Apache Ignite Documentation

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Welcome to the Apache Ignite developer hub run by GridGain. Here you'll find comprehensive guides and documentation to help you start working with Apache Ignite as quickly as possible, as well as support if you get stuck.


GridGain also provides Community Edition which is a distribution of Apache Ignite made available by GridGain. It is the fastest and easiest way to get started with Apache Ignite. The Community Edition is generally more stable than the Apache Ignite release available from the Apache Ignite website and may contain extra bug fixes and features that have not made it yet into the release on the Apache website.


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Per-Node Shared State

Share state between jobs or services on a cluster node.


It is often useful to share a state between different compute jobs or different deployed services. For this purpose, Ignite provides a shared concurrent node-local-map available on each node.

IgniteCluster cluster = ignite.cluster();

ConcurrentMap<String, Integer> nodeLocalMap = cluster.nodeLocalMap();

Node-local values are similar to thread locals in that these values are not distributed and kept only on the local node. Node-local data can be used by compute jobs to share the state between executions. It can also be used by deployed services.


As an example, let's create a job which increments a node-local counter every time it executes on some node. This way, the node-local counter on each node will tell us how many times a job had executed on that cluster node.

IgniteCallable<Long> job = new IgniteCallable<Long>() {
  private Ignite ignite;
  public Long call() {                  
    // Get a reference to node local.
    ConcurrentMap<String, AtomicLong> nodeLocalMap = ignite.cluster().nodeLocalMap();

    AtomicLong cntr = nodeLocalMap.get("counter");

    if (cntr == null) {
      AtomicLong old = nodeLocalMap.putIfAbsent("counter", cntr = new AtomicLong());
      if (old != null)
        cntr = old;
    return cntr.incrementAndGet();

Now let's execute this job 2 times on the same node and make sure that the value of the counter is 2.

ClusterGroup random = ignite.cluster().forRandom();

IgniteCompute compute = ignite.compute(random);

// The first time the counter on the picked node will be initialized to 1.
Long res = compute.call(job);

assert res == 1;

// Now the counter will be incremented and will have value 2.
res = compute.call(job);

assert res == 2;

Updated 9 months ago

Per-Node Shared State

Share state between jobs or services on a cluster node.

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