How to retrieve node information from DSC pull server

As described in “Push vs. Pull Mode” blog, DSC configuration can be applied on target nodes using pull or push mechanism.  In this blog I will talk about how to retrieve node information from DSC pull server. When the node pulls a configuration from the pull server and applies it locally, the pull can either succeed or fail. DSC compliance endpoint stores the pull operation status, configuration and node information in a database. Compliance endpoint can be used by admins to periodically check the status of the nodes to see if their configurations are in sync with pull server or not (using tools like Excel or write their own client application).

In this post I will cover the following:

  • Sending node’s information to pull server
  • Query node information in json from pull server

Before configuring a node to pull a configuration from pull server, you will need to setup DSC pull server in your environment that is covered in “DSC Resource for configuring pull server environment” blog.

You will also need to setup a compliance endpoint that will record the node information that is covered in the same blog.

DSC Compliance endpoint stores the following information about the nodes in database:

  • TargetName – Node name
  • ConfigurationId – Configuration ID associated with the node

  • StatusCode – Node status code (the status of very last pull operation).

Here is the list of status codes. Note that there might be additions or changes to the list in the future.

 

Status Code

Description

0

Pull operation was successful

1

Download Manager initialization failure

2

Get configuration command failure

3

Unexpected get configuration response from pull server

4

Configuration checksum file read failure

5

Configuration checksum validation failure

6

Invalid configuration file

7

Available modules check failure

8

Invalid configuration Id In meta-configuration

9

Invalid DownloadManager CustomData in meta-configuration

10

Get module command failure

11

Get Module Invalid Output

12

Module checksum file not found

13

Invalid module file

14

Module checksum validation failure

15

Module extraction failed

16

Module validation failed

17

Downloaded module is invalid

18

Configuration file not found

19

Multiple configuration files found

20

Configuration checksum file not found

21

Module not found

22

Invalid module version format

23

Invalid configuration Id format

24

Get Action command failed

25

Invalid checksum algorithm

26

Get Lcm Update command failed

27

Unexpected Get Lcm Update response from pull server

28

Invalid Refresh Mode in meta-configuration

29

Invalid Debug Mode in meta-configuration

  • NodeCompliant  – Configuration on the target node is in sync with the configuration stored on pull server or not.
  • ServerCheckSum – Checksum of the configuration mof file stored on the pull server
  • TargetCheckSum –Checksum of the configuration mof file that was applied on the node
  • LastComplianceTime – Last time the node run the configuration successfully
  • LastHeartbeatTime  -Last time the node connected to pull server.
  • Dirty – True if node status was recorded in the database, and false if not.

Compliance endpoint database connection is defined through its web.config settings. If you did not define it for your environment, compliance endpoint would not be recording node information into the database. Below snippet shows how to define database connection:

 

Set-Webconfig-AppSettings `

                 -path $env:HOMEDRIVE\inetpub\wwwroot\$complianceSiteName `

                 -key “dbprovider” `

                 -value “ESENT”

 

Set-Webconfig-AppSettings `

             -path $env:HOMEDRIVE\inetpub\wwwroot\$complianceSiteName `

             -key “dbconnectionstr” `

 -value “$env:PROGRAMFILES\WindowsPowerShell\DscService\Devices.edb”

 

 

Getting ready

First, we need to write a simple configuration that the node will be pulling from pull server, compile the configuration into mof, create it’s checksum file, deploy the mof and checksum files to the pull server. Then, configure the node to be in pull mode as by default LCM on the node is configured to be in push. For details please refer to “push vs. pull mode” blog.

 

Sending node’s status to pull server

When the node pulls a configuration from the pull server, the node includes the last pull operation status with the new pull request which then gets recorded by compliance endpoint into the database.

Query node information in json from pull server

We will use the following function to query the node’s information from pull server.

<#

# DSC function to query node information from pull server.

#>

function QueryNodeInformation

{

  Param (     

       [string] $Uri = “http://localhost:7070/PSDSCComplianceServer.svc/Status”,                         

       [string] $ContentType = “application/json”          

     )

  Write-Host “Querying node information from pull server URI  = $Uri -ForegroundColor Green

  Write-Host “Querying node status in content type  = $ContentType -ForegroundColor Green

 

 $response = Invoke-WebRequest -Uri $Uri -Method Get -ContentType $ContentType -UseDefaultCredentials -Headers
    @{Accept = $ContentType}

 

 if($response.StatusCode -ne 200)

 {

     Write-Host “node information was not retrieved.” -ForegroundColor Red

 }

 

 $jsonResponse = ConvertFrom-Json $response.Content

 

 return $jsonResponse

}

You need to replace Uri parameter with your_pull_ server_ URI.  To retrieve the node information in xml format, you should set the ContentType to ”application/xml”.

Now, let us retrieve the node information in the parameter $json and format the output to be in a table:

$json = QueryNodeInformation –Uri http://localhost:7070/PSDSCComplianceServer.svc/Status

 

$json.value | Format-Table TargetName, ConfigurationId, ServerChecksum, NodeCompliant, LastComplianceTime, StatusCode

 

In result you will see an output similar to:

 

TargetName       ConfigurationId      ServerCheckSum      NodeCompliant  LastComplianceTime   StatusCode

———-                —————            ————–               ————-                      —————–               ———-

Machine-975..  1C707B86-EF8E……  AE467E88D512…    True                    1899-12-30T00:00:00                  0

 

 

Hope this helps.

 

Thanks,

Narine Mossikyan

Software Engineer

 [ Updated 01/07/2014 ]