MongoDB

MongoDB Source Connector

Key Features​

• batch

• stream

• exactly-once

• column projection

• parallelism

• support user-defined split

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 reads against MongoDB.

Data Type Mapping​

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

MongoDB BSON type	Nexus Data type
ObjectId	STRING
String	STRING
Boolean	BOOLEAN
Binary	BINARY
Int32	INTEGER
Int64	BIGINT
Double	DOUBLE
Decimal128	DECIMAL
Date	Date
Timestamp	Timestamp
Object	ROW
Array	ARRAY

For specific types in MongoDB, we use Extended JSON format to map them to Nexus STRING type.

MongoDB BSON type	Nexus STRING
Symbol	{"_value": {"$symbol": "12"}}
RegularExpression	{"_value": {"$regularExpression": {"pattern": "^9$", "options": "i"}}}
JavaScript	{"_value": {"$code": "function() { return 10; }"}}
DbPointer	{"_value": {"$dbPointer": {"$ref": "db.coll", "$id": {"$oid": "63932a00da01604af329e33c"}}}}

Tips

1.When using the DECIMAL type in Nexus, be aware that the maximum range cannot exceed 34 digits, which means you should use decimal(34, 18).

Source Options​

Name	Type	Required	Default	Description
uri	String	Yes	-	The MongoDB standard connection uri. eg. mongodb://user:password@hosts:27017/database?readPreference=secondary&slaveOk=true.
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 Nexus data structure mapping.
match.query	String	No	-	In MongoDB, filters are used to filter documents for query operations.
match.projection	String	No	-	In MongoDB, Projection is used to control the fields contained in the query results.
partition.split-key	String	No	_id	The key of Mongodb fragmentation.
partition.split-size	Long	No	64 1024 1024	The size of Mongodb fragment.
cursor.no-timeout	Boolean	No	true	MongoDB server normally times out idle cursors after an inactivity period (10 minutes) to prevent excess memory use. Set this option to true to prevent that. However, if the application takes longer than 30 minutes to process the current batch of documents, the session is marked as expired and closed.
fetch.size	Int	No	2048	Set the number of documents obtained from the server for each batch. Setting the appropriate batch size can improve query performance and avoid the memory pressure caused by obtaining a large amount of data at one time.
max.time-min	Long	No	600	This parameter is a MongoDB query option that limits the maximum execution time for query operations. The value of maxTimeMin is in Minute. If the execution time of the query exceeds the specified time limit, MongoDB will terminate the operation and return an error.
flat.sync-string	Boolean	No	true	By utilizing flatSyncString, only one field attribute value can be set, and the field type must be a String. This operation will perform a string mapping on a single MongoDB data entry.
common-options		No	-	Source plugin common parameters, please refer to Source Common Options for details

Tips​

1.The parameter match.query is compatible with the historical old version parameter matchQuery, and they are equivalent replacements.

How to Create a MongoDB Data Synchronization Jobs​

The following example demonstrates how to create a data synchronization job that reads data from MongoDB and prints it on the local client:

# Set the basic configuration of the task to be performed
env {
  parallelism = 1
  job.mode = "BATCH"
}

# Create a source to connect to Mongodb
source {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "source_table"
    schema = {
      fields {
        c_map = "map<string, string>"
        c_array = "array<int>"
        c_string = string
        c_boolean = boolean
        c_int = int
        c_bigint = bigint
        c_double = double
        c_bytes = bytes
        c_date = date
        c_decimal = "decimal(38, 18)"
        c_timestamp = timestamp
        c_row = {
          c_map = "map<string, string>"
          c_array = "array<int>"
          c_string = string
          c_boolean = boolean
          c_int = int
          c_bigint = bigint
          c_double = double
          c_bytes = bytes
          c_date = date
          c_decimal = "decimal(38, 18)"
          c_timestamp = timestamp
        }
      }
    }
  }
}

# Console printing of the read Mongodb data
sink {
  Console {
    parallelism = 1
  }
}

Parameter Interpretation​

MongoDB Database Connection URI Examples​

Unauthenticated single node connection:

mongodb://192.168.0.100:27017/mydb

Replica set connection:

mongodb://192.168.0.100:27017/mydb?replicaSet=xxx

Authenticated replica set connection:

mongodb://admin:password@192.168.0.100:27017/mydb?replicaSet=xxx&authSource=admin

Multi-node replica set connection:

mongodb://192.168.0.1:27017,192.168.0.2:27017,192.168.0.3:27017/mydb?replicaSet=xxx

Sharded cluster connection:

mongodb://192.168.0.100:27017/mydb

Multiple mongos connections:

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.

