akka | Build highly concurrent , distributed , and resilient message

 by   akka Scala Version: 2.2.0-RC2 License: Non-SPDX

kandi X-RAY | akka Summary

kandi X-RAY | akka Summary

akka is a Scala library typically used in Programming Style applications. akka has no bugs and it has medium support. However akka has 1 vulnerabilities and it has a Non-SPDX License. You can download it from GitHub.

Akka [Latest version] Status(

            kandi-support Support

              akka has a medium active ecosystem.
              It has 12696 star(s) with 3606 fork(s). There are 590 watchers for this library.
              It had no major release in the last 12 months.
              There are 887 open issues and 7022 have been closed. On average issues are closed in 346 days. There are 24 open pull requests and 0 closed requests.
              It has a neutral sentiment in the developer community.
              The latest version of akka is 2.2.0-RC2

            kandi-Quality Quality

              akka has no bugs reported.

            kandi-Security Security

              akka has 1 vulnerability issues reported (1 critical, 0 high, 0 medium, 0 low).

            kandi-License License

              akka has a Non-SPDX License.
              Non-SPDX licenses can be open source with a non SPDX compliant license, or non open source licenses, and you need to review them closely before use.

            kandi-Reuse Reuse

              akka releases are available to install and integrate.
              Installation instructions are not available. Examples and code snippets are available.

            Top functions reviewed by kandi - BETA

            kandi's functional review helps you automatically verify the functionalities of the libraries and avoid rework.
            Currently covering the most popular Java, JavaScript and Python libraries. See a Sample of akka
            Get all kandi verified functions for this library.

            akka Key Features

            No Key Features are available at this moment for akka.

            akka Examples and Code Snippets

            Returns a web socket that listens to Akka streams .
            javadot img1Lines of Code : 13dot img1License : Permissive (MIT License)
            copy iconCopy
            public WebSocket akkaStreamsSocket() {
                    return WebSocket.Json.accept(
                      request -> {
                          Sink in = Sink.foreach(System.out::println);
                          MessageDTO messageDTO = new MessageDTO("1", "1", "Title", "Test Body");

            Community Discussions


            Appropriate Future Handling in Akka Actors Typed
            Asked 2022-Mar-28 at 02:34

            What is the proper way to handle Futures from inside an Akka (typed) Actor?

            For example, assume there is an Actor OrderActor that receives Commands to place orders... which it does by making an http call to an external service. Since these are http calls to an external service, Futures are involved. So, what is the right way to handle that Future from within the Actor.

            I read something about the pipeTo pattern. Is that what needs to happen here or something else?



            Answered 2022-Mar-28 at 02:34

            It's generally best to avoid doing Future transformations (map, flatMap, foreach, etc.) inside an actor. There's a distinct risk that some mutable state within the actor isn't what you expect it to be when the transformation runs. In Akka Classic, perhaps the most pernicious form of this would result in sending a reply to the wrong actor.

            Akka Typed (especially in the functional API) reduces a lot of the mutable state which could cause trouble, but it's still generally a good idea to pipe the Future as a message to the actor.

            So if orderFacade.placeOrder results in a Future[OrderResponse], you might add subclasses of OrderCommand like this

            Source https://stackoverflow.com/questions/71639985


            Can an Akka Actor Handle Multiple Message Types in Akka Typed
            Asked 2022-Mar-27 at 13:20

            Is it possible to handle multiple message types from a single actor.

            For example, assume there is an actor called TradingStrategy that trades stocks. It takes in pricing data pumped in from another Actor. When it decides to place a trade, it sends a message to an another Actor, call it OrderActor, to place a trade. But the TradingStrategy Actor is interested in knowing whether or not the order placed was successful or rejected, etc... because it may change its strategy based on the results from the place order action. In this example, it seems the TradingStrategy needs to handle messages for pricing updates AND order updates. Is this possible with Akka typed? Are there ways to handle this situation?

            Here is a code example: IEXData is the data message.



