Posts Tagged ‘kind’

Apache Webserver: No space left on device: Couldn’t create accept lock /var/lock/apache2/accept.lock – Fix

Wednesday, April 8th, 2015

Apache-http-server-no-space-left-on-device-semaphores-quotes-hard-disk-space-resolve-fix-howto
If out of a sudden your Apache webserver crashes and is refusing to start up by manually trying to restart it through its init script on Debian Linux servers – /etc/init.d/apache2 and RPM based ones: /etc/init.d/httpd

Checking in php_error.log there was no shown errors related to loading PHP modules, however apache's error.log show following errors:

[Wed Apr 08 14:20:14 2015] [error] [client 180.76.5.149] client denied by server configuration: /var/www/sploits/info/trojans_info/tr_data/y3190.html
[Wed Apr 08 14:20:39 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:20:39 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.15974) (5)
[Wed Apr 08 14:25:39 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:25:39 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.16790) (5)
[Wed Apr 08 14:27:03 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:27:03 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.16826) (5)
[Wed Apr 08 14:27:53 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:27:53 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.16852) (5)
[Wed Apr 08 14:30:48 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:30:48 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.17710) (5)
[Wed Apr 08 14:31:21 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:31:21 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.17727) (5)
[Wed Apr 08 14:32:40 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:32:40 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.17780) (5)
[Wed Apr 08 14:38:32 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?

As you can read the most likely reason behind above errors preventing for apache to start is /var/run/apache2.pid  unable to be properly written due to lack of disk space or due to disk quota set for users including for userID with which Apache is running.

First thing I did is of course to see how much free space is on the server:

df -h
Filesystem                     Size  Used Avail Use% Mounted on
/dev/mapper/vg00-rootvol       4.0G  1.7G  2.2G  44% /
udev                           7.8G  204K  7.8G   1% /dev
tmpfs                           24G     0   24G   0% /dev/shm
/dev/sda1                      486M   40M  422M   9% /boot
/dev/mapper/vg00-lv_crashdump 1008M   34M  924M   4% /crashdump
/dev/mapper/vg00-homevol       496M   26M  445M   6% /home
/dev/mapper/vg00-lv_opt         12G  1.4G  9.9G  13% /opt
/dev/mapper/vg00-tmpvol        2.0G   68M  1.9G   4% /tmp
/dev/mapper/vg00-varvol        7.9G  609M  6.9G   8% /var
/dev/mapper/vg00-crashvol      1.9G   35M  1.8G   2% /var/crash
/dev/mapper/vg00-auditvol      124M  5.6M  113M   5% /var/log/audit
/dev/mapper/vg00-webdienste     60G   12G   48G  19% /webservice

 

As visible from above df command output , there is enough disk on HDD, so this is definitely not the issue:

Then I Checked whether there is Quota enabled on the Linux server with repquota command shows there are no quotas enabled:

# repquota / var/
repquota: Mountpoint (or device) / not found or has no quota enabled.
repquota: Mountpoint (or device) /var not found or has no quota enabled.
repquota: Not all specified mountpoints are using quota.

 

So obviously the only few left possible reason for Apache failing to start after invoked via init script is  either due to left tainted semaphores or due to some server hardware  RAM problem / or a dying  hard disk with bad blocks.

So what are Semaphores? Generally speaking Semaphores are apparatus for conveying information by means of visual signals between applications (something like sockets).They're used for communicating between the active processes of a certain application. In the case of Apache, they’re used to communicate between the parent and child processes, hence if Apache can’t properly write and coordinate these things down, then it can’t communicate properly with all of the processes it starts and hence the Main HTTPD process can't spawn probably its childs preventing Webserver to enter "started mode" and write its PID file.

To check general information about system semaphore arrays there is the ipcs -s command, however my experience is that ipcs -a is more useful (because it lists generally all kind of semaphores) including Semaphore Shared Memory Signals which are the most likely to cause you the problem.

ipcs -a

—— Shared Memory Segments ——–
key        shmid      owner      perms      bytes      nattch     status

—— Semaphore Arrays ——–
key        semid      owner      perms      nsems
0x00000000 22970368   www-data   600        1

—— Message Queues ——–
key        msqid      owner      perms      used-bytes   messages

As you see in my case there is a Semaphore Arrays which had to be cleaned to make Apache2 be able to start again.
 

