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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><title>Saga over REST for microservices</title><meta content="yes" name="apple-mobile-web-app-capable"><meta content="black-translucent" name="apple-mobile-web-app-status-bar-style"><meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, minimal-ui" name="viewport"><link href="reveal.js/css/reveal.css" rel="stylesheet"><link rel="stylesheet" href="reveal.js/css/theme/redhat.css" id="theme"><link href="reveal.js/lib/css/zenburn.css" rel="stylesheet"><script>document.write( '<link rel="stylesheet" href="reveal.js/css/print/' + ( window.location.search.match( /print-pdf/gi ) ? 'pdf' : 'paper' ) + '.css" type="text/css" media="print">' );</script></head><body><div class="reveal"><div class="slides"><section class="title" data-state="title"><h1>Saga over REST for microservices</h1><div class="preamble"><div class="paragraph"><p>Ondra Chaloupka / <a href="mailto:ochaloup@redhat.com">ochaloup@redhat.com</a></p></div></div></section>
<section><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/wfly_narayana.png" alt="wfly narayana"></span></p></div>
<aside class="notes"><div class="ulist"><ul><li><p>Red Hat (<a href="https://developers.redhat.com" class="bare">https://developers.redhat.com</a>)</p></li><li><p>Wild Fly (<a href="http://wildfly.io" class="bare">http://wildfly.io</a>)</p></li><li><p>Naryana (<a href="http://narayana.io" class="bare">http://narayana.io</a>)</p></li></ul></div></aside></section>
<section><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/narayana_logo.png" alt="narayana logo"></span></p></div>
<div class="ulist"><ul><li><p>earlier <strong>Arjuna</strong>, renamed to <strong>Narayana</strong></p></li><li><p><strong>JTA</strong> implementation in JBoss/WildFly</p></li><li><p><strong>JTS</strong> distributed transaction over IIOP</p></li><li><p>webservice transactions (<strong>WS-AT/WS-BA</strong>)</p></li><li><p><strong>STM</strong> for <a href="http://vertx.io">Vert.x</a></p></li><li><p><strong>saga</strong> transactions over REST</p></li></ul></div></section>
<section id="_agenda"><h2>Agenda</h2><div class="ulist"><ul><li><p>What is meant under term <em>microservice</em> in scope of this presentation</p></li><li><p>How the the distributed transactions and 2PC works</p></li><li><p>What is saga and why could be good fit for microservice architecture</p></li><li><p>What are and how to use Narayana Long Running Actions</p></li></ul></div></section>
<section data-background-image="./misc/saga/kleppmann-txn-msa-quotation.png" data-background-size="cover"></section>
<section id="_microservice_architecture"><h2>Microservice architecture</h2><div class="paragraph"><p><span class="image noborder stretch"><img src="./misc/saga/posta-msa.png" alt="posta msa"></span></p></div>
<div class="paragraph"><p>(<em>credit: Christian Posta, <a href="http://blog.christianposta.com" class="bare">http://blog.christianposta.com</a></em>)</p></div>
<aside class="notes"><div class="ulist"><ul><li><p>Martin Fowler: <a href="https://martinfowler.com/articles/microservices.html" class="bare">https://martinfowler.com/articles/microservices.html</a></p></li><li><p>Burr Sutter: <a href="https://www.youtube.com/watch?v=35_yWad7IiQ" class="bare">https://www.youtube.com/watch?v=35_yWad7IiQ</a></p></li><li><p>Christian Posta: <a href="http://blog.christianposta.com/microservices/the-hardest-part-about-microservices-data" class="bare">http://blog.christianposta.com/microservices/the-hardest-part-about-microservices-data</a></p></li></ul></div></aside></section>
<section id="_distributed_transactions"><h2>Distributed transactions</h2><div class="paragraph stretch"><p><span class="image noborder stretch"><img src="./misc/saga/posta-msa-with-wfly.png" alt="posta msa with wfly"></span></p></div></section>
