {
 	if !ok {
 		t.Fatal("subtest failed")
 	}
+
+	t.Run("GetUsedNodesNoRunning", func(t *testing.T) {
+		contextUserValue := &schema.User{
+			Username:   "testuser",
+			Projects:   make([]string, 0),
+			Roles:      []string{"api"},
+			AuthType:   0,
+			AuthSource: 2,
+		}
+
+		req := httptest.NewRequest(http.MethodGet, "/jobs/used_nodes?ts=123456790", nil)
+		recorder := httptest.NewRecorder()
+
+		ctx := context.WithValue(req.Context(), contextUserKey, contextUserValue)
+
+		r.ServeHTTP(recorder, req.WithContext(ctx))
+		response := recorder.Result()
+		if response.StatusCode != http.StatusOK {
+			t.Fatal(response.Status, recorder.Body.String())
+		}
+
+		var result api.GetUsedNodesAPIResponse
+		if err := json.NewDecoder(response.Body).Decode(&result); err != nil {
+			t.Fatal(err)
+		}
+
+		if result.UsedNodes == nil {
+			t.Fatal("expected usedNodes to be non-nil")
+		}
+
+		if len(result.UsedNodes) != 0 {
+			t.Fatalf("expected no used nodes for stopped jobs, got: %v", result.UsedNodes)
+		}
+	})
 }
diff --git a/internal/api/job.go b/internal/api/job.go
index 1b1e05d6..64f6a92c 100644
--- a/internal/api/job.go
+++ b/internal/api/job.go
@@ -1021,3 +1021,57 @@ func (api *RestAPI) getJobMetrics(rw http.ResponseWriter, r *http.Request) {
 		cclog.Errorf("Failed to encode response: %v", err)
 	}
 }
+
+// GetUsedNodesAPIResponse model
+type GetUsedNodesAPIResponse struct {
+	UsedNodes map[string][]string `json:"usedNodes"` // Map of cluster names to lists of used node hostnames
+}
+
+// getUsedNodes godoc
+// @summary     Lists used nodes by cluster
+// @tags Job query
+// @description Get a map of cluster names to lists of unique hostnames that are currently in use by running jobs that started before the specified timestamp.
+// @produce     json
+// @param       ts             query    int               true  "Unix timestamp to filter jobs (jobs with start_time < ts)"
+// @success     200            {object} api.GetUsedNodesAPIResponse  "Map of cluster names to hostname lists"
+// @failure     400            {object} api.ErrorResponse            "Bad Request"
+// @failure     401            {object} api.ErrorResponse            "Unauthorized"
+// @failure     403            {object} api.ErrorResponse            "Forbidden"
+// @failure     500            {object} api.ErrorResponse            "Internal Server Error"
+// @security    ApiKeyAuth
+// @router      /api/jobs/used_nodes [get]
+func (api *RestAPI) getUsedNodes(rw http.ResponseWriter, r *http.Request) {
+	if user := repository.GetUserFromContext(r.Context()); user != nil &&
+		!user.HasRole(schema.RoleApi) {
+		handleError(fmt.Errorf("missing role: %v", schema.GetRoleString(schema.RoleApi)), http.StatusForbidden, rw)
+		return
+	}
+
+	tsStr := r.URL.Query().Get("ts")
+	if tsStr == "" {
+		handleError(fmt.Errorf("missing required query parameter: ts"), http.StatusBadRequest, rw)
+		return
+	}
+
+	ts, err := strconv.ParseInt(tsStr, 10, 64)
+	if err != nil {
+		handleError(fmt.Errorf("invalid timestamp format: %w", err), http.StatusBadRequest, rw)
+		return
+	}
+
+	usedNodes, err := api.JobRepository.GetUsedNodes(ts)
+	if err != nil {
+		handleError(fmt.Errorf("failed to get used nodes: %w", err), http.StatusInternalServerError, rw)
+		return
+	}
+
+	rw.Header().Add("Content-Type", "application/json")
+	payload := GetUsedNodesAPIResponse{
+		UsedNodes: usedNodes,
+	}
+
+	if err := json.NewEncoder(rw).Encode(payload); err != nil {
+		handleError(err, http.StatusInternalServerError, rw)
+		return
+	}
+}
diff --git a/internal/api/rest.go b/internal/api/rest.go
index c0fa7c2a..0d52742e 100644
--- a/internal/api/rest.go
+++ b/internal/api/rest.go
@@ -89,8 +89,7 @@ func (api *RestAPI) MountAPIRoutes(r *mux.Router) {
 		r.HandleFunc("/jobs/stop_job/", api.stopJobByRequest).Methods(http.MethodPost, http.MethodPut)
 	}
 	r.HandleFunc("/jobs/", api.getJobs).Methods(http.MethodGet)
-	r.HandleFunc("/jobs/{id}", api.getJobByID).Methods(http.MethodPost)
-	r.HandleFunc("/jobs/{id}", api.getCompleteJobByID).Methods(http.MethodGet)
+	r.HandleFunc("/jobs/used_nodes", api.getUsedNodes).Methods(http.MethodGet)
 	r.HandleFunc("/jobs/tag_job/{id}", api.tagJob).Methods(http.MethodPost, http.MethodPatch)
 	r.HandleFunc("/jobs/tag_job/{id}", api.removeTagJob).Methods(http.MethodDelete)
 	r.HandleFunc("/jobs/edit_meta/{id}", api.editMeta).Methods(http.MethodPost, http.MethodPatch)
@@ -98,6 +97,8 @@ func (api *RestAPI) MountAPIRoutes(r *mux.Router) {
 	r.HandleFunc("/jobs/delete_job/", api.deleteJobByRequest).Methods(http.MethodDelete)
 	r.HandleFunc("/jobs/delete_job/{id}", api.deleteJobByID).Methods(http.MethodDelete)
 	r.HandleFunc("/jobs/delete_job_before/{ts}", api.deleteJobBefore).Methods(http.MethodDelete)
+	r.HandleFunc("/jobs/{id}", api.getJobByID).Methods(http.MethodPost)
+	r.HandleFunc("/jobs/{id}", api.getCompleteJobByID).Methods(http.MethodGet)
 
 	r.HandleFunc("/tags/", api.removeTags).Methods(http.MethodDelete)