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Amazon SWF
Amazon Simple Workflow (Amazon SWF) is a task coordination and state management service for cloud applications. With Amazon SWF, you can stop writing complex glue-code and state machinery and invest more in the business logic that makes your applications unique. The Amazon Simple Workflow Service (Amazon SWF) makes it easier to develop asynchronous and distributed applications by providing a programming model and infrastructure for coordinating distributed components and maintaining their execution state in a reliable way. By relying on Amazon SWF, you are freed to focus on building the aspects of your application that differentiate it.
The fundamental concept in Amazon SWF is the workflow. A workflow is a set of activities that carry out some objective, together with logic that coordinates the activities. For example, a workflow could receive a customer order and take whatever actions are necessary to fulfill it.
Each workflow runs in an AWS resource called a domain, which controls the workflow's scope.
An AWS account can have multiple domains, each of which can contain multiple workflows, but workflows in different domains cannot interact.
When designing an Amazon SWF workflow, you precisely define each of the required activities. You then register each activity with Amazon SWF as an activity type. When you register the activity, you provide information such as a name and version, and some timeout values based on how long you expect the activity to take. For example, a customer may have an expectation that an order will ship within 24 hours. Such expectations would inform the timeout values that you specify when registering your activities.
In the process of carrying out the workflow, some activities may need to be performed more than once, perhaps with varying inputs. For example, in a customer-order workflow, you might have an activity that handles purchased items. If the customer purchases multiple items, then this activity would have to run multiple times. Amazon SWF has the concept of an activity task that represents one invocation of an activity. In our example, the processing of each item would be represented by a single activity task.
An activity worker is a program that receives activity tasks, performs them, and provides results back. Note that the task itself might actually be performed by a person, in which case the person would use the activity worker software for the receipt and disposition of the task. An example might be a statistical analyst, who receives sets of data, analyzes them, and then sends back the analysis.
Let’s have an example of SWF, in a customer-order workflow, you might have an activity that handles purchased items. If the customer purchases multiple items, then this activity would have to run multiple times. Amazon SWF has the concept of an activity task that represents one invocation of an activity. In this example, the processing of each item would be represented by a single activity task.
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