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I upgraded my service tier on only our App Service app (not the other resources). A day after doing this, the app will no longer start up - giving the following:
HTTP Error 500.30 - ASP.NET Core app failed to start
If I connect to the App Service portal and use Kudu to start it via a debug cmd prompt, I see
Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-
specific error occurred while establishing a connection to SQL Server. The server was not
found or was not accessible. Verify that the instance name is correct and that SQL Server
is configured to allow remote connections. (provider: TCP Provider, error: 0 - No such
host is known.)
System.ComponentModel.Win32Exception (11001): No such host is known.
Storage queue startup also fails with my queue hostname. In kudu I also tried
C:\home\site\wwwroot>nameresolver mydatabase.database.windows.net
Server: Default
*** Can't find mydatabase.database.windows.net: Non-existent domain
(not my actual server name...) but same thing for google.com or any other hostname
also:
C:\home\site\wwwroot>ping 142.251.32.142
Unable to contact IP driver. General failure.
but this seems to be expected?
I am not using any fancy VPNs, private networks, groups or whatnot - this is as plain vanilla as I could make it. This has worked for months before the upgrade. It works when run locally. My firewall for the database allows all azure services and my work/remote IP. I tried connection strings in the app service configuration only as well as only in appsettings.json. The connection string works in VS 2019, 2022, and sql management studio as well as the query tool within Azure portal itself. I've restarted the App service many times. OpenDNS cache check shows multiple different IPs for my database server but is this expected for regions? Why is the DNS apparently broken? How can I get this back to a functional state?
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@BackCode LLC . Thank you for reaching out regarding the error you are receiving accessing Azure SQL via Azure WebApp . We apologize for the frustration that you have encountered.
1/2:
I understand you have tried several options to narrow-down the issue. For a deeper investigation on this, I’ll need your WebApp name and other subscription related info, for this I’ll reach out you privately.
In regard to the Ping command you’re leveraging - Just to highlight, all Azure Web Apps (as well as Mobile App/Services, WebJobs and Functions) run in a secure environment called a sandbox. Each app runs inside its own sandbox, isolating its execution from other instances on the same machine as well as providing an additional degree of security and privacy.
In native Windows Azure WebApp Apps, the tools ping, nslookup, and tracert won't work through the console because of security constraints. However, to test DNS functionality, you may use nameresolver.exe. See this doc for more info: overview-vnet-integration#tools
Typically, the error 500.30 In-Process Startup Failure occurs when the ASP.NET Core Module attempts to start the .NET Core CLR in-process, but it fails to start. The cause of a process startup failure can usually be determined from entries in the Application Event Log and the ASP.NET Core Module stdout log.
2/2:
To fetch more details on the error, you may use to troubleshoot your Web App are fail request logs and profiling, this will break down errors for you and where is the Web App spending time at.
Note: Kindly do not share any PII data on the public forum.
Here is some of the launch output:
C:\home\site\wwwroot>dotnet .\LinkHerderWeb.dll
fail: Microsoft.EntityFrameworkCore.Database.Connection[20004]
An error occurred using the connection to database 'linkmoney_prod' on server 'tcp:linkmoneydb.database.windows.net,1433'.
fail: Microsoft.EntityFrameworkCore.Query[10100]
An exception occurred while iterating over the results of a query for context type 'LinkHerderWeb.Data.ApplicationDbContext'.
Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - No such host is known.)
---> System.ComponentModel.Win32Exception (11001): No such host is known.
[snip]
ClientConnectionId:00000000-0000-0000-0000-000000000000
Error Number:11001,State:0,Class:20
Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - No such host is known.)
---> System.ComponentModel.Win32Exception (11001): No such host is known.
at Microsoft.Data.ProviderBase.DbConnectionPool.CheckPoolBlockingPeriod(Exception e)
[snip]
truncated...
Thanks for sharing the requested details.
I see that you're leveraging these config:
"resource_group_name": "linkmoney_resources",
"sku": "Basic",
From the initial checks, it appears to be an issue with Azure DNS resolution on the instance. To rectify this, kindly try changing the instance via a scale up operation.
• Scale-up up to Standard tier.
• You can scale back down to Basic instance after ~10- 15 mins, so that you land on a different instance.
We're doing this as a test, to isolate the issue, you can scale down the App Service Plan tier later.
Kindly let me know how it goes I'll follow-up further.
Our sincere apologies for the inconvenience caused due to this issue.
Thanks - I scaled it up to the first standard tier and waited 1/2 hour.
Then I scaled it back down to the B1 tier I was wanting and restarted it.
Browsing to this instance it continued to fail with DNS errors
I stopped the app, then waited another 30 minutes and restarted it.
I continue to get DNS errors on startup.
@BackCode LLC , Apologies you're still experiencing this issue. I'm investigating this further and will get back to you shortly.
<<Private message Note>>: This is a private message which only you as Original Poster and Microsoft Moderators can view. Please respond directly to this comment to privately share the requested information. For your privacy, please do not share any Personal Identifiable Information (PII) as a public comment. All private messages will be periodically deleted from the site.
After the initial investigation-
I wish to engage with you offline for a deeper investigation, and so I can help provide a specialized assistance, please send an email with subject line “Attn:Ajay” to AzCommunity[at]Microsoft[dot]com referencing this thread ( | I have your subscription ID), I will follow-up with you.
Thanks for your patience and cooperation!
FYI - MS support contacted me and the service started working again with no changes from me after 6 days. So - there is no answer.
BackCodeLLC-6938, Thanks for the follow-up and sharing the offline/support discussion.
Apologies for any inconvenience this issue may have caused.
Kindly be assured that I’ have also relayed this feedback internally to our PG team.
Thanks for patience and cooperation!