<section id="_an_acid_transaction"><h2>An ACID transaction</h2><div class="ulist"><ul><li><p>An atomic unit of the work where everything or nothing is finished</p><div class="ulist"><ul><li><p>usually in regards of data manipulation</p></li></ul></div></li><li><p>Protecting shared resources from multiple users</p></li><li><p>A notion of a global consensus</p></li><li><p>ACID properties guaranteed</p></li></ul></div></section>
<section><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/test-tubes.png" alt="test tubes"></span></p></div>
<div class="ulist"><ul><li><p><span class="red">A</span>tomicity</p></li><li><p><span class="orange">C</span>onsistency</p></li><li><p><span class="green">I</span>solation</p></li><li><p><span class="blue">D</span>urability</p></li></ul></div>
<aside class="notes"><div class="dlist"><dl><dt class="hdlist1"><strong>Atomicity</strong></dt><dd><p>"all or nothing", all operations in a transaction succeed or every operation is rolled back</p></dd><dt class="hdlist1"><strong>Consistency</strong></dt><dd><p>on the completion of a transaction, the database is structurally sound
that covers e.g. preserve foreign keys, uniqueness defined by schema etc.</p></dd><dt class="hdlist1"><strong>Isolation</strong></dt><dd><p>transactions do not contend with one another. Contentious access to data is moderated by the database
so that transactions appear to run sequentially.</p></dd><dt class="hdlist1"><strong>Durability</strong></dt><dd><p>the results of applying a transaction are permanent, even in the presence of failures</p><div class="ulist"><ul><li><p>Martin Kleppmann: <a href="https://www.youtube.com/watch?v=5ZjhNTM8XU8" class="bare">https://www.youtube.com/watch?v=5ZjhNTM8XU8</a></p></li></ul></div></dd></dl></div></aside></section>
<section id="_distributed_vs_xa_transaction"><h2>Distributed vs. XA transaction</h2><div class="ulist"><ul><li><p>distributed transaction runs over multiple services</p></li><li><p>XA transaction joins operations over multiple resources</p></li></ul></div></section>
<section id="_xa_handling"><h2>XA handling</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/xa_handling.png" alt="xa handling"></span></p></div></section>
<section id="_xa_transaction_2pc"><h2>XA transaction: 2PC</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/2pc.png" alt="2pc"></span></p></div></section>
<section id="_demo"><h2>Demo</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/posta-msa-with-wfly-xa.png" alt="posta msa with wfly xa"></span></p></div>
<aside class="notes"><div class="ulist"><ul><li><p>XA transaction coordinates non-homogenous participants</p></li><li><p>scaling troubles in distributed environment</p></li><li><p><a href="https://developer.jboss.org/wiki/TwoPhaseCommit2PC" class="bare">https://developer.jboss.org/wiki/TwoPhaseCommit2PC</a></p></li></ul></div></aside></section>
<section id="_acid_distributed_transactions_assuming"><h2>ACID distributed transactions: assuming</h2><div class="ulist"><ul><li><p>closely coupled environment</p><div class="ulist"><ul><li><p>harder to scale</p></li><li><p>tight data coupling</p></li></ul></div></li><li><p>short duration</p><div class="ulist"><ul><li><p>locking reduces parallelism</p></li></ul></div></li></ul></div></section>
<section id="_microservice_architecture_expecting"><h2>Microservice architecture: expecting</h2><div class="ulist"><ul><li><p>loosely coupling</p></li><li><p>scaling</p></li><li><p>long duration activities</p></li></ul></div></section>
<section id="_sagas"><h2>Sagas</h2><div class="ulist"><ul><li><p>Transactional model for long living transaction</p></li><li><p>Saga paper (H. Garcia-Molina, K. Salem; 1987)</p></li><li><p>Relaxing ACID properties</p></li><li><p>Eventual consistent</p></li><li><p>Web services: WS-BA specification, SOA design pattern</p></li><li><p>REST and event sourcing: microservices</p></li></ul></div>
<aside class="notes"><div class="paragraph"><p>Original paper talks about Saga as a solution for long-lived database transactions.
