Distributed Data Structures

Apache Ignite® allows for most of the data structures from java.util.concurrent framework to be used in a distributed fashion. For example, you can take java.util.concurrent.BlockingDeque and add something to it on one node and poll it from another node. Or have a distributed ID generator, which would guarantee uniqueness of IDs on all nodes.

Supported Data Structures:

Code Examples:

                            Ignite ignite = Ignition.ignite();

                            // Non-colocated queue which will be distributed
                            // across all data nodes.
                            IgniteQueue<String> queue = ignite.queue("queueName", 20, new CollectionConfiguration());

                            // Add queue elements.
                            for (int i = 0; i < 20; i++)
                                queue.add("Value " + Integer.toString(i));

                            // Poll queue elements.
                            for (int i = 0; i < 20; i++)
                                System.out.println("Polled value: " + queue.poll());

                            Ignite ignite = Ignition.ignite();

                            // Initialize new set.
                            IgniteSet<String> set = ignite.set("setName", null);

                            // Add set elements.
                            for (int i = 0; i < 10; i++)
                                set.add(Integer.toString(i));

                            // Iterate over set.
                            for (String item : set)
                                System.out.println("Set item: " + item);

                            Ignite ignite = Ignition.ignite();

                            // Initialize atomic sequence.
                            IgniteAtomicSequence seq = ignite.atomicSequence("seqName", 0, true);

                            for (int i = 0; i < 100; i++)
                                System.out.println("Next sequence value: " + seq.incrementAndGet());

                            Ignite ignite = Ignition.ignite();

                            // Initialize atomic long.
                            IgniteAtomicLong atomicLong = ignite.atomicLong("myAtomicLong", 0, true);

                            for (int i = 0; i < 100; i++)
                                System.out.println("Incremented value: " + atomicLong.incrementAndGet());

                            Ignite ignite = Ignition.ignite();

                            String val = "123";

                            // Initialize distributed atomic reference.
                            IgniteAtomicReference<String> ref = ignite.atomicReference(refName, val, true);

                            ref.compareAndSet(val, "456");

                            Ignite ignite = Ignition.ignite();

                            // Initialize distributed count down latch.
                            final IgniteCountDownLatch latch = ignite.countDownLatch(latchName, 10, false, true);

                            IgniteCompute asyncCompute = ignite.compute().withAsync();

                            // Asynchronously execute closures on the cluster
                            // which will simply count down the latch on remote nodes.
                            for (int i = 0; i < 10; i++)
                                asyncCompute.run(() -> latch.countDown());

                            // Wait for all closures to complete.
                            latch.await();

GitHub Examples:

Also see data structure examples available on GitHub.

Data Structure Features

Feature	Description
Queue and Set	Ignite provides an implementation of a fast Distributed Blocking Queue and Distributed Set. Docs for this feature
Collocated vs. Non-Collocated	Queues and Sets can be deployed in `collocated` or `non-collocated` mode. In collocated mode all the elements of a collection will reside on the same cluster node. This mode should be used for relatively small collections. In non-collocated mode, the elements of the collection will be equally distributed within the cluster allowing to keep very large collections in memory. Docs for this Feature
Bounded Queues	Bounded queues allow users to have queues with predefined maximum size which gives a better control over the overall cache capacity. Docs for this Feature
Atomic Types	Ignite supports distributed AtomicLong and AtomicReference. Docs for this feature
CountDownLatch	Ignite CountDownLatch allows you to synchronize jobs on all Ignite nodes. Docs for this feature
Reservation-based ID Generator	ID Generator is implemented with `AtomicSequence`. Whenever you perform `incrementAndGet()` (or any other atomic operation) on an atomic sequence, the data structure reserves ahead a range of values, which are guaranteed to be unique across the cluster for this sequence instance. Docs for this Feature
Semaphore	Ignite's distributed semaphore implementation and behavior is similar to java.util.concurrent.Semaphore. Docs for this feature