Hibernate second level cache

Second level cache(2LC) of hibernate boosts the performance of websites.
One needs to be careful to handle the cache refresh.
By default hibernate 3 comes with EHcache for session level
cache(primary cache).
EhCache can also be used for secondary level cache.


Setup of 2LC using EHcache:

1. Setup the session factory with the below details:
hibernate.cache.provider_class as org.hibernate.cache.EhCacheProvider
hibernate.cache.use_query_cache as true

Optionally cache statistics can be enabled by using below

   hibernate.generate_statistics as true
   hibernate.cache.use_structured_entries as true


2. In the hbm files just under the class element put the below:
   cache region="com.xmp.web2.model.Article" usage="read-only"

   --in the above, the region is used to identify as cache key.

3. For query cache, set the Query as cacheable programatically.

   Query queryObj = session.createQuery(query);
   queryObj.setCacheable(true);

   -- This will cache all the query result, thus reducing DB hits.

4. To refresh a query programatically, do the below:
   --  sessionFactory.evict(Article.class, id);    //this will remove from the cache the article object instance with the primary key id. Note that the id is serializable and the type should be the same as defined in hbm.

5. To optionally print the statistics, enable statistic monitoring as told in step 1 and use the below:

static void printCacheStatistics(String regionName) {
 Statistics statistics = sessionFactory.getStatistics();
 SecondLevelCacheStatistics secondLevelCacheStatistics = statistics.getSecondLevelCacheStatistics(regionName);             
 System.out.println("2nd level CACHE Statistics :"+secondLevelCacheStatistics.toString());
}

To check cache statistics use the JSP as below:
<%@ page language="java" import="org.springframework.web.context.*,org.springframework.web.context.support.*,org.hibernate.*,org.hibernate.stat.*"%>

<%
String cacheRegion="com.xmp.web2.model.Article";

WebApplicationContext ctx =
 WebApplicationContextUtils.getRequiredWebApplicationContext(
  this.getServletContext());
SessionFactory sessionFactory = (SessionFactory) ctx.getBean("sessionFactory");
out.print(sessionFactory);
Statistics statistics = sessionFactory.getStatistics();
SecondLevelCacheStatistics secondLevelCacheStatistics = statistics.getSecondLevelCacheStatistics(cacheRegion);
out.print("<br/>");
out.println("Query cache hit count :"+statistics.getQueryCacheHitCount());
out.print("<br/>");
out.print("<br/>");
out.println("2nd level CACHE Statistics :" + secondLevelCacheStatistics.toString());

%>

Reference:
http://doc.javanb.com/hibernate-reference-3-2-4-ga-en/performance.html
http://www.hibernate.org/hib_docs/v3/reference/en/html/performance.html#performance-cache

An excellent write-up on 2ndLC http://tech.puredanger.com/2009/07/10/hibernate-query-cache/

LinuxPerformance Tuning(apache,tomcat,linux) and related

Web profiling
-- HTTPAnalyzer --
-- YSlow --CSS,Javascript report , time/size measurement for individual component is good.
-- FireBug -- Net performance, for a quick analysis.
--Open STA
Tomcat profiling
-- JProfiler
-- Hot spots ,JDBC queries(J2ee components), object instance count are useful.

--Database connection pooling with optimal values.
Connection leakage in DBCP can be easily detected by settin logAbandoned=true in resource configuration (server.xml). This is a very nice feature and throws up the exact location of the code which is not closing the connection. These connection issues normally come up during load testing.Also the jndi resource configuration for DBCP should have ideal settings. The one used for our project is below:

[GlobalNamingResources]
[Resource
name="jdbc/cmpPubPool"
auth="Container"
type="javax.sql.DataSource"
driverClassName="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:oci:@[TNSNAME]"
removeAbandoned="true"
logAbandoned="true"
maxActive="2"
maxIdle="2"
initialSize="2"
maxWait="-1"
username="[USER_NAME]"
password="[USER_PASSWORD]"
validationQuery=”select 1 from dual” /]
[/GlobalNamingResources]


JVM Tuning
Modify the heap size in JAVA_OPTS.


Apache tuning
prefork or worker module can be used.
prefork is non thread based.
Worker module is multi threaded and may yield a better performance.

Linux
--$top -- to check CPU status

top

Top has probably hundreds of keys to do whatever you want. A few are most useful for me.

The > key sorts by the next column (%MEM) instead of the default (%CPU). < sorts by the previous column.

Hit c
to toggle the display of command line arguments. Useful for me when I
have a lot of processes that otherwise just show up as “java”

Typing A
brings up the alternate display, showing processes sorted by different
fields with different columns. One section shows a nice memory-centric
view, for example.
Hitting z turns on colors. Z brings you to a color selection screen where you can pick colors you want. B turns on bold for some fields.
Hit W to save all your configuration changes to ~/.toprc where it will be loaded next time.
Type k allows you to kill a process without exiting top.

-- kill -3 <TOMCAT_PID> will log the threads running/inactive details useful for troubleshooting performance issues.
On windows use CTRL +Break.

Hardware
-Linux memory size can be checked using
cat /proc/meminfo --Gives RAM size
free -m -- Gives RAM size in MB (-k for kb)
df -H -- Human readable format of hard disk size


Useful links
http://jha.rajeev.googlepages.com/web2push

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