Concurrent connection enforcement / no response from server

[Ron Michael Zettlemoyer]

I was wondering what is the expected response from Stardog if you hit the 8 concurrent connection limit in Community? I did some testing and it seems like you immediately get a 404 Unauthorized error. But I'm having weird cases where sometimes when my app queries Stardog I get no response at all back. Even when the app and Stardog are running on the same machine. Sometimes when this happens and I check the server, Stardog is using a lot of processor, so it's busy doing something, but I don't know what. (and I don't have enough data or complicated enough queries for it to be stuck doing anything that intensive) 

So I'm not sure if the concurrent connection restriction has anything to do with my issue.

I am running Stardog on a Windows 2012 server. Could it just be a Windows thing? I've been avoiding running Stardog on its own Linux server, just because this project is a startup and I'd rather not spin up and pay for a second cloud server if I don't need it... but if I really do need it, I'll do that.

[Mike Grove]

On Fri, Nov 7, 2014 at 10:00 AM, Ron Michael Zettlemoyer <r...@zettlemoyer.com> wrote:

I was wondering what is the expected response from Stardog if you hit the 8 concurrent connection limit in Community?

It'd block waiting for a free connection, and if that timed out, you'd get an exception (500 response code).

 

I did some testing and it seems like you immediately get a 404 Unauthorized error.

Which is it?  A 404 or an unauthorized error?

 

But I'm having weird cases where sometimes when my app queries Stardog I get no response at all back. Even when the app and Stardog are running on the same machine. Sometimes when this happens and I check the server, Stardog is using a lot of processor, so it's busy doing something, but I don't know what. (and I don't have enough data or complicated enough queries for it to be stuck doing anything that intensive) 

How are you accessing Stardog?  What are you doing?  What version of Stardog are you using?  What are the conditions we can use to reproduce the behavior?

Can you capture a thread-dump when it's busy?

 

So I'm not sure if the concurrent connection restriction has anything to do with my issue.

Probably not.

 

I am running Stardog on a Windows 2012 server. Could it just be a Windows thing? I've been avoiding running Stardog on its own Linux server, just because this project is a startup and I'd rather not spin up and pay for a second cloud server if I don't need it... but if I really do need it, I'll do that.

Hard to say.  Stardog should work the same on all environments, but there are some quirks that differ from system to system, such as how the host OS deals with memory mapped files.  But generally, running on Windows shouldn't be a problem.

Cheers,

Mike

 

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[Ron Michael Zettlemoyer]

Sorry. In testing, I was getting 401 Unauthorized every so often when I tried to intentionally overload the concurrent connection limit.

I was using 2.2.1 when I first tested this, with Stardog running on a remote Windows server hosted at Azure. Now I'm using again version 2.2.2. But now I'm no longer seeing 401s. I'm seeing timeouts, which sounds like is what I should expect; I just need to wait longer or retry.

Anyway, thanks for confirming what I should expect when there are no more free connections. That'll help a lot. I'll look at getting a thread dump if I see Stardog get busy without knowing why.