Openbravo Issue Tracking System - Openbravo ERP
From its documentation:
"Keeps track of statements associated with a connection and invokes close upon Connection.close() Useful for applications that dont close the associated statements after being done with a connection."
So it can be useful for those statements that are not closed when their connection is returned to the pool. But causes some performance degradation:
1. All statements in a connection are kept in a list till the connection is closed, in practice all statements in a transaction are kept in that list. For long lived transactions (ie. long background processes), the number of statements can be significant causing a big heap usage.
2. For each statement in the transaction it adds some overhead in time:
2.1. When it is created it is added to a list to keep track of it
2.3. When connection is returned to the pool, this list is iterated to close the statements again (even if they were already closed).
---
[1] https://tomcat.apache.org/tomcat-7.0-doc/api/org/apache/tomcat/jdbc/pool/interceptor/StatementFinalizer.html [^]
1. Memory overhead
Execute this code:
Connection con = OBDal.getInstance().getConnection();
try {
long i = 0L;
while (true) {
if (++i % 10000 == 0) {
System.out.println(i);
}
PreparedStatement st = con.prepareStatement("select count(*) from ad_system");
st.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
...
2720000
2730000
1f923ef8 77346 [http-8080-3] ERROR org.openbravo.base.exception.OBException - Exception thrown Java heap
space
java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:3181)
at java.util.ArrayList.grow(ArrayList.java:261)
at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235)
at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227)
at java.util.ArrayList.add(ArrayList.java:458)
at org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer.createStatement(StatementFinalizer.java:43)
at org.apache.tomcat.jdbc.pool.interceptor.AbstractCreateStatementInterceptor.invoke(AbstractCreateStatementInterceptor.java:69)
After creating ~2.7M statements OOM occurs while trying to grow the size of the ArrayList that tracks the statement in the transaction.
2. Time overhead
Profile Openbravo and execute this code:
Connection con = OBDal.getInstance().getConnection();
try {
long i = 0L;
while (i < 20000000) {
if (++i % 10000 == 0) {
System.out.println(i);
// connection is returned to the pool, in this moment statements are tried
// to be closed again and the list is cleaned up
OBDal.getInstance().commitAndClose();
con = OBDal.getInstance().getConnection();
}
PreparedStatement st = con.prepareStatement("select count(*) from ad_system");
st.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
OBDal.getInstance().getConnection() consumes 26s (22% of the total time). From those 26s, 24s (90%) is spent in StatementFinalizer closing again the already closed statement.
== Removing this finalizer ==
If finalizer is removed we get:
1. The first code snippet can be run indefinitely, as the used heap remains stable.
2. Time for the second one is reduced from 121s to 89s. Mainly in the overhead for the OBDal.commitAndClose, reduced from 26.9s to 2.6s; and in the prepareStatemt (overhead to maintain the list), reduced from 80s to 70s. (see attached graph).
Therefore, the overhead to include this feature does not pay off the potential benefit it brings, so the proposal is to remove this interceptor.
| related to | feature request | 0029564 | 3.0PR15Q4 | closed | inigosanchez | Include Connection Pool module into distribution |
Selection_125.png (51,050) 2016-11-15 15:39https://issues.openbravo.com/file_download.php?file_id=10047&type=bug