Replicate MongoDB® Collections to SingleStore
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SingleStore allows you to replicate your existing MongoDB® collections to your SingleStore Helios database using Change Data Capture (CDC).
-
MongoDB® wrapper commands through the SingleStore Kai endpoint
-
SQL commands
Note: Because MongoDB® time series collections do not support change streams, they cannot be replicated in SingleStore using CDC.
Source Database Requirements
The replication feature uses MongoDB® change streams, and it works only with replica sets.
-
Read the
admin
database for the operation log (oplog) -
Read the
config
database in the configuration server -
listDatabases
privilege -
Cluster-wide
find
andchangeStream
privileges -
Write permission to the
singlestore
database
Replicate MongoDB® Collections using MongoDB® Wrapper Commands
Note
SingleStore recommends using MongoDB® wrapper commands to replicate your MongoDB® collections into a SingleStore Kai-enabled workspace.
To replicate your MongoDB® collections using MongoDB® wrapper commands, perform the following tasks and run the respective commands on a SingleStore Kai-enabled workspace:
-
Create a link: Create a link using the URI of the (remote) MongoDB® instance.
db.runCommand({createLink:"<link_name>",uri:"mongodb://<username>:<password>@<hostname>:27017"})For MongoDB® Atlas instances, use the
mongodb+srv://
scheme.Refer to createLink for more information. -
Create a collection: Create a collection, and specify the link created in the previous step using the
from
option as follows:db.createCollection("<collection_name>", { from:{link:"<link_name>"} })Refer to createCollection for more information.
Here's an example:
db.runCommand({createLink:"pLink",uri:"mongodb://admin:pa55w0rd@svchost:27017"})db.createCollection("colTest", {from:{link:"pLink", database:"dbTest", collection:"example"}})
Replicate MongoDB® Collections using SQL
Note
SingleStore does not recommend using this feature if you are using a SingleStore Kai-enabled workspace as it may create table structures that are not optimal for the API.
To replicate your existing MongoDB® collections to your SingleStore Helios database using SQL syntax for pipelines, create a link to the MongoDB® endpoint using the CREATE LINK
statement, and use one of the following methods:
-
To replicate/migrate collections (as is), use the
CREATE {TABLES | TABLE} AS INFER PIPELINE .
SQL statement.. . Refer to Remarks for more information. -
To apply transformations and manually ingest the collections,
-
Create a table with a structure that can store the ingested collections.
-
Create a stored procedure to map the MongoDB® collection to the SingleStore table and implement other transformations required.
-
Create a pipeline to ingest the MongoDB® collections using the
CREATE AGGREGATOR PIPELINE
SQL statement.Refer to Parameters for a list of supported parameters. Note
The CDC feature only supports
AGGREGATOR
pipelines.
-
-
(Optional) Run the
CREATE {TABLES | TABLE} AS INFER PIPELINE .
SQL statement to infer the schema of the collection(s) and generate the relevant table(s), stored procedure, and aggregator pipeline, automatically.. . Subsequently, use the automatically generated stored procedure and pipeline as a base for custom transformations. To inspect the stored procedure and pipeline, use the SHOW CREATE PROCEDURE
andSHOW CREATE PIPELINE
commands, respectively.
Once all the components are configured, start the pipelines.
To ingest data in the JSON format instead of BSON, you need to manually create the required table structures, pipelines, and stored procedures for mapping the BSON data type to JSON.
Syntax
CREATE LINK [db_name.]connection_name AS MONGODBCREDENTIALS 'credentials_json' [<link_configuration>]
Refer to CREATE LINK for the complete syntax and related information.
CREATE TABLE [IF NOT EXISTS] <table_name> AS INFER PIPELINE AS LOAD DATA[ LINK <link_name> FORMAT AVRO ... ][ MONGODB <collection> CONFIG <conf_json> CREDENTIALS <cred_json> FORMAT AVRO ... ]CREATE TABLES [IF NOT EXISTS] AS INFER PIPELINE AS LOAD DATA[ LINK <link_name> FORMAT AVRO ... ][ MONGODB '*' CONFIG <conf_json> CREDENTIALS <cred_json> FORMAT AVRO ... ]
Refer to CREATE TABLE for related information.
CREATE [OR REPLACE] AGGREGATOR PIPELINE [IF NOT EXISTS] <pipeline_name> ASLOAD DATA MONGODB <link_configuration> ...<avro_format_options><link_configuration>:LINK [<database_name>.]<connection_name> '<path>'<avro_format_options>:FORMAT AVRO SCHEMA REGISTRY {uri}( {<column_name> | @<variable_name>} <- <subvalue_path>, ...)[SCHEMA '<avro_schema>'][KAFKA KEY ( {<column_name> | @<variable_name>} <- <subvalue_path>, ...)]
Refer to CREATE PIPELINE for the complete syntax and related information.
Refer to CREATE PROCEDURE for information on creating stored procedures.
