Tuesday, May 8, 2018

Azure @ Enterprise - Checking connectivity from AppServiceEnvironment to HDInsight

The background here is Enterprise Azure environment where most of the things are in vNet and their own subnets. When the Spark HDInsights are in separate Subnet other than the application, there will not be connectivity by default, if we need to submit jobs via Livy or anything like that (This again depends on the Enterprise policy). We have to open the routes from application subnet to HDInsight subnet. The route opening depends on how the infrastructure is laid out. If there are no firewalls of proxies in between application and HDInsight clusters, simple NSG rules would be sufficient.

Suppose there are 2 teams involved one is infrastructure and other development or QA teams, how can the development or QA can verify there is connectivity?

If the application is hosted in virtual machines, we can just log in and open the Ambari UI. Even we can run network troubleshooting commands. But what to do if the applications are hosted as AppService WebApps? If the applications are not client facing and need to be secured from neighbors, those may be inside their own AppServiceEnvironments. Basically no user interface available.

The solution is simple. Back to command line mode and somehow check the http connectivity to the HDICluster. Below is one powershell command which we can execute from the command line interface exposed from Kudu.

curl -Credential "user name" -Method "GET" -Uri "https://<cluster name>.azurehdinsight.net/livy/batches"

How to reach to the kudu console of an AppService instance is detailed in the below links.

The command tested for non domain joined HDInsight clusters. When we enter the above command it will ask for the password interactively. 

This is just a manual command to test the connectivity. If the scenario is multi-tenant and want to ensure connectivity from application, use WebClient or similar methods.

Update 1 @ 24Jan2019

If the below error occur when leveraging the same technique for web app to web app communication testing, try to force the connection via TLS 1.2

invoke-RestMethod : The underlying connection was closed: An unexpected error
PS D:\home>
occurred on a send. At line:1 char:1 + invoke-RestMethod -Method "GET" -Uri "https://eastus-sapkeyvaultservi ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:Htt pWebRequest) [Invoke-RestMethod], WebException + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShe ll.Commands.InvokeRestMethodCommand

TLS 1.2 can be enforced by below code snippet.
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

Update 2 @ 3Feb2019

Sometimes the below error can be thrown if the PowerShell is not able to format
The response content cannot be parsed because the Internet Explorer engine is not available, or Internet Explorer's first-launch configuration is not complete. Specify the UseBasicParsing parameter and try again

 The solution to this is to add the basic parsing switch.

curl -Credential "user name" -Method "GET" -Uri "https://<cluster name>.azurehdinsight.net/livy/batches" -UseBasicParsing

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