First demo of Flink

参考官方教程 https://ci.apache.org/projects/flink/flink-docs-release-1.7/tutorials/local_setup.html

macOS 可以使用 brew install apache-flink 直接安装。
不过我这里直接下载二进制包来测试。

此处不再赘述去官方下载二进制包和解压的步骤。
PS：我用的是 1.7.2 版本。

在本地启动

$ ./bin/start-cluster.sh  # Start Flink

可以看到已经启动起来了。

在浏览器打开 http://localhost:8081/#/overview
可以看到效果。

查看日志

tail log/flink-tony-standalonesession-0-TMBP.local.log

测试第一个程序 wordcount

java 代码:

public class SocketWindowWordCount {
    public static void main(String[] args) throws Exception {
        // the port to connect to
        final int port;
        try {
            final ParameterTool params = ParameterTool.fromArgs(args);
            port = params.getInt("port");
        } catch (Exception e) {
            System.err.println("No port specified. Please run 'SocketWindowWordCount --port <port>'");
            return;
        }
        // get the execution environment
        final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        // get input data by connecting to the socket
        DataStream<String> text = env.socketTextStream("localhost", port, "\n");
        // parse the data, group it, window it, and aggregate the counts
        DataStream<WordWithCount> windowCounts = text
            .flatMap(new FlatMapFunction<String, WordWithCount>() {
                @Override
                public void flatMap(String value, Collector<WordWithCount> out) {
                    for (String word : value.split("\\s")) {
                        out.collect(new WordWithCount(word, 1L));
                    }
                }
            })
            .keyBy("word")
            .timeWindow(Time.seconds(5), Time.seconds(1))
            .reduce(new ReduceFunction<WordWithCount>() {
                @Override
                public WordWithCount reduce(WordWithCount a, WordWithCount b) {
                    return new WordWithCount(a.word, a.count + b.count);
                }
            });
        // print the results with a single thread, rather than in parallel
        windowCounts.print().setParallelism(1);
        env.execute("Socket Window WordCount");
    }
    // Data type for words with count
    public static class WordWithCount {
        public String word;
        public long count;
        public WordWithCount() {}
        public WordWithCount(String word, long count) {
            this.word = word;
            this.count = count;
        }
        @Override
        public String toString() {
            return word + " : " + count;
        }
    }
}

编译成 jar 包（examples/streaming/ 目录下有现成的 SocketWindowWordCount.jar）
首先用 netcat 启动一个本地的 server

nc -l 9001 （由于我的本机 9000 端口被其他应用占用了，改用 9001）

然后提交 flink 应用侦听 9001

./bin/flink run examples/streaming/SocketWindowWordCount.jar --port 9001

开始测试：

由于是按时间窗口来统计的，所以输入较快的时候(5秒内输入多次)，可以看到 hello world 统计出来的效果