            Answered 2022-Mar-27 at 13:20

            TradingStrategy's protocol would have to include messages indicating order updates. A TradingStrategy actor can register a message adapter which will translate the messages sent by the order actor into TradingStrategy's protocol: the TradingStrategy can present the "virtual" ActorRef returned by the message adapter to the order actor without the order actor knowing that its a TradingStrategy.

            Source https://stackoverflow.com/questions/71636528


            Cloud2Edge package: error connectivity:connection.id.enforcement.failed
            Asked 2022-Feb-14 at 07:56

            I'm testing a deployment of the Eclipse IoT Cloud2Edge package and have followed the instructions here https://www.eclipse.org/packages/packages/cloud2edge/tour/ to test. After creating the new tenant and device, and configuring the connection between Hono and Ditto, I can send telemetry to the new device via the Hono http adapter as shown here:



            Answered 2022-Feb-14 at 07:56

            What you configured is the Connection source enforcement which makes sure that a Hono device (identified via the AMQP header device_id) may only updates the twin with the same "thing id" in Ditto.

            That enforcement fails as your thingId you set in the Ditto Protocol JSON is my-tenant:org.acme:my-device-1 - the topic's first segment is the namespace, the second segment the name - combined those 2 segments become the "thing ID", see also: Protocol topic specification.

            So you probably want to send the following message instead:

            Source https://stackoverflow.com/questions/71104483


            Kotlin: Is there a tool that allows me to control parallelism when executing suspend functions?
            Asked 2022-Feb-07 at 22:37

            I'm trying to execute certain suspend function multiple times, in such a way that never more than N of these are being executed at the same time.

            For those acquainted with Akka and Scala Streaming libraries, something like mapAsync.

            I did my own implementation using one input channel (as in kotlin channels) and N output channels. But it seems cumbersome and not very efficient.

            The code I'm currently using is somewhat like this:



            Answered 2022-Feb-07 at 15:51

            You can use the limitedParallelism-function on a Dispatcher (experimental in v1.6.0), and use the returned dispatcher to call your asynchronous functions. The function returns a view over the original dispatcher which limits the parallelism to a limit you provide. You can use it like this:

            Source https://stackoverflow.com/questions/71021135


            How to select a specific overload of a method?
            Asked 2021-Dec-07 at 00:45

            I'm calling a C# API which uses overloads and optional parameters. Unfortunately, one of the overloads is a params object[] and F# selects it over a more specific overload which I intend to call. How do I make F# select the overload I want?

            Here's a small repro. And here is a link to the actual API.



            Answered 2021-Dec-07 at 00:45

            To call the expression version with two arguments, you need:

            Source https://stackoverflow.com/questions/70253567


            Comprehension of Actor with ExecutionContext
            Asked 2021-Nov-27 at 18:23

            As I understand Akka parallelism, to handle each incoming message Actor use one thread. And this thread contains one state. As is it so, sequential messages does't share this states.

            But Actor may have an ExecutorContext for execute callbacks from Future. And this is the point, where I stop understanding parallelism clearly.

            For example we have the following actor:



            Answered 2021-Nov-27 at 18:23

            Broadly, actors run on an dispatcher which selects a thread from a pool and runs that actor's Receive for some number of messages from the mailbox. There is no guarantee in general that an actor will run on a given thread (ignoring vacuous examples like a pool with a single thread, or a dispatcher which always runs a given actor in a specific thread).

            That dispatcher is also a Scala ExecutionContext which allows arbitrary tasks to be scheduled for execution on its thread pool; such tasks include Future callbacks.

            So in your actor, what happens when a messageA is received?

            • The actor calls createApi() and saves it
            • It calls the callA method on api
            • It closes api
            • It arranges to forward the result of callA when it's available to the sender
            • It is now ready to process another message and may or may not actually process another message

            What this actually means depends on what callA does. If callA schedules a task on the execution context, it will return the future as soon as the task is scheduled and the callbacks have been arranged; there is no guarantee that the task or callbacks have been executed when the future is returned. As soon as the future is returned, your actor closes api (so this might happen at any point in the task's or callbacks' execution).

