Azure Application Gateway HTTP Status 0 Responses

Context: You have a website running on Azure App Service that has a Azure Application Gateway in front.

Problem: Your clients receive the dreaded ERR_CONNECTION_CLOSED error randomly.

 

Troubleshooting: If you look at the Application Gateway logs, you will notice that the HttpStatus is 0. It is not a standard HTTP status code. You will also notice that SentBytes is also 0.

In such cases, the App Gateway does not forward the traffic to your backend target.

Cause: The predominant cause of such issues is that your application exceeded a certain Application Gateway limits as described in https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/azure-subscription-service-limits#azure-application-gateway-limits . For example, you may have cookie data that exceeds the 16 KB limit for HTTP/2. You can check your cookie sizes in Developer tools as shown below.

 

 

Unfortunately, as of August 2025, the only way to know what limit you exceeded is by opening at ticket with Microsoft Support.  

Solution: Modify your application code or adjust the appropriate configuration values, if applicable. 

blog@aileronconsulting.com
 

Azure Automated ML Batch Endpoint Spacy 3.7.4 compatibility issue

 If you tried to create a Batch Endpoint on Azure ML Studio and receive an error like the one shown below, the solution is provided in this blog post. If you need any assistance, feel free to reach out to blog@aileronconsulting.com.

=========================================================

#10 401.7 The conflict is caused by:
#10 401.7     The user requested spacy==3.7.4
#10 401.7     en-core-web-sm 3.4.1 depends on spacy<3.5.0 and >=3.4.0
#10 401.7 
#10 401.7 To fix this you could try to:
#10 401.7 1. loosen the range of package versions you've specified
#10 401.7 2. remove package versions to allow pip attempt to solve the dependency conflict
#10 401.7 
#10 401.7 
#10 401.7 failed
#10 401.7 
#10 401.7 CondaEnvException: Pip failed

=========================================================

The issue is in the environment file and the package en_core_web_sm-3.4.1 is not compatible with spacy 3.7.4.

Reach out (blog@aileronconsulting.com) if you would like to create custom environment that uses en_core_web_sm-3.7.1, which is compatible with the spacy package and use this base image  https://mcr.microsoft.com/azureml/curated/ai-ml-automl-dnn-gpu:21.

  

Azure Front Door with Wildcard domains

 When setting up Azure Front Door with wildcard domain names, there are a few things that need to be taken care of to get everything working correctly. Here are some key steps -

1. Add your domain.
   
2. Create the Origin Group / Origin. When creating the Origin leave the Origin Host Header blank. If you have a Private Link to, say, a backend load balancer, then enable that as well.
   
   
   
   
3. In your Front Door Endpoint, add the route to your wildcard domain.
   
   
   
   
4. Since you would need to create a CNAME to point to the endpoint, use HTTP Forwarding from your DNS server (or DNS provider) for your naked domain to, say, www.whateveryourdomainis.com. Then create a CNAME for www to point to the Endpoint.
   
   
   
   
   If you have any questions, please reach out to blog@aileronconsulting.com. We are happy to assist.

blog@aileronconsulting.com

 

 

Azure SQL Iaas Agent Not Updating Data on Azure Portal

 On Azure Portal you can install "SQL Virtual Machine" resource to monitor your Windows Virtual Machines to automate management and administration tasks. Sometimes Azure Portal does not reflect the state of your VM and there would be no data displayed on the Azure Portal for the SQL VM resource. Your first option is to Force repair as shown below.

 

If that doesn't work you can try to run the following command from Azure CLI. Note that you will get a warning about sql_management_mode being deprecated but you can ignore it.

az sql vm create --name YOURSQLVMNAM --resource-group YOURRESOURCEGROUPNAME --location YOURRESOURCELOCATION --license-type payg --sql-mgmt-type Full

 

blog@aileronconsulting.com

 

Adding an existing database to Azure Elastic Pool - 'System' is not a valid database edition in this version of SQL Server. Error

 When adding an existing database to an Azure Elastic Pool you may encounter the "'System' is not a valid database edition in this version of SQL Server." error message. To address this issue, go to the "Compute + Storage" setting for your database and modify it to a "Standard" Service tier at a minimum.

blog@aileronconsulting.com

 

AI Testing Tools from NIST

NIST has released (July 2024) new AI testing tools.

Managing Misuse Risk for Dual-Use Foundation Models

Testing How AI System Models Respond to Attacks

Mitigating the Risks of Generative AI

Reducing Threats to the Data Used to Train AI Systems

blog@aileronconsulting.com

Azure Communication Service - Email hygiene

It is a good practice to review your Communication service email logs to remove any email addresses that are being bounced back. Follow the steps in this article to enable logging to Log Analytics - https://learn.microsoft.com/en-us/azure/communication-services/concepts/analytics/enable-logging. You can then use some of the out of the box queries such as ACSEmailStatusUpdateOperational and ACSEmailStatusUpdateOperational to view the results.

 

blog@aileronconsulting.com

Azure Bastion - How to connect natively from Windows

If you ever used the web based client for Azure Bastion service, you would have realized that you can't really limited on what you can do and is not the same as RDP (mstsc). There is a way to connect natively to Azure Bastion service if you used the Standard SKU. The official documentation is at https://learn.microsoft.com/en-us/azure/bastion/native-client#connect-windows.  The PowerShell script that will come handy is below.

az login
az account set --subscription "<<your subscription id>>"
#Launch RDP
az network bastion rdp --name "<<name of your bastion resource>>" --resource-group "<<resource group name>>" --target-resource-id "/subscriptions/<<subscription id>>/resourceGroups/<<resource group name>>/providers/Microsoft.Compute/virtualMachines/<<Virtual machine name>>"

blog@aileronconsulting.com

Azure Logic App - Send Email connector - Multiple TO addresses

When using Azure Logic App connector for Azure Communication Service, you no longer can have multiple email addresses in the TO parameter. That action has been deprecated. See https://learn.microsoft.com/en-us/connectors/acsemail/#send-email-(preview)---deprecated-%5bdeprecated%5d. Instead, use the additional CC and BCC parameters. See https://learn.microsoft.com/en-us/connectors/acsemail/#send-email.

blog@aileronconsulting.com

Azure Email Communication Service error - "Requested message could not be located. Couldn't find a record with the messageID"

 When using Azure Email Communication service, you may run into this error - "Requested message could not be located. Couldn't find a record with the messageID". This generally is not an issue. What seems to be happening is that a getstatus call is being made almost about the same time a send call is being made. The recommendation is to write your own polling logic. See https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/email/send-email-advanced/manually-poll-for-email-status?tabs=connection-string

blog@aileronconsulting.com

Azure Email communication service - EmailDroppedAllRecipientsSuppressed

When using Email communication service, if you receive this error most likely a previous email to the recipient bounced back and the Email Communication Service will not send an email for another x number of hours & days. See https://learn.microsoft.com/en-us/azure/communication-services/concepts/email/sender-reputation-managed-suppression-list .

 {'id':'xxxxxxxxx','status':'Failed','error':{'code':'EmailDroppedAllRecipientsSuppressed','message':'Message dropped because all recipients were suppressed','target':null,'details':null,'innererror':null}}

 blog@aileronconsulting.com

 

Uploading large files using Azure Storage REST API

When uploading files that are over 250 MB to Azure storage using the Azure Blob REST API will require you to break the file into multiple blocks that can be upto 100 MB. Use the Put Block operation to write each of the blocks to the storage. Then use the Put Block List operation to write a blob that specifies the list of block IDs that make up the blob. 

blog@aileronconsulting.com