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@goldstift #DV14 #jsr236 Concurrency in Enterprise Java Alexander Heusingfeld

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— Junior programmers think concurrency is hard. Experienced programmers think concurrency is easy. Senior programmers think concurrency is hard. Unknown @goldstift #dv14 #jsr236

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There ain’t no fuzz about this, right? @goldstift #dv14 #jsr236

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Runnable myRunnable = new Runnable() { public void run() { // do stuff in Thread } }; Thread myThread = new Thread(myRunnable); myThread.start(); // ...and off we go! @goldstift #dv14 #jsr236

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Nooooooo! http://www.flickr.com/photos/girlaphid/3818224024/sizes/l/

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1. No management of Thread lifecycle 2. No management of number of Threads 3. Monitoring tedious/ almost impossible 4. No propagation of context

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*sigh* Got alternatives? http://www.flickr.com/photos/spanishflea/215064063/sizes/o/

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> java.util.concurrent?! @goldstift #dv14 #jsr236

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ExecutorServices > Executors.newSingleThreadExecutor() > Executors.newCachedThreadPool() > Executors.newFixedThreadPool() > Executors.newScheduledThreadPool() @goldstift #dv14 #jsr236

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> JSR236 > javax.enterprise.concurrent @goldstift #dv14 #jsr236

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Why should I be interested? @goldstift #dv14 #jsr236

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Patterns of software stability

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Patterns of software stability > Timeouts - executor timeouts provide fallbacks

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Patterns of software stability > Timeouts - executor timeouts provide fallbacks > Bulkheads - separate your application components

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Patterns of software stability > Timeouts - executor timeouts provide fallbacks > Bulkheads - separate your application components > Circuit Breaker - fail-fast if no threads available

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Patterns of software stability > Timeouts - executor timeouts provide fallbacks > Bulkheads - separate your application components > Circuit Breaker - fail-fast if no threads available > Steady State - free unused resources

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Patterns of software stability > Timeouts - executor timeouts provide fallbacks > Bulkheads - separate your application components > Circuit Breaker - fail-fast if no threads available > Steady State - free unused resources http://michaelnygard.com/

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What’s in it for the devs? @goldstift #dv14 #jsr236

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ManagedThreadFactory

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ManagedThreadFactory > extends the Java SE ThreadFactory > same API as Thread.newThread(Runnable) > Threads returned implement ManageableThread > Enables use of Java SE concurrency utilities like Executors @goldstift #dv14 #jsr236

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ExecutorServices for Java EE Executors.newSingleThreadExecutor(ThreadFactory) Executors.newCachedThreadPool(ThreadFactory) Executors.newFixedThreadPool(int, ThreadFactory) Executors.newScheduledThreadPool(int, ThreadFactory) @goldstift #dv14 #jsr236

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@Resource ManagedThreadFactory factory; protected void processRequest(ServiceRequestData data) { // Creating Java SE style ExecutorService ExecutorService executor = Executors.newFixedThreadPool(10, factory); Future f = executor.submit(new MyTask(data)); } @goldstift #dv14 #jsr236

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1 public class MyTask implements Runnable { 2 public void run() { 3 InitialContext ctx = null; 4 try { 5 ctx = new InitialContext(); 6 UserTransaction ut = (UserTransaction) ctx.lookup( 7 "java:comp/UserTransaction"); 8 ut.begin(); 9 while (!((ManageableThread) Thread.currentThread()).isShutdown()){ 10 11 // Perform transactional business logic? 12 } 13 // do cleanup 14 ut.commit(); 15 } catch (Exception ex) { 16 ex.printStackTrace(); 17 } 18 } 19 } @goldstift #dv14 #jsr236

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ManagedExecutorService

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ManagedExecutorService extends the Java SE ExecutorService methods for submitting tasks to Java EE environment available via JNDI look-up or @Resource injection Tasks must implement Runnable or Callable Lifecycle APIs disabled -> throw IllegalStateException @goldstift #dv14 #jsr236