            In short, depending on how api is implemented (and you might not have control over how it's implemented) and on the implementation details, the following ordering is possible

            • Thread1 (processing messageA) sets up tasks in the dispatcher
            • Thread1 closes api and arranges for the result to be piped
            • Thread2 starts executing task
            • Thread1 moves on to processing some other message
            • Thread2's task fails because api has been closed

            In short, when mixing Futures and actors, the "single-threaded illusion" in Akka can be broken: it becomes possible for arbitrarily many threads to manipulate the actor's state.

            In this example, because the only shared state between Futureland and actorland is local to the processing of a single message, it's not that bad: the general rule in force here is:

            • As soon as you hand mutable (e.g. closeable) state from an actor to a future (this includes, unless you can be absolutely sure what's happening, calling a method on that stateful object which returns a future), it's best for the actor to forget about the existence of that object

            How then to close api?

            Well, assuming that callA isn't doing anything funky with api (like saving the instance in some pool of instances), after messageA is done processing and the future is completed, nothing has access to api. So the simplest, and likely most correct, thing to do is arrange for api to be closed after the future has completed, along these lines

            Source https://stackoverflow.com/questions/70137297


            How to keep my incoming websocket connection open all the time?
            Asked 2021-Nov-05 at 11:41

            I connected to my websocket service using this sample code client, but currently it just connects and then shutsdown.

            How can I keep this connection open and never close it?

            Once I make a connection, I want it to remain open until I shutdown the application.



            Answered 2021-Oct-19 at 10:28

            The Akka docs call out your situation:

            The Akka HTTP WebSocket API does not support half-closed connections which means that if either stream completes the entire connection is closed (after a “Closing Handshake” has been exchanged or a timeout of 3 seconds has passed).

            In your case, outgoing (being a Source.single) completes as soon as it has emitted the TextMessage. The webSocketFlow receives the completion message and then tears down the connection.

            The solution is to delay when outgoing completes, perhaps even delaying it forever (or at least until the application is killed).

            Two standard sources are potentially useful for delaying completion in the scenario where you don't want to send messages through the websocket.

            • Source.maybe materializes as a Promise which you can complete with an optional terminating message. It will not complete unless and until the promise is completed.

            • Source.never never completes. You could achieve this by just not completing Source.maybe, but this is less overhead than that.

            So what would it look like in code?

            Source https://stackoverflow.com/questions/69570037


            How to create a child actor in akka.net using F#?
            Asked 2021-Oct-09 at 10:06

            I have two actors - childActor and parentActor



            Answered 2021-Oct-09 at 10:06

            IActorRefFactory is an interface responsible for determining a parent and in case of Akka.FSharp it's implemented by ActorSystem and Actor<_> as well. So in your case just use:

            Source https://stackoverflow.com/questions/69505237


            Akka HTTP client server idle timeouts are not working
            Asked 2021-Aug-17 at 16:19

            I have written an API that takes couple of minutes to create a response. This apparently results in connection resets:



            Answered 2021-Aug-17 at 16:19

            There were two mistakes I found, fixing which solved the problem.

            Mistake 1

            I was forgetting to pass appConf as an argument while creating an instance of ActorSystem, without which ActorSystem was always getting created with default akka configs. Hence always make sure to pass appConf while creating an instance of ActorSystem otherwise your akka configurations will never take effect.


            Source https://stackoverflow.com/questions/68807082


            Multi dc replication using two Yugabyte instances
            Asked 2021-Jul-28 at 17:42

            I'm running the sample project from How to setup akka persistence project : https://developer.lightbend.com/start/?group=akka&project=akka-samples-persistence-dc-java




            Answered 2021-Jul-28 at 17:42

            Note that you're using the web interface to connect. The YCQL api is available on the 9042 port.

            Also note that akka will use the default Cassandra driver. And it's best to use the YugabyteDB fork: https://github.com/yugabyte/cassandra-java-driver

            Then you can also see how to setup a cluster in multiple regions https://docs.yugabyte.com/latest/deploy/multi-dc/

            Source https://stackoverflow.com/questions/68556458

            Community Discussions, Code Snippets contain sources that include Stack Exchange Network


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