feat(mcp): SNMP devices and Prometheus targets: their state, readings and series (#5840)

The snmp plugin registers list_snmp_devices and get_snmp_device; the
prometheus plugin registers list_prometheus_targets and
get_prometheus_target. Both are viewer-level, read what the poller and
scraper stored, and exist only while their plugin is enabled.
get_overview names a device or target whose last poll or scrape failed;
stale, pending and off are left out.

A device's community and v3 keys and a target's token are never
returned, and a password in a target URL is masked.

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

plugins/prometheus/__init__.py

@@ -68,3 +68,13 @@ def get_audit_entities() -> dict:
     from .models import PrometheusTarget, PrometheusWidgetTemplate
     return {"prometheus_target": (PrometheusTarget, "/plugins/prometheus/targets/{}"),
             "prometheus_template": (PrometheusWidgetTemplate, "/plugins/prometheus/templates/custom:{}")}
+
+
+def register_mcp_tools(register) -> None:
+    from .mcp_tools import register_tools
+    register_tools(register)
+
+
+async def mcp_overview(db) -> list[dict]:
+    from .mcp_tools import mcp_overview as findings
+    return await findings(db)

plugins/prometheus/mcp_tools.py

@@ -0,0 +1,114 @@
+"""The prometheus plugin's MCP tools and its get_overview findings (#5840).
+
+Registered through register_mcp_tools() in __init__.py, so they exist only
+while the plugin is enabled. They read what the scraper stored; nothing
+reaches a target, and a target's bearer token (or a password in its URL)
+is never returned.
+"""
+from __future__ import annotations
+
+from sqlalchemy import select
+
+from steward.core.metric_series import latest_values
+from steward.mcp.tools._shape import age_s, bounded, clamp_limit, db_session, iso, now_utc, pick, redact_url
+from steward.mcp.tools.overview import finding
+from steward.models.metrics import PluginMetricLatest
+from steward.models.users import UserRole
+
+from .models import PrometheusTarget
+from .routes import group_series
+from .service import OWN_METRICS, SOURCE, target_state
+
+REACHES = ("down", "stale", "pending", "up", "off")
+_ORDER = {r: i for i, r in enumerate(REACHES)}
+
+
+def _target_view(t: PrometheusTarget, own: dict, now) -> dict:
+    state = target_state(t, now)
+    return {"target_id": t.id, "name": t.name, "url": redact_url(t.url), "enabled": t.enabled,
+            "reach": state.reach, "says": state.says, "interval_s": t.interval_seconds,
+            "scraped_at": iso(t.last_scraped_at), "ok_at": iso(t.last_ok_at), "ok_age_s": age_s(t.last_ok_at, now),
+            "series_kept": t.last_kept, "series_dropped": t.last_dropped, "series_capped": t.last_capped,
+            "series_cap": t.series_cap, "keep": list(t.keep or []), "drop": list(t.drop or []),
+            "scrape_ms": own.get("scrape_ms")}
+
+
+async def list_prometheus_targets() -> dict:
+    """The /metrics endpoints Steward scrapes, not answering first.
+
+    `reach`: "down" (the last scrape failed; `says` is why), "stale" (not
+    scraped recently), "pending", "up" or "off". `series_kept` /
+    `series_dropped` count the newest scrape's series the keep/drop patterns
+    let through or left out; `series_capped` those past `series_cap`, which
+    were not stored. get_prometheus_target lists a target's series;
+    query_metrics(source_module="prometheus", resource=…, metric=…) reads
+    one's history.
+    """
+    now = now_utc()
+    async with db_session() as db:
+        targets = list((await db.execute(select(PrometheusTarget).order_by(PrometheusTarget.name))).scalars())
+        rows = (await db.execute(select(PluginMetricLatest).where(
+            PluginMetricLatest.source_module == SOURCE,
+            PluginMetricLatest.resource_name.in_([t.name for t in targets] or [""]),
+            PluginMetricLatest.metric_name == "scrape_ms"))).scalars()
+        own = {r.resource_name: {"scrape_ms": r.value} for r in rows}
+    views = [_target_view(t, own.get(t.name, {}), now) for t in targets]
+    views.sort(key=lambda v: (_ORDER[v["reach"]], v["name"].lower()))
+    return {"targets": views}
+
+
+async def get_prometheus_target(target: str, search: str = "", limit: int = 100) -> dict:
+    """One target's stored series, grouped by metric name, each with the
+    labels that tell its series apart and the newest value in its unit.
+
+    target: its name or id (list_prometheus_targets).
+    search: part of a metric name; empty for all.
+    limit: metric groups to return, default 100, max 500.
+
+    A state set (a series per state, one of them 1) is folded to the
+    current state. `resource` is what query_metrics takes for a series'
+    history (source_module "prometheus").
+    """
+    now = now_utc()
+    async with db_session() as db:
+        t = pick(target, list((await db.execute(select(PrometheusTarget))).scalars()),
+                 kind="Prometheus target", list_tool="list_prometheus_targets")
+        latest = await latest_values(db, SOURCE, t.name, include_children=True)
+    own = {r.metric_name: r.value for r in latest if r.resource_name == t.name and r.metric_name in OWN_METRICS}
+    groups = group_series(t.name, latest)
+    if search:
+        groups = [g for g in groups if search.lower() in g["metric"].lower()]
+
+    def row(r: dict, states: bool) -> dict:
+        if states:
+            return {"labels": r["labels"], "resource": r["resource"], "state": r["text"], "states": r["states"]}
+        return {"labels": r["labels"], "resource": r["resource"], "value": r["value"],
+                "shown": r["text"] or iso(r["moment"]), "at": iso(r["at"])}
+
+    shaped = [{"metric": g["metric"], "series": [row(r, g["states"]) for r in g["rows"][:50]],
+               **({"more_series": len(g["rows"]) - 50} if len(g["rows"]) > 50 else {})} for g in groups]
+    out = {"target": _target_view(t, own, now)}
+    out.update(bounded(shaped, clamp_limit(limit, 100, 500), key="metrics",
+                       more="Pass a `search`, or a larger `limit`."))
+    return out
+
+
+def target_findings(views: list[dict]) -> list[dict]:
+    """A target whose last scrape failed. Stale and off are the plugin or
+    the admin's choice, not the endpoint, so they are left out."""
+    return [finding("warning", "prometheus_target_down", v["name"],
+                    f"Prometheus target {v['name']} isn't answering: {v['says']}",
+                    since=v["_ok_at"], ids={"target_id": v["target_id"]},
+                    next=f'get_prometheus_target(target="{v["name"]}")')
+            for v in views if v["reach"] == "down"]
+
+
+async def mcp_overview(db) -> list[dict]:
+    now = now_utc()
+    targets = list((await db.execute(select(PrometheusTarget))).scalars())
+    return target_findings([_target_view(t, {}, now) | {"_ok_at": t.last_ok_at} for t in targets])
+
+
+def register_tools(register) -> None:
+    for fn in (list_prometheus_targets, get_prometheus_target):
+        register(fn, role=UserRole.viewer, read_only=True)