To clean all left semaphores (arrays) preventing Apache from start properly, use below for one liner bash loop:
 

for i in `ipcs -s | awk '/www-data/ {print $2}'`; do (ipcrm -s $i); done
ipcrm -m 0x63637069


Note that above for loop is specific to Debian on CentOS / Fedora / RHEL and other Linuxes the username with which stucked semaphores might stay will be apache or httpd

Depending on the user with which the Apache Webserver is running, run above loop like so:

For RPM based distros (CentOS / RHEL):

 

for i in `ipcs -s | awk '/apache/ {print $2}'`; do (ipcrm -s $i); done
ipcrm -m 0x63637069


For other distros such as Slackware or FreeBSD or any custom compiled Apache webserver:

for i in `ipcs -s | awk '/httpd/ {print $2}'`; do (ipcrm -s $i); done
ipcrm -m 0x63637069


If there is also Shared Memory Segments you can remove them with ipcrm i.e.:

ipcrm -m 0x63637069


An alternative way to get rid of left uncleaned semaphores is with xargs:
 

ipcs -s | grep nobody | awk ‘ { print $2 } ‘ | xargs ipcrm


Even though this fixes the issue I understood my problems were due to exceeding semaphores, to check default number of set semaphores on Linux Kernel level as well as few Semaphore related values run below sysctl:

sysctl -a | egrep kernel.sem\|kernel.msgmni
kernel.msgmni = 15904

kernel.sem = 250        32000   32      128


As you can see the number of maximum semaphores is quite large so in my case the failure because of left semaphores was most likely due to some kind of Cracker / Automated bot scanner attack or someone trying malicious against the webserver or simply because of some kind of Apache bug or enormous high load the server faced.

Extracting pages and page ranges, protect with password and remove password from PDF on GNU / Linux with QPDF – Linux Manipulating PDF files from command line

Friday, August 8th, 2014

qpdf-logo-extract-pages-page-ranges-protect-pdf-with-password-remove-password-from-pdf-linux-qpdf-manipulating-pdf-files-on-gnu-linux-and-bsd
If're a Linux user and you need to script certain page extraction from PDF files, crypt protect with password a PDF file or decrypt (remote password protection from PDF) or do some kind of structural transformation of existing PDF file you can use a QPDF command line utility. qpdf is in active development and very convenient tool for Website developers (PHP / Perl / Python), as often on websites its necessery to write code to cut / tailer / restructure PDFs.

1. Install QPDF from deb / rpm package

qpdf is instalalble by default in deb repositories on Debian / Ubuntu GNU / (deb derivative) Linux-es to install it apt-get it

apt-get install –yes qpdf

On RPM based distribution CentOS / SuSE / RHEL / Fedora Linux to install qpdf, fetch the respective distribution binary from rpmfind.net or to install latest version of qpdf build it from source code.

2. Install QPDF from source

To build latest qpdf from source

  • on RPM based distributions install with yum fullowing packages:

yum -y install zlib-devel pcre-devel gcc gcc-c++

  • on Deb based Linuces, you will need to install

apt-get install –yes build-essential gcc dpkg-dev g++ zlib1g-dev


Then to build gather latest qpdf source from here

 

cd /usr/local/src
wget -q http://www.pc-freak.net/files/qpdf-5.1.2.tar.gz
tar -zxvf qpdf-5.1.2.tar.gz
cd qpdf-5.1.2/
./configure
make
make install


Once it is installed, if you get error on qpdf runtime:
 

/usr/local/bin/qpdf: error while loading shared libraries: libqpdf.so.13: cannot open shared object file: No such file or directory

To solve the error find in your compile directory libqpdf.so.13 and copy it to /usr/lib or /usr/local/lib

 cp -rpf ./libqpdf/build/.libs/libqpdf.so.13 /usr/local/lib


3. Decrypt password encrypted (protected) PDF file

if you have time and you like reading be sure to check the extensive qpdf-manual.

To remove password from a PDF file protected with a password with qpdf

qpdf –password=SECRET-PASSWORD –decrypt input-file.pdf output-file.pdf

QPDF has a vast range of split and merge features. It can combine all the files in a folder (*.pdf), you can use it to try to recover damaged pdf files, extract individual pages from PDF, dump and reverse page range, make new created PDF with old PDF's reversed pages (pages 1,2,3,4 to become in order 4,3,2,1), apply some single pdf file metadata to multiple files.

4. Try to Recover damaged PDF file


To try to recover some damaged file with qpdf:
 

qpdf file-to-repair.pdf repaired-file.pdf

5. Extract certain pages or page range from PDF

It is recommended to use the version built from source to extract certain page range from PDF
 

/usr/local/bin/qpdf –empty –pages input-file.pdf 1-5 — outfile-file.pdf


If you wanted to take pages 1–5 from file1.pdf and pages 11–15 from file2.pdf in reverse, you would run
 

qpdf file1.pdf –pages file1.pdf 1-5 file2.pdf 15-11 — outfile.pdf

 

How to check Microsoft IIS webserver version

Monday, July 21st, 2014

If you have to tune some weirdly behaviour Microsoft IIS (Internet Information Services) webserver, the first thing to do is to collect information about the system you're dealing with – get version of installed Windows and check what kind of IIS version is running on the Windows server?

