Azure CosmosDB

This page describes the usage of the Stream Reactor Azure CosmosDB Sink Connector.

Version 10.0.0 introduces breaking changes: the connector has been renamed from DocumentDB, uses the official CosmosDB SDK, and supports new bulk and key strategies.

A Kafka Connect sink connector for writing records from Kafka to Azure CosmosDB using the SQL API.

Connector Class

io.lenses.streamreactor.connect.azure.cosmosdb.sink.CosmosDbSinkConnector

Example

For more examples see the tutorials.

name=cosmosdb
connector.class=io.lenses.streamreactor.connect.azure.cosmosdb.sink.CosmosDbSinkConnector
tasks.max=1
topics=orders-string
connect.cosmosdb.kcql=INSERT INTO orders SELECT * FROM orders-string
connect.cosmosdb.db=dm
connect.cosmosdb.endpoint=[YOUR_AZURE_ENDPOINT]
connect.cosmosdb.db.create=true
connect.cosmosdb.master.key=[YOUR_MASTER_KEY]
connect.cosmosdb.batch.size=10

KCQL support

You can specify multiple KCQL statements separated by**;** to have a connector sink multiple topics. The connector properties topics or topics.regex are required to be set to a value that matches the KCQL statements.

The following KCQL is supported:

INSERT | UPSERT
INTO <your-collection>
SELECT FIELD, ...
FROM kafka_topic
[PK FIELDS,...]

Examples:

-- Insert mode, select all fields from topicA
-- and write to tableA
INSERT INTO collectionA SELECT * FROM topicA

-- UPSERT mode, select 3 fields and
-- rename from topicB and write to tableB
-- with primary key as the field id from the topic
UPSERT INTO tableB SELECT x AS a, y, z AS c FROM topicB PK id

Insert Mode

Insert is the default write mode of the sink. It inserts messages from Kafka topics into CosmosDB.

Upsert Mode

The Sink supports CosmosDB upsert functionality which replaces the existing row if a match is found on the primary keys.

This mode works with at least once delivery semantics on Kafka as the order is guaranteed within partitions. If the same record is delivered twice to the sink, it results in an idempotent write. The existing record will be updated with the values of the second which are the same.

If records are delivered with the same field or group of fields that are used as the primary key on the target table, but different values, the existing record in the target table will be updated.

Since records are delivered in the order they were written per partition the write is idempotent on failure or restart. Redelivery produces the same result.

Bulk Mode

Bulk mode enables efficient batching of writes to CosmosDB, reducing API calls and improving throughput. Enable it with:

connect.cosmosdb.bulk.enabled=true

When enabled, you can control batching behavior using the KCQL PROPERTIES clause (flush.size, flush.count, flush.interval). If disabled, records are written individually.

Custom Key Strategy

You can control how the connector populates the id field in CosmosDB documents using:

connect.cosmosdb.key.source (Key, Metadata, KeyPath, ValuePath)
connect.cosmosdb.key.path (field path, used with KeyPath or ValuePath)

This allows you to use the Kafka record key, metadata, or a specific field from the key or value as the document ID.

Error Handling

Configure error handling and retry behavior with:

connect.cosmosdb.error.policy (NOOP, THROW, RETRY)
connect.cosmosdb.max.retries (max retry attempts)
connect.cosmosdb.retry.interval (milliseconds between retries)
connect.cosmosdb.error.threshold (number of errors tolerated before failing)

These settings control how the connector responds to errors during writes.

Throughput

You can set the manual throughput (RU/s) for new CosmosDB collections with:

connect.cosmosdb.collection.throughput=400

The default is 400 RU/s, which is the minimum allowed by Azure Cosmos DB and is cost-effective for most workloads.

Proxy

If you need to connect via a proxy, specify the proxy details with:

connect.cosmosdb.proxy=<proxy-uri>

Progress Reporting

Enable progress reporting to log how many records have been processed:

connect.progress.enabled=true

Option Reference

Name

Description

Type

Default Value

Authentication & Connection

connect.cosmosdb.endpoint

The Azure CosmosDB end point.

string

connect.cosmosdb.master.key

The connection master key.

password

connect.cosmosdb.proxy

Specifies the connection proxy details.

string

Database & Throughput

connect.cosmosdb.db

The Azure CosmosDB target database.

string

connect.cosmosdb.db.create

If set to true it will create the database if it doesn't exist. If this is set to default(false) an exception will be raised.

boolean

false

connect.cosmosdb.collection.throughput

The manual throughput to provision for new Cosmos DB collections (RU/s). The default is 400 RU/s, which is the minimum allowed by Azure Cosmos DB and is cost-effective for most workloads.

