"Lockness" eclipse thread dump analysis plugin

There is a eclipse plugin "Lockness" for thread dump analysis (http://lockness.plugin.free.fr/setup.php). Using this we can analyze the thread locks to diagonalize the problems. To download (http://lockness.plugin.free.fr/archive/com.cr.lockness.Lockness_3.0.0.jar), put this jar to eclipse3.x/plugins dir and restart eclipse.

How to take a thread dump:

Sending "kill -3 signal to the JBOSS/TOMCAT process" will give you the whole thread dump. Ex: kill -3 #### -> process id.

After executing the above command, you can find thread dump in catalina.out for tomcat or server.log for jboss.

You've to trim the thread dump contents exactly from above log files, such that the dump file starts with "Full thread dump" and end with "VM Thread".

Also, if you have some timestamps added in thread dump, you can trim that using below cut command. For ex: say each line has some time stamps added like "2010-10-25 13:29:23 PDT", then to skip the first 3 columns. Use below command

cat threaddump.txt | cut -d " " -f4- > cut_file_threaddump.txt

The above command will skip first 3 columns and saves rest of the columns what we needed to cut_file_threaddump.txt.

Then from eclipse, create a new java project, create folder pointing to above create dump dir and opening this using "Lockness" thread dump analyser plugin will give you the analysis.

How to redirect ports inside same machine using IPTABLES

As my mail server is running on port 8056, I got ended up searching to find a way to redirect all the mails which comes to port25 to port8056.

Below is one way of doing which helped me using iptables entry.


sudo iptables -t nat -A OUTPUT -p tcp -d 127.0.0.0/8 --dport 25 -j REDIRECT --to-port 8056
sudo iptables -t nat -A OUTPUT -p tcp -d x.x.x.x --dport 25 -j REDIRECT --to-port 8056
sudo iptables -t nat -A PREROUTING -p tcp --dport 25 -j REDIRECT --to-ports 8056


In the above commands

command 1 is to, forward port25 requests to port 8056 which are initiated via localhost. (i.e) telnet localhost 25.
command 2 is to, forward port25 requests to port 8056 which are initiated via IP address. (i.e) telnet x.x.x.x 25.
command 3 is to, forward the other network m/c requests to port 8056 through port25.

Soap calls using perl

This seems to be the quick way for testing soap api's.

#!/usr/bin/perl

#use SOAP::Lite +trace => debug;
use TeamForge;
use Data::Dumper;

my($tf,$sk);

$tf = new TeamForge;
$tf->proxy('http://cu021.cubit.maa.collab.net');
$sk = $tf->loginAnonymous("guestuser");

die "Login failed" unless ($sk);

print Dumper($tf->getProjectData($sk,'proj1007'));

Boolean values

0 - FALSE
1 - TRUE

Verfity certificate validity

openssl x509 -in server.crt -text|less

egrep command

egrep "28[u,w]|29[u,w]" /tmp/31752_lsof

egrep "(PROPFIND|OPTIONS)" | awk '{if ($6 > 60) print }'

Sending mail as different user

# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 hostname SMTP Server (JAMES SMTP Server 2.2.0) ready Mon, 20 Feb 2006 14:31:33 -0500 (EST)
ehlo yourEmailAddressDomain.com
250 hostname Hello yourEmailAddressDomain.com (hostname [127.0.0.1])
mail from:
250 Sender OK
rcpt to:
250 Recipient OK
data
354 Ok Send data ending with .
subject: test to testuser at JAMESServersConfigSetting.com

test

.
250 Message received
quit
221 hostname Service closing transmission channel
Connection closed by foreign host.
#

PostgreSQL Cheat Sheet

CREATE DATABASE

CREATE DATABASE dbName;

CREATE TABLE (with auto numbering integer id)

CREATE TABLE tableName (
id serial PRIMARY KEY,
name varchar(50) UNIQUE NOT NULL,
dateCreated timestamp DEFAULT current_timestamp
);

Add a primary key

ALTER TABLE tableName ADD PRIMARY KEY (id);

Create an INDEX

CREATE UNIQUE INDEX indexName ON tableName (columnNames);

Backup a database (command line)

pg_dump dbName > dbName.sql

Backup all databases (command line)

pg_dumpall > pgbackup.sql

Run a SQL script (command line)

psql -f script.sql databaseName

Search using a regular expression

SELECT column FROM table WHERE column ~ 'foo.*';