To get the version of installed Windows on the system you just logged in, the quickest way I use is:
 

Start -> My Computer (right mouse button) Properties

check-windows-server-version-screenshot-windows-2003-r2

Run regedit from cmd.exe and go and check value of registry value:

 

HKEY_LOCAL_MACHINE\SOFTWARE\MicrosoftInetStp\VersionString


check-iis-webserver-version-with-windows-registry-screenshot

As you can see in screenshot in this particular case it is IIS version 6.0.

An alternative way to check the IIS version in some cases (if IIS version return is not disabled) is to telnet to webserver:

telnet your-webserver 80
 


Once connected Send:

HEAD / HTTP/1.0


Also on some Windows versions it is possible to check IIS webserver version from Internet Information Services Management Cosnole:

To check IIS version from IIS Manager:

Start (button) -> Control Panel -> Administrative Tools -> "Internet Information Services" IIS Manager

From IIS Manager go to:

Help -> About Microsoft Management Console


Here is a list with most common IIS version output you will get depending on the version of Windows server:

 

Windows NT 3.51 1.0
Windows NT 4 2.0-4.0
Windows Server 2000 5.0
Windows XP Professional 5.1
Windows Server 2003 6.0
Windows Vista 7.0
Windows Server 2008 7.0
Windows Server 2008 R2 7.5
Windows 7 7.5
Windows Server 2012 8.0
Windows 8 8.0
Windows Server 2012 R2 8.5
Windows 8.1 8.5

If you have only an upload FTP access to a Folder served by IIS Webserver – i.e. no access to the Win server running IIS, you can also grasp the IIS version with following .ASP code:
 

<%
response.write(Request.ServerVariables("SERVER_SOFTWARE"))
%>


Save the file as anyfile.asp somewhere in IIS docroot and invoke it in browser.

Linux: how to show all users crontab – List all cronjobs

Thursday, May 22nd, 2014

linux-unix-list-all-crontab-users-and-scripts
I'm doing another server services decomissioning and part of decomissioning plan is: Removing application and all related scripts from related machines (FTP, RSYNC, …). In project documentation I found a list with Cron enabled shell scripts:

#Cron tab excerpt:
1,11,21,31,41,51 * * * */webservices/tools/scripts/rsync_portal_sync.sh

that has to be deleted, however there was nowhere mentioned under what kind of credentials (with what kind of user) are the cron scripts running? Hence I had to look up all users that has cronjobs and find inside each user's cronjobs whether respective script is set to run. Herein I will explain shortly how I did that.

Cronjobs by default has few locations from where cronjobs are setupped depending on their run time schedule. First place I checked for the scripts is

/etc/crontabs # cat /etc/crontabs SHELL=/bin/sh
PATH=/usr/bin:/usr/sbin:/sbin:/bin:/usr/lib/news/bin
MAILTO=root
#
# check scripts in cron.hourly, cron.daily, cron.weekly, and cron.monthly
#
-*/15 * * * * root test -x /usr/lib/cron/run-crons && /usr/lib/cron/run-crons >/dev/null 2>&1
59 * * * * root rm -f /var/spool/cron/lastrun/cron.hourly
14 4 * * * root rm -f /var/spool/cron/lastrun/cron.daily
29 4 * * 6 root rm -f /var/spool/cron/lastrun/cron.weekly
44 4 1 * * root rm -f /var/spool/cron/lastrun/cron.monthly

I was not really user via what user is shell script run, therefore I looked first if someone doesn't set the script to run via crontab's standard locations for Daily, Hourly,Weekly and Monthly cronjobs:
 

a) Daily set cron jobs are in:

/etc/cron.daily/

b) Hourly set cron jobs:

/etc/cron.hourly

c) Weekly cron jobs are in:

/etc/cron.weekly/

d) Monthly cron jobs:

/etc/cron.monthly

There is also a location read by crontab for all Software (package distribution) specific cronjobs – all run under root user privileges.:

e) Software specific script cron jobs are in:

/etc/cron.d/  
As the system has about 327 users in /etc/passwd, checking each user's cronjob manually with:

# crontab -u UserName -l

was too much time consuming thus it is a good practice to list

/var/spool/cron/*

directory and to see which users has cron jobs defined

 

