Server Overload

Lets say you have a company and you have a website, that website exchanges conversations between members. At first you start by a few users talking to each other. Then those users start to tell their friends about your website. And those friends start to tell other friends about your website, and so on. Till your servers can’t keep up with the demand. In order to work around this problem you either buy or rent some servers and set them up or ask someone else to set them up for you. Of course this approach costs a lot of money and takes a lot of time.

Now there is a better option, instead of hosting your website on a your dedicated server, you can host it on the Cloud. With cloud computing you have access to computing power almost instantly when you need it. So if you suddenly need more computing power you can scale up as much as you need in the cloud on demand. Thus, the clients won’t notice any difference. In general, with cloud computing you don’t focus on hardware or software, you only focus on what you need.

What’s Cloud Computing

Cloud Computing

A cloud computing is internet-based computing where shared resources, software and information are provided to computers and other devices on demand-like a public utility. “Wikipedia”

Orcale CEO Larry Ellison said: “Cloud Computing is using a computer that’s out-there”. The cloud in cloud computing provides the means through which everything – from computing power to computing infrastructure, applications, business processes to personal collaboration – can be delivered to you as a service wherever you need.

The term “cloud” is used as a metaphor for the “Internet” which is an abstraction of the infrastructure it represents. Cloud computing typically provide some online services which can be accessed using a web service or a browser while software and data are stored on servers.

Cloud Computing Characteristics

In general, Cloud computing users or customers(us) do not own the physical infrastructure. Thus, we don’t have to worry about the machines that runs the application because they don’t belong to us, so we don’t have to devote out time and resources for maintaining an application. On the other hand, all the hardware and software are on the cloud. You just subscribe for the resources you need as a service and only pay for the resources that you use. This approach leads to that overall computer usage rises dramatically as customers don’t have to engineer for the load limits.

Cloud Computing Key Features

Cloud computing has many features, some of the features are:

- Cost

Cost is claimed to be greatly reduced as you don’t need to buy any hardware or software, you only charged on the amount of resources you use. An example of a free cloud-computing service is GooGle Docs (http://docs.google.com/). With google docs you can create documents, spreadsheets and presentations online. So you don’t need to buy Microsoft office for windows or IWork for mac. All you need is a PC that’s capable of running a browser and internet connection.

-Virtualization

Virtualizing an application means packaging the application with everything it needs to run including database, middleware and operating system to be a self-contained image that can run anywhere on the cloud.

As we know, the cloud can offer the software as a service, but applications are so hard to deploy on new environments (to meet their requirements). So people thought of why not to separate the application from the infrastructure! So application and infrastructure become independent.Virtualization separates resources and services from the underlying physical delivery environment. Allowing servers to be easily shared by many applications.

-Multitenancy

Multitenancy is the opposite of virtualization, as in multitenancy environment, multiple customers share the same application, running on the same OS, on the same hardware. The distinction between the customers is achieved during application design, so they don’t share or see each other data. Multitenancy also improves the utilization of the systems as many customers will be using the same hardware.

-Scalability

Regarding hardware, its the ability to go from small to large amounts of processing power with the same architecture. Regarding software products such as databases, it refers to the consistency of performance per unit of power as hardware resources increase.

The service provider can’t anticipate how customers will use the service. One customer might use the service three times a year during peak selling seasons, whereas another might use it as a primary development platform for all of its applications. Therefore, the service needs to be available all the time and it has to be designed to scale upward for high periods of demand and downward for lighter ones. Scalability also means that an application can scale when additional users are added and when the application requirements change.

-Reliability

Improves through the use of multiple redundant sites and the ability of a system to provide uninterrupted service despite the failure of one or more of the system’s components, this’s called “Fault Tolerance” which is failure prevention.

-Maintenance

Since there is a third party that owns the hardware and software and just provide them as a service, maintenance isn’t our problem,the cloud service provider is the one responsible for hardware maintenance and software upgrades/maintenance.

