Cloud SQL odbc connection failed with 'waiting for initial communication packet' error

[binrip]

Hi
I am attempting to use a SQL Server 2014 linked server to connect to a Cloud SQL MySQL 8 Enterprise Plus instance. Connection established successfully via cloudsql auth proxy and able to run queries against MySQL database through linkedserver.

However, when I try to run multiple insert statements to insert data to multiple database tables, I receive a generic error message. Sometimes it works without error during off-peak hours. The error message I receive is:

OLE DB provider "MSDASQL" for linked server "MYSQL-LINKED-SERVER" returned message "[MySQL][ODBC 8.4(w) Driver]Lost connection to MySQL server at 'waiting for initial communication packet', system error: 10060".

I have enabled following flags on the MySQL Instance.

• max_allowed_packet: 67108864
• wait_timeout: 86400
• connect_timeout: 28000
• net_read_timeout: 3600
• interactive_timeout: 28773
• net_write_timeout: 3600
• bulk_insert_buffer_size: 4294967295

Can someone please help me pinpoint what could be causing the issue?

[binrip]

Cloudsql show the following error message:
failed to connect to instance: Dial error: failed to dial (connection name = "instance-name"): dial tcp ip:port: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

[ms4446]

The error message indicates that the connection to the MySQL server is lost at the point of "waiting for initial communication packet," with system error 10060. This issue seems to occur predominantly during peak hours, suggesting that it may be related to resource constraints or network congestion.

Several factors could be contributing to this problem. One possibility is that the MySQL server's max_connections parameter is set too low to handle the number of concurrent connections during peak times. Increasing this limit can allow more simultaneous connections, reducing the likelihood of timeouts.

Another factor to consider is server resource utilization. High CPU or memory usage on the MySQL instance can cause it to become unresponsive, leading to connection timeouts. Monitoring the server's performance during peak hours can help identify if it's under strain. If resource bottlenecks are detected, upgrading the instance to a machine type with more CPU and memory may be necessary.

Network latency and reliability can also impact connection stability. High latency or packet loss between the SQL Server and the MySQL instance can lead to failed connections. Ensuring that both servers are located in the same region or connected via a reliable VPN can minimize latency issues. Additionally, verifying that firewall rules and network configurations allow for uninterrupted communication is essential.

The Cloud SQL Auth Proxy, which facilitates secure connections to your Cloud SQL instance, might introduce its own limitations. It's important to ensure that the proxy is running on a machine with sufficient resources and that it's updated to the latest version. Implementing connection pooling can also help manage resources more efficiently by reusing existing connections rather than creating new ones for each request.

Adjusting timeout settings on both the MySQL server and the client side can provide more leeway for connections to establish and complete transactions. Even though you've already increased various timeout parameters, revisiting these settings in the context of your current workload might yield improvements. On the client side, modifying ODBC driver settings or linked server configurations to extend timeouts can prevent premature disconnections.

Optimizing your data insertion techniques can significantly reduce the load on both servers. Instead of executing multiple individual insert statements, batching them or using bulk insert operations can decrease the number of round trips and reduce overhead. Wrapping these operations in transactions can further enhance performance and reliability.

Lastly, reviewing detailed logs from both the MySQL server and Cloud SQL can offer insights into the root cause of the connection failures. Enabling comprehensive logging and monitoring can help pinpoint specific issues, whether they're related to resource constraints, network problems, or configuration errors.