Mongo event

Overview

The MongoDB Event stream source works similar to Cinchy's Change Data Capture functionality. The listener subscribes to monitor the change stream of a specific collection in the database of the MongoDB server. Any actions performed on document(s) inside of that collection are picked up by the listener and sent to the queue.

Limitations

To use change streams in MongoDB, there are a few requirements your environment must meet.

• The database must be in a replica set or sharded cluster.

• The database must use the WiredTiger storage engine.

• The replica set or sharded cluster must use replica set protocol version 1.

The MongoDB Event source supports real-time syncs.

Info tab

You can find the parameters in the Info tab below (Image 1).

Values

Parameter	Description	Example
Title	Mandatory. Input a name for your data sync	Mongo Event to Cinchy
Variables	Optional. Review our documentation on Variables here for more information about this field.
Permissions	Data syncs are role based access systems where you can give specific groups read, write, execute, and/or all of the above with admin access. Inputting at least an Admin Group is mandatory.

Image 1: The Info Tab

Source tab

The following table outlines the mandatory and optional parameters you will find on the Source tab (Image 2).

Source Details

The following parameters will help to define your data sync source and how it functions.

Parameter	Description	Example
Source	Mandatory. Select your source from the drop down menu.	MongoDB Event

Listener Configuration

To set up a real-time sync, you must configure your Listener values. You can do so through the Connections UI.

Note that If there is more than one listener associated with your data sync, you will need to configure the addition listeners via the Listener Configuration table.

Reset Behaviour

Parameter	Description	Example
Auto Offset Reset	Earliest, Latest or None. In the case where the listener is started and either there is no last message ID, or when the last message ID is invalid (due to it being deleted or it's just a new listener), it will use this column as a fallback to determine where to start reading events from. Earliest will start reading from the beginning on the queue (when the CDC was enabled on the table). This might be a suggested configuration if your use case is recoverable or re-runnable and if you need to reprocess all events to ensure accuracy. Latest will fetch the last value after whatever was last processed. This is the typical configuration. None won't read or start reading any events. You are able to switch between Auto Offset Reset types after your initial configuration through the process outlined here.	None

Topic JSON

The below table can be used to help create your Topic JSON needed to set up a real-time sync.

Parameter	Description	Example
Database	Mandatory. The name of your MongoDB database.	Cinchy
Collection	Mandatory. The name of your MongoDB collection.	Employee
Pipeline Stages	Optional. This parameter allows you to specify pipeline stages with filters. In MongoDB, an aggregation pipeline consists of one or more stages that process documents: Each stage performs an operation on the input documents. For example, a stage can filter documents, group documents, and calculate values. The documents that are output from a stage are passed to the next stage. An aggregation pipeline can return results for groups of documents. For example, return the total, average, maximum, and minimum values.	See the Example Topic JSON below. Our example config uses a filter to return documents with an ID between 0 and 10,000 AND documents with the location set to Montreal, OR where the operation type is 'delete'

Example Topic JSON

{
	"database": "cinchy",
	"collection": "employee",
        "changeStreamSettings": {
		"pipelineStages": [
			"{ $match: {
                                       $or: [ 
                                           { $and: [
                                                { 'fullDocument.id': { $gt: 0, $lt: 10000 } }, 
                                                { 'fullDocument.location': 'Montreal' } ] 
                                           }, 
                                           { 'operationType': 'delete' } 
                                      ]
                                } }"
		]
	}
}

Connection Attributes

The below table can be used to help create your Connection Attributes JSON needed to set up a real-time sync.

Parameter	Description	Example
connectionString	Mandatory. Your MongoDB connection string.	mongodb://localhost:9877

{
	"connectionString": "mongodb://localhost:9877"
}

Schema

The Schema section is where you define which source columns you want to sync in your connection. You can repeat the values for multiple columns.

Parameter	Description	Example
Name	Mandatory. The name of your column as it appears in the source. This field is case sensitive and preserves spaces.	Name
Alias	Optional. You may choose to use an alias on your column so that it has a different name in the data sync.
Data Type	Mandatory. The data type of the column values. You can review the supported data types and their translations here.	Text
Description	Optional. You may choose to add a description to your column.

Select Show Advanced for more options for the Schema section.

Parameter	Description	Example
Mandatory	If both Mandatory and Validated are checked on a column, then rows where the column is empty are rejected If just Mandatory is checked on a column, then all rows are synced with the execution log status of failed, and the source error of "Mandatory Rule Violation" If just Validated is checked on a column, then all rows are synced.
Validate Data	If both Mandatory and Validated are checked on a column, then rows where the column is empty are rejected If just Validated is checked on a column, then all rows are synced.
Trim Whitespace	Optional if data type = text. For Text data types, you can choose whether to trim the whitespace._
Max Length	Optional if data type = text. You can input a numerical value in this field that represents the maximum length of the data that can be synced in your column. If the value is exceeded, the row will be rejected (you can find this error in the Execution Log).

You can choose to add in a Transformation > String Replacement by inputting the following:

Parameter	Description	Example
Pattern	Mandatory if using a Transformation. The pattern for your string replacement.
Replacement	What you want to replace your pattern with.

Note that you can have more than one String Replacement

Image 2: The Source Tab

Next steps

• Configure your Destination
• Define your Sync Actions.
• Add in your Post Sync Scripts, if required.
• If more than one listener is needed for a real-time sync, configure it/them via the Listener Config table.
• To run a real-time sync, enable your Listener from the Execution tab.