Easy steps to help maintain your classroom projector

Posted on by primaryt
1) When not in use please power down your projector. This will help prolong bulb and projector life.
2) Avoid placing classroom displays around the projector. Any disruption in airflow to the projector could result in premature overheating causing the unit to fail.
3) Never turn off the projector’s supply of power until it has finished its cooling cycle. This could lead to the bulb failing.
4) If visible, check the filters regularly. Dust build up can cause problems.
5) At the end of the school day please shut down your projector

Installing the NRPE client, daemon and nagios plugins on debian

Posted on by primaryt

We assuming have already configured nrpe on your nagios box and you are sudo’d/root

Steps:

adduser nagios (set the password)
cd /home/nagios
wget http://prdownloads.sourceforge.net/sourceforge/nagios/nrpe-2.12.tar.gz
* If this step fails visit http://www.nagios.org/download/addons for the latest URL

tar -zxvf nrpe-2.8.tar.gz
cd nrpe-2.12
apt-get install gcc gawk openssl
apt-get install make
apt-get install libssl-dev
apt-get install nagios-plugins
./configure
make all
make install-plugin
make install-daemon
make install-daemon-config
echo “only_from = 0.0.0.1” >> /usr/local/nagios/etc/nrpe.cfg
* Remember to replace 0.0.0.1 with your the IP address of your nagios server

cp init-script.debian /etc/init.d/nrpe
chmod 700 /etc/init.d/nrpe
/etc/init.d/nrpe start

You may want to make this script run on start up
update-rc.d nrpe defaults

Stress testing Etherpad Open source

Posted on by primaryt

Java goes to 99% cpu very easily when stress testing etherpad, I want to find out why and how to optimize the VM to stop it happening.
After X amount of users join my CPU hits 99%, memory is fully used up and a simple end of the java process and restart isn’t enough to fix the issue. The memory active (according to vmware client) is still 1.5gb+ which is .3 GB higher than the amount of memory granted. Top shows 5% Memory being used. The other VM’s running on the box are using a total of 200MB Ram (very quiet unix boxes doing no work). So the Etherpad VM should have 1.8 GB available at least.
Eventually the VM catches up with reality and I can reconnect (this takes 30 minutes+). Although I usually killall java and restart during this time, this doesn’t seem to help anything though..

Machine: Supermicro X7DA8 – 2 CPU x 1.6Ghz (Intel Xeon) 5110 – Hyperthreading = inactive – 2GB ram – VMWare 3i 3.5.0

Etherpad VM settings:
Max Memory use = 2GB
Reserved Memory = 750MB
Reserved CPU = 1277
Priority of access to resources = High

Etherpad is set to use 2GB(XMX) of memory in the start up script which could explain why it is trying to balloon into unavailable memory?
See below for command running Etherpad and see below that for modified command to drop XMX to 1.5GB to measure performance and avoid excessive ballooning or using non existent resources:
Old:
54.4 7.5 1777760 153760 pts/0 Sl+ 16:36 1:15 /usr/bin/java -classpath appjet-eth-dev.jar:data:lib/dnsjava-2.0.6.jar:lib/jbcrypt-0.2.jar:lib/jcommon-1.0.15.jar:lib/jfreechart-1.0.12.jar -server -Xmx2G -Xms2G -Djava.awt.headless=true -XX:MaxGCPauseMillis=500 -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:CMSIncrementalSafetyFactor=50 -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xloggc:./data/logs/backend/jvm-gc.log -Dappjet.jmxremote=true net.appjet.oui.main –configFile=./etc/etherpad.localdev-default.properties
New:
54.4 7.5 1777760 153760 pts/0 Sl+ 16:36 1:15 /usr/bin/java -classpath appjet-eth-dev.jar:data:lib/dnsjava-2.0.6.jar:lib/jbcrypt-0.2.jar:lib/jcommon-1.0.15.jar:lib/jfreechart-1.0.12.jar -server -Xmx1500M -Xms1500M -Djava.awt.headless=true -XX:MaxGCPauseMillis=500 -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:CMSIncrementalSafetyFactor=50 -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xloggc:./data/logs/backend/jvm-gc.log -Dappjet.jmxremote=true net.appjet.oui.main –configFile=./etc/etherpad.localdev-default.properties
Now for some stats with the old config –>
Experience: # of users = 24 (1500/24) = 62MB ram per user (ouch)

