MongoDB-CDC

Overview

The MongoDB CDC connector allows for reading snapshot data and incremental data from MongoDB. This document describes how to setup the MongoDB CDC connector to run SQL queries against MongoDB.

Supported Version

Extract Node	Version
MongoDB-CDC	MongoDB: >= 3.6

Dependencies

In order to setup the MongoDB CDC connector, the following table provides dependency information for both projects using a build automation tool (such as Maven or SBT) and SQL Client with SQL JAR bundles.

Maven dependency

<dependency>
    <groupId>org.apache.inlong</groupId>
    <artifactId>sort-connector-mongodb-cdc</artifactId>
    <version>1.8.0</version>
</dependency>

Setup MongoDB

Availability

• MongoDB version

  MongoDB version >= 3.6 We use change streams feature (new in version 3.6) to capture change data.

• Cluster Deployment

  replica sets or sharded clusters is required.

• Storage Engine

  WiredTiger storage engine is required.

• Replica set protocol version

  Replica set protocol version 1 (pv1) is required. Starting in version 4.0, MongoDB only supports pv1. pv1 is the default for all new replica sets created with MongoDB 3.2 or later.

• Privileges

  changeStream and read privileges are required by MongoDB Kafka Connector.

  You can use the following example for simple authorization. For more detailed authorization, please refer to MongoDB Database User Roles.

  use admin;
  db.createUser({
    user: "flinkuser",
    pwd: "flinkpw",
    roles: [
      { role: "read", db: "admin" }, // read role includes changeStream privilege 
      { role: "readAnyDatabase", db: "admin" } // for snapshot reading
    ]
  });

How to create a MongoDB Extract Node

Usage for SQL API

The example below shows how to create an MongoDB Extract Node with Flink SQL :

-- Set checkpoint every 3000 milliseconds                       
Flink SQL> SET 'execution.checkpointing.interval' = '3s';   

-- Create a MySQL table 'mongodb_extract_node' in Flink SQL
Flink SQL> CREATE TABLE mongodb_extract_node (
  _id STRING, // must be declared
  name STRING,
  weight DECIMAL(10,3),
  tags ARRAY<STRING>, -- array
  price ROW<amount DECIMAL(10,2), currency STRING>, -- embedded document
  suppliers ARRAY<ROW<name STRING, address STRING>>, -- embedded documents
  PRIMARY KEY(_id) NOT ENFORCED
) WITH (
  'connector' = 'mongodb-cdc-inlong',
  'hosts' = 'localhost:27017,localhost:27018,localhost:27019',
  'username' = 'flinkuser',
  'password' = 'flinkpw',
  'database' = 'inventory',
  'collection' = 'mongodb_extract_node'
);

-- Read snapshot and binlogs from mongodb_extract_node
Flink SQL> SELECT * FROM mongodb_extract_node;

Note

MongoDB’s change event record doesn’t have update before message. So, we can only convert it to Flink’s UPSERT changelog stream. An upsert stream requires a unique key, so we must declare _id as primary key. We can’t declare other column as primary key, becauce delete operation do not contain’s the key and value besides _id and sharding key.

Usage for InLong Dashboard

TODO: It will be supported in the future.

Usage for InLong Manager Client

TODO: It will be supported in the future.

MongoDB Extract Node Options

Option	Required	Default	Type	Description
connector	required	(none)	String	Specify what connector to use, here should be mongodb-cdc-inlong.
hosts	required	(none)	String	The comma-separated list of hostname and port pairs of the MongoDB servers. eg. localhost:27017,localhost:27018
username	optional	(none)	String	Name of the database user to be used when connecting to MongoDB. This is required only when MongoDB is configured to use authentication.
password	optional	(none)	String	Password to be used when connecting to MongoDB. This is required only when MongoDB is configured to use authentication.
database	required	(none)	String	Name of the database to watch for changes.
collection	required	(none)	String	Name of the collection in the database to watch for changes.
connection.options	optional	(none)	String	The ampersand-separated connection options of MongoDB. eg. replicaSet=test&connectTimeoutMS=300000
copy.existing	optional	true	Boolean	Whether copy existing data from source collections.
copy.existing.queue.size	optional	10240	Integer	The max size of the queue to use when copying data.
batch.size	optional	1024	Integer	The cursor batch size.
poll.max.batch.size	optional	1024	Integer	Maximum number of change stream documents to include in a single batch when polling for new data.
poll.await.time.ms	optional	1000	Integer	The amount of time to wait before checking for new results on the change stream.
heartbeat.interval.ms	optional	0	Integer	The length of time in milliseconds between sending heartbeat messages. Use 0 to disa
inlong.metric.labels	optional	(none)	String	Inlong metric label, format of value is groupId={groupId}&streamId={streamId}&nodeId={nodeId}.
scan.incremental.snapshot.enabled	optional	false	Boolean	Whether enable incremental snapshot. The incremental snapshot feature only supports after MongoDB 4.0.
scan.incremental.snapshot.chunk.size.mb	optional	64	Integer	The chunk size mb of incremental snapshot.
chunk-meta.group.size	optional	1000	Integer	The group size of chunk meta, if the meta size exceeds the group size, the meta will be divided into multiple groups.

Available Metadata

The following format metadata can be exposed as read-only (VIRTUAL) columns in a table definition.

Key	DataType	Description
database_name	STRING NOT NULL	Name of the database that contain the row.
collection_name	STRING NOT NULL	Name of the collection that contain the row.
op_ts	TIMESTAMP_LTZ(3) NOT NULL	It indicates the time that the change was made in the database. If the record is read from snapshot of the table instead of the change stream, the value is always 0.

The extended CREATE TABLE example demonstrates the syntax for exposing these metadata fields:

CREATE TABLE `mysql_extract_node` (
    db_name STRING METADATA FROM 'database_name' VIRTUAL,
    collection_name STRING METADATA  FROM 'collection_name' VIRTUAL,
    operation_ts TIMESTAMP_LTZ(3) METADATA FROM 'op_ts' VIRTUAL,
    _id STRING, // must be declared
    name STRING,
    weight DECIMAL(10,3),
    tags ARRAY<STRING>, -- array
    price ROW<amount DECIMAL(10,2), currency STRING>, -- embedded document
    suppliers ARRAY<ROW<name STRING, address STRING>>, -- embedded documents
    PRIMARY KEY(_id) NOT ENFORCED
) WITH (
      'connector' = 'mongodb-cdc-inlong', 
      'hostname' = 'YourHostname',
      'username' = 'YourUsername',
      'password' = 'YourPassword',
      'database' = 'YourDatabase',
      'collection' = 'YourTable' 
);

Data Type Mapping

BSON type	Flink SQL type
	TINYINT
	SMALLINT
Int	INT
Long	BIGINT
	FLOAT
Double	DOUBLE
Decimal128	DECIMAL(p, s)
Boolean	BOOLEAN
Date Timestamp	DATE
Date Timestamp	TIME
Date	TIMESTAMP(3) TIMESTAMP_LTZ(3)
Timestamp	TIMESTAMP(0) TIMESTAMP_LTZ(0)
String ObjectId UUID Symbol MD5 JavaScript Regex	STRING
BinData	BYTES
Object	ROW
Array	ARRAY
DBPointer	ROW\<\$ref STRING, \$id STRING>
GeoJSON	Point : ROW\<type STRING, coordinates ARRAY\<DOUBLE>> Line : ROW\<type STRING, coordinates ARRAY\<ARRAY\< DOUBLE>>> ...