StreamTcpException vs ConnectionException on HTTP outgoing connection

[Stephen Penney]

I am working on application that makes a request to a downstream service and want to identify if these fail due to a connection failure.

Currently using streams 1.0-M4, obtaining the connection with Http().outgoingConnection(address, port). When using the returned flow for a HttpRequest that should fail to connect it fails with a StreamTcpException("Connection failed."). Is this intentionally avoiding using the ConnectionException class and if so why is this beneficial? I want to avoid relying on the message text if possible.

I can't find any documentation in 1.0-M4 or 1.0-M5 for when the exceptions are thrown (looking at the ConnectionException is currently only thrown by the TcpListenStreamActor), so I want to check that I'm doing the right thing to identify these failures.

Thanks,
Stephen

[Akka Team]

On Fri, Apr 10, 2015 at 3:35 PM, Stephen Penney <stephen.pen...@gmail.com> wrote:

I am working on application that makes a request to a downstream service and want to identify if these fail due to a connection failure.

Currently using streams 1.0-M4, obtaining the connection with Http().outgoingConnection(address, port). When using the returned flow for a HttpRequest that should fail to connect it fails with a StreamTcpException("Connection failed."). Is this intentionally avoiding using the ConnectionException class and if so why is this beneficial?

We tend to wrap lower level exceptions into higher level ones. It would be nice if we could just provide semantic subclasses of that exception, but since the original ConnectionException does not give any other information than a localized, OS specific text, this probably won't happen.

 

I want to avoid relying on the message text if possible.

But how is that different from ConnectionException? It is localized even. In one of our tests we need to first provoke an aborted exception ("Connection reset by peer"), save it, and then use it in the assertions in the real tests (since the message might be "A távoli állomás kényszerítetten bezárta a kapcsolatot" or "拒绝连接" depending on our OS and locale).

-Endre

 

I can't find any documentation in 1.0-M4 or 1.0-M5 for when the exceptions are thrown (looking at the ConnectionException is currently only thrown by the TcpListenStreamActor), so I want to check that I'm doing the right thing to identify these failures.

Thanks,
Stephen

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[Stephen Penney]

Sorry I may not have made which ConnectionException I was expecting clear. I was talking about the ConnectionException in Akka streams which extends StreamTcpException. It is defined in https://github.com/akka/akka/blob/release-2.3-dev/akka-stream/src/main/scala/akka/stream/StreamTcpException.scala.

Looking at the name I was expecting that ConnectionException to be the error in the stream for connection failures and StreamTcpException for errors once the connection has been established (e.g. the remote server aborting the connection before sending the response). It would be nicer for my application if it behaved like this, however if there are no planned changes to this then the current implementation will work.