Parameters
The CREATE AGGREGATOR PIPELINE .
statement supports the following parameters in the CONFIG
/CREDENTIALS
clause:
-
mongodb.
: A comma-separated list of MongoDB® servers (nodes) in the replica set, inhosts 'hostname:[port]'
format.-
If
mongodb.
is set tomembers. auto. discover FALSE
, you must prefix the'hostname:[port]'
with the name of the replica set inmongodb.
, e.hosts g. , rset0/svchost-xxx:27017. The first node specified in mongodb.
is always selected as the primary node.hosts -
If
mongodb.
is set tomembers. auto. discover TRUE
, you must specify both the primary and secondary nodes in the replica set inmongodb.
.hosts
-
-
mongodb.
: Specifies whether the MongoDB® servers defined inmembers. auto. discover mongodb.
should be used to discover all the members of the replica set.hosts If disabled, the servers are used as is. -
mongodb.
: The name of the database user to use when connecting to MongoDB® servers.user -
mongodb.
: The password to use when connecting to MongoDB® servers.password -
mongodb.
: Enables the connector to use SSL when connecting to MongoDB® servers.ssl. enabled -
mongodb.
: Specifies the database containing MongoDB® credentials to use as an authentication source.authsource This parameter is only required when the MongoDB® instance is configured to use authentication with an authentication database other than admin
. -
collection.
: A comma-separated list of regular expressions that match fully-qualified namespaces (ininclude. list databaseName.
format) for MongoDB® collections to monitor.collectionName By default, all the collections are monitored, except for those in the local
andadmin
databases.When this option is specified, collections excluded from the list are not monitored. The collection.
andinclude. list collection.
parameters are mutually exclusive, i.exclude. list e. , they cannot be used in the same CREATE TABLE .
statement.. . AS INFER PIPELINE This parameter is only supported in CREATE TABLE .
statements.. . AS INFER PIPELINE -
collection.
: A comma-separated list of regular expressions that match fully-qualified namespaces (inexclude. list databaseName.
format) for MongoDB® collections to exclude from the monitoring list.collectionName By default, this list is empty. The collection.
andinclude. list collection.
parameters are mutually exclusive, i.exclude. list e. , they cannot be used in the same CREATE TABLE .
statement.. . AS INFER PIPELINE This parameter is only supported in CREATE TABLE .
statements.. . AS INFER PIPELINE -
database.
(Optional): A comma-separated list of regular expressions that match the names of databases to monitor.include. list By default, all the databases are monitored. When this option is specified, databases excluded from the list are not monitored. The database.
andinclude. list database.
parameters are mutually exclusive, i.exclude. list e. , they cannot be used in the same CREATE TABLE .
statement.. . AS INFER PIPELINE If this option is used with the collection.
orinclude. list collection.
option, it returns the intersection of the matches.exclude. list This parameter is only supported in CREATE TABLE .
statements.. . AS INFER PIPELINE -
database.
(Optional): A comma-separated list of regular expressions that match the names of databases to exclude from monitoring.exclude. list By default, this list is empty. The database.
andinclude. list database.
parameters are mutually exclusive, i.exclude. list e. , they cannot be used in the same CREATE TABLE .
statement.. . AS INFER PIPELINE If this option is used with the collection.
orinclude. list collection.
option, it returns the intersection of the matches.exclude'list This parameter is only supported in CREATE TABLE .
statements.. . AS INFER PIPELINE -
signal.
(Optional): A collection in the remote source that is used by SingleStore to generate special markings for snapshotting and synchronization.data. collection By default, this parameter is set to singlestore.
.signals The default signal collection is in the database named singlestore
.The MongoDB® user must have write permissions to this collection. -
max.
: Specifies the size of the queue inside the extractor process for records that are ready for ingestion.queue. size The default queue size is 1024. This variable also specifies the number of rows for each partition. Increasing the queue size results in an increase in the memory consumption by the replication process and you may need to increase the pipelines_ cdc_ java_ heap_ size. -
max.
: Specifies the maximum number of rows of data fetched from the remote source in a single iteration (batch).batch. size The default batch size is 512. max.
must be lower thanbatch. size max.
.queue. size -
poll.
: Specifies the interval for polling of remote sources if there were no new records in the previous iteration in the replication process.interval. ms The default interval is 500 milliseconds. -
snapshot.
: Specifies the snapshot mode for the pipeline.mode It can have one of the following values: -
"initial"
(Default): Perform a full snapshot first and replay CDC events created during the snapshot.Then, continue ingestion using CDC. -
"incremental"
: Start the snapshot operation and CDC simultaneously. -
"never"
: Skip the snapshot, and ingest changes using CDC.
Refer to CDC Snapshot Strategies for more information.
-
Remarks
-
The
CREATE TABLE [IF NOT EXISTS] <table_
statement,name> AS INFER PIPELINE -
Connects to the MongoDB® servers using the specified
LINK <link_
orname> MONGODB <collection> CONFIG <conf_
clause.json> CREDENTIALS <cred_ json> -
Discovers the available databases and collections filtered by
collection.
