I Can Do I.T.: July 2016

Friday 29 July 2016

[Eclipse] Favorite Plugins Software Sites

GEF releases

http://download.eclipse.org/tools/gef/updates/releases

Subversive

http://download.eclipse.org/technology/subversive/2.0/update-site

ER-Master

http://ermaster.sourceforge.net/update-site

Properties Editor
http://propedit.sourceforge.jp/eclipse/updates

PyDev
http://pydev.org/updates

Eclipse Color Theme
http://eclipse-color-theme.github.io/update/

Eclipse Class Decompiler
http://opensource.cpupk.com/decompiler/update/

More Clipboard
http://moreclipboard.sourceforge.net/updates/

Nebual Project (SWT Widget)
http://download.eclipse.org/nebula/snapshot/

Window Builder
Mars - http://download.eclipse.org/windowbuilder/WB/release/R201506241200-1/4.5/
Luna - http://download.eclipse.org/windowbuilder/WB/release/R201506241200-1/4.4/
Kepler - http://download.eclipse.org/windowbuilder/WB/release/R201406251200/4.3/

Monday 25 July 2016

[CentOS] How to set up NTP client (NTP 클라이언트 설정)

NTP(Network Time Protocol)

NTP is network time protocol for maintaining correct system time. It can adjust the time according to a radio or atomic clock and can be tailored to the millisecond time (1/1000 second).

Basically, NTP has a hierarchical structure of stratum.
straum 0 : Equipment for calculating the time. Ex) GPS, CS(cesium) Atomic Clock
straum 1 : Server synchronizing the time from straum 1.
straum 2 ~ n : Time server.

Setup

1. Install packages

1	#> yum -y install ntp

2. Edit configuration file

#> vi /etc/ntp.conf

3. Register NTP service

#> chkconfig ntpd on
#> chkconfig --list | grep ntpd

4. Start NTP service

#> service ntpd start

Friday 22 July 2016

[ActiveMQ] Broker configuration and Client Sample using ScheduledMessage (스케줄링 메시지를 위한 브로커 설정 및 클라이언트 샘플)

ActiveMQ from version 5.4 has an optional persistent scheduler built into the ActiveMQ message broker. It is enabled by setting the broker schedulerSupport attribute to true in the Xml Configuration.

<broker xmlns="http://activemq.apache.org/schema/core" brokerName="DorbaeBroker" useJmx="true" schedulerSupport="true">

.
.
.

</broker>

Schedule Properties

Property name	Type	Description
AMQ_SCHEDULED_DELAY	long	The time in milliseconds that a message will wait before being scheduled to be delivered by the broker
AMQ_SCHEDULED_PERIOD	long	The time in milliseconds to wait after the start time to wait before scheduling the message again
AMQ_SCHEDULED_REPEAT	int	If set period, the number of times to repeat scheduling a message for delivery. Total message count = 1 + repeat If set cron, the number of message repeat when execute cron
AMQ_SCHEDULED_CRON	String	Use a Cron entry to set the schedule

※ Be careful
If set AMQ_SCHEDULED_PERIOD, AMQ_SCHEDULED_REPEAT is the number of times to repeat scheduling a message for delivery.
(Total message count = 1 + repeat)

If set AMQ_SCHEDULED_CRON, AMQ_SCHEDULED_REPEAT is the number of times to repeat send message per 1 execution.
For example, you set
AMQ_SCHEDULED_REPEAT = 5
AMQ_SCHEDULED_CRON = * * * * *

6(1+5) messages are sent in destination per minute.

Client Sample

package pe.dorbae.test.jms.activemq;

import java.util.Properties;

/*
 * ************************************************************************************
 *
 * ScheduledMessage.java
 * 
 * ************************************************************************************
 * 
 * @version 1.0.00 2016-07-22 dorbae Initialize
 * @since 2016-07-22
 * @author dorbae
 * 
 * ************************************************************************************
 */
public class TestScheduledMessage {

 public TestScheduledMessage() {
  // TODO Auto-generated constructor stub
 }

 public static void main(String[] args) {
  String jmsFactory = "org.apache.activemq.jndi.ActiveMQInitialContextFactory";
  String connectionFactoryName = "ConnectionFactory";
  String jmsUrl = "tcp://localhost:61616";
  String clientId= "iSharkClient.Test.ScheduledMessage";
  String queueName = "DORBAE.TEST";

