q136/random_k2/random_2.md

INTRODUCING THE WINDOWS AZURE
PLATFORM

DAVID CHAPPELL

OCTOBER 2010

SPONSORED BY MICROSOFT CORPORATION

CONTENTS

An Overview of the Windows Azure Platform ....................................................................................... 3

Windows Azure ........................................................................................................................................ 4

SQL Azure ................................................................................................................................................. 6

Windows Azure AppFabric....................................................................................................................... 8

Windows Azure MarketPlace .................................................................................................................. 9

A Closer Look at the Technologies ....................................................................................................... 10

Windows Azure ...................................................................................................................................... 10

Compute ............................................................................................................................................ 11

Storage .............................................................................................................................................. 12

Fabric Controller ................................................................................................................................ 14

Content Delivery Network ................................................................................................................. 14

Connect ............................................................................................................................................. 15

SQL Azure ............................................................................................................................................... 15

Database ........................................................................................................................................... 15

Reporting ........................................................................................................................................... 17

Data Sync .......................................................................................................................................... 17

Windows Azure AppFabric..................................................................................................................... 19

Service Bus ........................................................................................................................................ 19

Access Control ................................................................................................................................... 21

Caching .............................................................................................................................................. 23

Windows Azure Marketplace ................................................................................................................ 24

Looking Ahead .................................................................................................................................... 26

Conclusions ......................................................................................................................................... 26

About the Author ................................................................................................................................ 27

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AN OVERVIEW OF THE WINDOWS AZURE PLATFORM

Using computers in the cloud can make lots of sense. Rather than buying and maintaining your own
machines, why not exploit the acres of Internet-accessible servers on offer today? For some applications,
both code and data might live in the cloud, where somebody else manages and maintains the systems
they use. Alternatively, applications that run inside an organization—on-premises applications—might
store data in the cloud or rely on other cloud infrastructure services. However it’s done, exploiting the
cloud’s capabilities can improve our world.

But whether an application runs in the cloud, uses services provided by the cloud, or both, some kind of
application platform is required. Viewed broadly, an application platform can be thought of as anything
that provides developer-accessible services for creating applications or storing data. In the on-premises
Windows world, this includes technologies such as Windows Server and SQL Server. To let applications
exploit the cloud, a cloud application platform must also exist.

This is exactly what the Microsoft Windows Azure platform provides. It’s a group of cloud technologies,
each providing a specific set of services to application developers. Figure 1 shows its components.

Figure 1: The Windows Azure platform supports applications, data, and infrastructure in the cloud,
together with a cloud marketplace.

The Windows Azure platform today has four parts:

  Windows Azure: A Windows environment for running applications and storing data on computers in

Microsoft data centers.

SQL Azure: Relational data services in the cloud based on SQL Server.

  Windows Azure AppFabric: Cloud-based infrastructure services for applications running in the cloud

or on premises.

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  Windows Azure Marketplace: An online service for purchasing cloud-based data and applications.

All four of these components run in Microsoft data centers located around the world: two in North
America, two in Europe, and two in Asia. Developers using the platform can control which data center
runs their applications and stores their data, giving them the ability to place both closer to their users.

Each part of the Windows Azure platform has its own role to play. This overview describes all four, first at
a high level, then in a bit more detail. The goal is to provide a big-picture introduction to this cloud
platform.

WINDOWS AZURE

At a high level, Windows Azure is simple to understand: It runs Windows applications and stores data in
the cloud. Figure 2 shows its components.

Figure 2: Windows Azure provides compute and storage services in the cloud.

The five parts of Windows Azure today are the following:

  Compute:  The Windows  Azure compute  service runs applications  on a Windows Server  foundation.
These applications can be created using the .NET Framework in languages such as C# and Visual Basic,
or they can be built without .NET in C++, Java, and other languages. Developers can use Visual Studio
or  other  development  tools,  and  they’re  free  to  use  technologies  such  as  ASP.NET,  Windows
Communication Foundation (WCF), and PHP.

Storage: This service allows storing binary large objects (blobs), provides queues for communication
between components of Windows Azure applications, and even offers a form of tables with a simple
query  language.  (Windows  Azure  applications  that  need  traditional  relational  storage  can  also  use

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SQL Azure.) Both Windows Azure applications and on-premises applications can access the Windows
Azure storage service, and both do it in the same way: using a RESTful approach.

Fabric  controller:  As  the  figure  suggests,  Windows  Azure  runs  on  a  large  number  of  machines.  The
fabric controller’s job is to knit the machines in a single Windows Azure data center into a cohesive
whole.  The  Windows  Azure  compute  and  storage  services  are  then  built  on  top  of  this  pool  of
processing power.

  Content  delivery  network  (CDN):  Caching  frequently  accessed  data  closer  to  its  users  speeds  up
access to that data. The Windows Azure CDN can do this for blobs, maintaining cached copies at sites
around the world.

  Connect: It’s often useful for organizations to interact with cloud applications as if they were inside
the  organization’s  own  firewall.  Windows  Azure  Connect  allows  this,  making  it  easier  for,  say,  a
Windows Azure application to access an on-premises database.

Running applications and storing data in the cloud can have clear benefits. Rather than buying, installing,
and operating its own systems, for example, an organization can rely on a cloud provider to do this for
them. Also, customers pay just for the computing and storage they use, rather than maintaining a large
set of servers only for peak loads. And applications written for Windows Azure can scale better, be more
reliable, and require less administration than those written using the traditional Windows Server
programming model.

To create, configure, and monitor applications, Windows Azure customers can use a browser-accessible
portal. A customer logs in with a Windows Live ID, then chooses whether to create a hosting account for
running applications, a storage account for storing data, or both. Microsoft then charges each customer
based on how much compute time, storage, and bandwidth that customer uses. How an application
charges its own customers—if it charges them at all—is entirely up to the people who create that
application.

