Intermittent connection issue between webserver and database ("The network path was not found")
Several times a day, we are getting this error message in our logs when our front-end webserver (i-08a436fb2d0811658) attempts to connect to our database server (i-0ddd3807ec3bac491):
The network path was not found: 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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
The configuration of these EC2 instances has not changed in years, and this issue just randomly started a few days ago. We tried stopping the web server and starting it again, to hopefully move it to new hardware, but the issue persists. There are no warnings or errors in the event logs on the web server or the database server indicating what might be the cause. TCP is the primary protocol to communicate with SQL Server. The reference to "named pipes" above indicates it was used a the secondary protocol after the TCP connection failed.
Can someone please assist us in troubleshooting this issue. Thank you.
After 4 days of these intermittent connectivity issues, the issue suddenly stopped with no action on our part other than making a post here. I'm assuming AWS monitors these posts and intervenes behind the scenes on issues like this, and that is what got our issue resolved.
I only wish there would have been some sort of confirmation or feedback to us if that's what occurred.
This could be a DNS issue (lookup is failing) or some other network problem. Given that this is an intermittent problem the best thing to do is to raise a support case and have the team troubleshoot this with you.
Hi Brett and thanks for the reply. Those two servers are on a VPC and communicate via IP address, so a DNS issue was not the likely cause. I do agree with you that a network issue was likely to blame. It also appears it was likely resolved by AWS. I say that because after having dozens of these connectivity issues daily, starting randomly last Saturday, the issue suddenly stopped after I made my post here yesterday with no action on our part. If AWS did intervene behind the scenes as I suspect, it would have been nice to have someone confirm something was in fact fixed on your end.
We do not have a support contract with you, so there was no way for us to raise what we believed was likely a networking issue on your end short of making this post and hoping someone there saw it. It would be nice if there was a more direct way of alerting you guys to probably issues outside of our control like this was.
A support contract is the "more direct way of alerting you guys". The forum is here to provide best-effort guidance but is no substitute for being in touch with the support team. Yes, some of the team do watch the forums but because there's no way to relate your forum username to an AWS account it's not that helpful. Sure, publishing your EC2 instances ids means they can find that but even then the team can't delve into the account without your permission.
Business-level support is not that expensive; can be cancelled if you don't want it; and does provide SLAs for response times. Well worth the money if you're running critical workloads.
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