Cloud Computing Layers

Cloud Computing Layers

Cloud computing consists of five layers:

1. Client.
2. Application.
3. Platform.
4. Infrastructure.
5. Servers.

Cloud infrastructure services or “Infrastructure as a Service (IaaS)” delivers computer infrastructure, typically a platform virtualization environment as a service. Rather than purchasing servers, software, data center space or network equipment, clients instead buy those resources as a fully outsourced service. The service is typically billed on a utility computing basis and amount of resources consumed will typically reflect the level of activity. It is an evolution of virtual private server offerings.

The Cloud Infrastucture consists of one or more servers. The servers layer consists of computer hardware and computer software products that are specifically designed for the delivery of cloud services, including multi-core processors, cloud-specific operating systems and combined offerings.

There are two different types of services that a cloud can offer:

1. Saas (Software as a Service): GooGle is one of the free Cloud providers that provides software as a service (Google apps).
2. HaaS (Hardware as a Service): Amazon’s Ec2 is one of the providers that offers different computing power models (See Amazon’s EC2 Section).

Amazon’s EC2

Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides resizable compute capacity in the cloud. It is designed to make web-scale computing easier for developers. It provides a basic measure of an EC2 compute unit: One EC2 Compute Unit (ECU) provides the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor.

Amazon EC2 instances are grouped into three families: Standard, High-Memory and High-CPU. Standard Instances have memory to CPU ratios suitable for most general purpose applications; High-Memory instances offer larger memory sizes for high throughput applications, including database and memory caching applications; and High-CPU instances have proportionally more CPU resources than memory (RAM) and are well suited for compute-intensive applications. When choosing instance types, you should consider the characteristics of your application with regards to resource utilization and select the optimal instance family and size.

Standard Instance

High-Memory

High Memory Instance

—

High CPU Instance

—They offer more CPU resources than memory (RAM) and are well suited for compute-intensive applications.

High CPU Instance

Cacutus

Cacutus is another cloud computing service provider (SaaS). It’s a complete network graphing solution designed to handle statistics and signal processing data like network bandwidth, temperatures, CPU load etc. it stores all of the necessary information to create graphs and populate them with data in a MySQL database.

References

• Wikipedia
• Amazon EC2 – http://aws.amazon.com/ec2/
• Judith Hurwitz, Robin Bloor, Marcia Kaufman, Fern Halper – 2009 – Cloud Computing For Dummies
• Dion Hinchcliffe – http://www.ebizq.net/blogs/enterprise/2009/08/what_does_cloud_computing_actu.php

First of all, i would like to thank Dr. Fatma for this great course as iam getting to know about open source community more than before. Last week, we were asked to edit a firefox extension which is called “Ubiquity”. The task was to enhance the Ubiquity addon by adding this command. Its a “feedback” command, simply it take 2 arguments: the first one is the command and the second is the feedback. After that it sends the feedback to the developer’s (author) email address which can be found according to this template

This will allow the users to help the developers by inform them about any bugs or a suggestion or even to thank them …

Well, at first i was like “WHAT” ?!!!! i didnt have a clue how to start or what to look for ! Although i had the source code and a link to a nice tutorial for Ubiquity, but still =/ ….
SO me and my friends started looking for how to get the command thats passed to the FEEDBACK command as AN OBJECT, in order to access the author’s email address to send the feedback ….

After some searching and testing we finally figured out how to get the command as AN OBJECT, as follows:
CmdUtils.CreateCommand(
names: ["test"],
execute: function showme_execute() {
e = CmdUtils.getCommand(“map”)
}
})

Unfortunately, we didn’t know about the template back then. So we started to hacking the MAP command (A predefined command in Ubiquity) code using JavaScript SEARCHING for an email field by accessing the Map object and print all variables and objects names it contains as follows:
CmdUtils.CreateCommand({
names: ["showme"],
execute: function showme_execute() {
c = CmdUtils.getCommand(“email”);
x=”";
for(i in c){
x=x+i+”: “+c[i]+”<br/>”;
}
CmdUtils.setSelection(x);
}
})

After 2 hour of hacking, we didn’t found any email field or even an author field … and as soon as we found about the template, we found that the map command doesn’t follow the template (OH MY GOD) thus it didn’t have any author or email fields … And Now all we need to do is to find a way to execute the email command using JavaScript and add the feedback to the email body ….