Add dashboard statistics module and refactor views for metrics handling

- Introduced a new `stats.py` module to encapsulate dashboard statistics building and cache key constants.
- Refactored `views.py` to utilize the new `build_stats` function for constructing metrics context, improving code organization and readability.
- Updated Prometheus query handling to streamline metrics fetching with a new `fetch_dashboard_metrics` function.
- Enhanced test cases to reflect changes in metrics fetching and context building, ensuring accurate functionality.
- Added new HTML templates for displaying detailed resource allocation and flavor statistics on the dashboard.

dashboard/prometheus_utils/query.py

@@ -1,9 +1,37 @@
+from concurrent.futures import ThreadPoolExecutor, as_completed
+
 import requests
 from watcher_visio.settings import PROMETHEUS_URL
 
 # Timeout for lightweight health check (seconds)
 CHECK_TIMEOUT = 5
 
+# Dashboard Prometheus queries (query_key -> query string), run in parallel
+DASHBOARD_QUERIES = {
+    "hosts_total": "count(node_exporter_build_info{job='node_exporter_compute'})",
+    "pcpu_total": (
+        "sum(count(node_cpu_seconds_total{job='node_exporter_compute', mode='idle'}) "
+        "without (cpu,mode))"
+    ),
+    "pcpu_usage": "sum(node_load5{job='node_exporter_compute'})",
+    "vcpu_allocated": "sum(libvirt_domain_info_virtual_cpus)",
+    "vcpu_overcommit_max": (
+        "avg(openstack_placement_resource_allocation_ratio{resourcetype='VCPU'})"
+    ),
+    "pram_total": "sum(node_memory_MemTotal_bytes{job='node_exporter_compute'})",
+    "pram_usage": "sum(node_memory_Active_bytes{job='node_exporter_compute'})",
+    "vram_allocated": "sum(libvirt_domain_info_maximum_memory_bytes)",
+    "vram_overcommit_max": (
+        "avg(avg_over_time("
+        "openstack_placement_resource_allocation_ratio{resourcetype='MEMORY_MB'}[5m]))"
+    ),
+    "vm_count": "sum(libvirt_domain_state_code)",
+    "vm_active": "sum(libvirt_domain_state_code{stateDesc='the domain is running'})",
+}
+
+# Keys that should be parsed as float (rest as int)
+DASHBOARD_FLOAT_KEYS = frozenset(("pcpu_usage", "vcpu_overcommit_max", "vram_overcommit_max"))
+
 
 def check_prometheus() -> dict:
     """
@@ -36,3 +64,23 @@ def query_prometheus(query: str) -> str | list[str]:
         return result
     else:
         return result[0]["value"][1]
+
+
+def fetch_dashboard_metrics() -> dict:
+    """Run all dashboard Prometheus queries in parallel and return a dict of name -> value."""
+    result = {}
+    with ThreadPoolExecutor(max_workers=len(DASHBOARD_QUERIES)) as executor:
+        future_to_key = {
+            executor.submit(query_prometheus, query=q): key for key, q in DASHBOARD_QUERIES.items()
+        }
+        for future in as_completed(future_to_key):
+            key = future_to_key[future]
+            try:
+                raw = future.result()
+                if key in DASHBOARD_FLOAT_KEYS:
+                    result[key] = float(raw)
+                else:
+                    result[key] = int(raw)
+            except (ValueError, TypeError):
+                result[key] = float(0) if key in DASHBOARD_FLOAT_KEYS else 0
+    return result