We can experiment with software transactional memory in akka built on top of scalastm. Software transactional memories for scala request pdf. This shows a simple hit counter implemented with software transactional memory stm, using the akka module for the play. If they did come out with hardware based transactional memory it would be after the fact of. Download software transactional memory in scala for free. Akka is using actors together with software transactional memory stm to create a unified runtime and programming model for scaling both. Weve built a lightweight software transactional memory for scala, inspired by the stms in haskell and clojure while taking advantage of scalas power and performance. Any realworld experience using software transactional memory. In computer science, software transactional memory stm is a concurrency control mechanism analogous to database transactions for controlling access to shared memory in concurrent computing. I believe akka has a number of other dimensions like how it handles failures, supervisors, etc. Here, only atomicity, consistency and isolation are satisfied because the mechanism runs inmemory.
Stm is a strategy implemented in software, rather than as a hardware component. Akka is using the actor model together with software transactional memory stm to raise the abstraction level and provides a better platform to. Akka actors may be distributed or combined with software transactional memory. Akka is an open source, eventdriven middleware project. A software transactional memory stm is a shared object which behaves like a memory that supports muldequeue begintransaction deleteditemreadtransactionalhead if deleteditemnull returnedvalueempty else ritetransactionalhead, deleteditemc. Akka is designed to run in a distributed environment using a pure messagepassing, asynchronous strategy. Scala provides one more platform and tool to deal with concurrency known as akka. Backed up by the cassandra highly scalable, eventually consistent, distributed, structured keyvalue store. An stm turns the java heap into a transactional data set with begincommit rollback semantics. Software transactional memory java akka documentation documentation. Akka is the platform for the next generation eventdriven, scalable and faulttolerant architectures on the jvm we believe that writing correct concurrent, fau. Akka provides a eventually consistent transactional persistent map, vector and ref. Akka is a toolkit for building highly concurrent, distributed, and resilient messagedriven applications for java and scala. From a programmers perspective stm is a way of handling concurrent reads and writes.
Software transactional memory nir shavit dan touitou mit and telaviv university abstract as we learn from the literature, flexibility in choosing synchroniation operations greatly simplifies the task of designing highly concurrent programs. Software transactional memory scala akka documentation. Please take the time to read this excellent document and view this presentation by rich hickey the genius behind clojure, since it forms the basis of akkas view on stm and state in general. Using the actor model together with software transactional memory we raise the abstraction level and provides a better platform to. Using the actor model together with software transactional memory we raise the abstraction level and provide a better platform to build correct concurrent and. However, scala is known for generating somewhat slower code than java so i would expect java with fibers to. This rule looks a lot like the volatile variable rule from. Software transactional memory in java using multiverse. The stm works with both persistent datastructures and inmemory datastructures see below. Akka s stm implements the concept in clojures stm view on state in general. In proceedings of the 34th annual international symposium on.
Akka an open source, eventdriven middleware project. Scalastm librarybased software transactional memory for scala. Using the actor model together with software transactional memory we raise the abstraction level and provide a better platform. Does anybody knows good example of architecture src or text or diagram or blueprints that uses akka actors or software transaction memory and implement persistence at the end. Refs are memory cells, holding an arbitrary immutable value, that implement cas compareandswap semantics and are managed and enforced by the stm for coordinated changes across many refs. Software transactional memory provides a viable option towards these use cases, as has been implemented in clojure and haskell. For faulttolerance akka adopts the let it crash, also called embrace failure, model which have been used with great success in the telecom industry to. Combine actors with software transaction memory stm to form transactional actors, which allow for atomic message flows and. Software transactional memory stm is a concept ported from the sql database world where each operation is executed within transactions that satisfy acid atomicity, consistency, isolation, durability properties. Weve built a lightweight software transactional memory for scala, inspired by the stms in haskell and clojure while. Akka is using the actors together with software transactional memory stm to create a unified runtime and programming model for scaling both up utilizing multicore processors and out.