Windows Azure is a general platform that can be used in a broad set of scenarios. Here are a few
examples:

  An  independent  software  vendor (ISV) creating a  software-as-a-service (SaaS) version of an  existing
on-premises  Windows  application  might  choose  to  build  it  on  Windows  Azure.  Because  Windows
Azure mostly provides a standard  Windows environment, moving the application’s business logic to
this  cloud  platform  won’t  typically  pose  many  problems.  And  once  again,  building  on  an  existing
platform  lets  the  ISV  focus  on  business  logic—the  thing  that  makes  them  money—rather  than
spending time on infrastructure.

  An  enterprise  creating  an  application  for  its  customers  or  employees  might  choose  to  build  it  on
Windows  Azure.  Because  Windows  Azure  supports  .NET,  developers  with  the  right  skills  aren’t
difficult  to  find,  nor  are  they  prohibitively  expensive.  Running  the  application  in  Microsoft  data
centers frees the enterprise from the responsibility and expense of managing its own servers, turning
capital  expenses  into  operating  expenses.  And  especially  if  the  application  has  spikes  in  usage—
maybe  it’s  an  on-line  flower  store  that  must  handle  the  Mother’s  Day  rush—letting  Microsoft
maintain the large server base required for this can make economic sense.

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  A start-up creating a new Web site—the next Facebook, say—could build its application on Windows
Azure.  Because  this  platform  supports  both  Web-facing  services  and  background  processes,  the
application  can  provide  an
interface  as  well  as  executing  work  for  users
asynchronously.  Rather  than  spending  time  and  money  worrying  about  infrastructure,  the  start-up
can  instead  focus  solely  on  creating  code  that  provides  value  to  its  customers  and  investors.  The
company  can  also  start  small,  incurring  low  costs  while  its  application  has  only  a  few  users.  If  the
application catches on and usage increases, Windows Azure can scale the application as needed.

interactive  user

These three examples illustrate the kinds of things organizations might do with Windows Azure, but
they’re not an exhaustive list. As interest in cloud computing continues to grow, expect to see a variety of
applications created for this cloud platform.

SQL AZURE

Along with running applications, another attractive way to use the cloud is for storing data. SQL Azure
addresses this area, offering cloud-based services for relational data. As Figure 3 shows, SQL Azure today
includes three components.

Figure 3: SQL Azure provides relational database services in the cloud.

The components of SQL Azure today are the following:

SQL Azure Database provides a cloud-based database management system (DBMS). This technology
lets on-premises and cloud applications store relational data on Microsoft servers in Microsoft data

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centers. As with other cloud technologies, an organization pays only for what it uses, increasing and
decreasing usage (and cost) as the organization’s needs change. Using a cloud database also allows
converting  what  would  be  capital  expenses,  such  as  investments  in  disks  and  DBMS  software,  into
operating expenses.

SQL  Azure  Reporting  is  a  version  of  SQL  Server  Reporting  Services  (SSRS)  that  runs  in  the  cloud.
Intended primarily for use with SQL Azure Database, it allows creating  and publishing standard SSRS
reports on cloud data.

SQL  Azure  Data  Sync  allows  synchronizing  data  between  SQL  Azure  Database  and  on-premises  SQL
Server  databases.  It  can  also  be  used  to  synchronize  data  across  different  SQL  Azure  databases  in
different Microsoft data centers.

SQL Azure is built on Microsoft SQL Server. As with SQL Server, developers can create indexes and views,
use stored procedures, define triggers, and more. Applications can access SQL Azure data using Entity
Framework, ADO.NET, and other Windows data access interfaces. In fact, applications that today access
SQL Server locally will largely work unchanged with data in SQL Azure. Customers can also use on-
premises software such as SQL Server Analysis Services to work with their cloud-based data.

While applications can use SQL Azure much as they do a local DBMS, the management requirements are
significantly reduced. Rather than worry about mechanics, such as monitoring disk usage and servicing log
files, a SQL Azure customer can focus on their data; Microsoft handles the operational details. And as with
other components of this cloud platform, customers use the common Windows Azure platform portal to
access its services.

Applications might use SQL Azure in a variety of ways. Here are some examples:

  A Windows Azure application can store its data in SQL Azure. While Windows Azure provides its own
storage,  relational  tables  aren’t  among  the  options  it  offers.  Since  many  existing  applications  use
relational storage and many developers know how to work with it, a significant number of Windows
Azure  applications  rely  on  SQL  Azure  to  work  with  data  in  this  familiar  way.  For  example,  a  SaaS
application built on Windows Azure might create a separate SQL Azure database for each customer,
providing  an  intrinsically  multi-tenant  design.  And  to  improve  performance,  customers  can  specify
that  a  particular  Windows  Azure  application  must  run  in  the  same  data  center  in  which  SQL  Azure
Database stores that application’s information.

  An application in a small business or a department of a larger organization might rely on SQL Azure.
Rather  than  storing  its  data  in  a  SQL  Server  or  Access  database  running  on  a  computer  under
somebody’s desk, the application can instead take advantage of the reliability and availability of cloud
storage. It can also create reports on this data using either SQL Azure Reporting or SSRS on-premises.
If the organization wishes to maintain an on-premises copy of the data as well, it can use SQL Azure
Data Sync to synchronize the cloud and on-premises databases.

Suppose  a  manufacturer  wishes  to  make  product  information  available  both  to  its  dealer  network
and  directly  to  customers.  Putting  this  data  in  SQL  Azure  would  let  it  be  accessed  by  applications
running at the dealers and by a customer-facing Web application run by the manufacturer itself.

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Whether it’s for supporting a Windows Azure application, making data more accessible, or other reasons,
data services in the cloud can be attractive. The goal of SQL Azure is to provide these services in a familiar,
usable way for cloud and on-premises applications.

WINDOWS AZURE APPFABRIC

Running applications and storing data in the cloud are both important aspects of cloud computing.
They’re far from the whole story, however. It’s also possible to provide cloud-based infrastructure
services. Filling this gap is the goal of Windows Azure AppFabric.

