feat(metrics): add collector + retention loops and wiring

backend/tests/test_metrics_collector.py

@@ -0,0 +1,51 @@
+"""Tests for metrics_collector.collect_once (unit-testable core)."""
+from unittest.mock import MagicMock
+from app.services.metrics_collector import collect_once
+
+
+def _client():
+    c = MagicMock()
+    # status/current
+    c.get_vm_status.return_value = {
+        "cpu": 0.5, "mem": 100, "maxmem": 200,
+        "netin": 1000, "netout": 2000, "diskread": 0, "diskwrite": 500,
+    }
+    c.get_vm_fsinfo.return_value = [{"used": 10, "total": 40}]
+    c.get_vm_blockstats.return_value = "drive-scsi0: rd_operations=100 wr_operations=50"
+    c.get_node_netstat.return_value = [
+        {"dev": "tap114i0", "vmid": "114", "in": "1000", "out": "2000"}]
+    return c
+
+
+def test_collect_once_first_tick_no_rates(db_session):
+    from app.models import InstanceMetric
+    items = [{"server_id": 1, "vmid": 114, "type": "qemu", "node": "prod", "status": "running"}]
+    clients = {1: _client()}
+    prev = {}
+    collect_once(db_session, items, clients, prev, _now=100.0)
+    db_session.commit()
+    m = db_session.query(InstanceMetric).one()
+    assert m.cpu == 0.5 and m.disk_used == 10 and m.disk_total == 40
+    assert m.netin_rate is None          # no previous counter yet
+    assert m.iops_read is None
+
+
+def test_collect_once_second_tick_computes_rates(db_session):
+    from app.models import InstanceMetric, InstanceNicMetric
+    items = [{"server_id": 1, "vmid": 114, "type": "qemu", "node": "prod", "status": "running"}]
+    c = _client()
+    clients = {1: c}
+    prev = {}
+    collect_once(db_session, items, clients, prev, _now=100.0)
+    # advance counters by 10 over 2 seconds
+    c.get_vm_status.return_value = {"cpu": 0.5, "mem": 100, "maxmem": 200,
+                                   "netin": 1020, "netout": 2040, "diskread": 0, "diskwrite": 500}
+    c.get_vm_blockstats.return_value = "drive-scsi0: rd_operations=110 wr_operations=56"
+    c.get_node_netstat.return_value = [{"dev": "tap114i0", "vmid": "114", "in": "1020", "out": "2040"}]
+    collect_once(db_session, items, clients, prev, _now=102.0)
+    db_session.commit()
+    rows = db_session.query(InstanceMetric).order_by(InstanceMetric.id).all()
+    assert rows[1].netin_rate == 10.0     # (1020-1000)/2
+    assert rows[1].iops_read == 5.0       # (110-100)/2
+    nic = db_session.query(InstanceNicMetric).order_by(InstanceNicMetric.id).all()[-1]
+    assert nic.in_rate == 10.0            # (1020-1000)/2