Monday, May 16, 2011

Windows Azure Diagnostics Logging

Although the logging functionality in Windows Azure uses the familiar Trace class, some extra steps are required. As I always forget them, a quick step-by-step guide:

Step 1: Adding DLL references

Remark: If you create a new cloud project and immediately add a web/worker role, the required DLL reference is already added.

Open the project you’ll host on Azure and add a reference to Microsoft.WindowsAzure.Diagnostics.dll. This is the dll that exposes the diagnostics configuration and management APIs.

Step 2: Register the Azure Diagnostics TraceListener

Remark: If you create a new cloud project and immediately add a web/worker role, the required tracelistener is already added to your configuration file.

Open your configuration file and add the following config settings:

<system.diagnostics>
<trace>
<listeners>
<add type="Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
name="AzureDiagnostics">
<filter type="" />
</add>
</listeners>
</trace>
</system.diagnostics>

Step 3: Configure a storage account

The diagnostics will be shipped from time to time to some specific tables inside a Windows Azure Storage account. Therefore you need to specify an Azure Storage connection string that can be used. The default VS template sets up the connection string name as ‘DiagnosticsConnectionString’ and the value as ‘UseDevelopmentStorage=true’. This particular connection string sets up Diagnostics Monitor to use Development Storage account. The connection string can be changed to point to a cloud storage account of your choice. Open up ServiceDefinition.cscfg or use the IDE to change this setting:

<ConfigurationSettings>
<Setting name="Microsoft.WindowsAzure.Plugins.Diagnostics.ConnectionString" value="DefaultEndpointsProtocol=https;AccountName=<accountname>;AccountKey=<key>" />
</ConfigurationSettings>

Step 4: Start the Diagnostics monitor

To enable log shipping you need to start the Diagnostics Monitor. Probably the best place to do this is inside the OnStart() method of your RoleEntryPoint class. In there add the following code:

public override bool OnStart() 
{ 
DiagnosticMonitorConfiguration dmc = DiagnosticMonitor.GetDefaultInitialConfiguration(); 
dmc.Logs.ScheduledTransferPeriod = TimeSpan.FromMinutes(1); 
dmc.Logs.ScheduledTransferLogLevelFilter = LogLevel.Verbose;

DiagnosticMonitor.Start("DiagnosticsConnectionString", dmc); 
} 

This configures the Diagnostic Monitor to ship the log data every minute to the Azure Storage. You can manipulate the Diagnostic Monitor configuration from outside Windows Azure, but this is something for another blog post.

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