Sink to Kafka
This topic describes how to sink data from RisingWave to a Kafka broker and how to specify security (encryption and authentication) settings.
A sink is an external target that you can send data to. To stream data out of RisingWave, you need to create a sink. Use the CREATE SINK
statement to create a sink. You can create a sink with data from a materialized view or a table. RisingWave only supports writing messages in non-transactional mode.
Syntax
NOTE
Names and unquoted identifiers are case-insensitive. Therefore, you must double-quote any of these fields for them to be case-sensitive. See also Identifiers.
Basic parameters
All WITH
options are required unless explicitly mentioned as optional.
Parameter or clause | Description |
---|---|
sink_name | Name of the sink to be created. |
sink_from | A clause that specifies the direct source from which data will be output. sink_from can be a materialized view or a table. Either this clause or a SELECT query must be specified. |
AS select_query | A SELECT query that specifies the data to be output to the sink. Either this query or a FROM clause must be specified. See SELECT for the syntax and examples of the SELECT command. |
connector | Sink connector type must be ‘kafka’ for Kafka sink. |
properties.bootstrap.server | Address of the Kafka broker. Format: ‘ip:port’. If there are multiple brokers, separate them with commas. |
topic | Address of the Kafka topic. One sink can only correspond to one topic. |
primary_key | Conditional. The primary keys of the sink. Use ’,’ to delimit the primary key columns. This field is optional if creating a PLAIN sink, but required if creating a DEBEZIUM or UPSERT sink. |
Additional Kafka parameters
When creating a Kafka sink in RisingWave, you can specify the following Kafka-specific parameters. To set the parameter, add the RisingWave equivalent of the Kafka parameter as a WITH
option. For additional details on these parameters, see the Configuration properties.
Kafka parameter name | RisingWave parameter name | Type |
---|---|---|
allow.auto.create.topics | properties.allow.auto.create.topics | bool |
batch.num.messages | properties.batch.num.messages | int |
batch.size | properties.batch.size | int |
client.id | properties.client.id | string |
enable.idempotence | properties.enable.idempotence | bool |
enable.ssl.certificate.verification | properties.enable.ssl.certificate.verification | bool |
max.in.flight.requests.per.connection | properties.max.in.flight.requests.per.connection | int |
message.max.bytes | properties.message.max.bytes | int |
message.send.max.retries | properties.message.send.max.retries | int |
message.timeout.ms | properties.message.timeout.ms | int |
queue.buffering.max.kbytes | properties.queue.buffering.max.kbytes | int |
queue.buffering.max.messages | properties.queue.buffering.max.messages | int |
queue.buffering.max.ms | properties.queue.buffering.max.ms | float |
request.required.acks | properties.request.required.acks | int |
retry.backoff.ms | properties.retry.backoff.ms | int |
receive.message.max.bytes | properties.receive.message.max.bytes | int |
ssl.endpoint.identification.algorithm | properties.ssl.endpoint.identification.algorithm | str |
NOTE
- Set
properties.ssl.endpoint.identification.algorithm
tonone
to bypass the verification of CA certificates and resolve SSL handshake failure. This parameter can be set to eitherhttps
ornone
. By default, it ishttps
. - Starting with version 2.0, the default value for
properties.message.timeout.ms
has changed from 5 seconds to 5 minutes, aligning with the default setting in the official Kafka library.
