new, simpler, cleaner, experimental timeout mechanism

etcd_wrapper.py

@@ -1,9 +1,13 @@
 import etcd3
 import json
 import signal
+import threading
+import time
 
-from dataclasses import dataclass
 from collections import namedtuple
+from dataclasses import dataclass
+from datetime import datetime
+from os import path
 
 PseudoEtcdMeta = namedtuple("PseudoEtcdMeta", ["key"])
 
@@ -47,26 +51,42 @@ class Etcd3Wrapper(object):
         for entry in r:
             yield EtcdEntry(*entry[::-1], value_in_json=value_in_json)
 
-    def watch_prefix(self, *args, timeout=0, 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:
+    #                 signal.alarm(0)
+    #                 # 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)
+    #                 signal.alarm(timeout)
+    #                 yield event
+    #         except TimeoutError:
+    #             _value = {"status": "TIMEOUT"}
+    #             yield EtcdEntry(PseudoEtcdMeta(key=b"TIMEOUT"), value=str.encode(json.dumps(_value)))
+    
+    def watch_prefix(self, key_prefix, timeout=0, value_in_json=False, **kwargs):
+        r, _ = self.client.watch_prefix(key_prefix, **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)
+            t = threading.Thread(target=create_timeout_event,
+                                 args=(timeout, key_prefix, self.client))
+            t.start()
         
-                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)))
+        for event in r:
+            if event.value:
+                event = EtcdEntry(event, event.value, value_in_json=value_in_json)
+                yield event        
 
-
-def raise_timeout(signum, frame):
-    _ = signum, frame
-    raise TimeoutError()
+def create_timeout_event(timeout, key_prefix, etcd_client):
+    while True:
+        time.sleep(timeout)
+        _value = {"status": "TIMEOUT", "last_timeout": datetime.utcnow().isoformat()}
+        _key = path.join(f"{key_prefix}", "TIMEOUT")
+        etcd_client.put(_key, _value, value_in_json=True)