# ls -al /var/spool/cron/*
-rw——- 1 root root 11 2007-07-09 17:08 /var/spool/cron/deny

/var/spool/cron/lastrun:
total 0
drwxr-xr-x 2 root root 80 2014-05-22 11:15 .
drwx—— 4 root root 120 2008-02-25 15:45 ..
-rw-r–r– 1 root root 0 2014-05-22 04:15 cron.daily

/var/spool/cron/tabs:
total 8
drwx—— 2 root root 72 2014-04-03 03:43 .
drwx—— 4 root root 120 2008-02-25 15:45 ..
-rw——- 1 root root 4901 2014-04-03 03:43 root
 


/var/spool/cron – is crond (/usr/bin/cron/)'s spool directory.

# ls -al /var/spool/cron/tabs/ total 8
drwx------ 2 root root 72 2014-04-03 03:43 .
drwx------ 4 root root 120 2008-02-25 15:45 ..
-rw------- 1 root root 4901 2014-04-03 03:43 root

Above output shows only root superuser has defined crons.

Alternative way to check all user crontabs is via quick Linux one liner shell script show all user cron jobs

for i in $(cat /etc/passwd | sed -e "s#:# #g" | awk '{ print $1 }'); do
echo "user $i --- crontab ---";
crontab -u $i -l 2>&1 >/dev/null;
echo '----------';
done|less

Note that above short script has to run with root user. Enjoy 🙂

Minsk Monastery trip to saint Elizabath’s Nun Convent – Spiritual realms of Belarus

Monday, April 7th, 2014

st_Elizabeth_Romanova-monastery-Church
If you happen to be in Belarus's capital Minsk and you're a Christian you would definitely will be interested to see the spiritual side of Belarus. I was in Minsk with my wife for a month and had the chance to go for a pilgrimage in st. Elisaberth's Orthodox Christian Convent.

In Belarus about 80% of population of population are Orthodox Christians with about 7% Catholics, some 4% protestants and 9% atheists. I'm Orthodox Christian myself so mostly I kept interest in exoeriencing Orthodox religion life there. The religious life in Belarus so deeply impressed me so I decided to even document it here.

I was in a couple of Orthodox Churches during the Great Lent first week attending afternoon (Great) Repentence services canon of St. Andrew of Crete. And was amazed how many people are religious in this God fearful country. All Churches where I was during the Great Canon or Holy Liturgy was so full of people that you cannot even enter the Church if you're late for the service. People attending were also very concentrated on the service and most of the people came to services bringing most of which holding a book with the Great Repentance Canon following the service and concentrated in praying and doing ground prostrations. One thing to note is Belarusian Orthodox Church is a sub-division of Russian Orthodox Church (ROC), Belarusian doesn't have their own patriarch but are under the patriarchy of Russian and all Moscow patriarch – Kiril I.

Few weeks ago for Sunday of All Orthodoxy (Triumph of All orthodoxy) for Holy Liturgy service me and Svetlana with a close friend of her Tatyiana went to St. Elisabeth's Monastery. 
Monastery is named in honour of St. Elizabeth Feodorovna Romanova – which is the last Russian Grand Princess of the Romanov family later executed with her husband and kids by Communists Bolsheviks, canonized by ROC in the 1990s.

Saint_Elizabeth_holy_orthodox_icon_monastery_Minskst_Elizabeth_Romanova-monastery-Church

The monastery as almost all Churches in Belarus is so full of people you cannot move (it seems in Russian Orthodox Church – there is an amazing spiritual awakening at the moment). I wanted to confess and even though I was in the Church building before beginning of the holy liturgy and there were two priests to confess the queue of people to confess was so long that confession lasted until the end of the Holy Liturgy. In order to able to confess I've waited on the "confession queue" for about 2 hours and a half. Even though Holy Liturgy completed confession continued and those who confessed after the Church service end was also offered the Holy Sacraments. Another stunning thing for me was the amount of young and obviously intelligent people who was in the Church – just to compare here in Bulgaria, seeing young people in most Churches and monasteries is a rare thing ..

Saint Elisabeth's Monastery is the only monastery situated in (very near 19 km away) from MINSK on Vigotskogo 6 str. We reached the monastery by taking bus from regular Minsktrans (state's bus company) city bus nr. 26, other bus and trolley riding there are – bus 18 and trolley 33, 38, 55.
Monastery was established in 1990 after dissolvement of USSR and is situatuated on a place where previously there was no church or a monastery. The SisterHood in monastery is enormous by size and consists nowadays of 7 Churches!!!

