Author: markt
Date: Sun Oct 16 20:10:21 2011
New Revision: 1184921
URL: http://svn.apache.org/viewvc?rev=1184921&view=rev
Log:
Update docs in light of https://issues.apache.org/bugzilla/show_bug.cgi?id=52025
Modified:
tomcat/tc7.0.x/trunk/ (props changed)
tomcat/tc7.0.x/trunk/webapps/docs/changelog.xml
tomcat/tc7.0.x/trunk/webapps/docs/jndi-datasource-examples-howto.xml
Propchange: tomcat/tc7.0.x/trunk/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Sun Oct 16 20:10:21 2011
@@ -1 +1 @@
-/tomcat/trunk:1156115,1156171,1156276,1156304,1156519,1156530,1156602,1157015,1157018,1157151,1157198,1157204,1157810,1157832,1157834,1157847,1157908,1157939,1158155,1158160,1158176,1158195,1158198-1158199,1158227,1158331,1158334-1158335,1158426,1160347,1160592,1160611,1160619,1160626,1160639,1160652,1160720-1160721,1160772,1160774,1160776,1161303,1161310,1161322,1161339,1161486,1161540,1161549,1161584,1162082,1162149,1162169,1162721,1162769,1162836,1162932,1163630,1164419,1164438,1164469,1164480,1164567,1165234,1165247-1165248,1165253,1165273,1165282,1165309,1165331,1165338,1165347,1165360-1165361,1165367-1165368,1165602,1165608,1165677,1165693,1165721,1165723,1165728,1165730,1165738,1165746,1165765,1165777,1165918,1165921,1166077,1166150-1166151,1166290,1166366,1166620,1166686,1166752,1166757,1167368,1167394,1169447,1170647,1171692,1172233-1172234,1172236,1172269,1172278,1172282,1172610,1172664,1172689,1172711,1173020-1173021,1173082,1173088,1173090,1173096,1173241,1173256
,1173288,1173333,1173342,1173461,1173614,1173630,1173659,1173722,1174061,1174239,1174322,1174325,1174329-1174330,1174337-1174339,1174343,1174353,1174799,1174882,1174884,1174983,1175155,1175158,1175167,1175182,1175190,1175201,1175272,1175275,1175283,1175582,1175589-1175590,1175594,1175602,1175613,1175633,1175690,1175713,1175889,1175896,1175907,1176584,1176590,1176799,1177050,1177060,1177125,1177152,1177160,1177245,1177850,1177862,1177978,1178209,1178228,1178233,1178449,1178542,1178681,1178721,1180261,1180907,1181028,1181123,1181125,1181136,1181291,1181743,1183328,1183492-1183494,1183605,1184917
+/tomcat/trunk:1156115,1156171,1156276,1156304,1156519,1156530,1156602,1157015,1157018,1157151,1157198,1157204,1157810,1157832,1157834,1157847,1157908,1157939,1158155,1158160,1158176,1158195,1158198-1158199,1158227,1158331,1158334-1158335,1158426,1160347,1160592,1160611,1160619,1160626,1160639,1160652,1160720-1160721,1160772,1160774,1160776,1161303,1161310,1161322,1161339,1161486,1161540,1161549,1161584,1162082,1162149,1162169,1162721,1162769,1162836,1162932,1163630,1164419,1164438,1164469,1164480,1164567,1165234,1165247-1165248,1165253,1165273,1165282,1165309,1165331,1165338,1165347,1165360-1165361,1165367-1165368,1165602,1165608,1165677,1165693,1165721,1165723,1165728,1165730,1165738,1165746,1165765,1165777,1165918,1165921,1166077,1166150-1166151,1166290,1166366,1166620,1166686,1166752,1166757,1167368,1167394,1169447,1170647,1171692,1172233-1172234,1172236,1172269,1172278,1172282,1172610,1172664,1172689,1172711,1173020-1173021,1173082,1173088,1173090,1173096,1173241,1173256
,1173288,1173333,1173342,1173461,1173614,1173630,1173659,1173722,1174061,1174239,1174322,1174325,1174329-1174330,1174337-1174339,1174343,1174353,1174799,1174882,1174884,1174983,1175155,1175158,1175167,1175182,1175190,1175201,1175272,1175275,1175283,1175582,1175589-1175590,1175594,1175602,1175613,1175633,1175690,1175713,1175889,1175896,1175907,1176584,1176590,1176799,1177050,1177060,1177125,1177152,1177160,1177245,1177850,1177862,1177978,1178209,1178228,1178233,1178449,1178542,1178681,1178721,1180261,1180907,1181028,1181123,1181125,1181136,1181291,1181743,1183328,1183492-1183494,1183605,1184917,1184919
Modified: tomcat/tc7.0.x/trunk/webapps/docs/changelog.xml
URL:
http://svn.apache.org/viewvc/tomcat/tc7.0.x/trunk/webapps/docs/changelog.xml?rev=1184921&r1=1184920&r2=1184921&view=diff
