Monthly Archives: October 2013

Switching garbage collection on in an Azure Worker role

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Whilst working on an issue with Microsoft on one of our production environments, we came across the fact that an Azure Worker role, by default, has it’s garbage collection set to workstation and not server mode.  If you are using medium or larger (hence multi-processor) you could see a performance benefit by switching to server mode.

Unfortunately the Azure tooling does not currently allow you to directly configure this setting, so you have to do it in a round about fashion, by creating a startup task that will perform changes as the instance boots.

First define a start up task in the Service Definition of your worker role:

<WorkerRole name="WorkerRole1" vmsize="Medium"> 
    <Startup>
        <Task commandLine="startup.cmd" executionContext="elevated" taskType="simple" /> 
    </Startup>

Now create a “startup.cmd” in the root of your worker that will be used to kick off the powershell that will modify the config file

@echo off 
powershell -command "Set-ExecutionPolicy RemoteSigned" 
powershell .\setServerGC.ps1 2>> err.out

And finally create the “setServerGC.ps1” file in the root of your worker role, this is the file that will actually make the modifications.

# Load up the XML
$configFile = "${env:RoleRoot}\base\x64\WaWorkerHost.exe.config"
[xml]$waXML = Get-Content $configFile

if (($waXML.configuration.runtime.gcServer -eq $null) -and ($waXML.configuration.runtime.gcConcurrent -eq $null))
{
    # Modify XML
    $gcServerEl = $waXML.CreateElement('gcServer')
    $gcConcurrentrEl = $waXML.CreateElement('gcConcurrent')

    $gcServerAtt = $waXML.CreateAttribute("enabled")
    $gcServerAtt.Value = "true"
    $gcConcurrentrAtt = $waXML.CreateAttribute("enabled")
    $gcConcurrentrAtt.Value = "true"

    $gcServerEl.Attributes.Append($gcServerAtt) | Out-Null
    $gcConcurrentrEl.Attributes.Append($gcConcurrentrAtt) | Out-Null


    $waXML.configuration.runtime.appendChild($gcServerEl) | Out-Null
    $waXML.configuration.runtime.appendChild($gcConcurrentrEl) | Out-Null

    $waXML.Save($configFile)
    
    # Restart WaWorkerHost.Exe
    Get-Process | ? {$_.name -match "WaHostBootstrapper"} | Stop-Process -Force
    Get-Process | ? {$_.name -match "WaWorkerHost"} | Stop-Process -Force
}

We saw a significant performance boost on the role we deployed this on, but your mileage will vary depending on your workload.

THIS POSTING AND CODE RELATED TO IT ARE PROVIDED “AS IS” AND INFERS NO WARRANTIES OR RIGHTS, USE AT YOUR OWN RISK

Simple Azure Storage Queue Monitor

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If you need to monitor the length of a queue in Azure, you can use the Azure PowerShell CmdLets to help you out.

Below is a sample ticker script that uses the Azure CmdLets (so make sure you have them installed) and it polls the configured queue every 10 seconds.  

clear
Import-Module Azure

$cert = Get-Item cert:\currentuser\my\<cert thumprint> # management cert
$subID = "<subscription ID>" # Subcription ID
$storageAccount = "<storage account>" # storage account where queue lives
$queueName = "<queueName>" # Queue you're interested in
$interval = 10 # Time between ticks


Set-AzureSubscription -SubscriptionID $subid -Certificate $cert `
    -SubscriptionName "CurrentSubscription"  `
    -CurrentStorageAccount $storageAccount
Select-AzureSubscription -SubscriptionName "CurrentSubscription"

# do forever loop
do
{
    # measure how long it takes to run the command
    $timeTaken = Measure-Command{
        # get the queue info
        $queueInfo1 = Get-AzureStorageQueue -Name $queueName 
        # write it to screen
        Write-Host (Get-Date) $queueInfo1.ApproximateMessageCount
    }
    # take the time take to run command off the interval time
    $totalTimeToWait = New-TimeSpan -Seconds $interval
    $timeToWait = $totalTimeToWait - $timeTaken
    # go to sleep 
    sleep ($timeToWait.TotalSeconds)
}while($true)