Configuring the diagnostic agent in Visual C#

Encoder Code 128 Code Set C in Visual C# Configuring the diagnostic agent

Figure 18.4 Finding the counter specifier using Performance Monitor. Browse to the correct category on the left, choose a counter, and then click Add. You join the category name and counter name with slashes, just like in a folder path. This example is showing \Memory\Available Bytes.

Finally, start the diagnostic agent. You need to provide it with the connection string to the storage account that you want the data uploaded to, and the configuration object you just built. The connection string defaults to the value DiagnosticsConnectionString, which is an entry in the cloud service configuration file. When you re playing with this on your development machine, you set the value to UseDevelopmentStorage=true, but in production you set it to be a connection string to your storage account in the cloud. The data will be uploaded to different destinations, depending on the data source. In the case of performance counters, the data will be uploaded to an Azure table called WADPerformanceCountersTable, an example of which is shown in figure 18.5. Figure 18.5 shows the results of the performance counter configuration. The agent tracked the available memory every 5 seconds, and stored that in the table. The entries were uploaded from the role instance to the table every minute, based on the configuration. The high order of the tick count is used as a partition key so that querying by time, which is the most likely dimension to be queried on, is fast and easy. The RoleInstance column contains the name of the instance, to differentiate entries across the different role instances. In this case, there s only one instance. Tracking log data can generate a lot of data. To make all this data easier to use, the diagnostic agent supports filters.

Figure 18.5 The performance counter data is stored in a table called WADPerformanceCountersTable. In this example, we re tracking the amount of available memory. You can see that the available memory starts at 3,452 MB and slowly drops to 3,436 MB. FILTERING THE UPLOADED DATA

The amount of data collected by the diagnostic agent can become voluminous. Sometimes you might want to track a great deal of data, but when you re trying to solve a particular problem, you might want only a subset of data to look through. The diagnostic agent configuration provides for filtering of the results. The agent still collects all the data locally. The filter is applied only when the data is uploaded to Azure storage. Filtering can narrow down the data you need to sift through, make your transfers faster, and reduce your storage cost. You can set the following property to filter based on the log level of the records that you ve specified:

transferOptions.LogLevelFilter = LogLevel.Error;

All the log data remains local to the agent; the agent uploads only the entries that match or exceed the filter level you set.

Being able to change the configuration inside the role instance is nice, but you ll probably do this only during the startup of the instance. Dynamic changes to the configuration are more likely to come from outside the role instance. The source of these changes will probably be either an overseer role that s monitoring the first role, or a management application of sorts that s running on your desktop. The agent s configuration is stored in a file local to the role instance that s running the agent. By default, this file is polled every minute for any configuration changes. You can change the polling interval if you want to by using the DiagnosticMonitorConfiguration.ConfigurationChangePollInterval property. You can set this property only from within the role the agent is running in. To update the configuration remotely, either from another role or from outside Azure, you can use two classes. The DeploymentDiagnosticManager class is a factory that returns diagnostic managers for any role you have access to. You can use this manager to change the configuration remotely by using it to create RoleInstanceDiagnosticManager objects. Each RoleInstanceDiagnosticManager object represents a collection of diagnostic agents for a given role, one for each instance running in that role. After you ve created this object, you can make changes to the configuration like you did in the previous section. The trick is that you have to change the configuration for each instance individually. The following listing shows how to update the configuration for a running role.