Re: [dotNetRDF-Support] "underlying connection was closed" errors when talking to Stardog

[Ron M. Z. <ro...@ze...>]

Thanks Rob. I have a message up on the Stardog forum to see if they have
any thoughts. I'll see what they say...


On Wed, Nov 12, 2014 at 4:32 AM, Rob Vesse <rv...@do...> wrote:

> Ron
>
> 1 - No idea why it would have changed, check with the Stardog folks to see
> if there have been any changes in their HTTP server implementation recently
>
> Particularly the fact that it tends to happen only with POSTs may imply
> some sort of issue on the server side.  Have you tried reproducing this
> using the same queries that fail via CURL or another SPARQL API?
>
> 2 - Well it is a proxy so it is doing something with the requests and adds
> an additional connection hop to the pathway.  Fiddler may be handling
> connections differently to .Net
>
> 3 - I'd prefer to see what the Stardog folks think before making these
> changes especially if there is a possibility of a bug in their server being
> the culprit.
>
> HTTP 1.0 is rather old now and there is a recent it is so infrequently
> used, one particular thing to be aware of is that it may not support more
> secure authentication mechanisms so you may be sending your Stardog
> credentials in clear text (or at best lightly encoded text) if you use HTTP
> 1.0
>
> Rob
>
> From: Ron Michael Zettlemoyer <ro...@ze...>
> Reply-To: dotNetRDF User Help and Support <
> dot...@li...>
> Date: Wednesday, 12 November 2014 02:59
> To: dotNetRDF User Help and Support <
> dot...@li...>
> Subject: [dotNetRDF-Support] "underlying connection was closed" errors
> when talking to Stardog
>
> I've just recently started getting these weird "The underlying connection
> was closed: A connection that was expected to be kept alive was closed by
> the server" errors when talking to a Stardog database. Here are the
> particulars:
>
>    - Mostly happens when the Stardog database is on a remote server - in
>    this case when I'm at home and querying a Windows 2012 server hosted at
>    Azure. When talking to the database locally from the same box (at Azure) it
>    rarely exhibits this behavior.
>    - Same thing happens if I query Stardog on a Linux server at Azure
>    - If I use a proxy between dotNetRDF and Stardog - like Fiddler - to
>    examine what's going on, it always works! But stop using the proxy and it
>    fails. Which makes it hard to diagnose.
>    - It only seems to fail when the SPARQL query is long and a POST is
>    necessary. GETs for query queries don't seem to fail.
>
> After playing around and Googling for a while, I found this post (
> http://stackoverflow.com/questions/13188058/httpwebrequest-the-underlying-connection-was-closed)
> that suggested setting these options in the WebRequest:
>
> request.KeepAlive = false;
> request.ProtocolVersion = HttpVersion.Version10;
>
> I added this to the CreateRequest function in BaseStardogConnector and it
> seems to have fixed the problem!
>
> So three questions:
>
> 1- Anyone have any ideas why this problem would seem to start for no
> reason, after it'd been working fine for months?
>
> 2- Any idea why proxying through Fiddler would hide the problem? Shouldn't
> it be passing the request straight through?
>
> 3- Is there any reason we shouldn't merge these changes into the codebase?
>
>
> - Ron
>
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