# MongoDB

> MongoDB Sink Connector

Support Those Engines
---------------------

> Spark<br/>
> Flink<br/>
> SeaTunnel Zeta<br/>

Key Features
------------

- [ ] [exactly-once](../../concept/connector-v2-features.md)
- [x] [cdc](../../concept/connector-v2-features.md)

**Tips**

> 1.If you want to use CDC-written features, recommend enable the upsert-enable configuration.

Description
-----------

The MongoDB Connector provides the ability to read and write data from and to MongoDB.
This document describes how to set up the MongoDB connector to run data writers against MongoDB.

Supported DataSource Info
-------------------------

In order to use the Mongodb connector, the following dependencies are required.
They can be downloaded via install-plugin.sh or from the Maven central repository.

| Datasource | Supported Versions |                                                  Dependency                                                   |
|------------|--------------------|---------------------------------------------------------------------------------------------------------------|
| MongoDB    | universal          | [Download](https://mvnrepository.com/artifact/org.apache.seatunnel/seatunnel-connectors-v2/connector-mongodb) |

Data Type Mapping
-----------------

The following table lists the field data type mapping from MongoDB BSON type to Seatunnel data type.

| Seatunnel Data Type | MongoDB BSON Type |
|---------------------|-------------------|
| STRING              | ObjectId          |
| STRING              | String            |
| BOOLEAN             | Boolean           |
| BINARY              | Binary            |
| INTEGER             | Int32             |
| TINYINT             | Int32             |
| SMALLINT            | Int32             |
| BIGINT              | Int64             |
| DOUBLE              | Double            |
| FLOAT               | Double            |
| DECIMAL             | Decimal128        |
| Date                | Date              |
| Timestamp           | Timestamp[Date]   |
| ROW                 | Object            |
| ARRAY               | Array             |

**Tips**

> 1.When using SeaTunnel to write Date and Timestamp types to MongoDB, both will produce a Date data type in MongoDB, but the precision will be different. The data generated by the SeaTunnel Date type has second-level precision, while the data generated by the SeaTunnel Timestamp type has millisecond-level precision.<br/>
> 2.When using the DECIMAL type in SeaTunnel, be aware that the maximum range cannot exceed 34 digits, which means you should use decimal(34, 18).<br/>

Sink Options
------------

|         Name          |   Type   | Required | Default |                                            Description                                            |
|-----------------------|----------|----------|---------|---------------------------------------------------------------------------------------------------|
| uri                   | String   | Yes      | -       | The MongoDB connection uri.                                                                       |
| database              | String   | Yes      | -       | The name of MongoDB database to read or write.                                                    |
| collection            | String   | Yes      | -       | The name of MongoDB collection to read or write.                                                  |
| schema                | String   | Yes      | -       | MongoDB's BSON and seatunnel data structure mapping                                               |
| buffer-flush.max-rows | String   | No       | 1000    | Specifies the maximum number of buffered rows per batch request.                                  |
| buffer-flush.interval | String   | No       | 30000   | Specifies the retry time interval if writing records to database failed, the unit is seconds.     |
| retry.max             | String   | No       | 3       | Specifies the max retry times if writing records to database failed.                              |
| retry.interval        | Duration | No       | 1000    | Specifies the retry time interval if writing records to database failed, the unit is millisecond. |
| upsert-enable         | Boolean  | No       | false   | Whether to write documents via upsert mode.                                                       |
| primary-key           | List     | No       | -       | The primary keys for upsert/update. Keys are in `["id","name",...]` format for properties.        |

**Tips**

> 1.The data flushing logic of the MongoDB Sink Connector is jointly controlled by three parameters: `buffer-flush.max-rows`, `buffer-flush.interval`, and `checkpoint.interval`.
> Data flushing will be triggered if any of these conditions are met.<br/>
> 2.Compatible with the historical parameter `upsert-key`. If `upsert-key` is set, please do not set `primary-key`.<br/>

How to Create a MongoDB Data Synchronization Jobs
-------------------------------------------------

The following example demonstrates how to create a data synchronization job that writes randomly generated data to a MongoDB database:

```bash
# Set the basic configuration of the task to be performed
env {
  execution.parallelism = 1
  job.mode = "BATCH"
  checkpoint.interval  = 1000
}

source {
  FakeSource {
      row.num = 2
      bigint.min = 0
      bigint.max = 10000000
      split.num = 1
      split.read-interval = 300
      schema {
        fields {
          c_bigint = bigint
        }
      }
    }
}

sink {
  MongoDB{
    uri = mongodb://user:password@127.0.0.1:27017
    database = "test"
    collection = "test"
    schema = {
      fields {
        _id = string
        c_bigint = bigint
      }
    }
  }
}
```

Parameter Interpretation
------------------------

**MongoDB Database Connection URI Examples**

Unauthenticated single node connection:

```bash
mongodb://127.0.0.0:27017/mydb
```

Replica set connection:

```bash
mongodb://127.0.0.0:27017/mydb?replicaSet=xxx
```

Authenticated replica set connection:

```bash
mongodb://admin:password@127.0.0.0:27017/mydb?replicaSet=xxx&authSource=admin
```

Multi-node replica set connection:

```bash
mongodb://127.0.0..1:27017,127.0.0..2:27017,127.0.0.3:27017/mydb?replicaSet=xxx
```

Sharded cluster connection:

```bash
mongodb://127.0.0.0:27017/mydb
```

Multiple mongos connections:

```bash
mongodb://192.168.0.1:27017,192.168.0.2:27017,192.168.0.3:27017/mydb
```

Note: The username and password in the URI must be URL-encoded before being concatenated into the connection string.

**Buffer Flush**

```bash
sink {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "users"
    buffer-flush.max-rows = 2000
    buffer-flush.interval = 1000
    schema = {
      fields {
        _id = string
        id = bigint
        status = string
      }
    }
  }
}
```

**Why is Not Recommended to Use Transactions for Operation?**

Although MongoDB has fully supported multi-document transactions since version 4.2, it doesn't mean that everyone should use them recklessly.
Transactions are equivalent to locks, node coordination, additional overhead, and performance impact.
Instead, the principle for using transactions should be: avoid using them if possible.
The necessity for using transactions can be greatly avoided by designing systems rationally.

**Idempotent Writes**

By specifying a clear primary key and using the upsert method, exactly-once write semantics can be achieved.

If `primary-key` and `upsert-enable` is defined in the configuration, the MongoDB sink will use upsert semantics instead of regular INSERT statements. We combine the primary keys declared in upsert-key as the MongoDB reserved primary key and use upsert mode for writing to ensure idempotent writes.
In the event of a failure, Seatunnel jobs will recover from the last successful checkpoint and reprocess, which may result in duplicate message processing during recovery. It is highly recommended to use upsert mode, as it helps to avoid violating database primary key constraints and generating duplicate data if records need to be reprocessed.

```bash
sink {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "users"
    upsert-enable = true
    primary-key = ["name","status"]
    schema = {
      fields {
        _id = string
        name = string
        status = string
      }
    }
  }
}
```

## Changelog

### 2.2.0-beta

- Add MongoDB Source Connector

### 2.3.1-release

- [Feature]Refactor mongodb source connector([4620](https://github.com/apache/incubator-seatunnel/pull/4620))

### Next Version

- [Feature]Mongodb support cdc sink([4833](https://github.com/apache/seatunnel/pull/4833))

