title	description	ms.service	ms.date	ms.topic	author	ms.author
Create pre and post events using Azure Functions.	In this tutorial, you learn how to create the pre and post events using Azure Functions.	azure-update-manager	11/21/2023	tutorial	SnehaSudhirG	sudhirsneha

Tutorial: Create pre and post events using Azure Functions

Applies to: ✔️ Windows VMs ✔️ Linux VMs ✔️ On-premises environment ✔️ Azure VMs ✔️ Azure Arc-enabled servers.

This tutorial explains how to create pre and post events to start and stop a VM in a schedule patch workflow using Azure Functions.

In this tutorial, you learn how to:

[!div class="checklist"]

Prerequisites

Create a function app

Create a function

Create an event subscription

[!INCLUDE pre-post-prerequisites.md]

Create a function app

Follow the steps to Create a function app.
After you create the function app, Go to resource, ensure that you load the dependencies by following these steps:

[!NOTE] You have to load the dependencies only for the first time.
1. On the Function App, select App files.
2. Under the host.json, enable ManagedDependecy to True and select requirments.psd1.
3. Under the requirements.psd1, paste the following code:
```
 @{
 'Az'='5.*' 
 'Az.ResourceGraph'='0.13.0' 
 'Az.Resources'='6.*' 
 'ThreadJob' = '2.*'
 }
```
4. Select Save.
Restart the function app from the Overview tab to load the dependencies that are mentioned in the requirments.psd1 file.

Create a function

After you create the function app, go to Resource, and in Overview, select Create in Azure portal.
In the Create function window, make the following selections:
1. For the Development environment property, select Develop in portal
2. In Select a template, select Event Grid.
3. In Template details, enter the name in New Function and then select Create. :::image type="content" source="./media/tutorial-using-functions/create-function.png" alt-text="Screenshot that shows the options to select while creating a function." lightbox="./media/tutorial-using-functions/create-function.png":::

In the Event grid function, select Code+Test from the left menu, paste the following code and select Save.

Start VMs

# Make sure that we are using eventGridEvent for parameter binding in Azure function.
param($eventGridEvent, $TriggerMetadata)
            
Connect-AzAccount -Identity
            
# Install the Resource Graph module from PowerShell Gallery
# Install-Module -Name Az.ResourceGraph
            
$maintenanceRunId = $eventGridEvent.data.CorrelationId
$resourceSubscriptionIds = $eventGridEvent.data.ResourceSubscriptionIds
            
if ($resourceSubscriptionIds.Count -eq 0) {
    Write-Output "Resource subscriptions are not present."
    break
}
            
Write-Output "Querying ARG to get machine details [MaintenanceRunId=$maintenanceRunId][ResourceSubscriptionIdsCount=$($resourceSubscriptionIds.Count)]"
            
$argQuery = @"
    maintenanceresources 
    | where type =~ 'microsoft.maintenance/applyupdates'
    | where properties.correlationId =~ '$($maintenanceRunId)'
    | where id has '/providers/microsoft.compute/virtualmachines/'
    | project id, resourceId = tostring(properties.resourceId)
    | order by id asc
"@
            
Write-Output "Arg Query Used: $argQuery"
            
$allMachines = [System.Collections.ArrayList]@()
$skipToken = $null
            
do
{
    $res = Search-AzGraph -Query $argQuery -First 1000 -SkipToken $skipToken -Subscription $resourceSubscriptionIds
    $skipToken = $res.SkipToken
    $allMachines.AddRange($res.Data)
} while ($skipToken -ne $null -and $skipToken.Length -ne 0)
if ($allMachines.Count -eq 0) {
    Write-Output "No Machines were found."
    break
}
            
$jobIDs= New-Object System.Collections.Generic.List[System.Object]
$startableStates = "stopped" , "stopping", "deallocated", "deallocating"
            
$allMachines | ForEach-Object {
    $vmId =  $_.resourceId
            
    $split = $vmId -split "/";
    $subscriptionId = $split[2]; 
    $rg = $split[4];
    $name = $split[8];
                
    Write-Output ("Subscription Id: " + $subscriptionId)

    $mute = Set-AzContext -Subscription $subscriptionId
    $vm = Get-AzVM -ResourceGroupName $rg -Name $name -Status -DefaultProfile $mute

    $state = ($vm.Statuses[1].DisplayStatus -split " ")[1]
    if($state -in $startableStates) {
        Write-Output "Starting '$($name)' ..."
            
        $newJob = Start-ThreadJob -ScriptBlock { param($resource, $vmname, $sub) $context = Set-AzContext -Subscription $sub; Start-AzVM -ResourceGroupName $resource -Name $vmname -DefaultProfile $context} -ArgumentList $rg, $name, $subscriptionId
        $jobIDs.Add($newJob.Id)
    } else {
        Write-Output ($name + ": no action taken. State: " + $state) 
    }
}

$jobsList = $jobIDs.ToArray()
if ($jobsList)
{
    Write-Output "Waiting for machines to finish starting..."
    Wait-Job -Id $jobsList
}

foreach($id in $jobsList)
{
    $job = Get-Job -Id $id
    if ($job.Error)
    {
        Write-Output $job.Error
    }
}

Stop VMs

# Make sure that we are using eventGridEvent for parameter binding in Azure function.
param($eventGridEvent, $TriggerMetadata)
            