Please take the time to read this excellent document and view this presentation by rich hickey the genius behind clojure, since it forms the basis of akka s view on stm and state in general. Software transactional memory stm has become a popular alternative to conventional synchronization models, both as programming language libraries 17, 25, 40 and as standalone systems 1. Akka simpler scalability, faulttolerance, concurrency. The mentioned above akka framework combines the facilities of actors and transactional memory receiving agents and transactors, which will blow your mind. If you dont know it, check out part 1 of this post. Microsofts experiments with software transactional memory. Library that offers users an easy to use interface to synchronize shared data access following the software transactional memory principle. This rule looks a lot like the volatile variable rule from the jmm. Ive been experimenting with software transactional memory stm in scala. Akka uses the actor model together with software transactional memory to raise the abstraction level and provide a better platform to build correct concurrent and scalable applications. Introduced notion of software transactional memory approach to concurrency based on the use of transactions to update identities or refs that have a mutable association with an immutable value at any one point in time, the ref has one and only one value in a transaction, we can change the refs association to a different.
Convenience ive looked at nathan bronsons ccstm and daniel spiewaks blog impl. In addition to stm, akka provides several other concurrency abstractions. Scala software transactional memory and akka actorsagents. Clojure in particular has an excellent implementation which uses mvcc multiversion concurrency control rather than a rolling commit log. On the other hand shared mutable atomicinteger is far from akkas share. My solution was to scalastm with actors accessing a singletonshared tmap. Akka, designed by jonas boner, offers transactors, that combine the benefits of actors and stm, along with a pluggable storage model. Net high level outline here, gonna teach you the model since only have 5 minutes no leslie lamport shit in here pebble story avoid dupes, ensure critical ops dont. Erlang and parts of akka are both designed to help ease programming when its already known that the actor model is the more appropriate construct to implement concurrency. The stm is based on transactional references referred to as refs. Dana groff has announced the end of microsofts experiment with software transactional memory for the. To address this problem, akka uses software transactional memory stm, which makes it possible to modify the state of many objects at once, reverting all changes if the transaction fails. On the other hand shared mutable atomicinteger is far from akkas sharenothing spirit.
There are clearly some issues around convenience of apis and standardization, that id like to discuss. Software engineering stack exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle. Akkas software transactional memory stm also provides a happens before rule. Presuming that actor model is the appropriate construct in the given cont. An integrated hardwaresoftware approach to flexible transactional memory. However, multiple miners can receive data on the same entity. Both have a similar api, both with the same problems, which i think. Learn more scala software transactional memory and akka actorsagents. Stm cant provide durability, because memory isnt durable e. Akkas stm implements the concept in clojures stm view on state in general. Comparing languages for engineering server software.
Theyve done a bit on stm software transactional memory. Scala or clojure functional programming best practices. I hope this short post will get you interested in the series im. Software transactional memory you might have a feeling that a separate actor to simply wrap one int is an overkill. Akka is a separate open source framework that provides actorbased concurrency. Ill solve a classic concurrency problem all three ways and we can see which way is best. It is designed to allow developers to write simpler, correct concurrent applications using actors, stm software transactional memory and. Stack overflow for teams is a private, secure spot for you and your coworkers to find and share information. Scalastm librarybased software transactional memory for. Software transactional memory stm brings transactions to locations in memory that are referenced by variables see also peytonjones2007.
Akka will add support for terracotta, redis, memcached, voldemort, tokyo cabinettyrant and hazelcast shortly. Software transactional memory last updated february 22, 2020. Stm software transactional memory akka concurrency. I use multiple actors to query a data source and then i log incremental changes to text files. Software transactional memory scala akka documentation documentation. It provides a unified set of data structures managed by the stm and backed by a. When your code accesses some memory, you lock it up. Software transactional memory java akka documentation. The stm supported in akka is scalastm which will be soon included in the scala standard library the stm is based on transactional references referred to as refs. In computer science, software transactional memory stm is a concurrency control mechanism.
Scalastm is a single jar with no dependencies, and includes. Functional programming for java developers oreilly media. Akka transactors combine the actor model and stm to provide the best of both worlds allowing you to write transactional, asynchronous, eventbased message flow applications and gives you composed atomic arbitrary, deep message flows. Software transactional memory stm software transactional memory for composable message flows. Distributed transactions will come very soon, backed up by zookeeper. Software transactional memory akka documentation documentation. Any good exampleidea for transactional memory, actors, dataflow, tuple spaces in real life applications is welcome.
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