clan_lib: add 'get_metrics' API endpoint

pkgs/clan-cli/clan_lib/metrics/telegraf.py

@@ -0,0 +1,71 @@
+import json
+import logging
+import urllib.request
+from base64 import b64encode
+from collections.abc import Iterator
+from typing import Any, TypedDict, cast
+
+from clan_cli.vars.get import get_machine_var
+
+from clan_lib.errors import ClanError
+from clan_lib.machines.machines import Machine
+from clan_lib.ssh.host import Host
+
+log = logging.getLogger(__name__)
+
+
+class MetricSample(TypedDict):
+    fields: dict[str, Any]
+    name: str
+    tags: dict[str, str]
+    timestamp: int
+
+
+def get_metrics(
+    machine: Machine,
+    target_host: Host,
+) -> Iterator[MetricSample]:
+    """Fetch Prometheus metrics from telegraf and return them as streaming metrics.
+    Args:
+        machine: The Machine instance to check.
+        target_host: Remote instance representing the target host.
+    Returns:
+        Iterator[dict[str, Any]]: An iterator yielding parsed metric dictionaries line by line.
+    """
+
+    # Example: fetch Prometheus metrics with basic auth
+    url = f"http://{target_host.address}:9990"
+    username = "prometheus"
+    var_name = "telegraf/password"
+    password_var = get_machine_var(machine, var_name)
+    if not password_var.exists:
+        msg = (
+            f"Missing required var '{var_name}' for machine '{machine.name}'.\n"
+            "Ensure the 'monitoring' clanService is enabled and run `clan machines update {machine.name}`."
+            "For more information, see: https://docs.clan.lol/reference/clanServices/monitoring/"
+        )
+        raise ClanError(msg)
+
+    password = password_var.value.decode("utf-8")
+    credentials = f"{username}:{password}"
+
+    encoded_credentials = b64encode(credentials.encode("utf-8")).decode("utf-8")
+    headers = {"Authorization": f"Basic {encoded_credentials}"}
+    req = urllib.request.Request(url, headers=headers)
+
+    try:
+        response = urllib.request.urlopen(req)
+        for line in response:
+            line_str = line.decode("utf-8").strip()
+            if line_str:
+                try:
+                    yield cast(MetricSample, json.loads(line_str))
+                except json.JSONDecodeError:
+                    log.warning(f"Skipping invalid JSON line: {line_str}")
+                    continue
+    except Exception as e:
+        msg = (
+            f"Failed to fetch Prometheus metrics from {url} for machine '{machine.name}': {e}\n"
+            "Ensure the telegraf.service is running and accessible."
+        )
+        raise ClanError(msg) from e