Comment duplicate setting in rough c3p0.properties, add some dev-notes.

dev-notes.md

@@ -0,0 +1,40 @@
+# dev-notes
+
+* It looks like throwing of PropertyVetoException may not be implemented for ostensibly constrained parameters:
+  - `connectionTesterClassName` (should classname params be constrained?)
+  - `contextClassLoaderSource`
+  - `markSessionBoundaries`
+  - `taskRunnerFactoryClassName` (should classname params be constrained?)
+  - `userOverridesAsString`
+  It might be disruptive to "fix" this now, as installations may have configs that are stable despite
+  bad (vetoable) settings.
+
+  If class name properties should be constrained, probably so too ought be
+  - `connectionCustomizerClassName`
+
+* When testing against intentionally chaotic configs, we occasionally see, at debug level FINE:
+  ```plaintext
+  2024-05-06@00:53:59 [FINE] [com.mchange.v2.c3p0.impl.NewPooledConnection] An exception occurred while resetting a closed Connection. Invalidating Connection. 
+  org.postgresql.util.PSQLException: This connection has been closed.
+      at org.postgresql.jdbc.PgConnection.checkClosed(PgConnection.java:993)
+      at org.postgresql.jdbc.PgConnection.getAutoCommit(PgConnection.java:953)
+      at com.mchange.v2.c3p0.impl.C3P0ImplUtils.resetTxnState(C3P0ImplUtils.java:207)
+      at com.mchange.v2.c3p0.impl.NewPooledConnection.reset(NewPooledConnection.java:429)
+      at com.mchange.v2.c3p0.impl.NewPooledConnection.markClosedProxyConnection(NewPooledConnection.java:385)
+      at com.mchange.v2.c3p0.impl.NewProxyConnection.close(NewProxyConnection.java:2150)
+      at com.mchange.v1.db.sql.ConnectionUtils.attemptClose(ConnectionUtils.java:53)
+      at com.mchange.v2.c3p0.impl.ConnectionTesterConnectionTestPath.testPooledConnection(ConnectionTesterConnectionTestPath.java:123)
+      at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:784)
+      at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:775)
+      at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:743)
+      at com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:2048)
+      at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696)
+  ```
+  It appears to be harmless -- just a debug notification that a physical Connection has already been closed
+  when it is tested as an idle resource. Still, why?
+  - It looks like it's just multiple tests backed up in the Connection pool, the first one causes the Connection to be closed,
+    a second one sees the Connection already closed. It appears no longer to appear if all of the following params are not set
+    * maxConnectionAge
+    * maxIdleTime
+    * maxIdleTimeExcessConnections
+    That is, if Connections aren't timed out, the condition does not appear.

test/resources-local-rough/c3p0.properties

@@ -11,7 +11,7 @@ c3p0.minPoolSize=10
 c3p0.maxPoolSize=40
 c3p0.checkoutTimeout=2000
 c3p0.connectionIsValidTimeout=1
-c3p0.idleConnectionTestPeriod=30
+#c3p0.idleConnectionTestPeriod=30
 c3p0.idleConnectionTestPeriod=1
 c3p0.maxConnectionAge=1
 c3p0.maxIdleTime=2