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1 @Resource ManagedExecutorService mes; 2 3 protected String processRequest(ServiceRequest request) { 4 Future f = mes.submit(new Callable() { 5 public String call() { 6 // do something with context 7 return "result"; 8 } 9 }); 10 try { 11 return f.get(); 12 } catch (InterruptedException | ExecutionException ex) { 13 throw new IllegalStateException("Cannot get the answer", ex); 14 } 15 } @goldstift #dv14 #jsr236

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1 @Resource ManagedExecutorService mes; 2 3 class MyLongReturningTask implements Callable { . . . } 4 class MyDateReturningTask implements Callable { . . . } 5 6 protected void processRequest(ServiceRequest request) throws 7 ExecutionException { 8 9 ArrayList tasks = new ArrayList<(); 10 tasks.add(new MyLongReturningTask()); 11 tasks.add(new MyDateReturningTask()); 12 List> result = executor.invokeAll(tasks); 13 } @goldstift #dv14 #jsr236

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1 @WebServlet(urlPatterns = "/MyAsyncServlet", asyncSupported = true) 2 public class MyAsyncServlet extends HttpServlet { 3 4 @Resource ManagedExecutorService executor; 5 6 protected void doGet(HttpServletRequest request, HttpServletResponse 7 response) throws ServletException, IOException { 8 9 final AsyncContext ac = request.startAsync(); 10 Runnable task = new Runnable() { 11 public void run() { 12 // ... evaluate result 13 ac.getResponse().getWriter().print(result); 14 ac.complete(); 15 } 16 } 17 executor.submit(task); 18 } 19 } @goldstift #dv14 #jsr236

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ManagedScheduledExecutorService

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ManagedScheduledExecutorService > extends ManagedExecutorService > extends ScheduledExecutorService > additional methods to schedule tasks with new Trigger > new methods also return ScheduledFuture objects @goldstift #dv14 #jsr236

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@Resource ManagedScheduledExecutorService executor; protected void processRequest(ServiceRequest request) { ScheduledFuture f = executor.scheduleAtFixedRate( new MyRunnableTask(request), 5, 10, TimeUnit.SECONDS); } @goldstift #dv14 #jsr236

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1 public class MyTrigger implements Trigger { 2 3 private final Date firetime; 4 5 public MyTrigger(Date firetime) { this.firetime = firetime; } 6 7 @Override 8 public Date getNextRunTime(LastExecution le, Date taskScheduledTime) { 9 if (firetime.before(taskScheduledTime)) { 10 return null; 11 } 12 return firetime; 13 } 14 15 @Override 16 public boolean skipRun(LastExecution le, Date scheduledRunTime) { 17 return firetime.before(scheduledRunTime); 18 } 19 } @goldstift #dv14 #jsr236

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ContextService

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ContextService > creating contextual proxies > Examples of context: persistence, EJBs, security > customisable through ExecutionProperties > Can be run on transaction context of invoking thread (if any) @goldstift #dv14 #jsr236

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1 // within servlet or EJB method 2 @Resource ContextService service; 3 4 // Capture application context for later execution 5 IMessageProcessor processor = ...; 6 IMessageProcessor proxy = service.createContextualProxy(processor, 7 IMessageProcessor.class); 8 cache.put(IMessageProcessor.class, proxy); 12 // at a later time in a different thread retrieve the proxy from the cache 13 IMessageProcessor worker = cache.get(IMessageProcessor.class); 14 // and execute with the context of the servlet or EJB 15 worker.processMessage(msg); @goldstift #dv14 #jsr236

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ManagedTaskListener void taskSubmitted(java.util.concurrent.Future future, ManagedExecutorService executor, Object task) void taskStarting(java.util.concurrent.Future future, ManagedExecutorService executor, Object task) void taskAborted(java.util.concurrent.Future future, ManagedExecutorService executor, Object task, java.lang. Throwable exception) void taskDone(java.util.concurrent.Future future, ManagedExecutorService executor, Object task, java.lang.Throwable exception) @goldstift #dv14 #jsr236