The functions provided by AppFabric today address common challenges in building distributed
applications. Figure 4 shows its components.

Figure 4: Windows Azure AppFabric provides Windows Azure-based infrastructure services that can be
used by both cloud and on-premises applications.

As the figure suggests, all of the components of Windows Azure AppFabric are built on Windows Azure
(although they don’t all provide services solely to Windows Azure applications). Those components are
the following:

Service Bus: Exposing an application’s services on the Internet is harder than it might seem. The goal
of Service Bus is to make this simpler by letting an application expose endpoints in the cloud that can
be  accessed  by  other  applications,  whether  on-premises  or  in  the  cloud.  Each  exposed  endpoint  is
assigned a  URI, which clients can use to locate and access the service. Service Bus also handles the
challenges of dealing with network address translation and getting through firewalls without opening
new ports for exposed applications.

  Access  Control:  There  are  many  ways  for  a  user  to  get  a  digital  identity  today.  The  options  include
Active Directory, Windows Live ID, Google Accounts, Facebook, and more. If an application wants to
let users log in with any of these, the application’s creator faces the daunting challenge of supporting

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this plethora of approaches. Access Control simplifies this by providing built-in support for all of them
(and more). It also provides a single place for defining rules to control what each user  is allowed to
access.

  Caching: It’s common for applications to access the same data over and over. One way to speed up
this  kind  of  application  is  to  cache  frequently  accessed  information,  reducing  the  number  of  times
that  application  must  query  a  database.  The  Caching  service  provides  this—and  the  performance
boost it brings—for Windows Azure applications.

Microsoft has announced plans to add more services under the Windows Azure AppFabric banner, so
expect this list to grow in the not-too-distant future.

As with Windows Azure and SQL Azure, customers use a browser-accessible portal to sign up for
AppFabric. Once this has been done, these services can be used in a variety of ways. Here are some of the
possibilities:

Suppose an enterprise wished to let software at its trading partners access one of its applications. It
could expose this application’s functions through SOAP or RESTful services created using WCF, then
register those service endpoints with Service Bus. Its trading partners could then use Service Bus to
find these endpoints and access the services.

Imagine that the creator of this same application needs to let trading partners log in with a variety of
different identities. Rather than implementing support for these identities himself, he could use the
Access Control service to hide this complexity.

  A Windows Azure application created using ASP.NET might use the Session object to store per-client
state. By changing only a configuration setting, the application can cause this data to be kept in the
Caching  service  rather  than,  say,  Windows  Azure  Storage  tables.  Doing  this  is  likely  to  make  the
application faster and more scalable.

Along with the cloud-based services of Windows Azure AppFabric, Microsoft also provides an analogous
technology known as Windows Server AppFabric. As its name suggests, the services it provides run on
Windows Server—they support on-premises applications—rather than in the cloud. The on-premises
services aren’t exactly the same today as those in Windows Azure AppFabric (although Microsoft’s
announced plan is make the two congruent). Don’t be confused; throughout this paper, the name
“AppFabric” is used to refer to the cloud-based services. Also, don’t confuse Windows Azure AppFabric
with the Windows Azure fabric controller. Even though both contain the term “fabric”, they’re wholly
separate technologies addressing quite distinct problems.

WINDOWS AZURE MARKETPLACE

In the on-premises world, many applications are purchased rather than custom-built. Many organizations
also rely on datasets from commercial providers. With the rise of the cloud, why not let customers find
and buy cloud applications and cloud-accessible data? Making this possible is the goal of Windows Azure
Marketplace. Figure 5 shows its two components.

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Figure 5: Windows Azure Marketplace provides an online marketplace for cloud applications and data.

The two parts of Windows Azure Marketplace are:

  DataMarket (originally codenamed “Dallas”), providing a way for content providers to make datasets
available. Customers can browse the offerings, then purchase whatever they find useful. Applications,
both  custom  and  off-the-shelf  (such  as  Microsoft  Excel),  can  then  access  this  data  through  RESTful
requests or the OData protocol.

  AppMarket,  providing  a  way  for  creators  of  cloud  applications  to  expose  those  applications  to

potential customers. AppMarket will be available sometime after DataMarket.

Using the cloud to find, evaluate, and purchase data and applications makes sense. The goal of Windows
Azure Marketplace is to make these things easier to do.

A CLOSER LOOK AT THE TECHNOLOGIES

Having a broad understanding of the Windows Azure platform is an important first step. Making good
decisions require a deeper understanding of these technologies, however. This section takes a slightly
more in-depth look at each member of the family.

WINDOWS AZURE

Windows Azure provides what’s commonly called Platform as a Service (PaaS). Rather than offering a
cloud replica of the on-premises world, it offers a higher level of service that’s meant to make life easier
for both developers and administrators.   What follows walks through the five components that
collectively provide this service.

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Compute

An application built on the Windows Azure compute service is structured as one or more roles. When it
executes, the application typically runs two or more instances of each role, with each instance running as
its own virtual machine (VM). Figure 6 shows how this looks.

Figure 6: A running Windows Azure application consists of any combination of Web role instances,
Worker role instances, and VM role instances.

A Windows Azure application today can be created using three kinds of roles:

  Web  roles,  intended  primarily  for  running  Web-based  applications.  Each  Web  role  instance  has
Internet  Information  Services  (IIS)  7  pre-configured  to  run  inside  it,  so  creating  applications  using
ASP.NET, WCF, or other Web technologies is straightforward. It’s also possible to create applications
using PHP, Java, and other non-Microsoft technologies.

  Worker roles, designed to run a variety of code. A Worker role might run a simulation, for example,
or  video  processing  or  nearly  anything  else.  It’s  common  for  an  application  to  interact  with  users
through a Web role, then hand tasks off to a Worker role for processing.

  VM roles, which can run a user-provided Windows Server 2008 R2 image. A VM role can be the right

choice for moving some on-premises Windows Server applications to Windows Azure.

