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stefanstranger · 8 years ago

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PowerShell Azure Functions lessons learned

Lately I’m playing with PowerShell Azure Functions and I learned there are some things I needed to learn and that’s why I want to share some more info about this topic.

What are Azure Functions?

Azure Functions is an event driven, compute-on-demand experience that extends the existing Azure application platform with capabilities to implement code triggered by events occurring in virtually any Azure or 3rd party service as well as on-premises systems. Azure Functions allows developers to take action by connecting to data sources or messaging solutions, thus making it easy to process and react to events. Azure Functions scale based on demand and you pay only for the resources you consume. (from Github)

On the Github page about Azure Functions you can find all the info to get started.

PowerShell Azure Functions

Azure Functions enables you to create scheduled or triggered units of code implemented in various programming languages. PowerShell is one of those programming languages.

A good starting point is a blog post from David O’Brien Azure Functions – PowerShell.

If you look at an example from David you see a special variable being used ‘$res’. At first it was not clear to me where this variable was being defined. To find out more I started to create a Function using the Get-Variable cmdlet.

Use the following PowerShell script in your Function to retrieve the automatic variables available in Azure PowerShell functions.

[sourcecode language='powershell' padlinenumbers='true'] write-Output 'Getting variables' $result = Get-Variable | out-string [/sourcecode]

If you run this in your Azure PowerShell function you will see the following in your logs section.

[sourcecode language='powershell' ] 2017-01-29T16:01:51.538 Function started (Id=6528a25c-61cc-4d16-90ad-4869e47dc599) 2017-01-29T16:01:51.867 Getting variables 2017-01-29T16:01:51.898 Name Value ---- ----- $ ? True ^ args {} ConfirmPreference High ConsoleFileName DebugPreference SilentlyContinue Error {} ErrorActionPreference Continue ErrorView NormalView ExecutionContext System.Management.Automation.EngineIntrinsics false False FormatEnumerationLimit 4 HOME Host System.Management.Automation.Internal.Host.Int... input System.Collections.ArrayList+ArrayListEnumerat... InvocationId 6528a25c-61cc-4d16-90ad-4869e47dc599 MaximumAliasCount 4096 MaximumDriveCount 4096 MaximumErrorCount 256 MaximumFunctionCount 4096 MaximumHistoryCount 4096 MaximumVariableCount 4096 MyInvocation System.Management.Automation.InvocationInfo NestedPromptLevel 0 null OutputEncoding System.Text.ASCIIEncoding outputFile D:\local\Temp\Functions\Binding\6528a25c-61cc-... PID 9936 ProgressPreference Continue PSBoundParameters {} PSCommandPath PSCulture en-US PSDefaultParameterValues {} PSEmailServer PSHOME D:\Windows\SysWOW64\WindowsPowerShell\v1.0 PSScriptRoot PSSessionApplicationName wsman PSSessionConfigurationName http://ift.tt/2g2ttdZ... PSSessionOption System.Management.Automation.Remoting.PSSessio... PSUICulture en-US PSVersionTable {PSVersion, WSManStackVersion, SerializationVe... PWD D:\Windows\system32 req D:\local\Temp\Functions\Binding\6528a25c-61cc-... REQ_HEADERS_ACCEPT application/json, */* REQ_HEADERS_ACCEPT-ENCODING gzip, deflate, peerdist REQ_HEADERS_ACCEPT-LANGUAGE en-US, en-GB; q=0.8, en; q=0.6, nl-NL; q=0.4, ... REQ_HEADERS_CONNECTION Keep-Alive REQ_HEADERS_DISGUISED-HOST stsfunctionappdemo.azurewebsites.net REQ_HEADERS_HOST stsfunctionappdemo.azurewebsites.net REQ_HEADERS_MAX-FORWARDS 10 REQ_HEADERS_ORIGIN http://ift.tt/1MC1oPy REQ_HEADERS_REFERER http://ift.tt/2g2o1rE... REQ_HEADERS_USER-AGENT Mozilla/5.0 (Windows NT 10.0; Win64; x64) Appl... REQ_HEADERS_WAS-DEFAULT-HOS... stsfunctionappdemo.azurewebsites.net REQ_HEADERS_X-ARR-LOG-ID b61667f6-86d8-4bd1-a67c-bc0821ee2170 REQ_HEADERS_X-ARR-SSL 2048|256|C=US, S=Washington, L=Redmond, O=Micr... REQ_HEADERS_X-FORWARDED-FOR 217.122.212.62:4004 REQ_HEADERS_X-FUNCTIONS-KEY EOm0H6fRai398YoJRGKkjzAZ7SV2E/zgnOjTaCOVs55W8h... REQ_HEADERS_X-LIVEUPGRADE 1 REQ_HEADERS_X-ORIGINAL-URL /api/HttpTriggerPowerShellDemo?code=fYnNjQpSyo... REQ_HEADERS_X-P2P-PEERDIST Version=1.1 REQ_HEADERS_X-P2P-PEERDISTEX MinContentInformation=1.0, MaxContentInformati... REQ_HEADERS_X-SITE-DEPLOYME... stsfunctionappdemo REQ_METHOD GET REQ_QUERY_CODE fYnNjQpSyoUtXrR3fJ/vXn/L252RcTrzaeVFGP5vsMG6aa... res D:\local\Temp\Functions\Binding\6528a25c-61cc-... result {System.Management.Automation.PSVariable, Syst... ShellId Microsoft.PowerShell StackTrace true True VerbosePreference SilentlyContinue WarningPreference Continue WhatIfPreference False 2017-01-29T16:01:52.976 Function completed (Success, Id=6528a25c-61cc-4d16-90ad-4869e47dc599) 2017-01-29T16:03:40 No new trace in the past 1 min(s). [/sourcecode]

An interesting variable is “res” if we look at the value of this res variable we see that the value in my Azure Function is D:\local\Temp\Functions\Binding\677636fe-4384-42d2-94a4-55d14101ac99\res

But I was still wondering where this variable was configured because in the examples I often saw the variable being used to output the result.

Example where $res variable is being used:

[sourcecode language='powershell' ] $Result = $psversiontable | ConvertTo-Json Out-File -encoding Ascii -FilePath $res -inputObject $Result [/sourcecode]

It turned out this variable is being configured in the integration configuration section of the Azure Function.

So in above example the output result being show when the Azure Http Trigger PowerShell Function is being called stores the output of the Result variable in a file defined in the res variable. Hope this clarifies the $res variable seen in many examples on the internet about Azure PowerShell functions.

If you are also interested in the available environment variables within Azure PowerShell functions you can use the following PowerShell script in your Azure Function:

[sourcecode language='powershell' ] write-Output 'Getting environment variables' $result = ls env: | out-string write-output $result [/sourcecode]

I hope you have learned some new things about Azure PowerShell functions and you are interested to get started.

References:

Azure Function on Github

Azure Functions Get Started

David O’Brien Azure Functions – PowerShell

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