FORMAT and ENCODE options
NOTE
These options should be set in FORMAT data_format ENCODE data_encode (key = 'value')
, instead of the WITH
clause
Field | Notes |
---|---|
data_format | Data format. Allowed formats: PLAIN: Output data with insert operations. DEBEZIUM: Output change data capture (CDC) log in Debezium format. UPSERT: Output data as a changelog stream. primary_key must be specified in this case. To learn about when to define the primary key if creating an UPSERT sink, see the Overview. |
data_encode | Data encode. Allowed encodes: JSON: Supports PLAIN JSON, UPSERT JSON and DEBEZIUM JSON sinks. AVRO: Supports UPSERT AVRO and PLAIN AVRO sinks. PROTOBUF: Supports PLAIN PROTOBUF and UPSERT PROTOBUF sinks. For UPSERT PROTOBUF sinks, you must specify key encode text, while it remains optional for other format/encode combinations. |
force_append_only | If true, forces the sink to be PLAIN (also known as append-only), even if it cannot be. |
timestamptz.handling.mode | Controls the timestamptz output format. This parameter specifically applies to append-only or upsert sinks using JSON encoding. - If omitted, the output format of timestamptz is 2023-11-11T18:30:09.453000Z which includes the UTC suffix Z. - When utc_without_suffix is specified, the format is changed to 2023-11-11 18:30:09.453000. |
schemas.enable | Only configurable for upsert JSON sinks. By default, this value is false for upsert JSON sinks and true for debezium JSON sinks. If true, RisingWave will sink the data with the schema to the Kafka sink. Note that this is not referring to a schema registry containing a JSON schema, but rather schema formats defined using Kafka Connect. |
key_encode | Optional. When specified, the key encode can only be TEXT, and the primary key should be one and only one of the following types: varchar, bool, smallint, int, and bigint; When absent, both key and value will use the same setting of ENCODE data_encode ( … ). |
Avro specific parameters
When creating an Avro sink, the following options can be used following FORMAT UPSERT ENCODE AVRO
or FORMAT PLAIN ENCODE AVRO
.
Field | Notes |
---|---|
schema.registry | Required. The address of the schema registry. |
schema.registry.username | Optional. The user name used to access the schema registry. |
schema.registry.password | Optional. The password associated with the user name. |
schema.registry.name.strategy | Optional. Accepted options include topic_name_strategy (default), record_name_strategy, and topic_record_name_strategy. |
key.message | Required if schema.registry.name.strategy is set to record_name_strategy or topic_record_name_strategy. |
message | Required if schema.registry.name.strategy is set to record_name_strategy or topic_record_name_strategy. |
Syntax:
For data type mapping, the serial type is supported. We map the serial type to the 64-bit signed integer.
Protobuf specific parameters
When creating an append-only Protobuf sink, the following options can be used following FORMAT PLAIN ENCODE PROTOBUF
or FORMAT UPSERT ENCODE PROTOBUF
.
Field | Notes |
---|---|
message | Required. Package qualified message name of the main Message in the schema definition. |
schema.location | Required if schema.registry is not specified. Only one of schema.location or schema.registry can be defined. The schema location. This can be in either file://, http://, https:// format. |
schema.registry | Required if schema.location is not specified. Only one of schema.location or schema.registry can be defined. The address of the schema registry. |
schema.registry.username | Optional. The user name used to access the schema registry. |
schema.registry.password | Optional. The password associated with the user name. |
schema.registry.name.strategy | Optional. Accepted options include topic_name_strategy (default), record_name_strategy, and topic_record_name_strategy. |
NOTE
The file://
format is not recommended for production use. If it is used, it needs to be available for both meta and compute nodes.
Syntax:
For data type mapping, the serial type is supported. We map the serial type to the 64-bit signed integer.
JSON specific parameters
jsonb.handling.mode
The jsonb.handling.mode
determines how jsonb
data types are encoded. This parameter has two possible values:
string
: Encodes thejsonb
type to a string. For example, if you set this parameter,{"k": 2}
will be converted to"{\"k\": 2}"
.dynamic
: Dynamically encodes ajsonb
type value to a JSON type value. For example, if you set this parameter,{"k": 2}
will be converted to{"k": 2}
. Here thejsonb
value is encoded to a JSON object type value.
You can set this parameter in the WITH
clause of ENCODE JSON
.
Note for serial types
For data mapping, the serial type is supported. However, note that it is mapped into a JSON string like "0x05fb93d677c4e000"
instead of a JSON number 431100738685689856
. This string form avoids JSON number precision issues with large int64 values, and you can still order by the fixed-length hexadecimal string to obtain the same order as the serial number (whereas variable-length string "12"
sorts before "7"
).