Connect-AzAccount -Identity
            
# Install the Resource Graph module from PowerShell Gallery
# Install-Module -Name Az.ResourceGraph
            
$maintenanceRunId = $eventGridEvent.data.CorrelationId
$resourceSubscriptionIds = $eventGridEvent.data.ResourceSubscriptionIds

if ($resourceSubscriptionIds.Count -eq 0) {
    Write-Output "Resource subscriptions are not present."
    break
}
            
Start-Sleep -Seconds 30
Write-Output "Querying ARG to get machine details [MaintenanceRunId=$maintenanceRunId][ResourceSubscriptionIdsCount=$($resourceSubscriptionIds.Count)]"
            
$argQuery = @"
    maintenanceresources 
    | where type =~ 'microsoft.maintenance/applyupdates'
    | where properties.correlationId =~ '$($maintenanceRunId)'
    | where id has '/providers/microsoft.compute/virtualmachines/'
    | project id, resourceId = tostring(properties.resourceId)
    | order by id asc
"@
            
Write-Output "Arg Query Used: $argQuery"
            
$allMachines = [System.Collections.ArrayList]@()
$skipToken = $null
            
do
{
    $res = Search-AzGraph -Query $argQuery -First 1000 -SkipToken $skipToken -Subscription $resourceSubscriptionIds
    $skipToken = $res.SkipToken
    $allMachines.AddRange($res.Data)
} while ($skipToken -ne $null -and $skipToken.Length -ne 0)
            
if ($allMachines.Count -eq 0) {
    Write-Output "No Machines were found."
    break
}
            
    $jobIDs= New-Object System.Collections.Generic.List[System.Object]
    $stoppableStates = "starting", "running"
            
    $allMachines | ForEach-Object {
    $vmId =  $_.resourceId
            
    $split = $vmId -split "/";
    $subscriptionId = $split[2]; 
    $rg = $split[4];
    $name = $split[8];
            
    Write-Output ("Subscription Id: " + $subscriptionId)
            
    $mute = Set-AzContext -Subscription $subscriptionId
    $vm = Get-AzVM -ResourceGroupName $rg -Name $name -Status -DefaultProfile $mute
            
    $state = ($vm.Statuses[1].DisplayStatus -split " ")[1]
if($state -in $stoppableStates) {
    Write-Output "Stopping '$($name)' ..."
            
    $newJob = Start-ThreadJob -ScriptBlock { param($resource, $vmname, $sub) $context = Set-AzContext -Subscription $sub; Stop-AzVM -ResourceGroupName $resource -Name $vmname -Force -DefaultProfile $context} -ArgumentList $rg, $name, $subscriptionId
    $jobIDs.Add($newJob.Id)
    } else {
    Write-Output ($name + ": no action taken. State: " + $state) 
    }
}
    $jobsList = $jobIDs.ToArray()
    if ($jobsList)
    {
    Write-Output "Waiting for machines to finish stop operation..."
    Wait-Job -Id $jobsList
    }
        
    foreach($id in $jobsList)
    {
    $job = Get-Job -Id $id
    if ($job.Error)
    {
    Write-Output $job.Error
    }
}

Cancel schedule

Invoke-AzRestMethod `
-Path "<Correlation ID from EventGrid Payload>?api-version=2023-09-01-preview" `
-Payload 
'{
"properties": {
"status": "Cancel"
}
}' `
-Method PUT

Select Integration from the left menu and edit the Event Trigger parameter name under Trigger. Use the same parameter name given in the Code+Test window. In the example, the parameter is eventGridEvent.

:::image type="content" source="./media/tutorial-using-functions/parameter-event-grid.png" alt-text="Screenshot that shows the parameter eventGridEvent." lightbox="./media/tutorial-using-functions/parameter-event-grid.png":::
Select Save

Create an Event subscription

Sign in to the Azure portal and go to your Azure Update Manager.
Under Manage, select Machines, Maintenance Configuration.
On the Maintenance Configuration page, select the configuration.
Under Settings, select Events.
Select +Event Subscription to create a pre/post maintenance event.
On the Create Event Subscription page, enter the following details:
1. In the Event Subscription Details section, provide an appropriate name.
2. Keep the schema as Event Grid Schema.
3. In the Event Types section, Filter to Event Types.
  1. Select Pre Maintenance Event for a pre-event.
    - In the Endpoint details section, select the Azure Function endpoint and select Configure and Endpoint.
    - Provide the appropriate details such as Resource groups, function app to trigger the event.
  2. Select Post Maintenance Event for a post-event.
    - In the Endpoint details section, the Azure Function endpoint and select Configure and Endpoint.
    - Provide the appropriate details such as Resource group, Function app to trigger the event.
Select Create.

You can also use Azure Storage accounts and Event hub to store, send, and receive events. Learn more on how to create Event hub and Storage queues.

Next steps

Learn about managing multiple machines.

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tutorial-using-functions.md

tutorial-using-functions.md

Tutorial: Create pre and post events using Azure Functions

Create a function app

Create a function

Start VMs

Stop VMs

Cancel schedule

Create an Event subscription

Next steps

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Tutorial: Create pre and post events using Azure Functions

Create a function app

Create a function

Start VMs

Stop VMs

Cancel schedule

Create an Event subscription

Next steps