HTTP

This page describes the usage of the Stream Reactor HTTP Sink Connector.

A Kafka Connect sink connector for writing records from Kafka to HTTP endpoints.

Features

• Support for Json/Avro/String/Protobuf messages via Kafka Connect (in conjunction with converters for Schema-Registry based data storage).

• URL, header and content templating ability give you full control of the HTTP request.

• Configurable batching of messages, even allowing you to combine them into a single request selecting which data to send with your HTTP request.

Connector Class

io.lenses.streamreactor.connect.http.sink.HttpSinkConnector

Example

For more examples see the tutorials.

name=lenseshttp
connector.class=io.lenses.streamreactor.connect.http.sink.HttpSinkConnector
tasks.max=1
topics=topicToRead
value.converter=org.apache.kafka.connect.storage.StringConverter
key.converter=org.apache.kafka.connect.storage.StringConverter
connect.http.authentication.type=none
connect.http.method=POST
connect.http.endpoint=http://endpoint.local/receive
connect.http.request.content="My Static Content Template"
connect.http.batch.count=1

Content Template

The Lenses HTTP sink comes with multiple options for content templating of the HTTP request.

Static Templating

If you do not wish any part of the key, value, headers or other data to form a part of the message, you can use static templating:

connect.http.request.content="My Static Content Template"

Single Message Templating

When you are confident you will be generating a single HTTP request per Kafka message, then you can use the simpler templating.

In your configuration, in the content property of your config, you can define template substitutions like the following example:

(please note the XML is only an example, your template can consist of any text format that can be submitted in a http request)

connect.http.request.content="<product><id>{{value.name}}</id></product>"

Multiple Message Templating

To collapse multiple messages into a single HTTP request you can use the multiple messaging template. This is automatic if the template has a messages tag. See the below example:

  <messages>
    {{#message}}
        <message>
          <topic>{{topic}}</topic>
          <employee>{{value.employeeId}}</employee>
          <order>{{value.orderNo}}</order>
          <groupDomain>{{value.groupDomain}}</groupDomain>
        </message>
    {{/message}}
  </messages>

Again, this is an XML example but your message body can consist of anything including plain text, json or yaml.

Your connector configuration will look like this:

connect.http.request.content="<messages>{{#message}}<message><topic>{{topic}}</topic><employee>{{value.employeeId}}</employee><order>{{value.orderNo}}</order><groupDomain>{{value.groupDomain}}</groupDomain></message>{{/message}}</messages>"

The final result will be HTTP requests with bodies like this:

  <messages>
    <message>
      <topic>myTopic</topic>
       <employee>Abcd1234</employee>
       <order>10</order>
       <groupDomain>myExampleGroup.uk</groupDomain>
    </message>
    <message>
       <topic>myTopic</topic>
       <employee>Efgh5678</employee>
       <order>11</order>
       <groupDomain>myExampleGroup.uk</groupDomain>
    </message>
  </messages>

Available Keys

When using simple and multiple message templating, the following are available:

Field	Usage Example
Header	{{header.correlation-id}}
Value	{{value}}
	{{value.product.id}}
Key	{{key}}
	{{key.customer.number}}
Topic	{{topic}}
Partition	{{partition}}
Offset	{{offset}}
Timestamp	{{timestamp}}

URL Templating

URL including protocol (eg. http://lenses.io). Template variables can be used.

The URL is also a Content Template so can contain substitutions from the message key/value/headers etc. If you are batching multiple kafka messages into a single request, then the first message will be used for the substitution of the URL.

Authentication Options

Currently, the HTTP Sink supports either no authentication, BASIC HTTP authentication and OAuth2 authentication.

No Authentication (Default)

By default, no authentication is set. This can be also done by providing a configuration like this:

connect.http.authentication.type=none

BASIC HTTP Authentication

BASIC auth can be configured by providing a configuration like this:

connect.http.authentication.type=basic
connect.http.authentication.basic.username=user
connect.http.authentication.basic.password=password

OAuth2 Authentication

OAuth auth can be configured by providing a configuration like this:

connect.http.authentication.type=oauth2
connect.http.authentication.oauth2.token.url=http://myoauth2.local/getToken
connect.http.authentication.oauth2.client.id=clientId
connect.http.authentication.oauth2.client.secret=client-secret
connect.http.authentication.oauth2.token.property=access_token
connect.http.authentication.oauth2.client.scope=any
connect.http.authentication.oauth2.client.headers=header:value

Headers List

To customise the headers sent with your HTTP request you can supply a Headers List.

Each header key and value is also a Content Template so can contain substitutions from the message key/value/headers etc. If you are batching multiple kafka messages into a single request, then the first message will be used for the substitution of the headers.

