From d9eac6659aec6d0199ccf9d8b9078970397e281e Mon Sep 17 00:00:00 2001
From: John Thiltges <jthiltges2@unl.edu>
Date: Fri, 26 May 2023 15:36:43 -0500
Subject: [PATCH 1/2] Periodically reload topology data in a background thread

---
 src/app.py           | 31 +++++++++++++++++++++++++++++++
 src/webapp/models.py | 28 +++++++++++++++++-----------
 2 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/src/app.py b/src/app.py
index 366ab6a4d..8033a097d 100755
--- a/src/app.py
+++ b/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 = min(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"""
diff --git a/src/webapp/models.py b/src/webapp/models.py
index d8748ee74..21df4c8f9 100644
--- a/src/webapp/models.py
+++ b/src/webapp/models.py
@@ -261,20 +261,26 @@ def get_topology(self) -> Optional[Topology]:
         May return None if we fail to get the data for the first time.
         """
         if self.topology.should_update():
-            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.

From bc07037b74fcef3c71195f15d73dd016c1ae1032 Mon Sep 17 00:00:00 2001
From: John Thiltges <jthiltges2@unl.edu>
Date: Tue, 30 Apr 2024 16:42:56 -0500
Subject: [PATCH 2/2] Fix bg_update_freq logic, using max instead of min.

Thanks for noticing it, Mat!
---
 src/app.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/app.py b/src/app.py
index 8033a097d..eddc96d49 100755
--- a/src/app.py
+++ b/src/app.py
@@ -121,7 +121,7 @@ def _verify_config(cfg):
 #############################################################################
 # Background update thread
 # Run when the topology cache is 2/3 to expiration
-bg_update_freq = min(global_data.topology.cache_lifetime*2/3, 60) # seconds
+bg_update_freq = max(global_data.topology.cache_lifetime*2/3, 60) # seconds
 bg_update_thread = threading.Thread()
 
 def bg_update_run():