Kubernetes on Ash Tewari

Kusto Queries on AKS Clusters

Sun, 25 Apr 2021 19:40:55 +0000

Kusto query language can be used to get insights into Azure Kubernetes Service (AKS) clusters. Container insights collects data from AKS clusters and forwards it to Log Analytics workspace, if enabled for a cluster. This data is available for querying in the Azure Monitor. Here is an example of how you can query the pods not in running state in specific namespaces.

KubePodInventory
| where Namespace in ("dv","test","prod")
| where ContainerStatus != "Running"
| where ContainerStatusReason !in ("", "Completed")
| distinct Namespace, Name

The following query includes the name of the AKS cluster and renders the output as a stacked bar chart.

KubePodInventory
| where Namespace in ("dv","test","prod")
| where ContainerStatus != "Running"
| where ContainerStatusReason !in ("", "Completed")
| distinct ClusterName, Namespace, Name
| summarize dcount(Name) by ClusterName, Namespace
| render columnchart kind=stacked100

You can include multiple AKS clusters in the scope in which this query is executed by clicking on [Select scope] hyperlink.

Create an Azure Dashboard panel with this output by clicking on [Pin to dashboard] button.

You can also execute this Kusto query directly using powershell.

$workspaceName = "DefaultWorkspace-6637b095-xxxx-xxxx-xxxx-xxxxxxxxxxx-EUS"
$workspaceRG = "defaultresourcegroup-eus"
$WorkspaceID = (Get-AzOperationalInsightsWorkspace -Name $workspaceName -ResourceGroupName $workspaceRG).CustomerID

$query = 'KubePodInventory | where Namespace in ("dv","test","prod") | where ContainerStatus != "Running" | where ContainerStatusReason !in ("", "Completed") | distinct ClusterName, Namespace, Name | summarize dcount(Name) by ClusterName, Namespace'

$result = Invoke-AzOperationalInsightsQuery -WorkspaceId $WorkspaceID -Query $query -Timespan (New-TimeSpan -days 1)
$result.results

This allows you to include the results of your custom Kusto queries in any reports you might run using Azure Automation Runbooks.

AKS - Adding SSH Keys to VMSS Nodes

Sun, 28 Mar 2021 03:33:11 +0000

You can connect to Azure Kubernetes Service (AKS) nodes using ssh. It is documented here: Connect with SSH to Azure Kubernetes Service (AKS) cluster nodes for maintenance or troubleshooting.

I needed to access nodes on the System node pool for collecting some logs recently, but the process documented above was not working for me. It turns out that there were two different issues, both related to adding your SSH keys to the nodes in a virtual machine scale set (VMSS).

This is the az cli command that adds the ssh keys to the VMSS:

az vmss extension set \
 --resource-group $CLUSTER_RESOURCE_GROUP \
 --vmss-name $SCALE_SET_NAME \
 --name VMAccessForLinux \
 --publisher Microsoft.OSTCExtensions \
 --version 1.4 \
 --protected-settings "{\"username\":\"azureuser\", \"ssh_key\":\"$(cat ~/.ssh/id_rsa.pub)\"}"

I was running this command from powershell on a windows host. So, the first modification I needed was to escape the double quotes by doubling them. You can also use back ticks instead of doubling the double quotes.

az vmss extension set \
 --resource-group $CLUSTER_RESOURCE_GROUP \
 --vmss-name $SCALE_SET_NAME \
 --name VMAccessForLinux \
 --publisher Microsoft.OSTCExtensions \
 --version 1.4 \
 --protected-settings "{\""username\"":\""azureuser\"", \""ssh_key\"":\""$(cat ~/.ssh/id_rsa.pub)\""}"

The second issue was due to the fact that ssh-keygen adds a comment to the id_rsa.pub file. By default, it adds username@hostname as the comment at the end of the file . Normally, this comment wouldn’t cause any problems, but in this case it was causing an error - “Invalid escape sequence \uXXXX”.

