Akka Camel and Akka Streams

[Andreas Gies]

Hello HAkkers, 

we are maintaining an integration framework (OSGi) project built on top of ActiveMQ, Spray and Camel implemented in Scala [1]

Most of our internal API's rely on Akka and some also on the Akka-Camel integration. 

With the next major release we plan to upgrade our Spray routes to Akka-Http. Now that I have started looking at the concrete 

steps I have noticed that Akka-Camel is also deprecated and to be replaced with alpakka. 

I had a look through the Alpakka project. So far I haven't found the replacement for the Akka-Camel efforts in there. 

Perhaps I have overlooked something or is the replacement just on the roadmap ? 

Also I did have a look at the JMS part of Alpakka. It seems that this implementation currently only supports TextMessages 

and ignores any properties within the message. If I understand the implementation correctly, it would fail the stream in case 

of any JMSException and also when the buffer has been filled up ?

On a broader level I was wondering if the implementation should be in the form that the inbound stream fails if and only if 

the connection is irrecoverably broken and in other cases the Stream should reconnect transparently. 

Also on a broader level I have noticed, that the messages are acknowledged as soon as they pushed. Coming from a JMS

background that feels a bit strange to me, but that might be because I am unfamiliar with the streaming API. In our world 

a message is normally acknowledged when it has been processed successfully (which is normally it has been written to 

the file system, forwarded to another JMS destination or triggered some execution in the database). 

If the container crashes before it has acknowledged the message, the message will be redelivered. In cases we encounter 

an error we pass the message to an error handling destination or a retry destination. 

Apparently the architecture and the acceptance level of message loss changes when switching to a streaming approach. 

For now I have some concrete questions:

1) Have I missed the Camel replacement in Alpakka and if so, where is it located within Alpakka ?

2) How are others coping with the "window of potential message loss" when migrating from pure JMS flows to streams ?

3) Any pointers to good hands-on white papers are much appreciated. I have read through some and also through most 

    of the streams documentation, but I guess I need to get my hands dirty ... 

4) I don't dare to ask, but if anyone is using Akka / AkkaHttp and / or AkkaStream within OSGi I would be more than happy 

    to exchange experiences & ideas. 

[1] https://github.com/woq-blended/blended

Thanks in advance for your attention 

Best regards 

Andreas

[Martin Krasser]

Hi Andreas,

the replacement for akka-camel is the Streamz project with its Camel DSL for Akka Streams. It allows you to use any Camel component with Akka Streams for both inbound and outbound message exchanges. There is a Scala and Java API.

Best Regards,
Martin

[Konrad “ktoso” Malawski]

And it is listed under Alpakka projects too :-)

http://developer.lightbend.com/docs/alpakka/current/external-connectors.html#camel 

— Konrad

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[Andreas Gies]

Hi, 

thanks for the pointer to the Camel docs. I knew I had a blindspot somewhere.

Best regards 

Andreas

Am Dienstag, 11. Juli 2017 14:26:09 UTC+2 schrieb Andreas Gies:

[Sam D]

Martin,

Is there an Ack or Nack/Status.Failure mechanism with the new streamz camel api like in the akka-camel actor Consumer api?

Thanks,

Sam

[Martin Krasser]

Hi Sam,

not yet, only auto-acks at the moment. I created a ticket for application-level acks https://github.com/krasserm/streamz/issues/40. Feel free to comment if you think something is missing.

Cheers,
Martin

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