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ManagedExecutors class // Register listener for task with specific executionProperties. // Adopts executionProperties of ManageableTask Runnable managedTask(Runnable, ManagedTaskListener) Runnable managedTask(Runnable, Map,
 ManagedTaskListener) Callable managedTask(Callable, ManagedTaskListener) Callable managedTask(Callable, Map, 
 ManagedTaskListener) // Checks “currentThread instanceof ManageableThread” ManagedExecutors.isCurrentThreadShutdown()

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DevOps: How do we do it? @goldstift #dv14 #jsr236

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Setup - CLI $JBOSS_HOME/bin/jboss-cli.sh —connect “/subsystem=ee/managed-executor- service=async-http-mes/:add(
 core-threads=20,
 jndi-name=java:comp/async-http-mes,
 context-service=default,
 hung-task-threshold=110000,
 keepalive-time=60000,
 thread-factory=default,
 queue-length=50,
 reject-policy=ABORT,
 max-threads=500)” @goldstift #dv14 #jsr236

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WildFly CLI - Monitoring $JBOSS_HOME/bin/jboss-cli.sh --connect "/subsystem=ee/managed-executor- service=async-http-mes/:read-resource(recursive-depth=0,include-runtime=true)" {
 "outcome" => "success",
 "result" => {
 "context-service" => "default",
 "core-threads" => 20,
 "hung-task-threshold" => 110000L,
 "jndi-name" => "java:jboss/ee/concurrency/executor/async-http-mes",
 "keepalive-time" => 60000L,
 "long-running-tasks" => false,
 "max-threads" => 500,
 "queue-length" => 50,
 "reject-policy" => "ABORT",
 "thread-factory" => "default"
 }
 } @goldstift #dv14 #jsr236

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Too complicated? @goldstift #dv14 #jsr236

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Wildfly CLI command WildFly CLI comes with a command builder gui: $JBOSS_HOME/bin/jboss-cli.sh --gui @goldstift #dv14 #jsr236

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Wildfly CLI command WildFly CLI comes with a command builder gui: $JBOSS_HOME/bin/jboss-cli.sh --gui @goldstift #dv14 #jsr236

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Still too complicated? @goldstift #dv14 #jsr236

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Management & Monitoring > Everything published as JMX MBeans > -> values > -> operations > -> metadata @goldstift #dv14 #jsr236

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Ok, are we fine? @goldstift #dv14 #jsr236

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Gotcha!! http://www.flickr.com/photos/upturnedface/2700127506/sizes/o/

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1. The single ExecutorService

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@Resource ManagedExecutorService mes;
 
 protected void processRequest(ServiceRequest request) throws
 ExecutionException {
 Future f = mes.submit(new Callable() {...});
 System.out.println(“Callable result: “ + f.get()); } @goldstift #dv14 #jsr236

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@Resource ManagedExecutorService mes;
 
 protected void processRequest(ServiceRequest request) throws
 ExecutionException {
 Future f = mes.submit(new Callable() {...});
 System.out.println(“Callable result: “ + f.get()); } @goldstift #dv14 #jsr236 Only used here??

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@Resource ManagedExecutorService mes;
 
 protected void processRequest(ServiceRequest request) throws
 ExecutionException {
 Future f = mes.submit(new Callable() {...});
 System.out.println(“Callable result: “ + f.get()); } @goldstift #dv14 #jsr236 Only used here?? @Resource(lookup=“java:comp/service-request-executor“)

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2. The queue that queued

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@Resource ManagedThreadFactory factory;
 
 protected void processRequest(ServiceRequestData data) {
 
 // Creating Java SE style ExecutorService
 BlockingQueue queue = new LinkedBlockingQueue(10);
 ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 10,
 0L, TimeUnit.MILLISECONDS,
 queue, 
 factory); 
 // MyRunnable has to implement .equals() and .hashcode()!!!
 MyRunnable task = new MyRunnable(data);
 
 // prevent duplicate queue entries
 if (!queue.contains(task)) {
 executor.submit(task);
 }
 } @goldstift #dv14 #jsr236

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@Resource ManagedThreadFactory factory;
 
 protected void processRequest(ServiceRequestData data) {
 
 // Creating Java SE style ExecutorService
 BlockingQueue queue = new LinkedBlockingQueue(10);
 ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 10,
 0L, TimeUnit.MILLISECONDS,
 queue, 
 factory); 
 // MyRunnable has to implement .equals() and .hashcode()!!!
 MyRunnable task = new MyRunnable(data);
 
 // prevent duplicate queue entries
 if (!queue.contains(task)) {
 executor.submit(task);
 }
 } @goldstift #dv14 #jsr236 .contains() locks queue!

