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/

All about UK Visa.

HSMP is a 2 step process as of now.I applied for HSMP visa through a consultant y-axis in Bangalore, India.
They provided good service for getting step 1done(HSMP acceptance). The second part(Entry clearance)
was hopeless service by y-axis. I feel like chewing that consultant who processed it.

They are very keen about proof's (original documents) which has to be genuine and no scope for any errors.

Eg: Say you have your salary credited through cheques, then in the bank statement
you wont have the mention that your XYZ company paid you the salary. So you need
to get a letter for the same from bank or company stating you got the salary from
XYZ company. As long as you prove yourself with the documents the chances of
rejection is very low. Also all your salary slips should be attested by the
corresponding authority.

H1 vs HSMP:

• The chances of getting visa depends on your documentation which serves as the proof of you skills. Not entirely on luck like in H1.
  

• It is not like H1 visa (phaltu lottery system and only done once a year ). HSMP's points calculator is best and you can calculate before hand if you are eligible for it or not. Also you can apply any time of the year as long as you have your documents right. UK guys are smart at applying rules i guess.
  

As I said before, it is a 2 step process-

1. Get HSMP acceptance from UK consulate by sending your documents, 400 pounds and details to UK. It took me 3 weeks for getting the HSMP accepted. Actually gathering all the documents for proof of salary, bank stmts, medium of instruction letter etc. took me 1 month. On a whole you should get this first part done in 2-3 months.

2. Once u get HSMP acceptance from UK office, apply for Entry clearance in chennai or
mumbai. I applied through local VFS in bangalore(VFS sent it to chennai).Paid Rs.17,000
at VFS office fee for EC. It is already 3 weeks since I applied. Yet to get a response. HSMP
visa Entry clearance application status can be checked from here

I have got the first part done(got HSMP acceptance letter), the second one is also done. 
Overall the entire process took me 6 months as of now.  I could have saved some 2 months had I got all the documents ready. By and large 
4-6 months.

Right now I am in UK. More to blog soon.

UK HSMP visa useful Links:

1. hsmphelp.blogspot.com/
2. Check the blog ec-hsmp.blogspot.com HSMP blog .On the right you can find various useful section's. This blog is one of the best. No need to go to visa consultant and shell out so much fortune.
3. http://www.workpermit.com/uk/hsmp_calculator.htm --> HSMP point calculator. This may change in first quarter of 2008. Watch out.
4. Job assistance in Uk 00 44 114 207 6020 -Aman http://www.vertex-solutions.co.uk/technical-recruitment/immigrationservices.asp Tel (UK): 08456 448 441
   

http://forums.gumtree.com/about2685-25.html

1. Direct Dial: (+44) 144 222 1320
   
2. Buy tickets for UK to/from india at
   
1. http://www.ticketstoindia.co.uk/result_new.aspx
3. For currency, time, phone number conversion check
   
1. http://www.timeanddate.com
   

FAQ
What is the cheap and best place to stay in london. What is the price of apartments?
   Eastham is cheap with lot of asians but not so safe. For a bachelor it will cost around 300 pounds for  a shared acco of 3 people.
   Around 450 for 2 people. Thats a rough estimate...Depends on the owner.
 
How much cash should one carry for travel and job search?
 Around 300 pounds for flight + travel.. You might spend 600 pounds a month overall staying here.
If u r traveling for job search you will need some more like 100 pounds more.
So that might cost you 2- 3 lak rs for 2-3 months to come here and stay ,search a job.... Its ur best try and luck how 
soon u get the job.

Suggest some possible ways to get a job by seating here in india?
Sitting in India and trying a job is not a good idea. Chances are i can say only 10%. If u want to get work form India , chances are u end up with an Indian company who has UK requirement.... Also many consultants here dont call indian numbers. You need to prepare yourself with finances so that u survive in UK for atleast 2-3 months without a job(that might cost you 2- 3 lak rs).

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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