==============================================================================
--- tomcat/tc7.0.x/trunk/webapps/docs/changelog.xml (original)
+++ tomcat/tc7.0.x/trunk/webapps/docs/changelog.xml Sun Oct 16 20:10:21 2011
@@ -119,6 +119,10 @@
<bug>51630</bug>: Fix bug in async0 example that triggered an
IllegalStateException in the application log. (markt)
</fix>
+ <add>
+ <bug>52025</bug>: Add additional information regarding DriverManager,
+ the service provider mechanism and memory leaks. (markt)
+ </add>
</changelog>
</subsection>
<subsection name="Other">
Modified: tomcat/tc7.0.x/trunk/webapps/docs/jndi-datasource-examples-howto.xml
URL:
http://svn.apache.org/viewvc/tomcat/tc7.0.x/trunk/webapps/docs/jndi-datasource-examples-howto.xml?rev=1184921&r1=1184920&r2=1184921&view=diff
==============================================================================
--- tomcat/tc7.0.x/trunk/webapps/docs/jndi-datasource-examples-howto.xml
(original)
+++ tomcat/tc7.0.x/trunk/webapps/docs/jndi-datasource-examples-howto.xml Sun
Oct 16 20:10:21 2011
@@ -66,6 +66,46 @@ the section about Automatic Application
</p>
</section>
+<section name="DriverManager, the service provider mechanism and memory leaks">
+
+<p><code>java.sql.DriverManager</code> supports the
+<a href="http://download.oracle.com/javase/6/docs/api/index.html";>service
+provider</a> mechanism. However, the implementation is fundamentally broken in
+all Java versions for a servlet container environment.
+<code>java.sql.DriverManager</code> will only scan the first web application to
+use it for JDBC drivers using the service provider mechanism. Any JDBC drivers
+present in the web application or any parent class loader will be discovered
+correctly but no further scans will be performed for any other web
applications.
+For example, if there are two web applications each using a different JDBC
+driver packaged in WEB-INF/lib, the service provider mechanism will only work
+for the first web application to use DriverManager. The other web application
+will be required to register the Driver manually. Given that web application
+start order is undefined, the service provider mechanism can not be relied
upon.
+</p>
+
+<p>The <code>java.sql.DriverManager</code> is also a frequent source of memory
+leaks. Any Drivers registered with the DriverManager by a web application must
+be deregistered when the web application stops. If the service provider
+mechanism registers a JDBC driver, it will never deregister it. Tomcat will
+attempt to automatically deregister and registered JDBC drivers discovered
+when a web application stops. However, it is expected that applications do this
+for themselves via a <code>ServletContextListener</code>.
+</p>
+
+<p>There have been reports that the memory leak prevention code that
deregisters
+JDBC drivers can, in unusual circumstances, trigger a memory leak rather than
+fix it. To prevent this, the <a href="config/listeners.html">JRE Memory Leak
+Prevention Listener</a> includes protection for the DriverManager. This
+protection is enabled by default. Note that a side-effect of enabling this
+protection is that the service provider mechanism is always disabled for web
+applications. It is therefore necessary for applications to manually register
+(and deregister) and JDBC drivers they require that are packaged in the
+WEB-INF/lib directory. Given the known issues with the service provider
+implementation for DriverManager, most web applications will probably be doing
+this already.</p>
+
+</section>
+
<section name="Database Connection Pool (DBCP) Configurations">
<p>DBCP provides support for JDBC 2.0. On systems using a 1.4 JVM DBCP
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org
For additional commands, e-mail: dev-h...@tomcat.apache.org