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3. A self overtaking job

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@Resource ManagedScheduledExecutorService executor;
 
 protected void processRequest(ServiceRequest job) {
 ScheduledFuture f = executor.scheduleAtFixedRate(
 new MyRunnableTask(job), 5, 10, TimeUnit.SECONDS);
 
 }
 @goldstift #dv14 #jsr236

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4. Know your RejectionPolicy

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@goldstift #dv14 #jsr236 Competition from Spring

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@goldstift #dv14 #jsr236 Competition from Spring ManagedExecutors can only ABORT

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5. Go Java 8 and shine

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WildFly compatible with Java 8 @goldstift #dv14 #jsr236

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WildFly compatible with Java 8 Possibility to combine executors with @goldstift #dv14 #jsr236

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WildFly compatible with Java 8 Possibility to combine executors with -> Lambdas @goldstift #dv14 #jsr236

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WildFly compatible with Java 8 Possibility to combine executors with -> Lambdas -> Streams @goldstift #dv14 #jsr236

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WildFly compatible with Java 8 Possibility to combine executors with -> Lambdas -> Streams -> CompletableFuture @goldstift #dv14 #jsr236

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WildFly compatible with Java 8 Possibility to combine executors with -> Lambdas -> Streams -> CompletableFuture @goldstift #dv14 #jsr236

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WildFly compatible with Java 8 Possibility to combine executors with -> Lambdas -> Streams -> CompletableFuture Are you sure?? @goldstift #dv14 #jsr236

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Java 8 Streams API @goldstift #dv14 #jsr236

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Java 8 Streams API final List products = productUris.parallelStream()
 .map(productUri -> CompletableFuture.supplyAsync(() -> resolveProducts(productUri)))
 .map(CompletableFuture::join)
 .filter(res -> res.second.hasBody())
 .map(this::responsePairToProduct)
 .collect(Collectors.toList()); @goldstift #dv14 #jsr236

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Java 8 Streams API final List products = productUris.parallelStream()
 .map(productUri -> CompletableFuture.supplyAsync(() -> resolveProducts(productUri)))
 .map(CompletableFuture::join)
 .filter(res -> res.second.hasBody())
 .map(this::responsePairToProduct)
 .collect(Collectors.toList()); ForkJoinPool @goldstift #dv14 #jsr236

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Java 8 Streams API final List products = productUris.parallelStream()
 .map(productUri -> CompletableFuture.supplyAsync(() -> resolveProducts(productUri)))
 .map(CompletableFuture::join)
 .filter(res -> res.second.hasBody())
 .map(this::responsePairToProduct)
 .collect(Collectors.toList()); ForkJoinPool incompatible with ManagedThreads @goldstift #dv14 #jsr236

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Java 8 Streams API final List products = productUris.parallelStream()
 .map(productUri -> CompletableFuture.supplyAsync(() -> resolveProducts(productUri)))
 .map(CompletableFuture::join)
 .filter(res -> res.second.hasBody())
 .map(this::responsePairToProduct)
 .collect(Collectors.toList()); ForkJoinPool incompatible with ManagedThreads Cannot recommend to use parallel Streams API in Java EE! @goldstift #dv14 #jsr236

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No Java 8? Try Guava! https://code.google.com/p/guava-libraries/wiki/ListenableFutureExplained @goldstift #dv14 #jsr236

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No Java 8? Try Guava! https://code.google.com/p/guava-libraries/wiki/ListenableFutureExplained @goldstift #dv14 #jsr236 @Resource(name = "BackendCallExecutorService")
 ManagedExecutorService executor;


