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HTTP Sink connector

The HTTP Sink connector is a Stateless NiFi dataflow developed by Cloudera that is running in the Kafka Connect framework. Learn about the connector, its properties, and configuration.

The HTTP Sink connector obtains messages from a Kafka topic and transfers their content in a HTTP POST requests to a specified endpoint. The topic the connector receives messages from is determined by the value of the topics parameter in the configuration. The connector can forward the data it reads from Kafka as is (raw data) or can be configured to execute record processing. When record processing is enabled, the connector expects the incoming data in Avro or JSON format. In case of Avro, the connector can either read the record schema from the Avro file it receives (provided that the schema is embedded) or it can fetch the schema from Schema Registry. In case of JSON, it can either infer the schema or fetch it from Schema Registry. What strategy is used to retrieve the schema is determined by the Schema Access Strategy property.

If Schema Registry is used, and it is on a Kerberized cluster, the krb5.file property must point to the krb5.conf file that provides access to the cluster on which Schema Registry is present. This means that the krb5.conf file must be on the same cluster node that the connector runs on. The connections to Schema Registry and the HTTP server can be secured by TLS. The keystore and truststore files necessary for securing these connections must also be on the same cluster node that the connector runs on.

Properties and configuration

Configuration is passed to the connector in a JSON file during creation. The properties of the connector can be categorized into three groups. These are as follows:

Common connector properties
These are the properties of the Kafka Connect framework that are accepted by all connectors. For a comprehensive list of these properties, see the Apache Kafka documentation.
Stateless NiFi Sink properties
These are the properties that are specific to the Stateless NiFi Sink connector. All Stateless NiFi Sink connectors share and accept these properties. For a comprehensive list of these properties, see the Stateless NiFi Sink properties reference.
Connector/dataflow-specific properties
These properties are unique to this specific connector. Or to be more precise, unique to the dataflow running within the connector. These properties use the following prefix:
parameter.[***CONNECTOR NAME***] Parameters:
For a comprehensive list of these properties, see the HTTP Sink properties reference.

Notes and limitations

  • Required properties must be assigned a valid value even if they are not used in the particular configuration. If a required property is not used, either leave its default value, or completely remove the property from the configuration JSON.
  • If a property that has a default value is completely removed from the configuration JSON, the system uses the default value.
  • Properties not marked as required must be completely removed from the configuration JSON if not set.
  • Schema Branch and Schema Version can not be specified at the same time.
  • The value of the Schema Access Strategy property is not independent of the value of the Kafka Message Data Format property. As a result, you must exercise caution when configuring Schema Access Strategy.
    • If the value of Kafka Message Data Format is AVRO, the possible values for Schema Access Strategy are Schema Registry, Embedded Schema or HWX Content-Encoded Schema Reference.
    • If the value of Kafka Message Data Format is JSON, the possible values for Schema Access Strategy are Schema Registry or Infer Schema.

Configuration example

In this example, the connector receives data in any format and forwards the raw data as the content of an HTTP POST request.

{
 "connector.class": "org.apache.nifi.kafka.connect.StatelessNiFiSinkConnector",
 "meta.smm.predefined.flow.name": "HTTP Sink",
 "meta.smm.predefined.flow.version": "1.0.0",
 "key.converter": "org.apache.kafka.connect.converters.ByteArrayConverter",
 "value.converter": "org.apache.kafka.connect.converters.ByteArrayConverter",
 "tasks.max": "1",
 "nexus.url": "https://repository.cloudera.com/artifactory/repo",
 "extensions.directory": "/tmp/nifi-stateless-extensions",
 "working.directory": "/tmp/nifi-stateless-working",
 "input.port": "Input from Kafka",
 "failure.ports": "Failure",
 "topics": "[***KAFKA TOPIC NAME***]",
 "parameter.HTTP Sink Parameters:Forward Raw Data": "true",
 "parameter.HTTP Sink Parameters:Remote URL": "http://[***SERVER HOSTNAME***]:[***PORT***]/[***PATH***]"
}
The following list collects the properties from the configuration example that must be customized for this use case.
topics
The name of the Kafka topic the connector fetches messages from.
Forward Raw Data
Specifies whether messages from Kafka should be forwarded as is or converted to JSON. In this example, the property is set to true, meaning that the connector does not process any records. It forwards incoming data as is.
Remote URL
Identifies the HTTP endpoint that receives the messages sent by this connector. In this example, SSL is not used. As a result, the URL starts with http not https. For example, http://my.http-server.com:22000/contentListener.

