Tuesday, 13 September 2022

Sending test messages to Azure Event Hubs

Case
I want to send dummy messages to Azure Event Hubs to test the streaming process before the actual service starts sending real messages.  Is there an easy way to send a bulk load of test messages to Azure Event Hubs?
Sending messages to Azure Event Hubs











Solution
Yes we could use for example a little bit of PowerShell code to send dummy messages to Azure Event Hubs via a Rest API. To do that we first need to collect some names and a key from Azure Event Hubs.

1)  Namespace and Event Hub name
Go to your Event Hubs Namespace in the Azure Portal and click on Event Hubs on the left side. In the top left corner you will find the Event Hubs Namespace (1) and in the list in the center of the page you will find the name of your Event Hub (2). Copy these names to your Powershell editor.
Namespace and Event Hub name


















2) Shared access policies Name and Key
Now click on your Event Hub in the list above and then click on Shared access policies in the left menu. If there is no policy then create one (send is enough for testing). Then click on the policy to reveal the keys. Copy the Name (3) and one of the keys (4) to your Powershell editor.
Shared access policies name and key








3) The script
Now you have all the things you need from your event hub. Time to do some PowerShell coding. The top part of the script is to create a Shared Access Signature token (SAS token). This token is needed for authorization in the Rest API. In this part of the script you will also need to specify the names and key from the previous two steps under EventHubs Parameters.

The second part is sending a messsage via a Rest API to your event hub. To make it a little more usefull there is a loop to send multiple messages with a pause between each message. You must adjust the dummy message to your own needs by changing the column names and values. You can also specify the number of messages and the pause between each message.
####################################################################
# Create SAS TOKEN FOR AZURE EVENT HUBS
####################################################################
# EventHubs Parameters
$EventHubsNamespace = "bitools"
$EventHubsName = "myeventhub"
$SharedAccessPolicyName = "SendOnly"
$SharedAccessPolicyPrimaryKey = "1fhvzfOkVs+MxsZ/fakeZwrHTImD3YCCN7CGqYCAFN8kU="

# Create SAS Token
[Reflection.Assembly]::LoadWithPartialName("System.Web")| out-null
$URI = "$($EventHubsNamespace).servicebus.windows.net/$($EventHubsName)"
$Expires = ([DateTimeOffset]::Now.ToUnixTimeSeconds())+3600
$SignatureString = [System.Web.HttpUtility]::UrlEncode($URI)+ "`n" + [string]$Expires
$HMACSHA256 = New-Object System.Security.Cryptography.HMACSHA256
$HMACSHA256.key = [Text.Encoding]::ASCII.GetBytes($SharedAccessPolicyPrimaryKey)
$SignatureBytes = $HMACSHA256.ComputeHash([Text.Encoding]::ASCII.GetBytes($SignatureString))
$SignatureBase64 = [Convert]::ToBase64String($SignatureBytes)
$SASToken = "SharedAccessSignature sr=" + [System.Web.HttpUtility]::UrlEncode($URI) + "&sig=" + [System.Web.HttpUtility]::UrlEncode($SignatureBase64) + "&se=" + $Expires + "&skn=" + $SharedAccessPolicyName


####################################################################
# SEND DUMMY MESSAGES
####################################################################
# Message Parameters
$StartNumber = 1
$NumberOfMessages = 10
$MillisecondsToWait = 1000

# Determine URL and header
$RestAPI = "https://$($EventHubsNamespace).servicebus.windows.net/$($EventHubsName)/messages"

# API headers
$Headers = @{
            "Authorization"=$SASToken;
            "Content-Type"="application/atom+xml;type=entry;charset=utf-8";
            }

# Screenfeedback
Write-Host "Sending $($NumberOfMessages) messages to event hub [$($EventHubsName)] within [$($EventHubsNamespace)]"

# Loop to create X number of dummy messages
for($i = $StartNumber; $i -lt $NumberOfMessages+$StartNumber; $i++)
{
    # Create dummy message to sent to Azure Event Hubs
    $Body = "{'CallId':$($i), 'DurationInSeconds':$(Get-Random -Maximum 1000)}"

    # Screenfeedback
    Write-Host "Sending message nr $($i) and then waiting $($MillisecondsToWait) milliseconds"

    # execute the Azure REST API
    Invoke-RestMethod -Uri $RestAPI -Method "POST" -Headers $Headers -Body $Body

    # Wait a couple of milliseconds before sending next dummy message
    Start-Sleep -Milliseconds $MillisecondsToWait
}
When you run the PowerShell script with these parameters then 10 messages will be sent to your Event Hub.

Executing the Powershell script

















4) Check messages in the Event Hub
Now we can check the messages in your event hub. Go to your eventhub (myeventhub in our case) and click on Process data. Then find the Stream Analytics Query editor and execute the query.
Stream Analytics Query editor























Here can see the contents of your 10 dummy messages with a very basic query.
The result












Conclusion
In this post you learned how to test the setup of your Event Hub and if you for example also connect to Azure Stream Analytics and a Power BI streaming dataset with a report and dashboard then you can also see the messages arriving live in your Power BI Dashboard. This will be shown in a separate post.

Note that the script is sending the messages one by one with an even period between each message. You could for example also make the pause period random or even execute the script in multiple PowerShell ISE editors at once to simulate a more random load of arriving messages.

Do you have an easier way to send test messages or a more sophisticated script then please share your knowledge in the comments below.

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