When a developer gives Windows Azure an application to run, she submits configuration information
along with it. Among other things, this information tells the platform how many instances of each role to
run. The Windows Azure fabric controller then creates a VM for each instance, running the code for the

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appropriate role in each VM. And as Figure 6 indicates, requests from the outside world are load balanced
across all instances of a role.

This has an important implication: To be scalable, Windows Azure role instances shouldn’t maintain their
state themselves between requests. Because the load balancer doesn’t allow creating an affinity with a
particular role instance—there’s no support for sticky sessions—there’s no way to guarantee that multiple
requests from the same user will be sent to the same instance. Instead, any client-specific state should be
written to Windows Azure storage, stored in SQL Azure Database, or maintained externally in some other
way.

For role instances, Windows Azure lets developers choose from several VM sizes, each with a specific
number of processor cores and memory. Since each instance can be assigned one or more cores,
applications have predictable performance. And to increase the load an application can handle, its owner
or the application itself can request an increase in the number of running instances for one or more roles.
The Windows Azure fabric controller will then spin up new VMs for these instances and start them
running. It’s also possible to explicitly decrease the number of instances for a role, letting an application
grow and shrink as needed to handle changing loads.

For developers, building a Windows Azure application looks much like building a traditional Windows
application. Microsoft provides Visual Studio project templates, for instance, to help developers create
Windows Azure applications. Also, the Windows Azure software development kit includes a version of the
Windows Azure environment that runs on the developer’s machine. Known as the Windows Azure
development fabric, it implements a local replica of the Windows Azure compute and storage services. A
developer can create and debug his application using this local simulacrum, then deploy it to Windows
Azure in the cloud when it’s ready. Windows Azure also provides other services for developers, such as
information about a running application’s CPU consumption, incoming and outgoing bandwidth, and
storage usage.

Storage

Applications work with data in many different ways. Sometimes, all that’s required are simple blobs, while
other situations call for a more structured way to store information. And in some cases, all that’s really
needed is a way to exchange data between different parts of an application. Windows Azure storage
addresses all three of these requirements, as Figure 7 shows.

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Figure 7: Windows Azure provides blobs, tables, and queues, all accessed in a RESTful style via HTTP,
HTTPS, or OData.

The simplest way to store data in Windows Azure storage is to use blobs. As Figure 7 suggests, there’s a
simple hierarchy: A storage account can have one or more containers, each of which holds one or more
blobs. Blobs can be big—as large as a terabyte each—and to make transferring large blobs more efficient,
they can potentially be subdivided into blocks. If a failure occurs, retransmission can resume with the
most recent block rather than sending the entire blob again. Blobs can also have associated metadata,
such as information about where a JPEG photograph was taken or who the composer is for an MP3 file.

Another way to use blobs is through Windows Azure drives, which can be mounted by a role instance. The
underlying storage for a drive is a blob, and so once a drive is mounted, the instance can read and write
file system data that gets stored persistently in a blob.

Blobs are just right for some kinds of data, but they’re too unstructured for many situations. To allow
applications to work with data in a more fine-grained way, Windows Azure storage provides tables. Don’t
be misled by the name: These aren’t relational tables. In fact, even though they’re called “tables”, the
data they contain is actually stored in a set of entities with properties. A table has no defined schema;
instead, properties can have various types, such as int, string, Bool, or DateTime. And rather than using
SQL, an application can access a table’s data using the simple query language defined by OData. A single
table can be quite large, with billions of entities holding terabytes of data, and Windows Azure storage
can partition it across many servers if necessary to improve performance.

Blobs and tables are both focused on storing data. The third option in Windows Azure storage, queues,
has a somewhat different purpose. A primary use of queues is to let Web role instances communicate
with Worker role instances. For example, a user might submit a request to perform some compute-

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intensive task via a Web page implemented by a Windows Azure Web role. The Web role instance that
receives this request can write a message into a queue describing the work to be done. A Worker role
instance that’s waiting on this queue can then read the message and carry out the task it specifies. Any
results can be returned via another queue or handled in some other way.

Regardless of how it’s stored—in blobs, tables, or queues—all data held in Windows Azure storage is
replicated three times. This replication allows fault tolerance, since losing a copy isn’t fatal. The system
guarantees consistency, however, so an application that reads data it has just written will get what it
expects.

Windows Azure storage can be accessed either by a Windows Azure application or by an application
running somewhere else. In both cases, all three Windows Azure storage styles use the conventions of
REST (and the OData protocol for tables) to identify and expose data. Everything is named using URIs and
accessed with standard HTTP operations, so clients can be created using .NET, Java, or other familiar
technologies.

The Windows Azure platform charges independently for compute and storage resources. This means that
an on-premises application can use just Windows Azure storage, accessing its data in the RESTful way just
described. For example, a Windows Server application running in an enterprise data center might choose
to store backups in Windows storage blobs.

Fabric Controller

Even though a Windows Azure application runs in VMs, a developer doesn’t explicitly create and manage
those VMs. Instead, as described earlier, she just tells the platform how many instances the application
needs, and Windows Azure silently creates the necessary VMs and runs her application. This magic is
performed by the fabric controller, a fundamental aspect of Windows Azure.

Along with creating VMs and starting the applications that run in them, the fabric controller also monitors
all running instances. A role instance might fail for many reasons; maybe the code threw an exception or
the VM crashed or the physical server it’s running on went down. Whatever the reason, the fabric
controller will start a new instance to maintain the total number of instances required for this application.

The fabric controller also handles housekeeping tasks like patching the operating system and other
system software, which minimizes the need for administrators. These are all examples of why Windows
Azure is viewed as PaaS: It provides a platform that lets customers run applications without worrying
about administering the environment they run in.

Content Delivery Network

One common use of blobs is to store information that will be accessed from many different places. Think
of an application that serves up videos, for example, to Flash, Silverlight, or HTML 5 clients around the
world. To improve performance in situations like this, Windows Azure provides a content delivery
network. The CDN stores copies of a blob at sites closer to the clients that use it. This speeds up delivery
of frequently accessed content, improving performance for users of this information.

