MongoDB

Question

我有一个Java应用程序，它处理avro消息的Kafka流，并为每条消息对mongoDB集合执行查询。

在正确处理了几十条消息后，应用程序停止运行并抛出“com.mongodb.MongoSocketReadExc0019：过早到达流的结尾”。

这是代码：

    JavaPairInputDStream<String, byte[]> directKafkaStream = KafkaUtils.createDirectStream(jsc,
            String.class, byte[].class, StringDecoder.class, DefaultDecoder.class, kafkaParams, topics);

    directKafkaStream.foreachRDD(rdd ->{

        rdd.foreach(avroRecord -> {

            byte[] encodedAvroData = avroRecord._2;
            LocationType t = deserialize(encodedAvroData);

            MongoClientOptions.Builder options_builder = new MongoClientOptions.Builder();
            options_builder.maxConnectionIdleTime(60000);
            MongoClientOptions options = options_builder.build();
            MongoClient mongo = new MongoClient ("localhost:27017", options);

            MongoDatabase database = mongo.getDatabase("DB");
            MongoCollection<Document> collection = database.getCollection("collection");

            Document myDoc = collection.find(eq("key", 4)).first();
            System.out.println(myDoc);

        });
    });

Answer 1

首先，你不应该为每条记录打开mongo连接！然后你应该关闭你的mongo连接。

Mongo不喜欢你打开很多（成百上千？）不关闭它们。

以下是通过RDD打开mongo连接的示例：

directKafkaStream.foreachRDD(rdd ->{
    rdd.foreachPartition(it -> {

        // Opens only 1 connection per partition
        MongoClient mongo = new MongoClient ("localhost:27017");
        MongoDatabase database = mongo.getDatabase("DB");
        MongoCollection<Document> collection = database.getCollection("collection");

        while (it.hasNext()) {
            byte[] encodedAvroData = it.next()._2;
            LocationType t = deserialize(encodedAvroData);

            Document myDoc = collection.find(eq("key", 4)).first();
            System.out.println(myDoc);
        }

        mongo.close();
    });
});