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This presents us with a double bind; each user’s content is customised and there is a service expectation of 100% availability and responsiveness. In addition, we have issues of large scale and 24 x 7 availability we can see that constructing such a service is a serious web engineering exercise.

If you are not monitoring the service, then you are just running software.

It’s never good when the first person to tell you that your service has a problem is one of your consumers. Without appropriate monitoring software this will inevitably be the case, and in all probability they won’t tell you immediately.

So, the first key differentiator between a service and a system is Monitoring.

Choose the right tools.

When our service was first constructed a very expensive piece of software was purchased to perform availability monitoring, however, Mr. Heisenberg was forgotten and the load associated with that particular tool was sufficient to detrimentally impact the system. The tool itself was sold as the usual universal panacea, however, in implementation it was clear that its forte was component monitoring and not service monitoring.

Running a live system with this tool gave us all sorts of problems. The tool required agents on all machines and was really only designed around component availability and even then this was often measured from the wrong place (inside the firewall).

We took a look at the open source offerings available at that time and selected two.

Event monitoring

Nagios has won lots of awards. We use it to monitor events from two locations.

  • Our DMZ where it looks at all of our components every 90 seconds and critically has thresholds set for Green, Amber and Red. While most components in our large system are duplicated to provide resilience, it’s absolutely vital to know when one of your resilient components has failed in order to prevent a systems failure.
  • The public Internet. From this location, we can look at the service(s) from the perspective of the end user.

Nagios is used to provide event monitoring. Implementing such a tool is not to be undertaken lightly. Getting the sensitivity correct so as not to cry wolf, and embedding the culture such that when an alert is sent out, the operational staff respond rapidly is, in my opinion, more difficult than installing the system in the first place.

Trend and volume monitoring

The second open source monitoring tool we use provides trend monitoring, After looking around we found Cacti .

While Nagios tells us when we have a specific issue/problem, Cacti provides us with the information to understand or diagnose the root cause. In measuring volumes and their trends, Cacti allows us to look across the whole application stack at any point in time and examine critical volumes.

Cacti is used to measure volumes. If a system can return a number, Cacti can capture, store and trend it. These volumes can be business or technical volumes examples of which might include the number of users logged into the system over time or critical system volumes such as bandwidth, disk space, CPU, or Memory usage.

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
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Source:  OpenStax, The impact of open source software on education. OpenStax CNX. Mar 30, 2009 Download for free at http://cnx.org/content/col10431/1.7
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