Merge pull request opensciencegrid#3187 from jthiltges/pr/bgcache

Periodically reload topology data in a background thread

src/app.py

@@ -8,11 +8,13 @@
 from io import StringIO
 import logging
 import os
+import random
 import re
 import sys
 import traceback
 import urllib.parse
 import requests
+import threading
 from wtforms import ValidationError
 from flask_wtf.csrf import CSRFProtect
 
@@ -116,6 +118,35 @@ def _verify_config(cfg):
 csrf = CSRFProtect()
 csrf.init_app(app)
 
+#############################################################################
+# Background update thread
+# Run when the topology cache is 2/3 to expiration
+bg_update_freq = max(global_data.topology.cache_lifetime*2/3, 60) # seconds
+bg_update_thread = threading.Thread()
+
+def bg_update_run():
+    '''Background update task'''
+    app.logger.debug('Background update started')
+    global_data.update_topology()
+
+    # Add +/- 10% random offset to avoid thundering herds
+    delay = bg_update_freq
+    delay *= random.uniform(0.9, 1.1)
+
+    # Set next run
+    global bg_update_thread
+    bg_update_thread = threading.Timer(delay, bg_update_run, ())
+    bg_update_thread.daemon = True
+    bg_update_thread.start()
+    app.logger.info('Background update complete')
+
+# Start background update thread
+bg_update_thread = threading.Timer(bg_update_freq, bg_update_run, ())
+# Make it a daemon thread, so interpreter won't wait on it when exiting
+bg_update_thread.daemon = True
+bg_update_thread.start()
+#############################################################################
+
 
 def _fix_unicode(text):
     """Convert a partial unicode string to full unicode"""

src/webapp/models.py

@@ -288,20 +288,26 @@ def get_topology(self) -> Optional[Topology]:
         """
         if self.topology.should_update():
             with topology_update_summary.time():
-                ok = self._update_topology_repo()
-                if ok:
-                    try:
-                        self.topology.update(rg_reader.get_topology(self.topology_dir, self.get_contacts_data(), strict=self.strict))
-                    except Exception:
-                        if self.strict:
-                            raise
-                        log.exception("Failed to update topology")
-                        self.topology.try_again()
-                else:
-                    self.topology.try_again()
+                self.update_topology()
 
         return self.topology.data
 
+    def update_topology(self):
+        """
+        Update topology data
+        """
+        ok = self._update_topology_repo()
+        if ok:
+            try:
+                self.topology.update(rg_reader.get_topology(self.topology_dir, self.get_contacts_data(), strict=self.strict))
+            except Exception:
+                if self.strict:
+                    raise
+                log.exception("Failed to update topology")
+                self.topology.try_again()
+        else:
+            self.topology.try_again()
+
     def get_vos_data(self) -> Optional[VOsData]:
         """
         Get VO Data.