Example:

connect.http.request.headers="Content-Type","text/plain","X-User","{{header.kafkauser}}","Product","{{value.product.id}}"

SSL Configuration

Enabling SSL connections between Kafka Connect and HTTP Endpoint ensures that the communication between these services is secure, protecting sensitive data from being intercepted or tampered with. SSL (or TLS) encrypts data in transit, verifying the identity of both parties and ensuring data integrity. Please check out SSL Configuration Properties section in order to set it up.

Batch Configuration

The connector offers three distinct flush options for data management:

• Flush by Count - triggers a file flush after a specified number of records have been written to it.

• Flush by Size - initiates a file flush once a predetermined size (in bytes) has been attained.

• Flush by Interval - enforces a file flush after a defined time interval (in seconds).

It's worth noting that the interval flush is a continuous process that acts as a fail-safe mechanism, ensuring that files are periodically flushed, even if the other flush options are not configured or haven't reached their thresholds.

Consider a scenario where the flush size is set to 10MB, and only 9.8MB of data has been written to the file, with no new Kafka messages arriving for an extended period of 6 hours. To prevent undue delays, the interval flush guarantees that the file is flushed after the specified time interval has elapsed. This ensures the timely management of data even in situations where other flush conditions are not met.

The flush options are configured using the batchCount, batchSize and `timeInterval properties. The settings are optional and if not specified the defaults are:

Field	Default
batchCount	50_000 records
batchSize	500000000 (500MB)
timeInterval	3_600 seconds (1 hour)

connect.http.batch.count=50000
connect.http.batch.size=500000000
connect.http.time.interval=3600

Configuration Examples

Some configuration examples follow on how to apply this connector to different message types.

These include converters, which are required to instruct Kafka Connect on how to read the source content.

Static string template

In this case the converters are irrelevant as we are not using the message content to populate our message template.

connector.class=io.lenses.streamreactor.connect.http.sink.HttpSinkConnector
topics=mytopic
tasks.max=1
connect.http.method=POST
connect.http.endpoint="https://my-endpoint.example.com"
connect.http.request.content="My Static Content Template"
connect.http.batch.count=1

Dynamic string template

The HTTP request body contains the value of the message, which is retained as a string value via the StringConverter.

connector.class=io.lenses.streamreactor.connect.http.sink.HttpSinkConnector
topics=mytopic
tasks.max=1
connect.http.method=POST
connect.http.endpoint="https://my-endpoint.example.com"
connect.http.request.content="{{value}}"
connect.http.batch.count=1
key.converter=org.apache.kafka.connect.storage.StringConverter
value.converter=org.apache.kafka.connect.storage.StringConverter

Dynamic string template containing json message fields

Specific fields from the JSON message are substituted into the HTTP request body alongside some static content.

connector.class=io.lenses.streamreactor.connect.http.sink.HttpSinkConnector
topics=mytopic
tasks.max=1
key.converter=org.apache.kafka.connect.storage.StringConverter
value.converter=org.apache.kafka.connect.json.JsonConverter
connect.http.method=POST
connect.http.endpoint="https://my-endpoint.example.com"
connect.http.request.content="product: {{value.product}}"
connect.http.batch.size=1
value.converter.schemas.enable=false

Dynamic string template containing whole json message

The entirety of the message value is substituted into a placeholder in the message body. The message is treated as a string via the StringConverter.

connector.class=io.lenses.streamreactor.connect.http.sink.HttpSinkConnector
topics=mytopic
tasks.max=1
key.converter=org.apache.kafka.connect.storage.StringConverter
value.converter=org.apache.kafka.connect.storage.StringConverter
connect.http.method=POST
connect.http.endpoint="https://my-endpoint.example.com"
connect.http.request.content="whole product message: {{value}}"
connect.http.time.interval=5

Dynamic string template containing avro message fields

Fields from the AVRO message are substituted into the message body in the following example:

connector.class=io.lenses.streamreactor.connect.http.sink.HttpSinkConnector
topics=mytopic
tasks.max=1
connect.http.method=POST
connect.http.endpoint="https://my-endpoint.example.com"
connect.http.request.content="product: {{value.product}}"
key.converter=org.apache.kafka.connect.storage.StringConverter
value.converter=io.confluent.connect.avro.AvroConverter
value.converter.schemas.enable=true
value.converter.schema.registry.url=http://schema-registry:8081

Error/Success Reporter

Starting from version 8.1 as pilot release we give our customers ability to use functionality called Reporter which (if enabled) writes Success and Error processing reports to specified Kafka topic. Reports don't have key and you can find details about status in the message headers and value.

In order to enable this functionality we have to enable one (or both if we want full reporting) of the properties below:

connect.reporting.error.config.enabled=true
connect.reporting.success.config.enabled=true

Then we need to specify other connectivity properties just as we would when configuring Kafka Producer. Full configuration options can be found on Success Reporter Properties and Error Reporter Properties. Below you will be able to find two examples: one with local/plain configuration, other using SASL connection parameter.