St_Elizabeth_Monastery_Monastery_Minsk-picture

The main Church of the Monastery has saint relics from all around the known Orthodox Walls, to venerate all the saint relics you will need at least 20 minutes!! The Holy Relics of the monastery are so much that they remind me very much of Monasteries I've seen on Holy Mounth Athos. The spiritual father of the monastery is father Andreya Lemoshonka.

father-Andreya-Lemeshonka-spiritual-father-of-st-Elizabeth-monastery-Minsk


From ruromrs the sisterhood in monastery consists of about 120 sisters (and even maybe more), some of them are Nuns and others are the so called "Sisters of Mercy" (something like the "White Sisters" moveing in the Roman Catholic Church) – woman who deliberately decided to help the monastery often walking the streets shops and metro stations collecting charity for poor, sick and people in need. Sisters of mercy are something exception and seeing a lady dressed in white robes on the street or metro with a prayer book at hand is something rare to see in today's crazy materialistic world. Some of this kind sisters of mercy are novice nuns in the monastery and others are just worldly woman with family whom the monastery employes on a small renumeration.

Minsk-sister-of-mercy-sestri-miloserdie-Belarus

The cloister is a unique place next to the majestic Church buildings, the monastery has a coffeteria where you can have a coffee / snacks or even a dinner after service, there is a Church shops full of icon and all kind of orthodox spiritual literature,a Christian games for kids (Orthodox Lotto, kids collapsible Churches from cardboards) as well as a food store with fasting and non-fasting food and even a shop for Christian clothing "Православная Одежда". 

orthodox-clothes-shop

Orthodox Clothes Shop near St. Elizabeth's monastery Minsk

st_Elizabeth-monastery_minsk-medovaja_lavka

A Honey Store – St. Elizabeth Monastery Belarus

st_elizabeth_monastery-food-store

Orthodox Foodstore near St. Elizabeth Monastery Misnk

In one of the Churches there is a 3 floor tiny shop first floor sell icons, books and faith related things, monastic souvenirs and on the second floor there is a herbal pharmacy  with healing herbs for almost all kind of physical and nervological disorders etc. Part of monastic life is the evening and morning service which occur everyday in the monastery. The spiritual father of a monastery Andreya Lemoshonka who is a married priest is also leading frequent lectures on faith and is often helping people coming to him for a spiritual advice, a problem or question related to faith. The Nuns are fasting each Monday, Wednesday and Friday – fasting also in Mondays even though this fasting day was only observed in ancient Church and in many Orthodox monasteries, Monday fastings (In veneration of Angels) is no longer observed – i.e. sisterhood life is very strict. Near the monastery is situated a Mental Hospital and one of the duties of nuns is to often visit the mentally sick there. The sisterhood helps orphanage homes and is bringing for Holy sacraments often a lot of sick children.

st_elizabeth-monastery-minsk1

Part of monastery service is sheltering the homeless, alcoholics and drug addicts offering them encouragement and work in the small monastic farm. The monastery has also workshops where people with disability work in making gloves, icons, decorations, souvenirs embroided by hand. Near the monastery there is a wooden shop where one can order all kind of custom crafted wooden wardrobes, chairs or anything wooden you like for your home.

What I saw there make my heart joyful. It seems Minsk Monastery achieved something which is rarely seen in Orthodox world a symbiosis between Faith, charity and a monetary funding model that works
The monastery very much reminded me to an Orthodox movie Forpost and to the Godly initiate in Bulgaria by father Ioan of Novi Khan who by his efforts, Gods help and the charity of hundreds of bulgarian takes care for about 150 homeless orphans in a monastery.

 

'Forpost' (Outpost) – What the Church Can Accomplish. 

As a closure word I want say Thanks and Glory be to the Holy Trinity The Father, The Son and the Holy Spirit! for blessing me to the pilgrimage journet to St. Elizabeth's monastery!

Web Application Load Balancer types and when to use what kind of Load Balancer

Monday, February 3rd, 2014

General load balancer types description / active / passive / static / dynamic and additional
In this small article I will try to clear it up the general types of Web Server Load Balancers available. Whether one choose a Load Balancer he has the option to use a software LB or a hardware LB one there are plenty of software load balancer scripts out there. In this pos t I will mention just what choice is available in hardware load balancer interface BigIP LTM F5 standard. Generally BigIP LTM Load Balancers can be grouped in Static, Dynamic and Additional. One or more Load Balancers can be configured in front of group or farm of appplication servers. When more than one load balancer is used in front of application Load Balancer could be Active Load Balancer and Passive Load Balancer.
Below information will hopefully be useful to Web and Middleware working sys admins and anybody involved in frequent and large web systems integration.

