1 files changed, 54 insertions, 0 deletions
diff --git a/python/knot_resolver/utils/systemd_notify.py b/python/knot_resolver/utils/systemd_notify.py
new file mode 100644
index 00000000..44e8dee1
--- /dev/null
+++ b/python/knot_resolver/utils/systemd_notify.py
@@ -0,0 +1,54 @@
+import enum
+import logging
+import os
+import socket
+
+logger = logging.getLogger(__name__)
+
+
+class _Status(enum.Enum):
+    NOT_INITIALIZED = 1
+    FUNCTIONAL = 2
+    FAILED = 3
+
+
+_status = _Status.NOT_INITIALIZED
+_socket = None
+
+
+def systemd_notify(**values: str) -> None:
+    global _status
+    global _socket
+
+    if _status is _Status.NOT_INITIALIZED:
+        socket_addr = os.getenv("NOTIFY_SOCKET")
+        os.unsetenv("NOTIFY_SOCKET")
+        if socket_addr is None:
+            _status = _Status.FAILED
+            return
+        if socket_addr.startswith("@"):
+            socket_addr = socket_addr.replace("@", "\0", 1)
+
+        try:
+            _socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
+            _socket.connect(socket_addr)
+            _status = _Status.FUNCTIONAL
+        except Exception:
+            _socket = None
+            _status = _Status.FAILED
+            logger.warning(f"Failed to connect to $NOTIFY_SOCKET at '{socket_addr}'", exc_info=True)
+            return
+
+    elif _status is _Status.FAILED:
+        return
+
+    if _status is _Status.FUNCTIONAL:
+        assert _socket is not None
+        payload = "\n".join((f"{key}={value}" for key, value in values.items()))
+        try:
+            _socket.send(payload.encode("utf8"))
+        except Exception:
+            logger.warning("Failed to send notification to systemd", exc_info=True)
+            _status = _Status.FAILED
+            _socket.close()
+            _socket = None