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Connect

Windows Azure applications can interact with the outside world via HTTP, HTTPS, or TCP. But suppose
you’d like to connect a role in an application to a machine outside the cloud at the IP level. For example,
suppose an organization decides to move an existing ASP.NET application to Windows Azure, but wishes
to keep the application’s data in an on-premises SQL Server database. Windows Azure Connect allows
this.

Using this option requires running Windows Azure Connect software on the on-premises machine that
contains SQL Server, and it also requires some straightforward configuration. (This configuration can be
done by the developer—there’s no need to get a network administrator involved.) Once this is done, all of
the instances in the Web role can behave as if they’re on the same IP network as the SQL Server machine.
In fact, they can use the same SQL Server connection string as when the application was running on
premises—there’s no difference.

Note that this isn’t a full-fledged virtual private network (VPN). While Microsoft has announced plans to
let customers connect to Windows Azure via a VPN, this isn’t currently supported. It is possible to use
Windows Azure Connect to domain-join a Windows Azure application to an on-premises Active Directory,
however. Doing this allows single sign-on by on-premises users to the cloud application, and it also lets
the application use existing Active Directory accounts and groups for access control.

The goal of application platforms, whether on-premises or in the cloud, is to support applications and
data. Windows Azure provides a home for both of these things. Going forward, expect to see a substantial
share of what would have been on-premises Windows applications instead running on this new cloud
platform.

SQL AZURE

A DBMS in the cloud is attractive for many reasons. Letting a specialized service provider ensure reliability
and perform essential management functions can make sense, especially for organizations that find these
things hard to do on their own. Data in the cloud can also be accessed by applications running anywhere,
even on mobile devices. And given the economies of scale that a service provider enjoys, using a cloud
database may well be cheaper than doing it yourself.

SQL Azure provides these things, together with cloud-based reporting and data synchronization services.
And while all of them are important, the place to start is with the foundation: SQL Azure Database.

Database

SQL Azure Database is simple to understand. As seen by an application, it provides the core database
functions of SQL Server as a cloud service.  Figure 8 shows the basics of this technology.

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Figure 8: Applications access data in SQL Azure Database through Microsoft’s TDS protocol or via OData.

An application using SQL Azure Database might run on Windows Azure, in an enterprise’s data center, on
a mobile device, or somewhere else. Wherever it runs, the application typically accesses data via a
protocol called Tabular Data Stream (TDS). This is the same protocol used to access a local SQL Server
database, and so a SQL Azure Database application can use any existing SQL Server client. This includes
Entity Framework, ADO.NET, ODBC, PHP and others. And because SQL Azure Database looks like an
ordinary SQL Server system, standard tools can also be used, including SQL Server Management Studio,
SQL Server Integration Services, and BCP for bulk data copy. Also, as Figure 8 shows, applications can
optionally access SQL Azure Database using OData.

Each SQL Azure account can have one or more logical servers. (Note that these provide a way to organize
the data and billing for an account—they aren’t actual instances of SQL Server.) Each server can then have
multiple databases, each of which can be up to 50 gigabytes in size. A user is free to use multiple
databases if required, spreading data across them for better performance or for other reasons. It’s also
possible to store a snapshot of one SQL Azure database into another, providing a simple backup
mechanism.

For the most part, an application using SQL Azure Database sees a familiar SQL Server environment. A few
things are omitted in the technology’s current release, however, such as the SQL Common Language
Runtime (CLR) and support for full-text search. (Microsoft says that both will be available in a future
version.) Also, because administration is handled by Microsoft, the service doesn’t expose physical
administrative functions. A customer can’t shut down the system, for example, or interact directly with
the hardware it runs on. And as you’d expect in a shared environment, a query can run for only a limited
time—no single request can take up more than a pre-defined amount of resources.

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Yet while the environment looks quite standard, the service an application gets is more robust than what
a single instance of SQL Server provides. As in Windows Azure storage, all data stored in SQL Azure
Database is replicated three times for high availability. Also like Windows Azure storage, the service
provides strong consistency: When a write returns, the data has been made persistent. The goal is to
provide reliable data storage even in the face of system and network failures.

Whether an application needs multiple databases or just one, SQL Azure Database can help developers
address a range of scenarios. Whatever problem is being solved, the technology’s fundamental goal
remains the same: to provide a familiar, reliable, and low-cost cloud database for many kinds of
applications.

Reporting

Storing data in SQL Azure Database can be useful. But as soon as that data exists, there’s likely to be a
demand for reports based on that data. Meeting this demand is the purpose of SQL Azure Reporting.
Based on SQL Server Reporting Services (SSRS), this technology provides a cloud-based way to create
reports.

Given that SQL Azure Database looks like SQL Server to an application, it’s always possible to use SSRS on-
premises with the data it contains. So why bother to provide a cloud reporting service as well? SQL Azure
Reporting today targets two main scenarios:

  Reports created using SQL Azure Reporting can be published to a SQL Azure Reporting portal, letting

users access it there, or made accessible directly via a URL.

  An ISV can embed reports published to the SQL Azure Reporting portal in any application, including
Windows Azure applications. This lets users access those reports without leaving the application. To
do this, the ISV can use the standard  ReportViewer controls in Visual Studio—it’s no different  from
embedding on-premises reports into applications.

SQL Azure Reporting is designed to work with data stored in SQL Azure Database. Reports used with SQL
Azure Reporting are created on-premises, however, with Business Intelligence Developer Studio, the
Visual Studio-hosted tool that’s also used to create SSRS reports. In fact, SQL Azure Reporting relies on the
same reporting format, expressed in the Report Definition Language (RDL), used with SSRS.

Like other aspects of SQL Azure, SQL Azure Reporting doesn’t provide all of the functions offered by SSRS
on premises. There’s currently no support for scheduling and subscriptions, for example, that let a report
be run and delivered at regular intervals. Still, cloud-based reporting services can be useful, and they’re an
important part of the SQL Azure technology family.