Static Load Balancing

LB_RoundRobin_ type of load balancing example picture


Round Robin
Load Balancing

This is the default load balancing method. Round Robin mode passes each new connection request to the next server in line, eventually distributing connections evenly across the array of machines being load balanced.
Round Robin mode works well in most configurations, especially if the equipment that you are load balancing is roughly equal in processing speed and memory.

ratio_member_load_balancer picture diagram

Ratio (member) / Ratio (node) Load Balancer

   
The Ratio (member) system distributes connections among pool members or nodes in a static rotation according to ratio weights that you define. In this case, the number of connections that each system receives over time is proportionate to the ratio weight you defined for each pool member or node. You set a ratio weight when you create each pool member or node.

These are static load balancing methods, basing distribution on user-specified ratio weights that are proportional to the capacity of the servers.

dynamic_ratio_member_load_balancer picture diagram

Dynamic Load Balancers

 

Dynamic Ratio (member) Dynamic Ratio (node) LB

The Dynamic Ratio load balancing select a server based on various aspects of real-time server performance analysis. These methods are similar to the Ratio methods, except that with Dynamic Ratio methods, the ratio weights are system-generated, and the values of the ratio weights are not static. These methods are based on continuous monitoring of the servers, and the ratio weights are therefore continually changing.
   
The Dynamic Ratio LBs are used specifically for load balancing traffic to RealNetworks® RealSystem® Server platforms, Windows® platforms equipped with Windows Management Instrumentation (WMI), or any server equipped with an SNMP agent such as the UC Davis SNMP agent or Windows 2000 Server SNMP agent.

dynamic_load_balancing load balancer diagram picture with circles

Fastest (node) /Fastest (application) LB

   
The Fastest methods select a server based on the least number of current sessions. The following rules apply to the Fastest load balancing methods:

These LB require that you assign both a Layer 7 and a TCP type of profile to the virtual server interface where LB IP is binded.
If a Layer 7 profile is not configured, the virtual server falls back to Least Connections load balancing mode.

Note: If the OneConnect feature is enabled, the Least Connections methods do not include idle connections in the calculations when selecting a pool member or node. The Least Connections balancing use only active connections in their calculations.
   
Fastest node load balancing is useful in environments where nodes are distributed across separate logical networks.

 

Least Connections (member) / Least Connections (node) LB    

The Least Connections method are relatively simple in that the system passes a new connection to the pool member or node that has the least number of active connections.

Note: If the OneConnect feature is enabled, the Least Connections methods do not include idle connections in the calculations when selecting a pool member or node. The Least Connections methods use only active connections in their calculations.
   
The Least Connections balancing function best in environments where the servers have similar capabilities. Otherwise, some amount of latency can occur.

For example, consider the case where a pool has two servers of differing capacities, A and B. Server A has 95 active connections with a connection limit of 100, while server B has 96 active connections with a much larger connection limit of 500. In this case, the Least Connections method selects server A, the server with the lowest number of active connections, even though the server is close to reaching capacity.

If you have servers with varying capacities, consider using the Weighted Least Connections load balancing instead.

 

Weighted Least Connections (member) / Weighted Least Connections (node)

Like  Least Connections, these load balancing methods select pool members or nodes based on the number of active connections. However, the Weighted Least Connections methods also base their selections on server capacity.

The Weighted Least Connections (member) method specifies that the system uses the value you specify in Connection Limit to establish a proportional algorithm for each pool member. The system bases the load balancing decision on that proportion and the number of current connections to that pool member. Example is member_a has 40 connections and its connection limit is 200, so it is at 20% of capacity. Similarly, member_b has 40 connections and its connection limit is 400, so it is at 10% of capacity. In this case, the system select selects member_b. This algorithm requires all pool members to have a non-zero connection limit specified.

The Weighted Least Connections (node) method specifies that the system uses the value you specify in the node's Connection Limit setting and the number of current connections to a node to establish a proportional algorithm. This algorithm requires all nodes used by pool members to have a non-zero connection limit specified.

If all servers have equal capacity, these load balancing  behave in the same way as the Least Connections methods.

Note: If the OneConnect feature is enabled, the Weighted Least Connections methods do not include idle connections in the calculations when selecting a pool member or node. The Weighted Least Connections  use only active connections in their calculations.
   

Weighted Least Connections methods work best in environments where the servers have differing capacities.
For example, if two servers have the same number of active connections but one server has more capacity than the other, the BIG-IP system calculates the percentage of capacity being used on each server and uses that percentage in its calculations.

 

Observed (member) / Observed (node)

With the Observed methods, nodes are ranked based on the number of connections. The Observed methods track the number of Layer 4 connections to each node over time and creates a ratio for load balancing.
   