  Properties jmsProps = new Properties();
  jmsProps.put( javax.naming.Context.INITIAL_CONTEXT_FACTORY, jmsFactory); 
  jmsProps.put( javax.naming.Context.PROVIDER_URL, jmsUrl);
  
  javax.naming.InitialContext jndi = null;
  javax.jms.ConnectionFactory connectionFactory = null;
  javax.jms.Connection conn = null;
  javax.jms.Session session = null;
  javax.jms.Destination destination = null;
  javax.jms.Message message = null;
  javax.jms.MessageProducer producer = null;
  
  try {
   jndi = new javax.naming.InitialContext( jmsProps);
   connectionFactory = ( javax.jms.ConnectionFactory)jndi.lookup( connectionFactoryName);
   conn = connectionFactory.createConnection();
   conn.setClientID( clientId);
   session = conn.createSession( false, javax.jms.Session.AUTO_ACKNOWLEDGE); // Not Transacted
   destination = session.createQueue( queueName);
   producer = session.createProducer( destination);
   message = session.createTextMessage( "http://dorbae.blogspot.com");
   
   /*
    * For Delay Message
    * 
    * Message will be sent to destination after delay times
    *  
    * 
   long delayTime = 60L * 1000L; // 1 Minute
   message.setLongProperty( org.apache.activemq.ScheduledMessage.AMQ_SCHEDULED_DELAY, delayTime);
    *
    */
   
   /*
    * For Period Repeat
    * 
    * Repeated messages will be sent to destination waiting period times between each re-delivery 
    * 
   long period = 10L * 1000L;
   int repeat = 5;
   message.setLongProperty( org.apache.activemq.ScheduledMessage.AMQ_SCHEDULED_PERIOD, period);
   message.setIntProperty( org.apache.activemq.ScheduledMessage.AMQ_SCHEDULED_REPEAT, repeat);
    *
    */
   
   /*
    * For Cron
    * 
    * Message will be sent to destination according as cron pattern 
    *
    */
   message.setStringProperty( org.apache.activemq.ScheduledMessage.AMQ_SCHEDULED_CRON, "0 * * * *");
   
   producer.send( message);
   
  } catch ( Exception e) {
   e.printStackTrace();
   
  } finally {
   if ( session != null)
    try {
     session.close();
    } catch ( Exception e) {}
   
   if ( conn != null)
    try {
     conn.close();
    } catch ( Exception e) {}
  }
 }

}

ScheduledMessage.AMQ_SCHEDULED_CRON	AMQ_SCHEDULED_CRON
ScheduledMessage.AMQ_SCHEDULED_DELAY	AMQ_SCHEDULED_DELAY
ScheduledMessage.AMQ_SCHEDULED_ID	scheduledJobId
ScheduledMessage.AMQ_SCHEDULED_PERIOD	AMQ_SCHEDULED_PERIOD
ScheduledMessage.AMQ_SCHEDULED_REPEAT	AMQ_SCHEDULED_REPEAT
ScheduledMessage.AMQ_SCHEDULER_ACTION	AMQ_SCHEDULER_ACTION
ScheduledMessage.AMQ_SCHEDULER_ACTION_BROWSE	BROWSE
ScheduledMessage.AMQ_SCHEDULER_ACTION_END_TIME	ACTION_END_TIME
ScheduledMessage.AMQ_SCHEDULER_ACTION_REMOVE	REMOVE
ScheduledMessage.AMQ_SCHEDULER_ACTION_REMOVEALL	REMOVEALL
ScheduledMessage.AMQ_SCHEDULER_ACTION_START_TIME	ACTION_START_TIME
ScheduledMessage.AMQ_SCHEDULER_MANAGEMENT_DESTINATION	ActiveMQ.Scheduler.Management

※ Be careful
The message property scheduledJobId is reserved for use by the Job Scheduler. If this property is set before sending, the message will be sent immediately and not scheduled. Also, after a scheduled message is received, the property scheduledJobId will be set on the received message so keep this in mind if using something like a Camel Route which might automatically copy properties over when re-sending a message.

A Scheduled message is canceled only using JMX unfortunately. There's an open issue to support rescheduling.