Data Sync

Storing data in SQL Azure Database can make it accessible to any application with an Internet connection.
Still, there are often situations where it makes sense to maintain a copy of this cloud-based data in some
other place. Suppose an organization needs to have an on-premises copy of the same information, for
example, for performance reasons or to ensure access if the network fails. For scenarios like this, the
ability to synchronize data in SQL Azure Database with other data stores is useful.

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It’s always possible to write synchronization code yourself using the Microsoft Sync Framework. To make
this easier, Microsoft provides SQL Azure Data Sync. Rather than requiring its user to write code, this
technology is entirely configuration-driven (although unsurprisingly, it’s built on the Microsoft Sync
Framework). As Figure 9 shows, SQL Azure Data Sync supports two options today.

Figure 9: SQL Azure Data Sync can synchronize data between SQL Azure databases or between a SQL
Azure database and on-premises SQL Server databases.

The two synchronization options are the following:

Synchronizing data between a SQL Azure database and an on-premises SQL Server database. Having
an on-premises copy of cloud data might make sense for a variety of reasons. Maybe an organization
wants  to  make  sure  that  this  data  is  always  available,  for  instance,  even  in  the  event  of  network
failures, or perhaps regulations require that a copy of the data always be available within a country’s
borders. And even though SQL Azure’s built-in data replication guards against hardware failures, the
data’s owner might choose to maintain an on-premises backup copy in case of administrative errors,
such as incorrect table deletions.

Synchronizing data  between  SQL  Azure databases in different  Microsoft  data  centers.  For  example,
suppose an ISV or a global enterprise creates an application that’s used by people around the world.
To provide good performance for all of them, its creator might choose to run this application in three
different  Windows  Azure  data  centers:  one  each  in  North  America,  Europe,  and  Asia.  If  the
application  stores  data  in  SQL  Azure  Database,  it  might  rely  on  SQL  Azure  Data  Sync  to  keep
information synchronized across these three data centers.

SQL Azure Data Sync uses a hub-and-spoke model. All changes are copied first to the SQL Azure database
hub, then out to the spokes (referred to as members). The members might be other SQL Azure databases

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or on-premises SQL Server databases. In both cases, the technology provides synchronization of an entire
database or just specific tables, with changes made to any copy propagated to all of the others. And while
it’s possible to initiate synchronization manually, SQL Azure Data Sync also includes a scheduling service.
This lets users schedule, say, hourly synchronization between a pair of databases. However it’s used, the
purpose is the same: providing a straightforward way to synchronize data between a SQL Azure database
in a Microsoft data center and one or more databases located somewhere else.

 WINDOWS AZURE APPFABRIC

Applications exist because their business logic has value. Yet applications rely on infrastructure to provide
a foundation for that logic. A good application platform provides this infrastructure; application
developers shouldn’t need to write it themselves.

Windows Azure AppFabric provides infrastructure for applications. The people who create applications
can benefit from different kinds of infrastructure, and so AppFabric contains various parts. This section
takes a closer look at Service Bus, Access Control, and Caching, the three components of Windows Azure
AppFabric today.

Service Bus

Suppose you have an application running inside your organization that exposes a Web service built with
Windows Communication Foundation (WCF). Suppose further that you’d like to connect this service
through the Internet to software running outside your organization. This client software might be running
on a cloud platform, such as Windows Azure, or inside another organization.

At first glance, this can seem like a simple problem. Since your application provides its functionality
through Web services (either RESTful or SOAP-based), you can just make those Web services visible to the
outside world. When you actually try to do this, though, some problems appear.

First, how can clients in other organizations find endpoints they can connect to for your service? It would
be nice to have some kind of registry where others could locate your application. And once they’ve found
it, how can requests from software in other organizations get through to your service? Network address
translation (NAT) is very common, so an application frequently doesn’t have a fixed IP address to expose
externally. And even if NAT isn’t being used, how can requests get through your firewall? It’s possible to
open firewall ports to allow access to your application, but network administrators frown on this.

Service Bus addresses these challenges. Figure 10 shows how.

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Figure 10: A WCF service can register endpoints with Service Bus, then have clients discover and use
those endpoints to access the service.

To begin, your WCF service registers one or more endpoints with Service Bus (step 1). For each registered
endpoint, Service Bus exposes its own corresponding endpoint (step 2). Service Bus assigns your
organization a URI root, below which you’re free to create any naming hierarchy you like. This allows your
endpoints to be assigned specific, discoverable URIs.

When a client running in the cloud or on-premises at some other organization wishes to access your
service, it contacts the Service Bus registry (step 3) to find the endpoint, providing the endpoint’s URI. This
request uses the Atom Publishing Protocol, and it returns an AtomPub service document with references
to the endpoints Service Bus exposes on behalf of your application. Once it has these, the client can
invoke operations on the services exposed through these endpoints (step 4). For each request Service Bus
receives, it invokes the corresponding operation in the endpoint exposed by your WCF service (step 5).
(Although it’s not shown in the figure, Service Bus establishes a direct connection between an application
and its client whenever possible, making their communication more efficient.)

There’s an obvious question here: How exactly does step 5 work? How does the request from Service Bus
back to your service deal with the challenges of NAT and firewalls? The answer is that in step 1, your
service opened a TCP connection with Service Bus for this exposed endpoint. Service Bus holds this
connection open, which solves two problems. First, NAT is no longer an issue, since traffic on the open
connection with Service Bus will always be routed to your application. Second, because the connection
was initiated from inside the firewall, there’s no problem passing information back to the application via
this connection—the firewall won’t block this traffic.

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Along with making communication easier, Service Bus can also improve security. Because clients now see
only an IP address provided by Service Bus, there’s no need to expose any IP addresses from within your
organization. This effectively makes your application anonymous, since the outside world can’t see it.
Service Bus acts as an external DMZ, providing a layer of indirection to deter attackers.