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No Java 8? Try Guava! https://code.google.com/p/guava-libraries/wiki/ListenableFutureExplained @goldstift #dv14 #jsr236 @Resource(name = "BackendCallExecutorService")
 ManagedExecutorService executor;
 final String productId = ...;
 ListeningExecutorService service = MoreExecutors.listeningDecorator(executor);

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No Java 8? Try Guava! https://code.google.com/p/guava-libraries/wiki/ListenableFutureExplained @goldstift #dv14 #jsr236 @Resource(name = "BackendCallExecutorService")
 ManagedExecutorService executor;
 final String productId = ...;
 ListeningExecutorService service = MoreExecutors.listeningDecorator(executor); 
 ListenableFuture product = service.submit(new Callable() {
 public Product call() {
 return resolveProduct(productId);
 }
 });


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No Java 8? Try Guava! https://code.google.com/p/guava-libraries/wiki/ListenableFutureExplained @goldstift #dv14 #jsr236 @Resource(name = "BackendCallExecutorService")
 ManagedExecutorService executor;
 final String productId = ...;
 ListeningExecutorService service = MoreExecutors.listeningDecorator(executor); 
 ListenableFuture product = service.submit(new Callable() {
 public Product call() {
 return resolveProduct(productId);
 }
 });
 Futures.addCallback(explosion, new FutureCallback() {
 public void onSuccess(Product product) {
 addProductToCart(product);
 }
 public void onFailure(Throwable thrown) { 
 offerFallbackProduct(); // business decision!!
 }
 });

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Anything else? http://www.flickr.com/photos/weaselmcfee/3721267658/sizes/o/

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sounds familiar? @goldstift #dv14 #jsr236

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sounds familiar? > Yes! Xebia came up with something alike for Spring in 2011 @goldstift #dv14 #jsr236

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sounds familiar? > Yes! Xebia came up with something alike for Spring in 2011 async-http-mes/:add(
 core-threads=20,
 jndi-name=java:comp/async-http-mes,
 context-service=default,
 hung-task-threshold=110000,
 keepalive-time=60000,
 thread-factory=default,
 queue-length=50,
 reject-policy=ABORT,
 max-threads=500) WildFly @goldstift #dv14 #jsr236

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sounds familiar? https://code.google.com/p/xebia-france/wiki/XebiaManagementExtras @goldstift #dv14 #jsr236

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sounds familiar? https://code.google.com/p/xebia-france/wiki/XebiaManagementExtras > Yes! Xebia came up with something alike for Spring in 2011 @goldstift #dv14 #jsr236

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A note on Hystrix > Netflix Hystrix is a well-known implementation of the stability patterns - especially Circuit-Breaker > Hystrix in Java EE is no free lunch > set env var 
 “-Dhystrix.plugin.HystrixConcurrencyStrategy.implementation=\
 full.package.of.MyConcurrencyStrategy” @goldstift #dv14 #jsr236

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Spring 4.0 supports JSR236 Provides configurability & monitoring via JSR236 -> ConcurrentTaskExecutor auto-detects JSR236 classes -> Uses specified ManagedExecutor transparently -> executor manageable via CLI or JMX -> Check the code, it’s open-source! @Github #4004e53 @goldstift #dv14 #jsr236

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Summary > good mix of convenience & flexibility > still potential for optimisation: > API to create ManagedExecutorService instead of defaults > validation/ constraints for ManagedExecutorService properties > Runtime.availableProcessors() for parallelism is deceptive!!! > Please become compatible with ForkJoinPool/ JDK8 Streams API @goldstift #dv14 #jsr236

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Links JSR236 spec: https://jcp.org/en/jsr/detail?id=236 Java EE 7 JavaDoc: http://docs.oracle.com/javaee/7/api/ Java EE 7 samples: https://github.com/javaee-samples/javaee7-samples Wildfly docs: https://docs.jboss.org/author/display/WFLY8/EE+Subsystem+Configuration @goldstift #dv14 #jsr236

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Thanks for your attention! Alexander Heusingfeld, @goldstift [email protected] https://www.innoq.com/people/alex/ @goldstift #dv14 #jsr236