Stateless NiFi Sink properties reference

Review the following reference for a comprehensive list of the connector properties that are specific to the Stateless NiFi Sink connector.

In addition to the properties listed here, Stateless NiFi connectors also accept the properties of the Kafka Connect framework. For a comprehensive list of these properties, see the Apache Kafka documentation.

attribute.prefix

Description
The prefix to add to the key of each header that matches the regular expression specified in headers.as.attributes.regex. For example, if the header key is MyHeader, its value is MyValue, headers.as.attributes.regex is set to My.*, and this property is set to kafka, the flowfile that is created for the Kafka message will have an attribute named kafka.MyHeader with a value of MyValue.
Default Value
Accepted Values
Required
false

dataflow.timeout

Description
Specifies the maximum amount of time to wait for the dataflow to complete. If the dataflow does not complete before this timeout, the thread is interrupted and the dataflow is considered as a failure. The session is rolled back and the connector retriggers the flow. Defaults to 60 seconds if not specified.
Default Value
60 seconds
Accepted Values
Required
false

extensions.directory

Description
Specifies the directory that stores downloaded extensions. Extensions are the NAR (NiFi Archive) files containing the processors and controller services a flow might use. Since Stateless NiFi is only the NiFi engine, it does not contain any of the processors and controller services you might use in your flow. When deploying the connector with the custom flow, the system needs to download the specific extensions that your flow uses from Nexus (unless they are already present in this directory). These extensions are stored in this directory. Because the default directory might not be writable, and to aid in upgrade scenarios, Cloudera recommends that you always specify an extensions directory.
Default Value
/tmp/nifi-stateless-extensions
Accepted Values
Required
true

failure.ports

Description
A comma separated list of output ports that are considered as failure conditions. If any flowfile is routed to an output port specified in this property, the dataflow is considered a failure and the session is rolled back. After a set amount of time, the dataflow reattempts to process the Kafka record. Any data transferred to an output port that is not in the list of failure ports is discarded.

Because of how Stateless NiFi Sink connectors behave, even if a single flowfile ends up in an output port that is marked as failure, the entire sessions is rolled back with all messages in the batch. Furthermore, if a flowfile ends up in a failure port in each subsequent iteration, the result is an endless loop. With some sink connectors (for example. MQTT Sink) this is the desired behavior. For more information regarding this behavior, see Dataflow execution and scheduling.

Default Value
Accepted Values
Required
false

flow.snapshot

Description
Specifies the dataflow to run. When using Streams Messaging Manager to deploy a connector, the value you set in this property must be a JSON object. URLs, file paths, or escaped JSON strings are not supported when using Streams Messaging Manager. Alternatively, if using the Kafka Connect REST API to deploy a connector, this can be a file containing the dataflow, a URL that points to a dataflow, or a string containing the entire dataflow as an escaped JSON. Cloudera however, does not recommend using the Kafka Connect REST API to interact with this connector or Kafka Connect.
Default Value
Accepted Values
Required
true

headers.as.attributes.regex

Description
A Java regular expression that is evaluated against all Kafka record headers. Headers are added to the flowfile as an attribute if the header key matches the regular expression. The header key is used as the attribute name. The header value is used as the attribute value. Additionally, the name of the attribute can also contain an optional prefix which is defined by the attribute.prefix property.
Default Value
Accepted Values
Required
false

input.port

Description
The name of the input port in the NiFi dataflow that Kafka records are sent to. If the dataflow contains exactly one input port, this property is optional and can be omitted. However, if the dataflow contains multiple input ports, this property must be specified.
Default Value
Accepted Values
Required
false

krb5.file

Description
Specifies the krb5.conf file to use if the dataflow interacts with any services that are secured using Kerberos. Defaults to /etc/krb5.conf if not specified.
Default Value
/etc/krb5.conf
Accepted Values
Required
false