.include. list -
Infers the schema of the collection and then creates a table (named <table_
name>) in SingleStore using the inferred schema. You can also specify a table name that differs from the name of the source MongoDB® collection. If the specified table already exists, a new table is not created and the existing table is used instead. -
Creates a pipeline (named <source_
db_ name>. <table_ name>) and stored procedure (named <source_ db_ name>. <table_ name>) that maps the AVRO data structure to the SingleStore data structure. The [IF NOT EXISTS]
clause is ignored for pipelines and stored procedures.If a pipeline or stored procedure with the same name already exists, the CREATE TABLE .
statement returns an error.. . AS INFER PIPELINE
-
-
The
CREATE TABLES [IF NOT EXISTS] AS INFER PIPELINE
statement creates a table for each collection in the source database using the same set of operations as theCREATE TABLE [IF NOT EXISTS] <table_
statement (specified in the previous list item).name> AS INFER PIPELINE -
The
MONGODB
source only supportsAVRO
data type. -
Use the
SYNC PIPELINE <pipeline_
statement to replicate (sync with) the data source.name>
CDC Snapshot Strategies
SingleStore supports the following strategies for creating snapshots:
-
Perform a full snapshot before CDC: The pipeline captures the position in the oplog and then performs a full snapshot of the data.
Once the snapshot is complete, the pipeline continues ingestion using CDC. This strategy is enabled by default. To use this strategy, set
"snapshot.
in themode":"initial" CONFIG
JSON.Requirement: The oplog retention period must be long enough to maintain the records while the snapshot is in progress.
Otherwise, the pipeline will fail and the process will have to be started over. -
CDC only: The pipeline will not ingest existing data, and only the changes are captured using CDC.
To use this strategy, set
"snapshot.
in themode":"never" CONFIG
JSON. -
Perform a snapshot in parallel to CDC: The pipeline captures the position in the oplog and starts capturing the changes using CDC.
In parallel, the pipeline performs incremental snapshots of the existing data and merges it with the CDC records. To use this strategy, set
"snapshot.
in themode":"incremental" CONFIG
JSON.Requirement: The oplog retention period must be long enough to compensate for unexpected pipeline downtime.
-
Manually perform the snapshot and capture changes using the CDC pipeline:
-
Create a pipeline and then wait for at least one batch of ingestion to capture the oplog position.
-
Stop the pipeline.
-
Snapshot the data using any of the suitable methods, for example,
mongodump
andmongorestore
. -
Start the pipeline.
To use this strategy, set
"snapshot.
in themode":"never" CONFIG
JSON.Requirement: The oplog retention period must be long enough to maintain the records while the snapshot is in progress.
Otherwise, the pipeline will fail and the process will have to be started over. -
Configure Ingestion Speed Limit
Use the pipelines_
engine variable to limit the impact of CDC pipelines on the master aggregator node.1000000
.
Use the max.
parameter in the CONFIG
JSON to control the ingestion speed.max.
to half of max.
.pipelines_
engine variable accordingly.INFORMATION_
table for information on pipeline batch performance.
Examples
Example 1 - Replicate Collections using SQL
The following example replicates data from an existing MongoDB® Atlas cluster into SingleStore Helios.
-
Create a link to the MongoDB® endpoint, for example, the primary node of a MongoDB® Atlas cluster.
CREATE LINK <linkname> AS MONGODBCONFIG '{"mongodb.hosts":"<Hostname>","collection.include.list": "<Collection list>","mongodb.ssl.enabled":"true","mongodb.authsource":"admin"}'CREDENTIALS '{"mongodb.user":"<username>","mongodb.password":"<password>"}'; -
Create tables in SingleStore Helios.
## Infer tables from sourceCREATE TABLES AS INFER PIPELINE AS LOAD DATA LINK <linkname> '*' FORMAT AVRO; -
Once the link and the tables are created, run the following command to start all the pipelines and begin the data replication process:
## Start pipelinesSTART ALL PIPELINES;
To view the status of all the pipelines, query the information_
table.
SELECT SOURCE_PARTITION_ID,EARLIEST_OFFSET,LATEST_OFFSET,LATEST_EXPECTED_OFFSET-LATEST_OFFSET as DIFF,UPDATED_UNIX_TIMESTAMPFROM information_schema.pipelines_cursors;
To view the ingested BSON data, SingleStore recommends the following:
-
Use the Kai Shell or other supported MongoDB tools, such as MongoDB Compass.
-
Cast the columns to JSON using the following SQL command:
SELECT _id :> JSON , _more :> JSON FROM <table_name>;
Example 2 - Create Tables with Different Names from the Source Collection
To create tables in SingleStore with names that differ from the name of the source MongoDB® collection, use the following syntax:
CREATE TABLE <new_table_name> AS INFER PIPELINE AS LOAD DATALINK <link_name> '<source_db.source_collection>' FORMAT AVRO;
You can also use this command to import collections if a table with the same name already exists in SingleStore.
Last modified: April 30, 2024