Tuesday 12 July 2016

[JDBC] java.lang.ClassNotFoundException: sun.jdbc.odbc.JdbcOdbcDriver Exception occuring

JDBC-ODBC Bridge has been removed since Java 8. If you want to use JDBC-ODBC driver, you should run on below Java 7. If had been used JDBC-ODBC driver for interfacing with Microsoft Access database, you can use 'UCanAccess' library that is open-source pure java JDBC driver.

http://ucanaccess.sourceforge.net/site.html

Monday 4 July 2016

[Maria/MySQL] How to allow remote client access database (원격 접속 허용 설정)

1. Connect database as root

#> mysql -uroot -p

2. Check current status

SELECT host FROM mysql.user WHERE user='[USER_NAME]';

3. Add remote authority

INSERT INTO mysql.user (host,user,password) VALUES ('[Allowed IP]', '[USER_NAME]', password('[PASSWORD]'));

GRANT ALL PRIVILEGES ON *.* TO '[USER_NAME]'@'[Allowed IP]';
FLUSH PRIVILEGES;

[Ubuntu] How to change hostname

hostnamectl [OPTIONS...] COMMAND ...

Query or change system hostname.

-h --help Show this help
--version Show package version
--transient Only set transient hostname
--static Only set static hostname
--pretty Only set pretty hostname
--no-ask-password Do not prompt for password
-H --host=[USER@]HOST Operate on remote host

Commands:
status Show current hostname settings
set-hostname NAME Set system hostname
set-icon-name NAME Set icon name for host
set-chassis NAME Set chassis type for host

#> hostnamectl set-hostname [HOSTNAME]

[Ubuntu] Install and Setup NFS Client (NFS 클라이언트 설치 및 설정하기)

1. Install package

#> apt-get install nfs-common

2. Mount directory

#> mount -t nfs [NFS_SERVER_HOST]:[REMOTE_DIRECTORY] [LOCAL_DIRECTORY]

3. Register /etc/fstab

#> vi /etc/fstab

[NFS_SERVER_HOST]:[REMOTE_DIRECTORY]

[LOCAL_DIRECTORY]

nfs

[OPTIONS]

[Ubuntu] Install and Setup NFS Server (NFS서버 설치 및 설정하기)

1. Install packages for NFS server

#> apt-get install nfs-common nfs-kerne-server rpcbind

2. Make directory for sharing

#> mkdir [DIRECTORY]

3. Setup directory and authority

#> vi /etc/exports

Directory

Allowed IP(Options)

Options

ro	read only
rw	read/write
root_squash	Prevents root users connected remotely from having root privileges and assigns them the user ID for the user nfsnobody
no_root_squash	Turns off root squashing
async	Allows the server to write data at non-regular intervals. This setting works best if the exported file system is read-only
sync	All file writes are committed to the disk before the write request by the client is completed
wdelay	Improve performance by reducing the number of times the disk must be accessed by separate write commands, reducing write overhead
no_wdelay	Turns off this feature, but is only available when using the sync option.

4. Restart NFS Server

#> nfs-kernel-server restart

5. Restart rpcbind

#> rpcbind restart

[Linux] How to get processes id using named files, sockets, or filesystems (Named 파일, 파일시스템, 소켓을 사용중인 프로세스 ID 찾기)

Usage: fuser [ -a | -s | -c ] [ -n SPACE ] [ -SIGNAL ] [ -kimuv ] NAME...
[ - ] [ -n SPACE ] [ -SIGNAL ] [ -kimuv ] NAME...
fuser -l
fuser -V
Show which processes use the named files, sockets, or filesystems.

-a display unused files too
-c mounted FS
-f silently ignored (for POSIX compatibility)
-i ask before killing (ignored without -k)
-k kill processes accessing the named file
-l list available signal names
-m show all processes using the named filesystems
-n SPACE search in this name space (file, udp, or tcp)
-s silent operation
-SIGNAL send this signal instead of SIGKILL
-u display user IDs
-v verbose output
-V display version information
-4 search IPv4 sockets only
-6 search IPv6 sockets only
- reset options

udp/tcp names: [local_port][,[rmt_host][,[rmt_port]]]

[Linux] How to get process id using specific TCP/UDP port (특정 TCP/UDP 포트를 사용중인 프로세스 ID 찾기)

#> netstat -nap | grep [PORT]

I Can Do I.T.