The problem was that my domain user name starts with character ‘u’ and “domain\userid1” was being interpreted as containing a unicode character “\useri” which is obviously not a valid unicode character. The workaround here is to either delete the comment from the id_rsa.pub file (it works just fine without it) or to override the default comment when generating the ssh key by specifying your own comment via -C command line option.

ssh-keygen -C mycomment

Finally, there is another way to execute az vmss extension set command to get around both of these issues by creating a json file and passing that as the value of –protected-settings argument. Here is how -

Create a json file, protected_settings.json, with the following content:

{
	"username" : "azureuser",
	"ssh_key" : "REPLACE_THIS_WITH_CONTENT_OF_ID_RSA_PUB_FILE"
}

Pass this file as the command line argument:

az vmss extension set \
 --resource-group $CLUSTER_RESOURCE_GROUP \
 --vmss-name $SCALE_SET_NAME \
 --name VMAccessForLinux \
 --publisher Microsoft.OSTCExtensions \
 --version 1.4 \
 --protected-settings protected_settings.json

Works like a charm!

AKS Supported Kubernetes Versions

Mon, 09 Nov 2020 03:08:17 +0000

Azure Kubernetes Service (AKS) supports specific versions of Kubernetes.
It is necessary to regularly monitor the release of new versions and upgrade your AKS clusters to supported versions in order to remain in compliance with AKS Kubernetes Version Support Policy.

AKS announces the planned date of a new minor version release and corresponding old version deprecation via AKS Release notes at least 30 days prior to removal. An email notification is sent to the subscription administrators with the planned version removal dates. You get 30 days from version removal to upgrade to a supported minor version release. Patch versions can be released anytime and you get 30 days from the removal date to upgrade to a supported patch version.

You should test new target Kubernetes versions and upgrade your AKS clusters in a timely manner. For that, it is necessary to proactively monitor the AKS release notes. This can easily become a chore in a large Enterprise environment. Here is a Powershell script to make it easier to stay on top of Kubernetes version releases in AKS and publish/share it with others: Get-AksSupportedVersions.

$aksVersionsJson = az aks get-versions --location eastus

$aksVersions = $aksVersionsJson | ConvertFrom-Json
$aksVersions.orchestrators.upgrades.orchestratorVersion

$data = $aksVersions.orchestrators | Select-Object `
 -Property @{Name="Version";Expression={$_.orchestratorVersion}} `
 , @{Name="Default";Expression={$_.default}} `
 , @{Name="Preview";Expression={$_.isPreview}} `
 , @{Name="Upgrades";Expression={$_.upgrades.orchestratorVersion -join ", "}}

$versionTable = $data | ConvertTo-Html -Fragment
$versionTableString = $versionTable | Out-String
$html = New-Object -ComObject "HTMLFile"
$html.IHTMLDocument2_write($versionTableString)
$tables = $html.body.getElementsByTagName("table")

$rptString = ""
ForEach($table in $tables){
 ForEach($row in $table.rows){
 $cellCount = 0
 ForEach($cell in $row.cells){
 $cellCount++
 if(($cellCount -eq 2) -and ($cell.innertext -eq 'True'))
 {
 $row.className = "OkStatus"
 }
 if(($cellCount -eq 3) -and ($cell.innertext -eq 'True'))
 {
 $row.className = "WarningStatus"
 }
 }
 }
 $rptString += $table.outerHTML
}

$reportDate = $(get-date -DisplayHint DateTime) | Out-String
$fileTS = $(get-date -Format "yyyyMMdd")
$fileName = "aks-versions-$fileTS.html"

$rptTitle = "<h1>AKS Kubernetes Versions</h1><p>$reportDate</p>"
$report = ConvertTo-Html -Title "AKS Versions" -Body "$rptTitle $rptString" -Head $header
$report | Out-File "$fileName"

It creates an HTML report of currently supported Kubernetes versions in AKS along with their respective upgrade paths. Here is an example of the report generated by the script referenced above :

AKS Kubernetes Versions

Sunday, November 8, 2020 8:47:42 PM

Version	Default	Preview	Upgrades
1.16.13			1.16.15, 1.17.9, 1.17.11
1.16.15			1.17.9, 1.17.11
1.17.9			1.17.11, 1.18.6, 1.18.8
1.17.11	True		1.18.6, 1.18.8
1.18.6			1.18.8, 1.19.0
1.18.8			1.19.0
1.19.0		True

Reference: How To Create An HTML Report With PowerShell