Re: [akka-user][deprecated] Reliability of akka-streams and akka-http

2019-01-18 Thread Brian Maso 
Akka-streams (specifically the ActorMaterializer implementation of streams)
yields single-VM, ephemeral implementations of graphs.
Multi-VM/multi-restart message persistence is orthogonal to its design and
goals. You can use additional features of Akka (PersistentActors, DData,
Akka clusters and cluster sharding) to implement "eventually processed at
least once" behavior, but you'll need to employ more than just akka-streams
to do it. You'll need to add message persistence features in yourself.

Brian Maso

On Thu, Jan 17, 2019 at 10:08 PM adgang  wrote:

> This is a post(set of questions really) regarding the implications of
> at-most-once(maybe-once) delivery reliability offered by akka actors on
> APIs and software based on akka. From my understanding, even messages sent
> by actors to self can be lost.
>
> Till now, I have been in scenarios where delivery guarantee is not
> necessary so life was good. But now, I need reliability from my service at
> least to the extent that a subscriber should know that a message has been
> lost.
> 1. If messages can be lost in actor system, and akka-streams are based on
> actors, does that mean akka-streams are leaky? Thats pretty scary to think
> about. Specifically does a Flow(or GraphStage) ensure that stream entities
> are not lost?
> For example, is the below code(based on Source.single doc
> )
> guaranteed to print `[hello]`?
> import akka.stream.*;
>
> CompletionStage> future = Source.single("hello").runWith(
> Sink.seq(), materializer);
> CompletableFuture> completableFuture = future.
> toCompletableFuture();
> completableFuture.thenAccept(result -> System.out.println(result));
>
> 2. If messages can be lost in actor system, and akka-http is based on
> actors, does that mean akka-http APIs, lets say websocket API randomly
> drops messages.
> For example, in:
> http.singleWebSocketRequest(WebSocketRequest.create("wss://
> api.example.com"), flow, mat)
>
> is it at least guaranteed that my flow will reliably receive
> everything on the websocket in order?
> 3. In actor world, I would have a sequence number on each message and let
> the receiver actor take remedial measures on a lost(probably never because
> of at-most-once reliability issues so far) sequence number. In case we live
> in a dystopian world where the answers to 1. and 2. are yes, this wouldn't
> work because the external web service I consume does not implement sequence
> numbers. Because any sequence number I generate within the application will
> only add sequence numbers to messages that are not already lost. Is this a
> correct understanding?
>
> --
>
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> >>
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>> 
>>  Read the docs: http://akka.io/docs/
>>  Check the FAQ: 
>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>  Search the archives: https://groups.google.com/group/akka-user
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[akka-user][deprecated] Reliability of akka-streams and akka-http

2019-01-17 Thread adgang 
This is a post(set of questions really) regarding the implications of 
at-most-once(maybe-once) delivery reliability offered by akka actors on 
APIs and software based on akka. From my understanding, even messages sent 
by actors to self can be lost.

Till now, I have been in scenarios where delivery guarantee is not 
necessary so life was good. But now, I need reliability from my service at 
least to the extent that a subscriber should know that a message has been 
lost.
1. If messages can be lost in actor system, and akka-streams are based on 
actors, does that mean akka-streams are leaky? Thats pretty scary to think 
about. Specifically does a Flow(or GraphStage) ensure that stream entities 
are not lost?
For example, is the below code(based on Source.single doc 
) 
guaranteed to print `[hello]`?
import akka.stream.*;

CompletionStage> future = Source.single("hello").runWith(
Sink.seq(), materializer);
CompletableFuture> completableFuture = future.
toCompletableFuture();
completableFuture.thenAccept(result -> System.out.println(result));

2. If messages can be lost in actor system, and akka-http is based on 
actors, does that mean akka-http APIs, lets say websocket API randomly 
drops messages.
For example, in:
http.singleWebSocketRequest(WebSocketRequest.create(
"wss://api.example.com"), flow, mat)

is it at least guaranteed that my flow will reliably receive everything 
on the websocket in order?
3. In actor world, I would have a sequence number on each message and let 
the receiver actor take remedial measures on a lost(probably never because 
of at-most-once reliability issues so far) sequence number. In case we live 
in a dystopian world where the answers to 1. and 2. are yes, this wouldn't 
work because the external web service I consume does not implement sequence 
numbers. Because any sequence number I generate within the application will 
only add sequence numbers to messages that are not already lost. Is this a 
correct understanding? 

-- 
*
** New discussion forum: https://discuss.akka.io/ replacing akka-user 
google-group soon.
** This group will soon be put into read-only mode, and replaced by 
discuss.akka.io
** More details: https://akka.io/blog/news/2018/03/13/discuss.akka.io-announced
*
>> 
>>  Read the docs: http://akka.io/docs/
>>  Check the FAQ: 
>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>  Search the archives: https://groups.google.com/group/akka-user
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