Function app stopped working complaining of connection when nothing has changed

Question

Function app stopped working complaining of connection when nothing has changed

Philip Yoxall 0

Function app that was working ok for many months has suddenly stopped working due to :

"format of the initialization string does not conform to specification starting at index 0." This function uses a shared SQL Azure db connection string which other functions use without issue. So this is just this function that has stopped working. Any help appreciated

Khadeer Ali 4,235 Reputation points Microsoft External Staff

2025-01-30T16:02:09.31+00:00
@Philip Yoxall ,
Welcome to Microsoft Q&A Platform!

Thanks for reaching out.That error about the connection string means something's wrong with how your function is trying to talk to the database. Since other parts of your app work fine, we know the database itself is probably okay. Here's a breakdown of what to check:

Double-Check for Typos: Go into the Azure portal and look at your Function App's settings. Make absolutely sure the connection string there is exactly the same as the one your other functions use. Even a tiny typo, a missing semicolon, or an extra space can cause this. If you're using Azure Key Vault, make sure the secret stored there is correct and that your function has permission to access it.

Is the Format Right? A connection string has a very specific format. It needs things like the server address, database name, username, and password, all separated by semicolons. Make sure everything is there and that you haven't accidentally used any special characters (like @ or !) in your password without escaping them. Sample Connection String:

Server=tcp:{server-name}.database.windows.net,1433;Initial Catalog={db-name};Persist Security Info=False;User ID={username};Password={password};MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=False;Connection Timeout=30;

Try Restarting: It sounds simple, but sometimes Azure just needs a little kick. Restart your Function App.

Test the Connection Directly: Use a tool like SQL Server Management Studio to try connecting to the database directly using the connection string. This will tell you if the problem is with the string itself or something else in your function.

Code Check: Make sure your code is actually using the correct connection string name. Also, if you're testing locally, make sure your local settings aren't overriding the settings in Azure.

What Changed Recently? Think back – did you deploy any updates recently or change any settings? Check the deployment logs in Azure to see if anything went wrong.

Dig Deeper: Use Application Insights or the Kudu console in Azure to get more detailed error messages. This can help pinpoint exactly where the problem is.

Last Resort: Redeploy: If all else fails, try redeploying your Function App. Sometimes things just get a bit scrambled, and a fresh deployment can fix it.

If you're still having trouble after trying these steps, please let us know. We're happy to help you troubleshoot further.

We hope this helps! Please let us know if you have any other questions.

If this resolved your issue, please click "Accept Answer" and mark the "Was this answer helpful?" question as "Yes." If you need more help, just let us know!

References:

Troubleshoot transient connection errors in SQL Database and SQL Managed Instance

Connection string is missing
Khadeer Ali 4,235 Reputation points Microsoft External Staff

2025-01-31T15:44:08.4933333+00:00

@Philip Yoxall ,

I wanted to check in and see if my earlier response addressed your question. If you still need assistance or have additional questions, feel free to share more details, and I’d be happy to help!
Khadeer Ali 4,235 Reputation points Microsoft External Staff

2025-02-04T16:06:16.7433333+00:00

@Philip Yoxall ,

Just following up again to see if you were able to resolve the issue or if there's anything else I can assist you with. Let me know if you need further help
Philip Yoxall 0 Reputation points

2025-02-04T16:12:18.2333333+00:00

looks like TrustServerCertificate=False needed to be true

1 answer

Your answer

Khadeer Ali 4,235 Reputation points Microsoft External Staff

2025-01-31T15:44:08.4933333+00:00

@Philip Yoxall ,

I wanted to check in and see if my earlier response addressed your question. If you still need assistance or have additional questions, feel free to share more details, and I’d be happy to help!
Khadeer Ali 4,235 Reputation points Microsoft External Staff

2025-02-04T16:06:16.7433333+00:00

@Philip Yoxall ,

Just following up again to see if you were able to resolve the issue or if there's anything else I can assist you with. Let me know if you need further help
Philip Yoxall 0 Reputation points

2025-02-04T16:12:18.2333333+00:00

looks like TrustServerCertificate=False needed to be true

Answer 1

@Philip Yoxall ,

I’m glad to hear that you were able to resolve your issue, and thank you for sharing your solution! It’s great to see your contribution, as it helps others in the community who may face a similar issue.Since the Microsoft Q&A community policy states, "The question author cannot accept their own answer. They can only accept answers by others" I’m reposting your solution here so you can mark it as accepted if it resolves your query:

Reposted Solution:

The resolution was modifying TrustServerCertificate=True to the connection string. The function app was previously working without this, but something must have changed on the server or client side that now requires this explicit setting.

If you have any further questions, feel free to reach out.

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Function app stopped working complaining of connection when nothing has changed

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