Lesson Learned #400:Reigniting a Dormant Extended Event in Azure SQL Database with PowerShell

[Jose_Manuel_Jurado]

Extended events provide essential insights in Azure SQL Database, enabling efficient monitoring and troubleshooting. However, when an extended event becomes stops unexpectedly, it can hinder our ability to diagnose issues effectively. In this article, we will explore the process of re-starting an extended event using a PowerShell script designed specifically for Azure SQL Database.

Understanding the Challenge

When an extended event halts unexpectedly, it can be caused by various factors such, configuration conflicts, or transient errors. Detecting and resolving the problem promptly is crucial to ensure uninterrupted data capture for effective monitoring and troubleshooting.

The Solution: PowerShell Script for Event Reactivation

To overcome the challenge of a halted extended event, we can leverage PowerShell and the System.Data.SqlClient module. The provided script automates the process of checking the status of extended events and reactivating them if necessary. Let's dive into the script's functionality and how it helps reactivate stalled extended events.

1. Database Connection Parameters

The script begins by defining the necessary connection parameters, including the Azure SQL Server name, database name, and authentication credentials. Adjust these parameters to match your Azure SQL Database environment.

2. Extended Events to Check and Enable

Specify the names of the extended events that you want to monitor and reactivate. These events should correspond to the ones that have unexpectedly halted.

3. Connection Retry Policy

To ensure a reliable database connection, the script incorporates a connection retry policy. It attempts to establish a connection with the specified Azure SQL Database, allowing for a specified number of connection retries with a delay between each attempt. This improves the script's resilience against intermittent connectivity issues.

4. Check and Enable Extended Events

The main function of the script iterates through the specified extended events. It checks the status of each event using SQL queries against the sys.dm_xe_database_sessions system view. If an extended event is found to be inactive, the script activates it using an ALTER EVENT SESSION statement. Additionally, you could add your code for sending an email notification function to inform stakeholders about the successful event reactivation.

 

Conclusion

Remember to customize the script to match your specific Azure SQL Database environment and extend its functionality to meet your requirements. With this powerful tool at your disposal, you can proactively address stalled extended events, enabling seamless data collection and enhancing your database management processes.

# Database connection parameters
$serverName = "ServerName"
$databaseName = "DBName"
$connectionString = "Server=tcp:$serverName.database.windows.net,1433;Database=$databaseName;Integrated Security=False;User ID=UserName;Password=Password!;"
$maxConnectionRetries = 3
$retryIntervalSeconds = 5

# Extended events to check and enable
$extendedEvents = @(
    "Extend_Event1",
    "Extend_Event2"
)


# Function to check and enable extended events
function CheckAndEnableExtendedEvents {
    param (
        [string]$connectionString,
        [string[]]$extendedEvents
    )

    $retryCount = 0
    $connection = $null
    
    while ($retryCount -lt $maxConnectionRetries) {
        try {
            $connection = New-Object System.Data.SqlClient.SqlConnection($connectionString)
            $connection.Open()
            break
        }
        catch {
            $retryCount++
            if ($retryCount -eq $maxConnectionRetries) {
                Write-Host "Error: Connection to the database failed after $maxConnectionRetries attempts."
                return
            }
            
            Write-Host "Error: $_.Exception.Message"
            Write-Host "Retrying connection in $retryIntervalSeconds seconds..."
            Start-Sleep -Seconds $retryIntervalSeconds
        }
    }

    foreach ($eventName in $extendedEvents) {
        try {
            # Check if the extended event is active
            $query = "SELECT COUNT(*) FROM sys.dm_xe_database_sessions WHERE name = '$eventName'"
            $command = $connection.CreateCommand()
            $command.CommandText = $query

            $eventCount = $command.ExecuteScalar()

            if ($eventCount -eq 0) {
                # Extended event is not active, enable it
                $enableQuery = "ALTER EVENT SESSION $eventName ON DATABASE STATE = START"
                $enableCommand = $connection.CreateCommand()
                $enableCommand.CommandText = $enableQuery
                $enableCommand.ExecuteNonQuery()

            }
        }
        catch {
            Write-Host "Error: $_.Exception.Message"
        }
    }
    
    # Close the connection
    if ($connection -ne $null -and $connection.State -eq 'Open') {
        $connection.Close()
    }
}

# Call the function to check and enable extended events
CheckAndEnableExtendedEvents -connectionString $connectionString -extendedEvents $extendedEvents