[jboss-user] Very Dangerous bug in XA connection pooling and SL EJBs with jboss-4.2.3 & latest postgresql-8.4-701.jdbc3.jar
Introduction
========
This bug has the potential effect of xactions which under certain condition should
rollback, to behave
as if autocommit is true.
The workaround is to use local-tx-datasource with the standard driver
org.postgresql.Driver instead of
xa-datasource with org.postgresql.xa.PGXADataSource.
The description below is with FreeBSD diablo-1.5 , but its exactly the same with SLES 10
SP1 and 1.5.0_15.
configuration
==============
server/default/deploy/postgres-xa-ds.xml
-------------------------------------------------------------------
<datasources>
<xa-datasource>
<jndi-name>pgsql</jndi-name>
<use-java-context>true</use-java-context>
<xa-datasource-class>org.postgresql.xa.PGXADataSource</xa-datasource-class>
<xa-datasource-property
name="ServerName">localhost</xa-datasource-property>
<xa-datasource-property
name="PortNumber">5432</xa-datasource-property>
<xa-datasource-property
name="DatabaseName">dynacom</xa-datasource-property>
<xa-datasource-property
name="User">postgres</xa-datasource-property>
<xa-datasource-property
name="Password">xxxxx</xa-datasource-property>
<xa-datasource-property
name="Compatible">8.2</xa-datasource-property>
<track-connection-by-tx/>
<min-pool-size>1</min-pool-size>
<max-pool-size>2</max-pool-size>
<metadata>
<type-mapping>PostgreSQL 8.0</type-mapping>
</metadata>
</xa-datasource>
</datasources>
Description
========
Consider the following test case:
This code is executed:
StatusHome sthome = (StatusHome) ic.lookup("java:comp/env/ejb/Status");
Status stat = sthome.create();
"Status" is a SL Session EJB, which is defined to run with @ejb.transaction type
= "Required"
Whenever the above is executed, i see in pgsql log:
postgres [23247] 2010-03-02 16:04:09.377 EET line:8 LOG: execute S_1: BEGIN
postgres [23247] 2010-03-02 16:04:09.378 EET line:9 LOG: execute <unnamed>: select
....
postgres [23247] 2010-03-02 16:04:09.380 EET line:11 LOG: execute S_2: COMMIT
which is correct behaviour. Then the following code (lets name it sql_xact) is executed:
sql_xact:
try {
DataSource ds = (javax.sql.DataSource)
ic.lookup("java:comp/env/jdbc/DynacomDB");
con = ds.getConnection();
con.setAutoCommit(false);
st = con.prepareStatement("select now();");
rs = st.executeQuery();
rs.close();
st.close();
con.commit();
}
catch (Exception e) {
out.println("<BR>\n");
out.println("Error: " + e.getMessage());
con.rollback();
e.printStackTrace();
}
finally {
if (con != null) con.close();
}
If the above is executed on the same postgresql backend and immediately after the previous
(EJB call) block of code, i see in pgsql log:
postgres [23247] 2010-03-02 16:07:24.088 EET line:24 LOG: execute <unnamed>: select
now()
which means no begin-commit/rollback block. at this point a xaction supposed to rollback,
is semi-commited.
Now, If however, i execute this block of code:
try {
DataSource ds = (javax.sql.DataSource)
ic.lookup("java:comp/env/jdbc/DynacomDB");
con = ds.getConnection();
con.setAutoCommit(true);
st = con.prepareStatement("select now();");
rs = st.executeQuery();
rs.close();
st.close();
}
catch (Exception e) {
out.println("<BR>\n");
out.println("Error: " + e.getMessage());
e.printStackTrace();
}
finally {
if (con != null) con.close();
}
and then sql_xact code again, then the connection gets back to normal, pgsql log looking
like:
postgres [23247] 2010-03-02 16:11:57.729 EET line:39 LOG: execute S_1: BEGIN
postgres [23247] 2010-03-02 16:11:57.729 EET line:40 LOG: execute <unnamed>: select
now()
postgres [23247] 2010-03-02 16:11:57.730 EET line:41 LOG: execute S_2: COMMIT
I dont think that the usage of XA connections are critical for our case, so i can live
with local connections (although i guess
i have a lot of garbage data since the above setup was deployed some 2 years ago....
imagine if i were selling open source to some bank)
Any thoughts as to where the problem might reside? The jboss camp or the pgsql-jdbc camp?
--
Achilleas Mantzios