We can use it for distributed environment too for not using two phase commit (a.k.a. locks).</p></div>
<div class="paragraph"><p>Other names:</p></div>
<div class="ulist"><ul><li><p>Sagas</p></li><li><p>Saga transactions</p></li><li><p>Saga actions</p></li><li><p>Business Activities (BA)</p></li><li><p>Long running actions (LRA)</p></li><li><p>Long Living transactions (LLT)</p></li><li><p><a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf" class="bare">https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf</a> (Princeton University, 1987)</p></li><li><p><a href="http://jbossts.blogspot.cz/2017/06/sagas-and-how-they-differ-from-two.html" class="bare">http://jbossts.blogspot.cz/2017/06/sagas-and-how-they-differ-from-two.html</a></p></li><li><p><a href="http://microservices.io/patterns/data/saga.html" class="bare">http://microservices.io/patterns/data/saga.html</a></p></li><li><p><a href="https://www.youtube.com/watch?v=0UTOLRTwOX0" class="bare">https://www.youtube.com/watch?v=0UTOLRTwOX0</a> (JOTB17, Distributed Sagas: A Protocol for Coordinating Microservices, Caitie McCaffrey)</p></li><li><p><a href="http://docs.oasis-open.org/ws-tx/wstx-wsba-1.1-spec-os/wstx-wsba-1.1-spec-os.html" class="bare">http://docs.oasis-open.org/ws-tx/wstx-wsba-1.1-spec-os/wstx-wsba-1.1-spec-os.html</a> (Web Services Business Activity, 2007)</p></li></ul></div></aside></section>
<section id="_sagas_2"><h2>Sagas (#2)</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/saga_confirm.png" alt="saga confirm"></span></p></div>
<div class="ulist"><ul><li><p>consists of a sequence of autonomous operations, each immediatelly visible to outer world</p></li><li><p>responsibility of failures handling to developer (handlers)</p></li><li><p>transaction manager is responsible for calling handlers</p></li></ul></div></section>
<section id="_sagas_3"><h2>Sagas (#3)</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/saga_compensate.png" alt="saga compensate"></span></p></div>
<div class="ulist"><ul><li><p>compensation handler defined by developer, called by transaction manager</p></li></ul></div></section>
<section id="_saga_transaction"><h2>Saga transaction</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/saga.png" alt="saga"></span></p></div>
<aside class="notes"><div class="paragraph"><p>The concept of the original paper talks about single node database but it could
be applied to distributed transactions (as was already shown).</p></div>
<div class="paragraph"><p>Saga could be classified as <code>Base</code> transaction (at least from my understanding)
as it does not lock resources a.k.a locks and letting data of resources being available
for other transactions to work with.</p></div>
<div class="paragraph"><p>As you could see the transaction handling introduced by Saga requires the application to
define compensation actions or define actions as idempotent (you can repeat operation on the
resource multiple times and you will get the same result - operation being repeated not leading to a different outcome).</p></div>
<div class="paragraph"><p>Still you can handle all the data integrity yourself in your application and design your system architecture
to handle with failures. It’s up to you if concept of Saga is useful for you or not.</p></div>
<div class="ulist"><ul><li><p><a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf" class="bare">https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf</a> (Sagas, Priceton University, 1987)</p></li><li><p><a href="http://queue.acm.org/detail.cfm?id=1394128" class="bare">http://queue.acm.org/detail.cfm?id=1394128</a> (Base: An Acid Alternative, base transactions)</p></li><li><p><a href="https://www.atomikos.com/Blog/ACAPSolutionProvingBrewerWrong" class="bare">https://www.atomikos.com/Blog/ACAPSolutionProvingBrewerWrong</a> (A CAP Solution (Proving Brewer Wrong) aka CQRS)</p></li></ul></div></aside></section>