The need for the Observered methods is rare, and they are not recommended for large pools.

Predictive (member) / Predictive (node)

The Predictive methods use the ranking methods used by the Observed methods, where servers are rated according to the number of current connections. However, with the Predictive methods, the BIG-IP system analyzes the trend of the ranking over time, determining whether a nodes performance is currently improving or declining. The servers with performance rankings that are currently improving, rather than declining, receive a higher proportion of the connections.
   

The need for the Predictive methods is rare, and they are not recommend for large pools.

Least Sessions LB type

The Least Sessions method selects the server that currently has the least number of entries in the persistence table. Use of this load balancing method requires that the virtual server reference a type of profile that tracks persistence connections, such as the Source Address Affinity or Universal profile type.

Note: The Least Sessions methods are incompatible with cookie persistence.
   
The Least Sessions method works best in environments where the servers or other equipment that you are load balancing have similar capabilities.

 

L3 Address

L3 Address is same LB type as Least Connections methods.
  

Web and Middleware JBoss Training at Hewlett Packard – Intro to JBoss JAVA application server

Thursday, November 21st, 2013

jboss application server logo- serve java servlet pages on Linux and Windows

I and my TEAM Web and Middleware Implementation Team @Hewlett Packard are assigned an online training to follow on topic of JBoss Application server.It is my first online training of this kind where a number of people are streamed a video from a trainer who explains in real time concepts of JBossA Community Drive open source middleware (Application Server), since some time JBoss is known under a new name (WildFly).

Wildfly new name of jboss application java servlet server

In short what is JBoss? – It is an application server similar to Apache Tomcat  -an open source software implementation of the Java Servlet and JavaServer Pages technologies.

Apache Tomcat java servlet application server logo

In case you wonder about what is Middleware it is a buzzword well established in Corporate world referring to all kind of servers in the middle between Servers on pure OS and hardware Level and end client. Middleware includes all kind of Web and Application servers like Apache, JBoss, Tomcat, Adobe's WebLogic Webserver, IBM WebSphere application server etc..

What this means is JBOSS is very similar to Tomcat but it is designed to run interpret through (Java Virtual Machine), higher scale of Java Applications and then return content to a a web browser. In other words if you need to have a Webserver with support for Java VM. JBoss is one of the open source technologies available which can be a substitute for Tomcat. In Fact Jboss itself started as a fork of Tomcat and n owadays, Jboss has an implementation of Tomcat embedded into itself. Jboss is mainly developed and supported by Redhat. It has 3 major releases used in IT Companies. Jboss 5, JBoss 6 and JBoss 7. In most production server systems running some kind of Java servlets currently still Jboss ver. 5 and Jboss v. 6 is used. Just like Tomcat, the server is messy in its structure. But if we have to compare Tomcat with Jboss then JBoss is at least 100 times more messy and hard to configure tune than Tomcat. Actually after getting to know JBoss 6 I would not advice anyone to use this Application server. Its too complex and all configuration and performance tuning is done through hundred of XML so it is like a hell for the usual System Administrator who likes clearness and simplicity. JBoss has a Web configuration interface which in version 7 is a bit advanced and easier to configure and get to know the server compared to previous versions. But same web interface for older releases is lousy and not nice. Just like Tomcat, JBoss supports clustering, here is full list of all features it supports:

  • Full clustering support for both traditional J2EE applications and EJB 3.0 POJO applications
  • Automatic discovery. Nodes in cluster find each other with no additional configuration.
  • Cluster-wide replicated JNDI context
  • Failover and load-balancing for JNDI, RMI and all EJB types
  • Stateful Session Bean state replication
  • HTTP Session replication
  • High Availability JMS
  • Farming. Distributed deployment of JBoss components. Deploying on one node deploys on all nodes.
     

Looks like JBoss is among the few Application Servers supporting deployment of Java JSP, WAR Archive files, SAR Archives, JMS (Java Message Service), JNDI (Java Naming and Directory Interface). Jboss supports load balancing between clustered nodes, supports SOAP, Java servlet faces and Java MQ (Messaging Queue). JBoss can be installed on GNU / Linux, FreeBSD and Windows. So far from what I've learned for JBOSS I prefer not to use it and don't recommend this Application server to anyone. Its too complex and doesn't worth the effort to learn. Proprietary products like WebLogic and Webspehere are in light years better.

