AWS for Developers For Dummies. Mueller John Paul
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can consist of additional workflows. In addition, workflows manage the interaction between users and underlying services. A process is the aggregation of services managed by workflows into a cohesive whole. The workflows may perform generic tasks, but processes tend to be specific and help users accomplish particular goals. A process-driven workflow is proactive and attempts to circumvent potential problems by
❯❯ Spotting failure patterns and acting on them
❯❯ Looking for trends that tend to lead to failures
❯❯ Locating and extinguishing potential threats
A function is the reactive use of services managed by workflows to address specific problems in real time. Even though it would be nice if process-driven workflows worked all the time, the reality is that even with 99.999 percent reliability, the process will fail at some point, and a function-driven workflow must be in place to address that failure. Although process-driven workflows focus on flexible completion of tasks, function-driven workflows focus on procedurally attenuating the effect of a failure. In short, function-driven workflows address needs. The AWS services and workflows also deal with this issue through the user interface, such as by manually restoring a backup to mitigate a system failure.
❯❯ Configuring the native functionality of AWS using wizards, AWS-driven scripts, or direct API calls through code
❯❯ Modifying AWS-driven scripts as needed to accomplish specific goals in the least amount of time possible
❯❯ Defining new configuration scenarios to meet workflow requirements by modifying underlying AWS configuration files, scripts, and code
❯❯ Using AWS-supplied tools, such as lambda functions (see https://aws.amazon.com/lambda/), to perform tasks without resorting to hard coding
❯❯ Developing applications that rely on API calls to perform tasks
Discovering IaaS
Even though this book frequently refers to virtual environments and services that you can’t physically see, these elements all exist as part of a real computer environment that Amazon hosts on your behalf. You need to understand how these elements work to some extent because they have a physical presence and impact on your personal or business needs. Three technologies enable anyone to create a virtual computer center using AWS:
❯❯ Infrastructure as a Service (IaaS): A form of cloud computing that provides virtualized computing resources. You essentially use IaaS to replace physical resources, such as servers, with virtual resources hosted and managed by Amazon.
❯❯ Software as a Service (SaaS): A software distribution service that lets you use applications without actually having the applications installed locally. Another term used to describe this service is software on demand. The host, Amazon, maintains the software, provides the required licenses, and does all the other work needed to make the software available.
❯❯ Platform as a Service (PaaS): A platform provides a complete solution for running software in an integrated manner on a particular piece of hardware. For example, Windows is a particular kind of platform. The virtual platform provided by PaaS allows a customer to develop, run, and manage applications of all sorts.
The following sections provide an extended discussion of these three technologies and help you understand how they interact with each other. The point of these sections is that each element performs a different task, yet you need all three to create a complete solution.
The simplest way to view IaaS is as a means of providing access to virtualized computer resources over an Internet connection. IaaS acts as one of three methods of sharing resources over the Internet, alongside SaaS and PaaS. AWS supports IaaS by providing access to virtualized hardware, software, servers, storage, and other infrastructure components. In short, you can use IaaS to replace every physical element in your computing setup except those required to establish and maintain Internet connectivity and those required to provide nonvirtualized services (such as printing). The advantages of IaaS are many, but here are the ones that most people consider essential:
❯❯ The host handles tasks such as system maintenance, backup, and resiliency planning.
❯❯ A client can gain immediate access to additional resources when needed and then doesn’t need to worry about getting rid of them when the need has ended.
❯❯ Detailed administrative tasks are handled by the host, but the client can manage overall administrative tasks, such as deciding how much capacity to use for a particular task.
❯❯ Users have access to desktop virtualization, which means that their desktop appears on whatever device they happen to use at a given moment.
❯❯ The use of policy-based services ensures that users must still adhere to company requirements when using computer resources.
❯❯ All required updates (software and hardware) occur automatically and without any interaction required by the client.
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❯❯ Billing can become complex because some services are billed at different rates and within different time frames. In addition, billing can include resource usage. The client must ensure that the amount on the bill actually matches real-world usage; paying too much for services that the client didn’t actually use can easily happen.
❯❯ Systems-management monitoring becomes more difficult. The client loses control over the precise manner in which activities occur.
❯❯ A lag often occurs between when a change in service is needed and when the host provides it, so the client can find that even though services are more flexible, they aren’t as responsive.
❯❯ Host downtime can affect a large group of people and prove difficult to fix, which means that a particular client may experience downtime at the worst possible time without any means to resolve it.
❯❯ Building and testing custom applications can become more difficult. Many experts recommend using in-house equipment for application-development needs to ensure that the environment is both protected and responsive.