patterns & practices Developer Center

affinity group. A named grouping that is in a single data center. It can include all the components associated with an application, such as storage, Windows Azure SQL Database instances, and roles.

ASP.NET MVC. A framework for developing web applications. It is based on the Model-View-Controller architectural design pattern.

autoscaling. Automatically scaling an application based on a schedule or on metrics collected from the environment.

claim. A statement about a subject; for example, a name, identity, key, group, permission, or capability made by one subject about itself or another subject. Claims are given one or more values and then packaged in security tokens that are distributed by the issuer.

cloud. A set of interconnected servers located in one or more data centers.

cloud service. Windows Azure environment where you host your application’s web and worker roles. Formally referred to as a hosted service.

code near. When an application and its associated database(s) are both in the cloud.

code far. When an application is on-premises and its associated database(s) are in the cloud.

compute emulator. The Windows Azure compute emulator enables you to run, test, debug, and fine-tune your application before you deploy it as a hosted service to Windows Azure. See also: storage emulator.

Content Delivery Network (CDN). A system composed of multiple servers that contain copies of data. These servers are located in different geographical areas so that users can access the copy that is closest to them.

continuation token. A technique, supported by Windows Azure table storage, which enables a client to page through records. In response to a query, a server returns a page of records and a continuation token. If the client submits the continuation token back to the server, the server delivers the next page of records.

elasticity. A property of a system that describes its ability to scale in and out dynamically.

Enterprise Library. A collection of reusable software components (application blocks) designed to assist software developers with common enterprise development cross-cutting concerns (such as logging, validation, data access, exception handling, and many others).

entity group transaction (EGT). A transaction with ACID properties across multiple entities stored in the same Windows Azure table partition.

federation. In Windows Azure SQL Database, a federation is a way to scale out horizontally by using additional servers. Also known as sharding.

federation provider. A special case of a Security Token Service (STS) that typically trusts a third-party identity provider. The federation provider may transform the claims in the token from the third-party identity provider into a format acceptable to your application.

horizontal scalability. The ability to add more servers that are copies of existing servers.

hosted service. Spaces where applications are deployed.

idempotent operation. An operation that can be performed multiple times without changing the result. An example is setting a variable.

identity provider. Typically, a separate system that is responsible for determining the identity of a user. An application trusts an identity provider to perform this task. The identity provider passes information about the user in the form of a token. An identity provider is a special case of a Security Token Service (STS).

Infrastructure as a Service (IaaS). A collection of infrastructure services such as storage, computing resources, and network that you can rent from an external partner.

lease. An exclusive write lock on a blob that lasts until the lease expires.

mock. A mock object is used in a test to simulate a real object. They are useful when it is impractical to use the real object in the test.

optimistic concurrency. A concurrency control method that assumes that multiple changes to data can complete without affecting each other; therefore, there is no need to lock the data resources. Optimistic concurrency assumes that concurrency violations occur infrequently and simply disallows any updates or deletions that cause a concurrency violation.

Platform as a Service (Paas). A collection of platform services that you can rent from an external partner that enable you to deploy and run your application without the need to manage any infrastructure.

poison message. A message that contains malformed data that causes the queue processor to throw an exception. The result is that the message isn't processed, stays in the queue, and the next attempt to process it once again fails.

Representational State Transfer (REST). An architectural style for retrieving information from websites. A resource is the source of specific information. Each resource is identified by a global identifier, such as a Uniform Resource Identifier (URI) in HTTP. The representation is the actual document that conveys the information.

role. A web or worker role to deploy to Windows Azure.

role instance. A running instance of a web or worker role in Windows Azure.

secure sockets layer (SSL). A cryptographic protocol that uses public key cryptography to secure communication over the internet, for example using the HTTPS protocol.

Security Token Service (STS). A service that issues claims in form of tokens. An application may be configured to trust the tokens issued by a specific STS.

service configuration file. Sets values for the service that can be configured while the hosted service is running. The values you can specify in the service configuration file include the number of instances that you want to deploy for each role, the values for the configuration parameters that you established in the service definition file, and the thumbprints for any SSL certificates associated with the service.

service definition file. Defines the roles that comprise a service, optional local storage resources, configuration settings, and certificates for SSL endpoints.

service level agreement (SLA). The formal definition of the level of service that a service provider undertakes to deliver to the customer. For example, specifying the number of hours that a service will be available for every month.

service package. Packages the role binaries and service definition file for publication to the Windows Azure Cloud Services.

sharding. See federation.

shared access signatures (SAS). A special URL that can be used to gain temporary access to data in Windows Azure table, queue, blob, and blob storage. By generating a SAS URL and giving it to a client, you can grant the client temporary and limited access to data.

snapshot. A read-only copy of a blob.

Storage Emulator. The Windows Azure storage emulator provides local instances of the blob, queue, and table services that are available in Windows Azure. If you are building an application that uses storage services, you can test locally by using the storage emulator.

throttling. The behavior of a Windows Azure service when it restricts the throughput from one client application in order to ensure that other client applications can continue to use the service.

transient faults. Error conditions that can occur in a distributed environment and that often disappear when you retry the operation. These are often caused by transient problems with the network.

vertical scalability. The ability to increase a computer's resources, such as memory or CPUs.

Web role. An interactive application that runs in the Windows Azure environment. A web role can be implemented with any technology that works with Internet Information Services (IIS) 7. See Windows Azure Cloud Services.

Windows Azure. Microsoft's platform for cloud-based computing. It is provided as a service over the Internet using either the PaaS or IaaS approaches. It includes a computing environment, the ability to run virtual machines, Windows Azure storage, and management services.

Windows Azure Cloud Services. Web and worker roles in the Windows Azure environment that enable you to adopt the PaaS approach.

Windows Azure Management Portal. A web-based administrative console for creating and managing your Windows Azure hosted services, including Cloud Services, SQL Database, storage, Virtual Machines, Virtual Networks, and Web Sites.

Windows Azure SQL Database. A relational database management system (RDBMS) in the cloud. Windows Azure SQL Database is independent of the storage that is a part of Windows Azure. It is based on SQL Server and can store structured, semi-structured, and unstructured data.

Windows Azure storage. Consists of blobs, tables, drives, and queues. It is accessible with HTTP/HTTPS requests. It is distinct from Windows Azure SQL Database.

Windows Azure Traffic Manager. A Windows Azure service that enables you to control how Windows Azure routes traffic to your cloud services.

Windows Azure Virtual Machine. Virtual machines in the Windows Azure environment that enable you to adopt the IaaS approach.

Windows Azure Virtual Network. Windows Azure service that enables you to create secure site-to-site connectivity, as well as protected private virtual networks in the cloud.

Windows Azure Web Sites. A Windows Azure service that enables you to quickly and easily deploy websites that use client and server side scripting and databases to the cloud.

Worker role. Performs batch processes and background tasks in the Windows Azure environment. Worker roles can make outbound calls and open endpoints for incoming calls. Worker roles typically use queues to communicate with Web roles. See Windows Azure Cloud Services.

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