Data Streaming

String[] text = { "hello", "world", "hello", "Ignite" };
CacheConfiguration<String, Long> cfg = new CacheConfiguration<>("wordCountCache");

IgniteCache<String, Long> stmCache = ignite.getOrCreateCache(cfg);

try (IgniteDataStreamer<String, Long> stmr = ignite.dataStreamer(stmCache.getName())) {
    // Allow data updates.
    stmr.allowOverwrite(true);

    // Configure data transformation to count instances of the same word.
    stmr.receiver(StreamTransformer.from((e, arg) -> {
        // Get current count.
        Long val = e.getValue();

        // Increment count by 1.
        e.setValue(val == null ? 1L : val + 1);

        return null;
    }));

    // Stream words into the streamer cache.
    for (String word : text)
        stmr.addData(word, 1L);

}

class MyEntryProcessor : ICacheEntryProcessor<string, long, object, object>
{
    public object Process(IMutableCacheEntry<string, long> e, object arg)
    {
        //get current count
        var val = e.Value;

        //increment count by 1
        e.Value = val == 0 ? 1L : val + 1;

        return null;
    }
}

public static void StreamTransformerDemo()
{
    var ignite = Ignition.Start(new IgniteConfiguration
    {
        DiscoverySpi = new TcpDiscoverySpi
        {
            LocalPort = 48500,
            LocalPortRange = 20,
            IpFinder = new TcpDiscoveryStaticIpFinder
            {
                Endpoints = new[]
                {
                    "127.0.0.1:48500..48520"
                }
            }
        }
    });
    var cfg = new CacheConfiguration("wordCountCache");
    var stmCache = ignite.GetOrCreateCache<string, long>(cfg);

    using (var stmr = ignite.GetDataStreamer<string, long>(stmCache.Name))
    {
        //Allow data updates
        stmr.AllowOverwrite = true;

        //Configure data transformation to count instances of the same word
        stmr.Receiver = new StreamTransformer<string, long, object, object>(new MyEntryProcessor());

        //stream words into the streamer cache
        foreach (var word in GetWords())
        {
            stmr.AddData(word, 1L);
        }
    }

    Console.WriteLine(stmCache.Get("a"));
    Console.WriteLine(stmCache.Get("b"));
}

static IEnumerable<string> GetWords()
{
    //populate words list somehow
    return Enumerable.Repeat("a", 3).Concat(Enumerable.Repeat("b", 2));
}

This API is not presently available for C++.

static class Instrument {
    final String symbol;
    Double latest;
    Double high;
    Double low;

    public Instrument(String symbol) {
        this.symbol = symbol;
    }

}

static Map<String, Double> getMarketData() {
    //populate market data somehow
    return new HashMap<>();
}

@Test
void streamVisitorExample() {
    try (Ignite ignite = Ignition.start()) {
        CacheConfiguration<String, Double> mrktDataCfg = new CacheConfiguration<>("marketData");
        CacheConfiguration<String, Instrument> instCfg = new CacheConfiguration<>("instruments");

        // Cache for market data ticks streamed into the system.
        IgniteCache<String, Double> mrktData = ignite.getOrCreateCache(mrktDataCfg);

        // Cache for financial instruments.
        IgniteCache<String, Instrument> instCache = ignite.getOrCreateCache(instCfg);

        try (IgniteDataStreamer<String, Double> mktStmr = ignite.dataStreamer("marketData")) {
            // Note that we do not populate the 'marketData' cache (it remains empty).
            // Instead we update the 'instruments' cache based on the latest market price.
            mktStmr.receiver(StreamVisitor.from((cache, e) -> {
                String symbol = e.getKey();
                Double tick = e.getValue();

                Instrument inst = instCache.get(symbol);

                if (inst == null)
                    inst = new Instrument(symbol);

                // Update instrument price based on the latest market tick.
                inst.high = Math.max(inst.high, tick);
                inst.low = Math.min(inst.low, tick);
                inst.latest = tick;

                // Update the instrument cache.
                instCache.put(symbol, inst);
            }));

            // Stream market data into the cluster.
            Map<String, Double> marketData = getMarketData();
            for (Map.Entry<String, Double> tick : marketData.entrySet())
                mktStmr.addData(tick);
        }
    }
}

class Instrument
{
    public readonly string Symbol;
    public double Latest { get; set; }
    public double High { get; set; }
    public double Low { get; set; }

    public Instrument(string symbol)
    {
        this.Symbol = symbol;
    }
}

private static Dictionary<string, double> getMarketData()
{
    //populate market data somehow
    return new Dictionary<string, double>
    {
        ["foo"] = 1.0,
        ["foo"] = 2.0,
        ["foo"] = 3.0
    };
}

public static void StreamVisitorDemo()
{
    var ignite = Ignition.Start(new IgniteConfiguration
    {
        DiscoverySpi = new TcpDiscoverySpi
        {
            LocalPort = 48500,
            LocalPortRange = 20,
            IpFinder = new TcpDiscoveryStaticIpFinder
            {
                Endpoints = new[]
                {
                    "127.0.0.1:48500..48520"
                }
            }
        }
    });

    var mrktDataCfg = new CacheConfiguration("marketData");
    var instCfg = new CacheConfiguration("instruments");

    // Cache for market data ticks streamed into the system
    var mrktData = ignite.GetOrCreateCache<string, double>(mrktDataCfg);
    // Cache for financial instruments
    var instCache = ignite.GetOrCreateCache<string, Instrument>(instCfg);

    using (var mktStmr = ignite.GetDataStreamer<string, double>("marketData"))
    {
        // Note that we do not populate 'marketData' cache (it remains empty).
        // Instead we update the 'instruments' cache based on the latest market price.
        mktStmr.Receiver = new StreamVisitor<string, double>((cache, e) =>
        {
            var symbol = e.Key;
            var tick = e.Value;

            Instrument inst = instCache.Get(symbol);

            if (inst == null)
            {
                inst = new Instrument(symbol);
            }

            // Update instrument price based on the latest market tick.
            inst.High = Math.Max(inst.High, tick);
            inst.Low = Math.Min(inst.Low, tick);
            inst.Latest = tick;
        });
        var marketData = getMarketData();
        foreach (var tick in marketData)
        {
            mktStmr.AddData(tick);
        }
        mktStmr.Flush();
        Console.Write(instCache.Get("foo"));
    }
}

This API is not presently available for C++.