<section id="_narayana_and_sagas"><h2>Narayana and Sagas</h2><div class="ulist"><ul><li><p>XTS: WS-BA (Web Services Business Activity)</p></li><li><p>Compensating transactions (CDI annotations)</p></li><li><p>LRA (Long Running Actions, over REST)</p></li></ul></div>
<aside class="notes"><div class="ulist"><ul><li><p><a href="https://developer.jboss.org/wiki/CompensatingTransactionsWhenACIDIsTooMuch" class="bare">https://developer.jboss.org/wiki/CompensatingTransactionsWhenACIDIsTooMuch</a> (Narayana: Compensating Transactions: When ACID is too much)</p></li></ul></div></aside></section>
<section id="_narayana_lra"><h2>Narayana LRA</h2><div class="ulist"><ul><li><p>LRA: Long Running Actions</p></li><li><p>Saga implementation for REST calls</p></li><li><p>based on the Eclipse MicroProfile stack (JAX-RS, CDI)</p></li></ul></div></section>
<section><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/microprofile.jpg" alt="microprofile" width="50%"></span></p></div>
<div class="ulist"><ul><li><p>Java EE stack for microservices</p></li><li><p><a href="https://github.com/jbosstm/microprofile-sandbox/blob/0009-LRA/proposals/0009-LRA/0009-LRA.md">LRA specification proposal, https://github.com/jbosstm/microprofile-sandbox</a></p></li><li><p><a href="https://groups.google.com/forum/#!msg/microprofile/CJirjFkM9Do/TrApz-fBDQAJ">Microprofile Google group, http://bit.ly/transactions-microprofile</a></p></li></ul></div></section>
<section id="_demo_2" data-transition="slide"><h2>Demo</h2><div class="paragraph"><p><span class="image noborder"><img src="./misc/saga/msa_calls.png" alt="msa calls"></span></p></div>
<aside class="notes"><div class="ulist"><ul><li><p><a href="https://github.com/redhat-helloworld-msa/helloworld-msa" class="bare">https://github.com/redhat-helloworld-msa/helloworld-msa</a></p></li><li><p><a href="https://developer.jboss.org/wiki/MSAQuickstartsWithLRAREST-ATOnMinishift" class="bare">https://developer.jboss.org/wiki/MSAQuickstartsWithLRAREST-ATOnMinishift</a></p></li></ul></div>
<div class="paragraph"><p>To get logs for the particular services:</p></div>
<div class="ulist"><ul><li><p><code>oc logs -f `oc get pods | grep ^ola | grep Running | awk '{ print $1 }'`</code></p></li><li><p><code>oc logs -f `oc get pods | grep ^hola | grep Running | awk '{ print $1 }'`</code></p></li><li><p><code>oc logs -f `oc get pods | grep ^aloha | grep Running | awk '{ print $1 }'`</code></p></li><li><p><code>oc logs -f `oc get pods | grep ^bonjour | grep Running | awk '{ print $1 }'`</code></p></li></ul></div></aside></section>
<section id="_summary"><h2>Summary</h2><div class="ulist"><ul><li><p>Narayana LRA - implementation of Saga for REST calls</p></li><li><p>a better fit for MSA than ACID transactions</p></li><li><p>a tool that can help in desiging the application</p><div class="ulist"><ul><li><p>MSA principles should be preserved</p></li></ul></div></li></ul></div></section>
<section id="_sources"><h2>Sources</h2><div class="ulist"><ul><li><p><a href="https://github.com/eclipse/microprofile-sandbox/tree/master/proposals/0009-LRA" class="bare">https://github.com/eclipse/microprofile-sandbox/tree/master/proposals/0009-LRA</a></p></li><li><p><a href="https://github.com/jbosstm/narayana/tree/master/rts/lra" class="bare">https://github.com/jbosstm/narayana/tree/master/rts/lra</a></p></li><li><p><a href="https://github.com/ochaloup/helloworld-msa/tree/lra" class="bare">https://github.com/ochaloup/helloworld-msa/tree/lra</a></p></li></ul></div></section>
<section><div class="paragraph"><p><span class="image noborder"><img src="./misc/entertain/cajk.jpg" alt="cajk" height="270"></span></p></div></section></div></div><script src="reveal.js/lib/js/head.min.js"></script><script src="reveal.js/js/reveal.js"></script><script>// See https://github.com/hakimel/reveal.js#configuration for a full list of configuration options
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