sriram krishnan program manager microsoft corporation [email protected] es03
TRANSCRIPT
Windows Azure: Cloud service development best practices
Sriram KrishnanProgram ManagerMicrosoft Corporation
ES03
1980
void quicksort(int* array, int left, int right)
{
if(left >= right)
return;
int index = partition(array, left, right);
quicksort(array, left, index - 1);
quicksort(array, index + 1, right);
}
simplicity
Act IArchitecture
Networks are unreliable
Hardware fails
A few design choices
Big, reliable,
expensive machine
Several commodity machines
Lots and lots of commodity machines
A few challenges
What do you do about that pesky thing called state?
Go horizontalGo stateless
Store state in Windows Azure storage
And it is the default out of the box!
Session state provider
<system.web>
...<sessionState mode="Custom"
customProvider="TableStorageSessionStateProvider"> <providers>
<add name="TableStorageSessionStateProvider“
type="Microsoft.Samples.ServiceHosting.AspProviders.TableStorageSessionStateProvider"
applicationName=“Foo” />
</providers></sessionState>
</system.web>
How do you deal with unreliable components?
Be loosely coupled
Use Windows Azure queues for separation of work
Default.aspx(Input + Making
Coffee)
LB
Tight coupling : Default.aspx.cs
public partial class _Default : System.Web.UI.Page { protected void Button1_Click(object sender,EventArgs e) { var order = txtOrder.Text; ProcessOrder(order); }
protected void ProcessOrder(string order) { //Make some coffee!
... }
}
Default.aspx(Input)
Windows Azure Queues
LB
Worker.cs(Make Coffee)
Loose coupling : Default.aspx.cs
public partial class _Default : System.Web.UI.Page { protected void Button1_Click(object sender,EventArgs e) { var order = txtOrder.Text;
QueueStorage qStore = QueueStorage.Create(_account);
MessageQueue orderQ = qStore.GetQueue("OrderQueue");
orderQ.PutMessage(new Message(order)); }
}
Loose coupling : WorkerRole.cs
public class WorkerRole : RoleEntryPoint { public override void Start() {
QueueStorage qStore = QueueStorage.Create(_account); MessageQueue orderQ = qStore.GetQueue("OrderQueue"); while (true) { Message msg = orderQ.GetMessage();
if( msg != null) ProcessOrder(msg.ContentAsString()); } } protected void ProcessOrder(string order) {
//Make some coffee! ...
}
How do you deal with varying load?
Build a thermostat for your service
How do you deal with failures?
Use Windows Azure storage for valuable data
Be prepared to reconstruct local state…
…since it can disappear any time
Retry on transient failures
But…
Be idempotent
Don’t launch a DoS attack on yourself
Be predictable
Avoid shutdown code
Know when to throttle and shed load
Case study: SmugMug and SkyNet
When is ‘good enough’ good enough?
The resiliency of email
Do all apps need the same guarantees?
It's a knob
Stateless front-endsLoose couplingBuilding a thermostatRetrying on failuresLoosening consistency
Recap
End of Act I
Act IIUpdates
Updates are hard
Hard to ‘undo’ a failed deployment
Need to deal with both code and schema changes
Code + data
Update only one at a time
Code vN Data vN
Code vN
Data vN
Code vN +1
Code vN
Data vN
Data vN+1
Be compatible
If it looks like a duck and walks like a duck…
http://www.flickr.com/photos/gaetanlee/298160415/
Use version numbers in schema
class Employee : TableStorageEntity { public Employee(string firstName, string lastName) : base(firstName, lastName) //partition key, row key {} public string JobTitle { get; set; } }
... var qResult = from emp in
svc.CreateQuery<Employee>(EmployeeDataServiceContext.EmployeeTable)
where emp.PartitionKey == "Steve" && emp.RowKey == "Marx select emp;
Schema without versioning }
class Employee : TableStorageEntity { public Employee(string firstName, string lastName) : base(firstName, lastName) {} public string JobTitle { get; set; }
public int Version { get; set;
}
} ... var qResult = from emp in
svc.CreateQuery<Employee>(EmployeeDataServiceContext.EmployeeTable)
where emp.PartitionKey == "Steve" && emp.RowKey == "Marx
&& emp.Version == 1 select emp;
Schema *with* versioning }
How do you do upgrades without downtime?
Windows Azure’s rolling upgrades
Stage Deployment Production Deployment
Swap for zero downtime upgrade
+Stop + start for big changes or if
downtime isn’t an issue
Future: Precise control
When is the best time to update a service?
Use the Pacific Ocean
Case study: Windows Live ID
Update code or dataMaintain compatVersioning in schemasRolling upgrades
Recap
End of Act II
December 4th, 1996
Oh Oh!
Trace logs
Trickiest patch ever
Act IIIWhen things go wrong…
How do I debug?
Use the Windows Azure SDK and debug locally to find bugs
Separate code and config
ServiceDefinition.csdef
<ServiceDefinition name="DemoService"> <WebRole name="WebRole"> <ConfigurationSettings>
<Setting name="Color"/>
</ConfigurationSettings> </WebRole></ServiceDefinition>
ServiceConfiguration.cscfg
<ServiceConfiguration serviceName="DemoService"> <Role name="WebRole"> <ConfigurationSettings>
<Setting name ="Color" value ="Red"/>
</ConfigurationSettings> </Role></ServiceConfiguration>
Configuration files
Windows Azure’s configuration update mechanism
How do I debug the cloud?
Logging
<?xml version="1.0"?><ServiceConfiguration serviceName=“DemoService”>
<Role name="WebRole">
<Instances count="1"/> <ConfigurationSettings>
<Setting name ="LogLevel" value ="Verbose"/>
</ConfigurationSettings> </Role></ServiceConfiguration>
...
Configurable logging
if (RoleManager.GetConfigurationSetting("LogLevel") == "Verbose") RoleManager.WriteToLog("Information", "Some log message");
Tag data with unique ID to track across the system
{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}
How do I get notified when something bad happens?
!
Windows Azure’s alerts
!
Email / IM / Phone
The Big Red Button
Use the SDKSeparate code and configConfigurable loggingAlertsThe Big Red Button
Recap
End of Act III
James Hamilton http://research.microsoft.com/~jamesrh/
Emre Kiciman http://research.microsoft.com/~emrek/
Pat Helland http://blogs.msdn.com/pathelland/
What really happened on Mars http://research.microsoft.com/~mbj/mars_pathfinder/
Flickr blog post http://code.flickr.com/blog/2008/09/26/flickr-engineers-do-it-offline/
Don MacAskill http://blogs.smugmug.com/don/
Credits & Acknowledgements
One final story
William of Ockhamc. 1288 - c. 1348
Numquam ponenda est pluralitas sine necessitate
Plurality ought never be posited without necessity
KISS
simplicity
Evals & Recordings
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out your
evaluation for
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Please use the microphones provided
Q&A
© 2008 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market
conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
