timeout option added in etcd_wrapper.watch_prefix()

etcd_wrapper.py

@@ -1,6 +1,11 @@
 import etcd3
 import json
+import signal
+
 from dataclasses import dataclass
+from collections import namedtuple
+
+PseudoEtcdMeta = namedtuple("PseudoEtcdMeta", ["key"])
 
 
 @dataclass(init=False)
@@ -42,11 +47,26 @@ class Etcd3Wrapper(object):
         for entry in r:
             yield EtcdEntry(*entry[::-1], value_in_json=value_in_json)
 
-    def watch_prefix(self, *args, value_in_json=False, **kwargs):
+    def watch_prefix(self, *args, timeout=0, value_in_json=False, **kwargs):
+        if timeout > 0:
+            signal.signal(signal.SIGALRM, raise_timeout)
+        while True:
+            try:
+                if timeout > 0:
+                    signal.alarm(timeout)
                 r, _ = self.client.watch_prefix(*args, **kwargs)
+
                 for event in r:
                     # if e.value is None don't propagate its value
                     if event.value is None:
                         continue
                     event = EtcdEntry(event, event.value, value_in_json=value_in_json)
                     yield event
+            except TimeoutError:
+                _value = {"status": "TIMEOUT"}
+                yield EtcdEntry(PseudoEtcdMeta(key=b"TIMEOUT"), value=str.encode(json.dumps(_value)))
+
+
+def raise_timeout(signum, frame):
+    _ = signum, frame
+    raise TimeoutError()