MatchQuery Scan​

In data synchronization scenarios, the matchQuery approach needs to be used early to reduce the number of documents that need to be processed by subsequent operators, thus improving performance. Here is a simple example of a Nexus using match.query

source {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "orders"
    match.query = "{status: \"A\"}"
    schema = {
      fields {
        id = bigint
        status = string
      }
    }
  }
}

The following are examples of MatchQuery query statements of various data types:

# Query Boolean type
"{c_boolean:true}"
# Query string type
"{c_string:\"OCzCj\"}"
# Query the integer
"{c_int:2}"
# Type of query time
"{c_date:ISODate(\"2023-06-26T16:00:00.000Z\")}"
# Query floating point type
{c_double:{$gte:1.71763202185342e+308}}

Please refer to how to write the syntax of match.query：https://www.mongodb.com/docs/manual/tutorial/query-documents

Projection Scan​

In MongoDB, Projection is used to control which fields are included in the query results. This can be accomplished by specifying which fields need to be returned and which fields do not. In the find() method, a projection object can be passed as a second argument. The key of the projection object indicates the fields to include or exclude, and a value of 1 indicates inclusion and 0 indicates exclusion. Here is a simple example, assuming we have a collection named users:

# Returns only the name and email fields
db.users.find({}, { name: 1, email: 0 });

In data synchronization scenarios, projection needs to be used early to reduce the number of documents that need to be processed by subsequent operators, thus improving performance. Here is a simple example of a Nexus using projection:

source {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "users"
    match.projection = "{ name: 1, email: 0 }"
    schema = {
      fields {
        name = string
      }
    }
  }
}

Partitioned Scan​

To speed up reading data in parallel source task instances, Nexus provides a partitioned scan feature for MongoDB collections. The following partitioning strategies are provided. Users can control data sharding by setting the partition.split-key for sharding keys and partition.split-size for sharding size.

source {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "users"
    partition.split-key = "id"
    partition.split-size = 1024
    schema = {
      fields {
        id = bigint
        status = string
      }
    }
  }
}

Flat Sync String​

By utilizing flat.sync-string, only one field attribute value can be set, and the field type must be a String. This operation will perform a string mapping on a single MongoDB data entry.

env {
  parallelism = 10
  job.mode = "BATCH"
}
source {
  MongoDB {
    uri = "mongodb://user:password@127.0.0.1:27017"
    database = "test_db"
    collection = "users"
    flat.sync-string = true
    schema = {
      fields {
        data = string
      }
    }
  }
}
sink {
  Console {}
}

Use the data samples synchronized with modified parameters, such as the following:

{
  "_id":{
    "$oid":"643d41f5fdc6a52e90e59cbf"
  },
  "c_map":{
    "OQBqH":"jllt",
    "rkvlO":"pbfdf",
    "pCMEX":"hczrdtve",
    "DAgdj":"t",
    "dsJag":"voo"
  },
  "c_array":[
    {
      "$numberInt":"-865590937"
    },
    {
      "$numberInt":"833905600"
    },
    {
      "$numberInt":"-1104586446"
    },
    {
      "$numberInt":"2076336780"
    },
    {
      "$numberInt":"-1028688944"
    }
  ],
  "c_string":"bddkzxr",
  "c_boolean":false,
  "c_tinyint":{
    "$numberInt":"39"
  },
  "c_smallint":{
    "$numberInt":"23672"
  },
  "c_int":{
    "$numberInt":"-495763561"
  },
  "c_bigint":{
    "$numberLong":"3768307617923954543"
  },
  "c_float":{
    "$numberDouble":"5.284220288280258E37"
  },
  "c_double":{
    "$numberDouble":"1.1706091642478246E308"
  },
  "c_bytes":{
    "$binary":{
      "base64":"ZWJ4",
      "subType":"00"
    }
  },
  "c_date":{
    "$date":{
      "$numberLong":"1686614400000"
    }
  },
  "c_decimal":{
    "$numberDecimal":"683265300"
  },
  "c_timestamp":{
    "$date":{
      "$numberLong":"1684283772000"
    }
  },
  "c_row":{
    "c_map":{
      "OQBqH":"cbrzhsktmm",
      "rkvlO":"qtaov",
      "pCMEX":"tuq",
      "DAgdj":"jzop",
      "dsJag":"vwqyxtt"
    },
    "c_array":[
      {
        "$numberInt":"1733526799"
      },
      {
        "$numberInt":"-971483501"
      },
      {
        "$numberInt":"-1716160960"
      },
      {
        "$numberInt":"-919976360"
      },
      {
        "$numberInt":"727499700"
      }
    ],
    "c_string":"oboislr",
    "c_boolean":true,
    "c_tinyint":{
      "$numberInt":"-66"
    },
    "c_smallint":{
      "$numberInt":"1308"
    },
    "c_int":{
      "$numberInt":"-1573886733"
    },
    "c_bigint":{
      "$numberLong":"4877994302999518682"
    },
    "c_float":{
      "$numberDouble":"1.5353209063652051E38"
    },
    "c_double":{
      "$numberDouble":"1.1952441956458565E308"
    },
    "c_bytes":{
      "$binary":{
        "base64":"cWx5Ymp0Yw==",
        "subType":"00"
      }
    },
    "c_date":{
      "$date":{
        "$numberLong":"1686614400000"
      }
    },
    "c_decimal":{
      "$numberDecimal":"656406177"
    },
    "c_timestamp":{
      "$date":{
        "$numberLong":"1684283772000"
      }
    }
  },
  "id":{
    "$numberInt":"2"
  }
}