The first N records

SELECT columns FROM table LIMIT 10;

Pagination

SELECT cols FROM table LIMIT 10 OFFSET 30;

Prepared Statements

PREPARE preparedInsert (int, varchar) AS
INSERT INTO tableName (intColumn, charColumn) VALUES ($1, $2);
EXECUTE preparedInsert (1,'a');
EXECUTE preparedInsert (2,'b');
DEALLOCATE preparedInsert;

Create a Function

CREATE OR REPLACE FUNCTION month (timestamp) RETURNS integer
AS 'SELECT date_part(''month'', $1)::integer;'
LANGUAGE 'sql';

Table Maintenance

VACUUM ANALYZE table;

Reindex a database, table or index

REINDEX DATABASE dbName;

Show query plan

EXPLAIN SELECT * FROM table;

Import from a file

COPY destTable FROM '/tmp/somefile';

Show all runtime parameters

SHOW ALL;

Grant all permissions to a user

GRANT ALL PRIVILEGES ON table TO username;

Perform a transaction

BEGIN TRANSACTION
UPDATE accounts SET balance += 50 WHERE id = 1;
COMMIT;

Basic SQL
Get all columns and rows from a table

SELECT * FROM table;

Add a new row

INSERT INTO table (column1,column2)
VALUES (1, 'one');

Update a row

UPDATE table SET foo = 'bar' WHERE id = 1;

Delete a row

DELETE FROM table WHERE id = 1;

MYSQL query output to a file

select
*
from
table
where
condition
into
outfile '/tmp/result'

Using meta tags to block access to your site

To entirely prevent a page's contents from being listed in the Google web index even if other sites link to it, use a noindex meta tag. As long as Googlebot fetches the page, it will see the noindex meta tag and prevent that page from showing up in the web index.

The noindex meta standard is described at http://www.robotstxt.org/meta.html. This method is useful if you don't have root access to your server, as it allows you to control access to your site on a page-by-page basis.

To prevent all robots from indexing a page on your site, place the following meta tag into the <head> section of your page:

<meta name="robots" content="noindex">

To allow other robots to index the page on your site, preventing only Google's robots from indexing the page:

<meta name="googlebot" content="noindex">

When we see the noindex meta tag on a page, Google will completely drop the page from our search results, even if other pages link to it. Other search engines, however, may interpret this directive differently. As a result, a link to the page can still appear in their search results.

Note that because we have to crawl your page in order to see the noindex meta tag, there's a small chance that Googlebot won't see and respect the noindex meta tag. If your page is still appearing in results, it's probably because we haven't crawled your site since you added the tag. (Also, if you've used your robots.txt file to block this page, we won't be able to see the tag either.)

If the content is currently in our index, we will remove it after the next time we crawl it. To expedite removal, use the URL removal request tool in Google Webmaster Tools.

Taken from: http://www.google.com/support/webmasters/bin/answer.py?answer=93710

Preventing DOS attack

DOS attack is an attempt to make a computer resource unavailable to its intended users.

In a public site, the usual vulnerability we see is a DOS attack. Most of the time it used to be a crawler/spiders/bots/web-rippers. What we do know to stop them from attacking our site is to block them by individual or range of IP at network level.

Some spider/bots are intelligent enough to spoof IPs and so after some time, we again see a threat from them since they change their IP/IP range.

One other way to stop such crawler/spiders/bots/web-rippers is to block them by using useragent control.

#This was achieved using below snippet in httpd.conf

----------------------------------------
#Block access to robots
BrowserMatch emailsiphon badrobot
BrowserMatch BPFTP badrobot
BrowserMatch MSIECrawler badrobot
BrowserMatch WebStripper badrobot
BrowserMatch Offline badrobot
BrowserMatch Teleport badrobot
BrowserMatch Alkaline badrobot
BrowserMatch DLExpert badrobot
BrowserMatch HTTrack badrobot
BrowserMatch Controller badrobot


deny from env=badrobot


Also, for more information on apache access control http://httpd.apache.org/docs/2.2/howto/access.html

Java GC logging parameters

-XX:HeapDumpPath=/tmp
-verbose:gc
-XX:+PrintGCTimeStamps
-XX:+PrintGCDetails