feat(snmp): devices you add, test and read on the SNMP page (milestone 491)

The operator, reviewing SNMP on #5214: "this system looks incomplete like
there's something missing from it". The one device shown was plugin.yaml's
example (core-switch 192.168.1.1, community public), polled every minute;
devices could only be defined by editing YAML in the image; a failed poll was
logged at DEBUG and stored nowhere, so the page said "waiting for the next
poll" forever; v3 ran as v2c; counters showed as lifetime totals.

- Devices are rows (snmp_devices, migration snmp_001): address, port,
  v1/v2c community or a v3 user with auth/priv protocols and keys (secrets
  encrypted), presets plus custom readings, an optional host binding, and
  the newest poll's outcome. The YAML device list and its example are gone.
- The SNMP page adds, edits and deletes them (admin, audited, with
  get_audit_entities so the audit log names and links a device). Readings
  come from presets (system uptime, interface traffic by number, UPS-MIB,
  Linux net-snmp) and custom "OID name [unit]" lines.
- One GET per device with every OID, devices polled at once. The outcome is
  written to the row in words ("No reply from … within 5 s. Check the address
  and port, that SNMP is on, and the community"), with readings it lacks.
  v1's whole-request error drops that OID and asks again. SNMPv3 signs in
  with USM (MD5/SHA-1/SHA-2, DES/3DES/AES).
- Test asks the unsaved form's device for its name, description, uptime and
  interfaces by number. It is an admin's explicit action; every page reads
  only stored rows (System 178's ruling).
- Each reading has a unit; a counter is stored as a per-second rate (bytes as
  bit/s), a reset or wrap skipped. The page, widget and host panel say values
  in units and why a device is silent; the device page draws a chart per
  reading on a dated axis.

Tests: readings and presets, the form and its secrets, v3 checks, rates,
the poller against a stand-in pysnmp (one GET, v1 retry, timeout wording,
USM), the pages, and an integration test of the poll writing outcomes and
rates on Postgres.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/plugins/snmp/test_snmp_widget.py

@@ -1,56 +1,37 @@
-"""The dashboard SNMP widget (#5255): a verdict, devices that stopped answering
-first, status in words, and key readings with their units."""
+"""The dashboard SNMP widget (#5255, milestone 491): a verdict, devices not
+answering first with since when, status in words, two readings in units."""
 from datetime import datetime, timedelta, timezone
 
-import pytest
-
-from plugins.snmp.routes import key_readings, snmp_reading
 from tests._templates import render_plugin_template
 
 
-@pytest.mark.parametrize("label, value, says", [
-    ("uptime_centisecs", 105_120_000, ("uptime", "12d 4h")),
-    ("battery_charge_pct", 99.6, ("battery charge", "100%")),
-    ("input_voltage_dV", 1203, ("input voltage", "120.3 V")),
-    ("if1_in_octets", 1536, ("if1 in", "1.5 KiB total")),
-    ("battery_status", 2, ("battery status", "2")),
-    ("temperature", 41.25, ("temperature", "41.25")),
-])
-def test_a_reading_reads_with_its_unit(label, value, says):
-    assert snmp_reading(label, value) == says
-
-
-def test_key_readings_prefer_gauges_to_counters_in_config_order():
-    oids = [{"oid": "a", "label": "if1_in_octets"}, {"oid": "b", "label": "uptime_centisecs"},
-            {"oid": "c", "label": "if1_out_octets"}, {"oid": "1.2.3"}]
-    readings = {"if1_in_octets": 10, "uptime_centisecs": 6000, "if1_out_octets": 20, "1.2.3": 7}
-    assert [n for n, _ in key_readings(oids, readings)] == ["uptime", "1.2.3"]
-    assert [n for n, _ in key_readings(oids[:1] + oids[2:3], readings)] == ["if1 in", "if1 out"]
-    assert key_readings(oids, {}) == []
-
-
-def _dev(name, reach, minutes_ago=None, key=()):
-    at = datetime.now(timezone.utc) - timedelta(minutes=minutes_ago) if minutes_ago is not None else None
-    return {"name": name, "reach": reach, "at": at, "readings": {}, "key": list(key)}
+def _dev(name, reach, ok_minutes=None, key=()):
+    now = datetime.now(timezone.utc)
+    return {"id": f"id-{name}", "name": name, "reach": reach, "says": "No reply.",
+            "polled_at": now - timedelta(seconds=30),
+            "ok_at": now - timedelta(minutes=ok_minutes) if ok_minutes is not None else None,
+            "key": [{"name": n, "text": t} for n, t in key]}
 
 
 async def test_a_silent_device_leads_with_since_when(app):
-    devices = [_dev("ups", "stale", 14, [("battery charge", "100%")]), _dev("printer", "pending"),
-               _dev("switch", "up", 1, [("uptime", "12d 4h")])]
+    devices = [_dev("ups", "down", 14, [("Charge", "100%")]), _dev("printer", "pending"),
+               _dev("switch", "up", 1, [("Uptime", "12d 4h")])]
     async with app.test_request_context("/plugins/snmp/widget"):
         page = await render_plugin_template(app, "snmp", "snmp/widget.html", devices=devices, more=0,
-                                            counts={"stale": 1, "pending": 1, "up": 1}, total=3)
+                                            counts={"down": 1, "stale": 0, "pending": 1, "up": 1}, total=3)
     page = " ".join(page.split())
-    assert "ups: no reply since" in page and ">14m ago<" in page
+    assert "ups isn't answering." in page and "no reply since" in page and ">14m ago<" in page
     assert page.count("<th>Device</th>") == 1
     assert page.index('title="ups"') < page.index('title="printer"') < page.index('title="switch"')
-    assert "no data yet" in page and "uptime</span> 12d 4h" in page
-    assert "detail →" not in page and "&#9675;" not in page
+    assert "not polled yet" in page and "Uptime</span> 12d 4h" in page
 
 
 async def test_all_answering_says_so(app):
     async with app.test_request_context("/plugins/snmp/widget"):
         page = await render_plugin_template(app, "snmp", "snmp/widget.html",
                                             devices=[_dev("switch", "up", 1)], more=0,
-                                            counts={"stale": 0, "pending": 0, "up": 1}, total=1)
+                                            counts={"down": 0, "stale": 0, "pending": 0, "up": 1}, total=1)
+        empty = await render_plugin_template(app, "snmp", "snmp/widget.html", devices=[], more=0,
+                                             counts={}, total=0)
     assert "All 1 device answering." in page and "—" in page
+    assert "No SNMP devices yet." in empty