Etherpad did a fine job of failing to monitor the # of users on the site but thankfully I was paying attention and counted a peek of 24.
Memory:
CPU:
Hard disk:
VMWare catching up with reality (here you can see the VM using more memory than is available):



Retesting with XMX at 1500 gave me terrible results. Etherpad crashed after 9 people joined. Time of crash was 18:10. It then didn’t respond, I had to kill the java process.
CPU:
Disk activity:
Memory activity (note how it doesn’t drop at 18:10 and is probably causing the disk activity)
Java Log dump (why is this not date/time stamped?!):
34.251: [GC 34.251: [DefNew: 13184K->522K(14784K), 0.1211500 secs] 13184K->522K(1534400K), 0.1213450 secs] [Times: user=0.01 sys=0.03, real=0.13 secs]
39.273: [GC [1 CMS-initial-mark: 0K(1519616K)] 6575K(1534400K), 0.3767920 secs] [Times: user=0.02 sys=0.07, real=0.37 secs]
39.707: [CMS-concurrent-mark-start]
84.577: [CMS-concurrent-mark: 44.608/44.870 secs] [Times: user=0.44 sys=4.40, real=44.87 secs]
84.577: [CMS-concurrent-preclean-start]
84.623: [CMS-concurrent-preclean: 0.035/0.045 secs] [Times: user=0.01 sys=0.01, real=0.05 secs]
84.623: [CMS-concurrent-abortable-preclean-start]
87.783: [GC 87.783: [DefNew: 13706K->1585K(14784K), 0.0858210 secs] 13706K->1585K(1534400K), 0.0859690 secs] [Times: user=0.02 sys=0.02, real=0.09 secs]
CMS: abort preclean due to time 89.876: [CMS-concurrent-abortable-preclean: 0.117/5.253 secs] [Times: user=1.25 sys=0.83, real=5.25 secs]
89.921: [GC[YG occupancy: 7906 K (14784 K)]89.921: [Rescan (non-parallel) 89.921: [grey object rescan, 0.0047960 secs]89.926: [root rescan, 0.0577760 secs], 0.0628440 secs]89.984: [weak refs processing, 0.0$
89.986: [CMS-concurrent-sweep-start]
89.986: [CMS-concurrent-sweep: 0.000/0.000 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
89.986: [CMS-concurrent-reset-start]
90.056: [CMS-concurrent-reset: 0.070/0.070 secs] [Times: user=0.03 sys=0.01, real=0.07 secs]
92.776: [GC 92.777: [DefNew: 14769K->903K(14784K), 1.6950470 secs] 14769K->2508K(1534400K) icms_dc=5 , 1.6951700 secs] [Times: user=0.02 sys=0.23, real=1.69 secs]
96.768: [GC [1 CMS-initial-mark: 1605K(1519616K)] 8927K(1534400K), 0.0135840 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
96.785: [CMS-concurrent-mark-start]
100.464: [GC 100.464: [DefNew: 14087K->912K(14784K), 1.4546970 secs] 15692K->3399K(1534400K) icms_dc=5 , 1.4548470 secs] [Times: user=0.07 sys=0.20, real=1.46 secs]
115.141: [GC 115.141: [DefNew: 14096K->739K(14784K), 0.0521690 secs] 16583K->4135K(1534400K) icms_dc=5 , 0.0523170 secs] [Times: user=0.02 sys=0.01, real=0.05 secs]
117.331: [GC 117.331: [DefNew: 13923K->1600K(14784K), 0.0184740 secs] 17319K->5255K(1534400K) icms_dc=5 , 0.0186180 secs] [Times: user=0.02 sys=0.01, real=0.02 secs]
118.617: [GC 118.617: [DefNew: 14784K->947K(14784K), 0.2542520 secs] 18439K->6186K(1534400K) icms_dc=5 , 0.2544010 secs] [Times: user=0.01 sys=0.07, real=0.25 secs]
