How to use

forRandom

method

in

org.apache.ignite.cluster.ClusterGroup

/**
 * @param loc Enforce local.
 * @return Local node cluster group.
 */
private ClusterGroup projection(boolean loc) {
  GridCacheContext<K, V> ctx = getContextSafe();
  if (loc || ctx.isLocal() || ctx.isReplicatedAffinityNode())
    return ctx.kernalContext().grid().cluster().forLocal();
  if (ctx.isReplicated())
    return ctx.kernalContext().grid().cluster().forDataNodes(cacheName).forRandom();
  return null;
}

/**
 * Compares checksums between primary and backup partitions of specified caches.
 * Works properly only on idle cluster - there may be false positive conflict reports if data in cluster is being
 * concurrently updated.
 *
 * @param ig Ignite instance.
 * @param caches Cache names (if null, all user caches will be verified).
 * @return Conflicts result.
 * @throws IgniteException If none caches or node found.
 */
protected IdleVerifyResultV2 idleVerify(Ignite ig, String... caches) {
  IgniteEx ig0 = (IgniteEx)ig;
  Set<String> cacheNames = new HashSet<>();
  if (F.isEmpty(caches))
    cacheNames.addAll(ig0.cacheNames());
  else
    Collections.addAll(cacheNames, caches);
  if (cacheNames.isEmpty())
    throw new IgniteException("None cache for checking.");
  ClusterNode node = !ig0.localNode().isClient() ? ig0.localNode() : ig0.cluster().forServers().forRandom().node();
  if (node == null)
    throw new IgniteException("None server node for verification.");
  VisorIdleVerifyTaskArg taskArg = new VisorIdleVerifyTaskArg(cacheNames);
  return ig.compute().execute(
    VisorIdleVerifyTaskV2.class.getName(),
    new VisorTaskArgument<>(node.id(), taskArg, false)
  );
}

/**
 * @throws Exception If failed.
 */
@Test
public void testEmptyGroup() throws Exception {
  ClusterGroup emptyGrp = ignite.cluster().forAttribute("nonExistent", "val");
  assertEquals(0, emptyGrp.forOldest().nodes().size());
  assertEquals(0, emptyGrp.forYoungest().nodes().size());
  assertEquals(0, emptyGrp.forAttribute("nonExistent2", "val").nodes().size());
  assertEquals(0, emptyGrp.forCacheNodes("cacheName").nodes().size());
  assertEquals(0, emptyGrp.forClientNodes("cacheName").nodes().size());
  assertEquals(0, emptyGrp.forClients().nodes().size());
  assertEquals(0, emptyGrp.forDaemons().nodes().size());
  assertEquals(0, emptyGrp.forDataNodes("cacheName").nodes().size());
  assertEquals(0, emptyGrp.forRandom().nodes().size());
  assertEquals(0, emptyGrp.forRemotes().nodes().size());
  assertEquals(0, emptyGrp.forServers().nodes().size());
  assertEquals(0, emptyGrp.forHost(ignite.cluster().localNode()).nodes().size());
  assertEquals(0, emptyGrp.forHost("127.0.0.1").nodes().size());
}

  /**
   * @throws Exception If failed.
   */
  @Test
  public void testSerializeClosure() throws Exception {
    Ignite client = ignite(CLIENT);

    final IgniteCache<Integer, Integer> clientCache = client.createCache(cacheConfiguration(PARTITIONED, ATOMIC));

    try {
      client.compute(client.cluster().forRemotes().forRandom()).call(new IgniteCallable<Object>() {
        @Override public Object call() throws Exception {
          clientCache.withKeepBinary();
          clientCache.withSkipStore();

          return null;
        }
      });
    }
    finally {
      client.destroyCache(DEFAULT_CACHE_NAME);
    }
  }
}

/**
 * @param loc Enforce local.
 * @return Local node cluster group.
 */
private ClusterGroup projection(boolean loc) {
  if (loc || ctx.isLocal() || ctx.isReplicatedAffinityNode())
    return ctx.kernalContext().grid().cluster().forLocal();
  if (ctx.isReplicated())
    return ctx.kernalContext().grid().cluster().forDataNodes(ctx.name()).forRandom();
  return null;
}