int

400

Key & Partitioning

connect.cosmosdb.key.source

The source of the key. There are 4 possible values: Key, Metadata, KeyPath or ValuePath.

string

Key

connect.cosmosdb.key.path

When used with key.source configurations of KeyPath or ValuePath, this is the path to the field in the object that will be used as the key. Defaults to 'id'.

string

Write & Consistency

connect.cosmosdb.consistency.level

Determines the write visibility. There are four possible values: Strong, BoundedStaleness, Session or Eventual.

string

Session

connect.cosmosdb.bulk.enabled

Enable bulk mode to reduce chatter.

boolean

false

connect.cosmosdb.kcql

KCQL expression describing field selection and data routing to the target CosmosDb.

string

Error Handling & Retries

connect.cosmosdb.error.policy

Specifies the action to be taken if an error occurs while inserting the data. Options: NOOP (swallow error), THROW (propagate error), RETRY (retry message). The number of retries is based on the error.

string

THROW

connect.cosmosdb.max.retries

The maximum number of times to try the write again.

int

connect.cosmosdb.retry.interval

The time in milliseconds between retries.

int

60000

connect.cosmosdb.error.threshold

The number of errors to tolerate before failing the sink.

int

Queue & Performance

connect.cosmosdb.flush.count.enable

Flush on count can be disabled by setting this property to 'false'.

boolean

true

connect.cosmosdb.upload.sync.period

The time in milliseconds to wait before sending the request.

int

100

connect.cosmosdb.executor.threads

The number of threads to use for processing the records.

int

connect.cosmosdb.max.queue.size

The maximum number of records to queue per topic before blocking. If the queue limit is reached the connector will throw RetriableException and the connector settings to handle retries will be used.

int

1000000

connect.cosmosdb.max.queue.offer.timeout.ms

The maximum time in milliseconds to wait for the queue to accept a record. If the queue does not accept the record within this time, the connector will throw RetriableException and the connector settings to handle retries will be used.

int

120000

Monitoring & Progress

connect.progress.enabled

Enables the output for how many records have been processed.

boolean

false

KCQL Properties

Note: The following KCQL PROPERTIES options are only available when connect.cosmosdb.bulk.enabled=true. If bulk mode is disabled, records are written individually.

The CosmosDB Sink Connector supports the following KCQL PROPERTIES options to control file flushing behavior:

Property

Description

Type

Default Value

flush.size

Specifies the size (in bytes) for the flush operation.

Long

(connector default)

flush.count

Specifies the number of records for the flush operation.

Int

(connector default)

flush.interval

Specifies the interval (in seconds) for the flush operation.

Long

(connector default)

Flush Options Explained:

Flush by Count: Triggers a flush after a specified number of records have been written.
Flush by Size: Initiates a flush once a predetermined size (in bytes) has been reached.
Flush by Interval: Enforces a flush after a defined time interval (in seconds), acting as a fail-safe to ensure timely data management even if other flush conditions are not met.

You can use these properties in your KCQL statement's PROPERTIES clause, for example:

INSERT INTO myCollection SELECT * FROM myTopic PROPERTIES('flush.size'=1000000, 'flush.interval'=30, 'flush.count'=5000)

Kafka payload support

This sink supports the following Kafka payloads:

Schema.Struct and Struct (Avro)
Schema.Struct and JSON
No Schema and JSON

Error policies

The connector supports Error policies.

Endpoint and Master Key Configuration

To connect to your Azure CosmosDB instance, the connector requires two essential configuration properties:

connect.cosmosdb.endpoint: This specifies the URI of your CosmosDB account. It should point to the connection endpoint provided in the Azure CosmosDB dashboard.
connect.cosmosdb.master.key: This is the authentication key used to access the database. Note: Azure often refers to this as the primary key, which can be confusing—the master.key in the connector configuration corresponds to Azure's primary key value.

Both properties are mandatory and must be set to establish a connection with CosmosDB.

Key Population Strategy

The connector offers flexible options for populating the id field of documents in CosmosDB. The behavior is controlled by two configurations:

connect.cosmosdb.key.source

Description: Defines the strategy used to extract or generate the document ID.
Valid Values:
- Key (default): Use the Kafka record key.
- Metadata: Use Kafka metadata (topic/partition/offset).
- KeyPath: Extract from a field within the Kafka key.
- ValuePath: Extract from a field within the Kafka value.
Display Name: Key strategy

connect.cosmosdb.key.path

Description: Specifies the field path to extract the key from, when using KeyPath or ValuePath.
Default: id
Example: If using ValuePath with connect.cosmosdb.key.path=id, the connector will use value.id as the document ID.

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