Is there BlockingMap as BlockingQueue in java?
I have simply used BlockingQueue<Map.Entry<K,V>> in the past. But recently, I came across this Blocking Map for Java. Haven’t used it myself, though.
java.util.concurrent
Hystrix command fails with “timed-out and no fallback available”
This is a Hystrix Command Timeout, this timeout is enabled by default per each command, you define the value using the property: execution.isolation.thread.timeoutInMilliseconds: This property sets the time in milliseconds after which the caller will observe a timeout and walk away from the command execution. Hystrix marks > the HystrixCommand as a TIMEOUT, and performs … Read more
Implementation of BlockingQueue: What are the differences between SynchronousQueue and LinkedBlockingQueue
SynchronousQueue is a very special kind of queue – it implements a rendezvous approach (producer waits until consumer is ready, consumer waits until producer is ready) behind the interface of Queue. Therefore you may need it only in the special cases when you need that particular semantics, for example, Single threading a task without queuing … Read more
How to give name to a callable Thread? [duplicate]
I’m currently doing it somewhat like this: someExecutor.execute(new Runnable() { @Override public void run() { final String orgName = Thread.currentThread().getName(); Thread.currentThread().setName(orgName + ” – My custom name here”); try { myAction(); } finally { Thread.currentThread().setName(orgName); } } });
Memory Consistency – happens-before relationship in Java [duplicate]
Modern CPUs don’t always write data to memory in the order it was updated, for example if you run the pseudo code (assuming variables are always stored to memory here for simplicity); a = 1 b = a + 1 …the CPU may very well write b to memory before it writes a to memory. … Read more
Thread safe Hash Map?
You are on the right track using ConcurrentHashMap. For each point: Check out the methods putIfAbsent and replace both are threadsafe and combine checking current state of hashmap and updating it into one atomic operation. The get method is not synchronized internally but will return the most recent value for the specified key available to … Read more
@GuardedBy , @ThreadSafe ,@NotThreadSafe
These are custom annotations that are not part of the standard JDK. To be able to use them in your code, you need to add a dependency. At jcip.net, there is a link to the library and its source in the bottom part of the page “Concurrency annotations: jar, javadoc, source“. Direct links: jar javadoc … Read more
ExecutorCompletionService? Why do need one if we have invokeAll?
Using a ExecutorCompletionService.poll/take, you are receiving the Futures as they finish, in completion order (more or less). Using ExecutorService.invokeAll, you do not have this power; you either block until are all completed, or you specify a timeout after which the incomplete are cancelled. static class SleepingCallable implements Callable<String> { final String name; final long period; … Read more
Do we need to make ConcurrentHashMap volatile?
If you can make it final then do that. If you cannot make it final then yes you would need to make it volatile. volatile applies to the field assignment and if it’s not final then there is a possibility (at least per the JMM) that a write of the CHM field by one thread … Read more
scala.concurrent.blocking – what does it actually do?
blocking is meant to act as a hint to the ExecutionContext that the contained code is blocking and could lead to thread starvation. This will give the thread pool a chance to spawn new threads in order to prevent starvation. This is what is meant by “adjust the runtime behavior”. It’s not magic though, and … Read more