While an application that exposes its services via Service Bus is typically implemented using WCF, clients
can be built with WCF or other technologies, such as Java. However they’re created, these clients can
make requests via TCP, HTTP, or HTTPS. Applications are also free to use their own security mechanisms,
such as encryption, to shield their communication from attackers.

Service Bus provides a few more useful features, including these:

Support  for  message  buffers,  which  act  like  simple  queues.  Rather  than  require  a  client  to  make
direct calls to a service, the client can place a message of up to 256 kilobytes into a message buffer.
The message is persisted to disk—it’s durable—and the service can then read this message at some
later  time.  And  as  usual  in  the  Windows  Azure  platform,  the  persisted  messages  are  replicated  to
guard against failures.

  The ability for multiple WCF services to listen on the same URI. Service Bus will then randomly spread
client requests across all of the listening services. The goal is to provide both load balancing and fault
tolerance for the WCF services.

Exposing applications to the outside world isn’t as simple as it might seem. The intent of Service Bus is to
make implementing these interactions as straightforward as possible.

Access Control

Working with identity is a fundamental part of most distributed applications. The modern approach to
this, called claims-based identity, lets a user send a token full of claims that contain identity information.
One claim might contain the user’s name, for example, while another contains her age or a group she
belongs to. An application can use the claims in a token to decide what the user is allowed to do or in
other ways.

In a claims-based world, tokens are issued by identity providers (IdPs). Some IdPs, such as Active Directory
Federation Services (AD FS) 2.0, exist inside organizations. Others, such as Windows Live ID and Google
Accounts, are accessible to anyone via the Internet. Each application can decide which IdPs it trusts and
thus which tokens it’s willing to accept. For example, an application running inside your company might
only accept tokens issued by your own AD FS server, while an application running on the Internet might
accept tokens issued by, say, Google and Facebook.

Yet different IdPs use different token formats, and they represent claims in different ways. An application
that directly accepts identities from Google, Facebook, and Yahoo, for instance, would need to handle
these differences itself. But why do this? Why not instead create an intermediary that can generate a
single token format with a common representation of claims? Doing this would make life simpler for the
people who create applications, since they now need to handle only one kind of token.

The Access Control service does exactly this, providing an intermediary in the cloud for working with
claims-based identity. Figure 11 shows how it works.

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Figure 11: The Access Control service makes it easier for applications to accept identity information
issued by different identity providers.

As the figure shows, an application that relies on Access Control can run either on-premises or in the
cloud. In either case, the process begins when a user attempts to access this application via a browser
(step 1). The application then redirects the browser to an IdP whose token this application will accept. The
user authenticates herself with this IdP, such as by entering a username and password, and the IdP
returns a token containing claims about her (step 2).

Next, the user’s browser sends the IdP token to Access Control (step 3). Access Control validates the
token, making sure that it really was issued by this IdP, then creates a new token according to whatever
rules have been defined for this application (step 4). Access Control contains a rules engine, allowing each
application’s administrator to define how tokens from various IdPs should be transformed into an Access
Control token. For example, if different IdPs use different formats for representing usernames, Access
Control rules can transform all of these into a common username string. Access Control then sends this
new token back to the browser (step 5), which submits it to the application (step 6). Once it has the
Access Control token, the application verifies that it really was issued by Access Control, then uses the
claims it contains (step 7).

While this process might seem a little complicated, it actually makes life significantly simpler for the
creator of the application. Rather than handle diverse tokens containing various claims, the application
can accept identities issued by multiple identity providers while still receiving only a single token with
familiar claims. And rather than require each application to be configured to trust various IdPs, these trust
relationships are instead maintained by Access Control—an application need only trust it.

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As Figure 11 shows, Access Control has built-in support for several identity providers, including AD FS 2.0,
Windows Live ID, Google, Yahoo, and Facebook. It can also work with any IdP that supports OpenID.
Browsers and other clients can request Access Control tokens using either OAuth 2 or WS-Trust, and these
tokens can have various formats, including SAML 1.1, SAML 2.0, and Simple Web Token (SWT). And to
create applications that accept Access Control tokens, Windows developers can use Windows Identity
Foundation (WIF). (It’s worth pointing out, however, that nothing about Access Control is tied to
Windows—it could just as well be used by a Linux application that accepted only Google and Facebook
identities.)

Working with identity is important in nearly every distributed application. The goal of Access Control is to
make it easier for developers to create secure applications that accept identities from diverse providers.
By putting this service in the cloud, Microsoft has made it available to any application running on any
platform.

Caching

For many applications, one of the most effective ways to improve performance is by caching frequently
accessed data. Since applications tend to use the same information over and over, making this
information more readily accessible can make the application faster. Doing this is the purpose of Windows
Azure AppFabric Caching. Figure 12 illustrates the idea.

Figure 12: Windows Azure AppFabric Caching speeds up access to frequently accessed data for
Windows Azure applications.

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The Caching service provides a distributed cache for Windows Azure applications, along with a library to
access this cache. As Figure 12 suggests, the service includes a local cache that can keep a copy of recently
accessed data items in each of an application’s role instances. If a data item the application needs isn’t
found in the local cache, the cache library automatically contacts the shared cache provided by the
Caching service. As the figure shows, this cache is spread across a number of Windows Azure instances,
each holding different cached data. This diversity isn’t visible to applications using the cache, however. An
application just requests a data item, then lets the cache find it (if it’s in the cache) and return it from
whatever instance contains it.

Recently accessed data isn’t automatically cached, however. Instead, the application explicitly inserts data
items in the cache, such as by using the Caching API. It’s also possible to configure an ASP.NET application
running on Windows Azure to store Session object data in the Caching service, speeding it up without
changing any of its code.

Windows Server AppFabric, the on-premises analog to Windows Azure AppFabric, also provides a Caching
service. In fact, the two are very similar. The biggest different is that unlike its on-premises counterpart,
Windows Azure AppFabric Caching is a service—there’s no need to configure servers and administer the
cache. Instead, all of this is handled automatically by the service itself. And the cloud Caching service is
multi-tenant, so each application using it gets its own instance. Because the application must authenticate
itself to this instance, data held in the Caching service isn’t accessible to other applications.