Examples
Create a sink by selecting an entire materialized view.
Create a sink with the Kafka configuration message.max.bytes
set at 2000 by setting properties.message.max.bytes
to 2000.
Create a sink by selecting the average distance
and duration
from taxi_trips
.
The schema of taxi_trips
is like this:
The table may look like this:
Create sink with PrivateLink connection
If your Kafka sink service is located in a different VPC from RisingWave, use AWS PrivateLink or GCP Private Service Connect to establish a secure and direct connection. For details on how to set up an AWS PrivateLink connection, see Create an AWS PrivateLink connection.
To create a Kafka sink with a PrivateLink connection, in the WITH section of your CREATE SINK
statement, specify the following parameters.
Parameter | Notes |
---|---|
privatelink.targets | The PrivateLink targets that correspond to the Kafka brokers. The targets should be in JSON format. Note that each target listed corresponds to each broker specified in the properties.bootstrap.server field. If the order is incorrect, there will be connectivity issues. |
privatelink.endpoint | The DNS name of the VPC endpoint. If you’re using RisingWave Cloud, you can find the auto-generated endpoint after you created a connection. See details in Create a VPC connection. |
connection.name | The name of the connection, which comes from the connection created using the CREATE CONNECTION statement. Omit this parameter if you have provisioned a VPC endpoint using privatelink.endpoint (recommended). |
Here is an example of creating a Kafka sink using a PrivateLink connection. Notice that {"port": 8001}
corresponds to the broker ip1:9092
, and {"port": 8002}
corresponds to the broker ip2:9092
.
TLS/SSL encryption and SASL authentication
RisingWave can sink data to Kafka that is encrypted with Transport Layer Security (TLS) and/or authenticated with SASL.
Secure Sockets Layer (SSL) was the predecessor of Transport Layer Security (TLS), and has been deprecated since June 2015. For historical reasons, SSL
is used in configuration and code instead of TLS
.
Simple Authentication and Security Layer (SASL) is a framework for authentication and data security in Internet protocols.
RisingWave supports these SASL authentication mechanisms:
SASL/PLAIN
SASL/SCRAM
SASL/GSSAPI
SASL/OAUTHBEARER
SSL encryption can be used concurrently with SASL authentication mechanisms.
To learn about how to enable SSL encryption and SASL authentication in Kafka, including how to generate the keys and certificates, see the Security Tutorial from Confluent.
You need to specify encryption and authentication parameters in the WITH section of a CREATE SINK
statement.
To sink data encrypted with SSL without SASL authentication, specify these parameters in the WITH section of your CREATE SINK
statement.
Parameter | Notes |
---|---|
properties.security.protocol | Set to SSL. |
properties.ssl.ca.location | |
properties.ssl.certificate.location | |
properties.ssl.key.location | |
properties.ssl.key.password |
NOTE
For the definitions of the parameters, see the librdkafka properties list. Note that the parameters in the list assumes all parameters start with properties.
and therefore do not include this prefix.
Here is an example of creating a sink encrypted with SSL without using SASL authentication.
Data type mapping - RisingWave and Debezium JSON
RisingWave Data Type | Schema Type in JSON | Schema Name in JSON |
---|---|---|
boolean | boolean | n/a |
smallint | int16 | n/a |
integer | int32 | n/a |
bigint | int64 | n/a |
real | float | n/a |
double precision | double | n/a |
character varying | string | n/a |
bytea | bytes | n/a |
numeric | string | n/a |
date | int32 | org.apache.kafka.connect.data.Date |
time without time zone | int64 | org.apache.kafka.connect.data.Time |
timestamp | int64 | org.apache.kafka.connect.data.Timestamp |
timestamptz | string | io.debezium.time.ZonedTimestamp |
interval | string | io.debezium.time.Interval |
JSONB | string | io.debezium.data.Json |
struct | string | n/a |
array | string | n/a |
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