120.143: [CMS-concurrent-mark: 0.792/23.359 secs] [Times: user=4.92 sys=3.58, real=23.36 secs]
120.143: [CMS-concurrent-preclean-start]
120.750: [GC 120.750: [DefNew: 14131K->862K(14784K), 0.0202510 secs] 19370K->7035K(1534400K) icms_dc=5 , 0.0203990 secs] [Times: user=0.00 sys=0.01, real=0.02 secs]
122.161: [CMS-concurrent-preclean: 0.052/2.018 secs] [Times: user=0.98 sys=0.46, real=2.02 secs]
122.161: [CMS-concurrent-abortable-preclean-start]
122.970: [CMS-concurrent-abortable-preclean: 0.162/0.809 secs] [Times: user=0.12 sys=0.25, real=0.81 secs]
122.990: [GC[YG occupancy: 7696 K (14784 K)]122.990: [Rescan (non-parallel) 122.991: [grey object rescan, 0.0048130 secs]122.995: [root rescan, 0.0579420 secs], 0.0629740 secs]123.054: [weak refs processing$
123.054: [CMS-concurrent-sweep-start]
123.093: [CMS-concurrent-sweep: 0.033/0.038 secs] [Times: user=0.00 sys=0.02, real=0.04 secs]
123.093: [CMS-concurrent-reset-start]
134.807: [GC 134.807: [DefNew: 13985K->967K(14784K), 2.8277290 secs] 20157K->7990K(1534400K) icms_dc=5 , 2.8278880 secs] [Times: user=0.10 sys=0.65, real=2.82 secs]
144.742: [CMS-concurrent-reset: 0.072/21.649 secs] [Times: user=2.13 sys=4.54, real=21.65 secs]
145.145: [GC 145.146: [DefNew: 14151K->1600K(14784K), 2.2576190 secs] 21174K->14140K(1534400K) icms_dc=9 , 2.2577710 secs] [Times: user=0.04 sys=0.58, real=2.25 secs]
154.100: [GC [1 CMS-initial-mark: 12540K(1519616K)] 20142K(1534400K), 0.0342300 secs] [Times: user=0.04 sys=0.00, real=0.04 secs]
154.148: [CMS-concurrent-mark-start]
154.499: [GC 154.500: [DefNew: 14784K->627K(14784K), 0.5930520 secs] 27324K->14768K(1534400K) icms_dc=10 , 0.5932170 secs] [Times: user=0.11 sys=0.18, real=0.60 secs]
156.652: [GC 156.653: [DefNew: 13811K->1271K(14784K), 0.0159730 secs] 27952K->15412K(1534400K) icms_dc=10 , 0.0161490 secs]

Another step towards mobile for the classroom

Posted on by primaryt

One of the frequent arguments used to cast out the use of Mobile phones in classrooms is the lack of charger or short battery life. No longer is that an issue…

The Airnergy WiFi Harvesting Charger “absorbs” power from your schools wireless network into a battery which can be used to charge devices such as mobile phones or PDA’s using a mini USB connection.

One of the best things about this is that any device that won’t use USB2 connectivity will be excluded. Hopefully this will encourage manufacturers to adopt more standards.
Of course that’s a dig at apple…

Google’s hidden gems

Posted on by primaryt

“Google’s hidden gems” is an arms length look at the Gem spitting Monster that is Google, with over 100 services covered the presentation will inspire, entertain and provoke parts of the brain you never even knew existed. Delivered by John McLear who is well known for his critical approach to business ethnics, we ask the question, is Google fulfilling it’s mission statement of “Don’t be evil” as we uncover a world of Google services never disclosed to the public.


Want me to deliver this presentation? Get in touch