Send Signal alert on alertmanager hook

README.md

@@ -8,6 +8,10 @@ Provide ways to send notifications to signal-cli through webhooks
 virtualenv -p python3 --system-site-packages venv
 source venv/bin/activate
 pip install -r requirements.txt
+
+# Configure
+cp signal_webhook/configuration.sample.py signal_webhook/configuration.py
+$EDITOR signal_webhook/configuration.py
 ```
 
 **Beware!** Sending messages to Signal requires `gi`, which cannot be installed

requirements.txt

@@ -0,0 +1,2 @@
+Flask
+pydbus

signal_webhook/.gitignore

@@ -0,0 +1 @@
+configuration.py

signal_webhook/app.py

@@ -0,0 +1,47 @@
+import typing as t
+from collections import defaultdict
+from flask import Flask, request
+from . import signal
+from . import configuration
+
+app = Flask(__name__)
+
+
+@app.route("/")
+def root() -> t.Tuple[str, int]:
+    return "Not supported.", 400
+
+
+@app.route("/alertmanager", methods=["POST"])
+def alertmanager():
+    data = request.get_json(cache=False)
+
+    if "version" not in data or int(data["version"]) != 4:
+        return "Bad API version", 400
+    if "alerts" not in data:
+        return "No alerts", 400
+    if "status" not in data:
+        return "No status", 400
+    if data["status"] != "firing":
+        # Ignore
+        return "OK", 200
+
+    severities = defaultdict(int)
+    alert_lines = []
+    for alert in data["alerts"]:
+        try:
+            severities[alert["labels"]["severity"]] += 1
+            alert_lines.append(
+                f"<{alert['labels']['alertname']}> {alert['annotations']['description']}"
+            )
+        except KeyError as exn:
+            alert_lines.append(f"(malformed alert — {exn})")
+
+    msg = f"[PROMETHEUS] {len(data['alerts'])} firing: "
+    msg += ", ".join([f"{count} {typ}" for typ, count in severities.items()])
+    msg += "\n\n"
+    msg += "\n".join(["* " + line for line in alert_lines])
+
+    signal.signal_send(configuration.RECIPIENTS[configuration.DEFAULT_RECIPIENT], msg)
+
+    return "OK", 200

signal_webhook/configuration.sample.py

@@ -0,0 +1,5 @@
+# Signal 'address book'
+RECIPIENTS = {"foo": "+42..."}  # FIXME
+
+# Recipient from the dict above to send to by default
+DEFAULT_RECIPIENT = "foo"  # FIXME

signal_webhook/signal.py

@@ -0,0 +1,18 @@
+import logging
+from pydbus import SystemBus
+from gi.repository.GLib import GError
+
+logger = logging.getLogger(__name__)
+
+
+def signal_send(recipient, message):
+    try:
+        bus = SystemBus()
+        signal_bus = bus.get("org.asamk.Signal")
+        signal_bus.sendMessage(
+            message,
+            [],
+            [recipient],
+        )
+    except GError as exn:
+        logger.error("Cannot send Signal notification: %s", exn)