From: Alan T. DeKok <aland@freeradius.org>
Date: Wed, 29 Nov 2023 15:25:48 +0000 (-0500)
Subject: more notes on connection starvation
X-Git-Tag: release_3_2_4~109
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a69bc4a6b236fd8aa985c5ef246f366ccb70cb41;p=thirdparty%2Ffreeradius-server.git

more notes on connection starvation
---

diff --git a/raddb/mods-available/sql b/raddb/mods-available/sql
index db58421ede..68ac4da753 100644
--- a/raddb/mods-available/sql
+++ b/raddb/mods-available/sql
@@ -291,6 +291,23 @@ sql {
 		#
 		#  Setting 'max' to MORE than the number of threads means
 		#  that there are more connections than necessary.
+		#
+		#  The setting here should be lower than the maximum
+		#  number of connections allowed by the database.
+		#
+		#  i.e. There is no point in telling FreeRADIUS to use
+		#  64 connections, while the database is limited to 32
+		#  connections.  That configuration will cause the
+		#  server to be "starved" of connections, and it will
+		#  block during normal operations, even when the
+		#  database is largely idle.
+		#
+		#  At the same time, if the database is slow, there is
+		#  no point in increasing "max".  More connections
+		#  will just cause the database to run more slowly.
+		#  The correct fix for a slow database is to fix it, so
+		#  that it responds to FreeRADIUS quickly.
+		#
 		max = ${thread[pool].max_servers}
 
 		#  Spare connections to be left idle