SQL Server timeout exception azure hyrbrid connection

Question

SQL Server timeout exception azure hyrbrid connection

Amal Edirisinghe 0

We have a Web application with Azure functions, a web app and an API manager. SQL database is located on an on-premise SQL database server. Functions apps connecting on-premise database via Azure hybrid connection. Suddenly we got the following error when the system was highly used. We are running the P1V3 premium app service plan.

Does anyone have experience with this error and do you have any recommendations here?

Error

Error] Error in GetCasesConnection Timeout Expired. The timeout period elapsed while attempting to consume the pre-login handshake acknowledgement. This could be because the pre-login handshake failed or the server was unable to respond back in time. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=0; handshake=14987;

Amal Edirisinghe 0 Reputation points

2025-01-08T13:17:46.3133333+00:00

Thank you so much for the quick response here. We will go through the recommendation.

Meanwhile, we have monitored during issues that occurred. The app service plan and SQL database performance are running as usual. It is not highly used.
Erland Sommarskog 121.4K Reputation points MVP Volunteer Moderator

2025-01-08T21:48:57.62+00:00

So this was a one-of-a-kind error? Or does this happen regularly? If it has only happened once, I would wait until it is more common. Because it is very difficult to troubleshoot.

But increasing the connection timeout is not a bad idea.

What sort of authentication are you using?
Shree Hima Bindu Maganti 4,775 Reputation points Microsoft External Staff Moderator

2025-01-09T14:35:34.4266667+00:00
Hi Amal Edirisinghe ,
Thankyou for your Response.
The App Service Plan and SQL database performance appear normal and the system is not highly used, the issue likely resides in network configurations, transient faults, or Hybrid Connection settings.
Use Azure Network Watcher to check for:

Latency or packet loss.

DNS resolution issues.

Run TCP Ping Tests to validate connectivity from the App Service to SQL Server.

Ensure the Hybrid Connection Manager is running without errors.

Check logs for connection interruptions or relay delays.

Verify relay bandwidth utilization during the issue.

Implement retry logic in the application to handle transient faults gracefully

for (int retry = 0; retry < 3; retry++) { try { /* SQL operation */ break; } catch (SqlException ex) { Thread.Sleep(TimeSpan.FromSeconds(Math.Pow(2, retry))); } }

Check handshake logs on both App Service and SQL Server.

Confirm SQL Server connection limits are not being reached.

Increase application connection timeout if necessary
"Server=myServer;Database=myDB;User Id=myUser;Password=myPassword;Connection Timeout=60;"

Test Hybrid Connection responsiveness using SQL tools or network monitoring.

Check on-premise resource usage (CPU, disk I/O) for bottlenecks.
Shree Hima Bindu Maganti 4,775 Reputation points Microsoft External Staff Moderator

2025-01-10T11:30:25.8766667+00:00

Hi Amal Edirisinghe ,

Following up to see if you have chance to check my previous response and help us with requested information is helpful.
Shree Hima Bindu Maganti 4,775 Reputation points Microsoft External Staff Moderator

2025-01-13T03:19:46.1966667+00:00

Hi Amal Edirisinghe ,

Following up to see if you have chance to check my previous response and help us with requested information is helpful.

1 answer

Your answer

Amal Edirisinghe 0 Reputation points

2025-01-08T13:17:46.3133333+00:00

Thank you so much for the quick response here. We will go through the recommendation.

Meanwhile, we have monitored during issues that occurred. The app service plan and SQL database performance are running as usual. It is not highly used.
Erland Sommarskog 121.4K Reputation points MVP Volunteer Moderator

2025-01-08T21:48:57.62+00:00

So this was a one-of-a-kind error? Or does this happen regularly? If it has only happened once, I would wait until it is more common. Because it is very difficult to troubleshoot.

But increasing the connection timeout is not a bad idea.

What sort of authentication are you using?
Shree Hima Bindu Maganti 4,775 Reputation points Microsoft External Staff Moderator

2025-01-09T14:35:34.4266667+00:00

Hi Amal Edirisinghe ,
Thankyou for your Response.
The App Service Plan and SQL database performance appear normal and the system is not highly used, the issue likely resides in network configurations, transient faults, or Hybrid Connection settings.
Use Azure Network Watcher to check for:

Latency or packet loss.

DNS resolution issues.

Run TCP Ping Tests to validate connectivity from the App Service to SQL Server.

Ensure the Hybrid Connection Manager is running without errors.

Check logs for connection interruptions or relay delays.

Verify relay bandwidth utilization during the issue.

Implement retry logic in the application to handle transient faults gracefully

for (int retry = 0; retry < 3; retry++) { try { /* SQL operation */ break; } catch (SqlException ex) { Thread.Sleep(TimeSpan.FromSeconds(Math.Pow(2, retry))); } }

Check handshake logs on both App Service and SQL Server.

Confirm SQL Server connection limits are not being reached.

Increase application connection timeout if necessary
"Server=myServer;Database=myDB;User Id=myUser;Password=myPassword;Connection Timeout=60;"

Test Hybrid Connection responsiveness using SQL tools or network monitoring.

Check on-premise resource usage (CPU, disk I/O) for bottlenecks.
Shree Hima Bindu Maganti 4,775 Reputation points Microsoft External Staff Moderator

2025-01-10T11:30:25.8766667+00:00

Hi Amal Edirisinghe ,

Following up to see if you have chance to check my previous response and help us with requested information is helpful.
Shree Hima Bindu Maganti 4,775 Reputation points Microsoft External Staff Moderator

2025-01-13T03:19:46.1966667+00:00

Hi Amal Edirisinghe ,

Following up to see if you have chance to check my previous response and help us with requested information is helpful.

Answer 1

Hi Amal Edirisinghe ,
Welcome to the Microsoft Q&A Platform!
The error you’re facing a timeout during the SQL Server pre-login handshake, which typically happens when the SQL Server is unable to respond within the expected time frame. This issue can arise due to high latency, network congestion, insufficient resources, or improper configuration.

Use tools like SSMS, Windows Performance Monitor, and SQL Profiler.
Optimize queries, add indexes, or increase server resources (CPU/RAM).
Update connection string. Connection Timeout=60;
Check diagnostic logs in Azure Portal for latency or dropped connections.
Configure a secondary hybrid connection for failover.
If possible, migrate the database to Azure SQL to reduce dependency on on-premise infrastructure.
Upgrade to a higher-tier plan like P2V3 or increase instance count.
Review firewall rules and use Azure Network Watcher to troubleshoot connectivity issues.
Add Max Pool Size=100; to the connection string.
Add retry mechanisms for transient errors.
```
  for (int retry = 0; retry < maxRetries; retry++) {  
      try { /* Attempt operation */ break; }  
      catch (SqlException ex) { Thread.Sleep(TimeSpan.FromSeconds(2)); }  
  }  
```
ref:https://learn.microsoft.com/en-us/azure/app-service/app-service-hybrid-connections Let me know if further assistance is required.
If the answer is helpful, please click Accept Answer and kindly upvote it

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SQL Server timeout exception azure hyrbrid connection

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