Plain Error Reporting

This is most common scenario for on-premises Kafka Clusters used just for monitoring

connect.reporting.error.config.enabled=true
connect.reporting.error.config.bootstrap.servers=localhost:9094
connect.reporting.error.config.topic=http-monitoring

Error Reporting using SASL

This is more robust scenario when Connecting to external Kafka Cluster

connect.reporting.error.config.enabled=true
connect.reporting.error.config.bootstrap.servers=my-kafka-cluster.com:9093
connect.reporting.error.config.security.protocol=SASL_SSL  
connect.reporting.error.config.sasl.mechanism=PLAIN  
connect.reporting.error.config.sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="MYUSER" password="MYPASSWORD";

Options

Configuration parameters

This sink connector supports the following options as part of its configuration:

Field	Type	Required	Values (Default)
connect.http.method	HttpMethod	Yes	POST, PUT, PATCH
connect.http.endpoint	String	Yes	URL Template
connect.http.request.content	String	Yes	Content Template
connect.http.authentication.type	Authentication	No	Authentication Options (none)
connect.http.request.headers	List[String]	No	Headers List
connect.http.batch.count	Int	No	The number of records to batch before sending the request, see Batch Configuration
connect.http.batch.size	Int	No	The size of the batch in bytes before sending the request, see Batch Configuration
connect.http.time.interval	Int	No	The time interval in milliseconds to wait before sending the request
connect.http.upload.sync.period	Int	No	Upload Sync Period (100) - polling time period for uploads in milliseconds
connect.http.error.threshold	Int	No	The number of errors to tolerate before failing the sink (5)
connect.http.retries.on.status.codes	List[String]	No	The status codes to retry on (408,429,500,502,5003,504)
connect.http.retries.max.retries	Int	No	The maximum number of retries to attempt (5)
connect.http.retries.max.timeout.ms	Int	No	The maximum time in milliseconds to retry a request. Backoff is used to increase the time between retries, up to this maximum (30000)
connect.http.connection.timeout.ms	Int	No	The HTTP connection timeout in milliseconds (10000)
connect.http.max.queue.size	int	No	For each processed topic, the connector maintains an internal queue. This value specifies the maximum number of entries allowed in the queue before the enqueue operation blocks. The default is 100,000.
connect.http.max.queue.offer.timeout.ms	int	No	The maximum time window, specified in milliseconds, to wait for the internal queue to accept new records. The default is 2 minutes

SSL Configuration Properties

Property Name	Description
ssl.truststore.location	Path to the truststore file containing the trusted CA certificates for verifying broker certificates.
ssl.truststore.password	Password for the truststore file to protect its integrity.
ssl.truststore.type	Type of the truststore (e.g., JKS, PKCS12). Default is JKS.
ssl.keystore.location	Path to the keystore file containing the client’s private key and certificate chain for client authentication.
ssl.keystore.password	Password for the keystore to protect the private key.
ssl.keystore.type	Type of the keystore (e.g., JKS, PKCS12). Default is JKS.
ssl.protocol	The SSL protocol used for secure connections (e.g., TLSv1.2, TLSv1.3). Default is TLSv1.3.
ssl.keymanager.algorithm	Algorithm used by the KeyManager to manage certificates. Default value is the key manager factory algorithm configured for the Java Virtual Machine.
ssl.trustmanager.algorithm	Algorithm used by the TrustManager to manage certificates. Default value is the key manager factory algorithm configured for the Java Virtual Machine.

Error Reporter Properties

Property Name	Description
connect.reporting.error.config.enabled	Specifies whether the reporter is enabled. false by default.
connect.reporting.error.config.bootstrap.servers	A list of host/port pairs to use for establishing the initial connection to the Kafka cluster. Required if reporter is enabled.
connect.reporting.error.config.topic	Specifies the topic for Reporter to write to.
connect.reporting.error.config.location	SASL Mechanism used when connecting.
connect.reporting.error.config.sasl.jaas.config	JAAS login context parameters for SASL connections in the format used by JAAS configuration files.
connect.reporting.error.config.sasl.mechanism	SASL mechanism used for client connections. This may be any mechanism for which a security provider is available.

Success Reporter Properties

Property Name	Description
connect.reporting.success.config.enabled	Specifies whether the reporter is enabled. false by default.
connect.reporting.success.config.bootstrap.servers	A list of host/port pairs to use for establishing the initial connection to the Kafka cluster. Required if reporter is enabled.
connect.reporting.success.config.topic	Specifies the topic for Reporter to write to.
connect.reporting.success.config.location	SASL Mechanism used when connecting.
connect.reporting.success.config.sasl.jaas.config	JAAS login context parameters for SASL connections in the format used by JAAS configuration files.
connect.reporting.success.config.sasl.mechanism	SASL mechanism used for client connections. This may be any mechanism for which a security provider is available.