Caching can make applications faster and more scalable with little effort from developers, and so using it
makes sense. By providing caching as a service, Windows Azure AppFabric Caching makes this easier to
do.

WINDOWS AZURE MARKETPLACE

Cloud platforms are useful, but they’re just a means to an end. The real goal is offering applications and
data that provide value for people. Since the Windows Azure platform provides a foundation for both,
why shouldn’t it also include a way for people to find the applications and data that they need?

The Windows Azure Marketplace is designed to address this need. Its two components, AppMarket and
DataMarket, let users find, try, and purchase applications and data, respectively. While both are
important, DataMarket will appear first, and so what follows focuses on this aspect of the Marketplace.

Buying applications is common today—nearly every organization does it. Buying data is less common, but
it’s no less important. Many firms sell many different kinds of data, including demographic information,
financial information, legal information, and much more. Yet using purchased data typically requires
figuring out whether the data you need exists, finding a firm that offers it, then determining whether their
data meets your needs.

All of this is more difficult than it needs to be. Why not create one place where customers can find all
kinds of data from all kinds of content providers? Why not let them examine the data to make sure it
meets their needs, then purchase what they need right then and there? The DataMarket component of
Windows Azure Marketplace was created to do these things. Figure 13 shows its main components.

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Figure 13: Built on Windows Azure, the DataMarket allows access to content partner datasets stored in
Windows Azure, SQL Azure, or externally.

As the figure suggests, both people and applications can access information through DataMarket. Using a
Windows Azure-based application called the Service Explorer, a user can see what datasets are available,
then purchase what she needs. Once this is done, applications can access that data using RESTful or OData
requests. The datasets made available by DataMarket can be stored on the Windows Azure platform itself
using Windows Azure Storage or SQL Azure Database. They can also be stored externally, such as in a data
center owned by the content provider. There’s no requirement to put everything in the cloud.

For customers, DataMarket provides a single place to find, buy, and access a variety of commercial
datasets. For content providers—the owners of those data sets—DataMarket offers a chance to expose
their offerings to more customers through Microsoft’s cloud platform. While content providers set prices
for their data, DataMarket provides a billing service that frees them from dealing directly with customers.
Microsoft will also vet the quality of the content providers, limiting DataMarket initially to just the top five
providers in a particular industry.

Applications are free to use purchased data in any way that the content provider’s license allows. Users of
Microsoft Excel 2010, for example, can access DataMarket’s information directly using an Excel add-in or
use the PowerPivot for Excel support for OData to access information from DataMarket for data analysis.
It’s also possible to combine data purchased from DataMarket with your own data, such as for reports
created using SQL Server Reporting Services.

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Getting business value from information technology requires the right applications, but it also requires
the right data. By making it easier to discover, evaluate, and buy commercially available datasets,
DataMarket intends to make it simpler for organizations to find and use the information they need.

LOOKING AHEAD

Microsoft has announced a number of updates that it plans to add to the Windows Azure platform in the
near future. They include the following:

  The  Windows  Azure  Platform  Appliance:  Microsoft  has  announced  plans  to  offer  a  Windows  Azure
Platform  Appliance,  allowing  hosters  and  enterprises  to  run  Windows  Azure  in  their  own  data
centers. Because Windows Azure requires a specific hardware configuration—it’s not just software—
this appliance will include servers, networking, and storage, all running Windows Azure. And while it
will  initially  be  targeted  only  at  large  organizations,  Microsoft’s  goal  is  eventually  to  make  the
Windows Azure Platform Appliance useful for smaller organizations as well.

  CDN  dynamic  content  caching:  Today,  the  Windows  Azure  CDN  works  only  with  blob  data.  This
forthcoming  functionality  will  let  the  CDN  also  cache  content  created  dynamically  by  a  Windows
Azure application.

  VM role snapshotting: In its first release, the Windows Azure VM role doesn’t save any changes made
to  the  OS  volume  while  it’s  running.  Snapshotting  will  change  this,  providing  a  way  to  periodically
save the state of this volume to persistent storage.

  Better Java support: While Windows Azure can run Java applications today, Microsoft plans to make
this better. The coming improvements include better Java performance, stronger support for Eclipse-
based tools, and a more complete set of Java libraries for Windows Azure.

Support  for  composite  applications:  To  make  it  easier  to  build  Windows  Azure  applications  by
combining  existing  components  and  services,  Windows  Azure  AppFabric  will  add  a  composition
model.  Accompanied  by  runtime  services  and  a  Visual  Studio-based  designer,  this  model  will  let
developers  work  with  the  various  parts  of  an  application  as  a  single  logical  entity  throughout  its
lifecycle.

 All of these changes target the same goal: making the Windows Azure platform useful in a broader range
of scenarios.

CONCLUSIONS

The truth is evident: Cloud computing is here. For developers, taking advantage of the cloud means using
cloud platforms. With the Windows Azure platform, Microsoft presents a range of options addressing a
variety of needs:

  Windows Azure provides a computing and storage environment in the cloud.

SQL Azure provides a relational DBMS in the cloud, together with reporting and data synchronization.

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  Windows Azure AppFabric offers cloud-based infrastructure supporting both cloud and on-premises

applications.

  Windows  Azure  Marketplace  is  an  online  store  for  finding  and  purchasing  datasets  from  content

providers, together with a forthcoming store for cloud applications.

These approaches address a variety of requirements, and not every developer will use all of them. Yet
whether you work for an ISV, a systems integrator, or an enterprise, some cloud platform services are
likely to be useful for applications your organization creates. A new world is unfolding; prepare to be part
of it.

ABOUT THE AUTHOR

David Chappell is Principal of Chappell & Associates (www.davidchappell.com) in San Francisco, California.
Through his speaking, writing, and consulting, he helps people around the world understand, use, and
make better decisions about new technologies.

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