MongoFlink

MongoFlink is a connector between MongoDB and Apache Flink. MongoFlink supports DataStream API and Table/SQL API. It acts as a Flink sink (and an experimental Flink source), and provides transaction mode(which ensures exactly-once semantics) for MongoDB 4.2 above, and non-transaction mode for MongoDB 3.0 above.

MongoFlink is in its early phase, and any use, feedback or contribution is welcome!

Start to use

Prerequisite

• Flink 1.12 above. MongoFlink is built on top of the new sink API added in FLIP-143 or Flink 1.12.0.
• MongoDB 3.0 above. The official MongoDB Java driver supports 3.0 above.
• JDK 1.8 above.

Dependency

For Maven users, add the following dependency in your project’s pom.xml.

<dependency>
    <groupId>org.mongoflink</groupId>
    <artifactId>mongo-flink</artifactId>
    <version>0.3</version>
</dependency>

MongoFlink heavily relies on Flink connector interfaces, but Flink interfaces may not have good cross version compatibility, thus it’s recommended to choose the version of MongoFlink that matches the version of Flink in your project.

version	flink version	mongo version
0.1	1.13.x	4.2.x
0.2	1.14.x	4.4.x
0.3	1.15.x	4.4.x

In case there’s no version that fits your need, it’s recommended to build your own one. See [Build from source] section below.

Code

Use MongoSink in your Flink DataStream application.

    StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

    // non-transactional sink with a flush strategy of 1000 documents or 10 seconds
    Properties properties = new Properties();
    properties.setProperty(MongoOptions.SINK_TRANSACTION_ENABLED, "false");
    properties.setProperty(MongoOptions.SINK_FLUSH_ON_CHECKPOINT, "false");
    properties.setProperty(MongoOptions.SINK_FLUSH_SIZE, String.valueOf(1_000L));
    properties.setProperty(MongoOptions.SINK_FLUSH_INTERVAL, String.valueOf(10_000L));

    env.addSource(...)
       .sinkTo(new MongoSink<>("mongodb://user:password@127.0.0.1:27017", "mydb", "mycollection",
                               new StringDocumentSerializer(), properties));

    env.execute();

Use MongoSink in your Flink Table/SQL application.

    TableEnvironment env = TableEnvironment.create(EnvironmentSettings.inStreamingMode());

    env.executeSql("create table tbl_user_gold (" +
            "    user_id long," +
            "    gold long," +
            "    PRIMARY key(user_id) NOT ENFORCED" +
            ") with (" +
            "    'connector'='mongo'," +
            "    'connect_string' = 'mongodb://user:password@127.0.0.1:27017'," +
            "    'database' = 'mydb'," +
            "    'collection' = 'user_gold'" +
            ")"

    Table userGold = env.executeQuery("select * from tbl_user_gold");
    );

Configuration

MongoFlink can be configured using properties.

MongoSink

key	description	default value
sink.transaction.enable	Whether use transactions in MongoSink (requires MongoDB 4.2+).	false
sink.flush.on-checkpoint	Whether flush the buffered documents on checkpoint barriers.	false
sink.flush.size	Max buffered documents before flush. Only valid when sink.flush.on-checkpoint is false.	1000
sink.flush.interval	Flush interval in milliseconds. Only valid when sink.flush.on-checkpoint is false.	30000

Build from source

Checkout the project, and use Maven to build the project locally.

$ mvn verify

Contribute to the project

Report an issue

Welcome to file an issue if you need help on adopting MongoFlink. Please describe your environment in the issue (e.g. what MongoDB/Flink version you’re using).

Contribute code

Welcome to open pull requests if you want to improve MongoFlink. Please state the purpose (and the design if it’s a big feature) for better review experience.