Add km module kafka

docs/zh/Kafka客户端/java_sequential_send.md

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+# Java客户端 消息顺序写入 Kafka例子
+
+## 发送例子
+
+例子中，客户端有序发送最重要的配置是`max.in.flight.requests.per.connection=1`。
+
+```java
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Properties;
+import org.apache.kafka.clients.producer.*;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+
+public class SequentialProducer {
+
+    private static Properties createProperties() {
+        Properties properties = new Properties();
+        properties.put("bootstrap.servers", "**kafka集群服务地址***");
+
+        properties.put("acks", "all");
+        properties.put("max.in.flight.requests.per.connection", 1); // 顺序发送必须加上
+        properties.put("retries", 30);
+        properties.put("request.timeout.ms", 12000);
+        properties.put("linger.ms", 10);
+        properties.put("batch.size", 65536);
+
+        properties.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
+        properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
+
+        // 安全管控配置，如若没有可进行去除下面三个配置
+        properties.put("security.protocol", "SASL_PLAINTEXT");
+        properties.put("sasl.mechanism", "PLAIN");
+        properties.put("sasl.jaas.config", "org.apache.kafka.common.security.plain.PlainLoginModule required " +
+                "username=\"{clusterId}.{username}\" password=\"{password}\";");
+
+        return properties;
+    }
+
+    private static boolean sendRecords(KafkaProducer<String, String> producer, List<ProducerRecord<String, String>> records) {
+        final CountDownLatch countDownLatch = new CountDownLatch(records.size());
+        final AtomicBoolean  failedFlag     = new AtomicBoolean(Boolean.FALSE);
+
+        for (ProducerRecord<String, String> record : records) {
+            System.out.println(record.value());
+            producer.send(new ProducerRecord<String, String>(record.topic(), record.key(), record.value()), new Callback() {
+
+                @Override
+                public void onCompletion(RecordMetadata metadata, Exception exception) {
+                    // 发送完成后的回调, 如果exception != null 表示发送失败了
+                    if (exception != null) {
+                        // 发送失败 -> 设置发送失败标记
+                        failedFlag.set(Boolean.TRUE);
+                    }
+                    countDownLatch.countDown();
+                }
+            });
+        }
+
+        boolean success = false;
+        try {
+            // 等待 60 秒超时
+            success = countDownLatch.await(60, TimeUnit.SECONDS);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+
+        if (failedFlag.get()) {
+            success = false;
+        }
+        return success;
+    }
+
+    public static void main(String[] args){
+        String mysqlTableName = "DB_Table_Name";
+
+        // kafka producer
+        KafkaProducer<String, String> producer = new KafkaProducer<String, String>(createProperties());
+
+        // 需要发送的数据数组
+        List<ProducerRecord<String, String>> records = new ArrayList<ProducerRecord<String, String>>();
+
+        // 发送的结果
+        boolean status = true;
+
+        long mysqlTableId = 1;
+        while (true) {
+            if (status) {
+                // 发送成功, 则清除上一次的数据, 然后获取新数据,
+                records.clear();
+                for (int i = 0; i < 5; ++i) {
+                    // 构造数据时, 需要指定key, key可以是mysql表的表名, 这样同个表的数据将会发送到同一个分区
+                    records.add(new ProducerRecord<String, String>("{topicName}", mysqlTableName, "hello kafka, id=" + mysqlTableId++));
+                }
+            } else {
+                // 发送失败, 则不做任何事情, 即继续尝试上一批数据的发送
+                System.out.println("send failed, ------- records:" + records.get(0));
+            }
+
+            status = sendRecords(producer, records);
+        }
+    }
+}
+```
+