Curious: Old ladies from Plovdiv, Bulgaria are knitting mobile and computer equipment hand made cases

Monday, November 11th, 2013

new business idea manual hand crafted knitted mobile device cases

While reading one of my daily tech news websites today I stimbled on very unusual news and a business idea, worthy to re-blog 😉 The idea of the new Innovative business is just genious and simple as that – knitted digital equipment cases. There are plenty of old ladies in Bulgaria who are used to knitting sweaters, hats and all kind of hand made winter clothes. Knitting was among the must have skills for ladies in Bulgaria until some years time even my grandmother when a bit younger used to knit in most of her free time. Thus most of grandmothers in Bulgaria still when get old and have a lot of free time, kill their time with the craft they learned as young. For the young European people who probably never heard of it knitting is unique kind of manufacture for producing winter clothes from yarn.

yarn in different colors the base material for knitting

Knitting was a top ladies craft before the boom of industrial manufacture before 19th century industrial revolution, nowadays its almost a forgotten craft. Now some genious people in Bulgaria decided to give work to this old ladies and pay them for knitting computer and mobile equipment cases (cases for Tablets, Smartphones, Notebooks etc.) Knitting of mobile equipment cases opens new work places and introduces new way for old people to earn some extra income, such extra income is absolutely necessary in Bulgaria nowdays as most old ladies receive ridiculous pension of 120 to 150 EUR per month (money insufficient to pay expensive winter heating bills and so expensive food that is nowdays in Bulgaria).

lady knitting a sweater or some kind of clothe

The company who invented this new business and introduced it for the masses is Snug Essentials and is started by enthusiastic young people who had grandmothers practicing the old craft. The innovative product is distributed via Etsy Global Platform for distributing hand crafted goods as well as in   Facebook, Twitter and Ebay. As of time of writting the companyis extremely small 6 old grandmas work on producing the knitted cases for digital equipment but the tendency is this to rise soon, as there are plenty of people who love the hand made cases.
The price of a case is also not too high, it costs only around 10$ per knitted case. Here are few nice knitted cases produced by grandmas 🙂

notebook laptop in knitted hand made case

Your girlfriend will love it if you gift her one of these 🙂

knitted notebook case original business idea

 

On God and computers and how computers copy God’s creation

Friday, October 25th, 2013

People are copying Gods creation the-tree model people don't invent they copy

I've been thinking for a long time. How computers and involved technology copy God's creation. This kind of thoughts poped up in my mind right after I became a believer. As I'm having a strong IT background I tend to view thinks in world via the prism of my IT knowledge. If I have to learn a new science my mind tend to compare how this translates to my previous knowledge obtained in IT. Probably some other people out there has the same kind of thinking? I'm not sure if this is a geek thinking or it is usual and people from other fields of science tend to also understand the world by using accommodated knowledge in field of profession they practice. Anyways since my days I believed in Jesus Christ, I started to also to compare my so far knowledge with what I've red in Holy Bible and  in the book of The Living of Saints (which btw is unknown to most protestant world). It is very interesting that if you deeply look into how all Information Technology knowledge is organized you can see how Computers resembles the visible God's creation. In reality I came to realization how Moden Man self-deceives himself. We think with every new modern technology we achieved something new revolutionory which didn't existed before. But is it really true? Lets take some technology like Microsoft Active Directory (using LDAP) for example. LDAP structures data in a tree form where each branch could have a number of sub branches (variables). In reality it appears LDAP is not new it a translation of previous already existent knowledge in universe served in a different kind of form. Let me give some other examples, lets pick up the Internet, we claim its a new invention and from human point of view it is. But if we look on it via the prism of existing created world. It is just a interconnection between "BIG DATA" in real world it is absolutely the same latest researches already know all in world is data and all data in world is interconnected. So obviously the internet is another copying of the wonderful things God created in material and for those who can accept (the spiritual world) world. Many who are hard-core atheists will argue that we copy things in the world but all the material world is just a co-incidence. But having in mind that the world is so perfectly tuned "for living beings to exist" it is near to impossible that all this life and perfection emerged by random. The tree structure model is existing everywhere in OS and programming. We can see it in hiearchy of a file system, we can see it in hashes (arrays) in programming and all this just copies the over-simplified model of a real tree (which we know well from Biology is innemous times more complex). Probably the future of computing is in Biotechnologies and people's attempts to copy how living organism works. We know from well from science-fiction and cyberpunk the future should be mostly in Bio-technologies and computer as we know it but even this high-tech next generation technology will be based on existent things. Meaning man doesn't invent something so different he does copy a model and then modify the model according to environment or just makes a combination of a number of models to achieve a next one. Sorry for the rant post but I'm thinking on this for quite a while and I thought i should spit it here and interested to hear what people think and what are the arguments for or against my thesis?