name

Description
The name of the connector. On the Streams Messaging Manager UI, the connector names are specified using the Enter Name field. The name that you enter in the Enter Name field is automatically set as the value of the name property when the connector is deployed. Because of this, the name property is omitted from the configuration template provided in Streams Messaging Manager. If you manually add the name property to the configuration in Streams Messaging Manager, ensure that the value you set matches the connector name specified in the Enter Name field. Otherwise, the connector fails to deploy.
Default Value
Accepted Values
Required
true

nexus.url

Description
Specifies the Base URL of the Nexus instance to source extensions from. If configuring a Nexus instance that has multiple repositories, include the name of the repository in the URL. For example, https://nexus-private.myorganization.org/nexus/repository/my-repository/. If the property is not specified, the necessary extensions (the ones used by the flow) must be provided in the extensions directory before deploying the connector.
Default Value
Accepted Values
Required
true

parameter.[***FLOW PARAMETER NAME***]

Description
Specifies a parameter to use in the dataflow. For example, assume that you have the following entry in your connector configuration "parameter.Directory": "/mydir". In a case like this, any parameter context in the dataflow that has a parameter named Directory gets the specified value (/mydir). If the dataflow has child process groups, and those child process groups have their own parameter contexts, the value is used for all parameter contexts that contain a parameter named Directory. Parameters can also be applied to specific parameter contexts only. This can be done by prefixing the parameter name (Directory) with the name of the parameter context followed by a colon. For example, parameter.My Context:Directory only applies the specified value for the Directory parameter in the Parameter Context named My Context.
Default Value
Accepted Values
Required
false

working.directory

Description
Specifies a directory on the Connect server that NiFi should use for unpacking extensions that it needs to perform the dataflow. The contents of extensions.directory are unpacked here. Defaults to /tmp/nifi-stateless-working if not specified.
Default Value
/tmp/nifi-stateless-working
Accepted Values
Required
false

HTTP Sink properties reference

Review the following reference for a comprehensive list of the connector properties that are specific to the HTTP Sink connector.

The properties listed in this reference must be added to the connector configuration with the following prefix:
parameter.[***CONNECTOR NAME***] Parameters:

In addition to the properties listed here, this connector also accepts certain properties of the Kafka Connect framework as well as the properties of the NiFi Stateless Sink connector. When creating a new connector using the Streams Messaging Manager UI, all valid properties are presented in the default configuration template. You can view the configuration template to get a full list of valid properties. In addition, for more information regarding the accepted properties not listed here, you can review the Apache Kafka documentation and the Stateless NiFi Sink properties reference.

Basic Authentication Password

Description
The password to be used for authentication when connecting to the URL specified in the Remote URL property. If an authentication method other than Basic Authentication is used, this property must be completely removed from the configuration JSON.
Default Value
Accepted Values
Required
false

Basic Authentication Username

Description
The username used for authentication when connecting to the URL specified in the Remote URL property. Cannot include control characters (0-31), ':', or DEL (127). If an authentication method other than Basic Authentication is used, this property must be completely removed from the configuration JSON.
Default Value
Accepted Values
Required
false

Content-Type

Description
The Content-Type to specify in the HTTP header of the POST request sent by this connector.
Default Value
application/octet-stream
Accepted Values
Required
true

Date Format

Description
Specifies the format to use when reading date fields from JSON. If Forward Raw Data is set to false, the format defined here also applies to the date fields in the output JSON message.
Default Value
yyyy-MM-dd
Accepted Values
Required
true

Forward Raw Data

Description
Specifies whether messages from Kafka should be forwarded as is or converted to JSON. If set to false the Kafka Message Data Format parameter must be specified.
Default Value
true
Accepted Values
true, false
Required
true

Kafka Message Data Format

Description
Specifies the format of the messages the connector receives from Kafka. If the Forward Raw Data property is set to true then this property is ignored. However, even in a case like this, this property must be assigned a valid value.
Default Value
AVRO
Accepted Values
AVRO, JSON
Required
true

Kerberos Keytab for Schema Registry

Description
The fully-qualified filename of the Kerberos keytab associated with the principal for accessing Schema Registry.
Default Value
The location of the default keytab which is empty and can only be used for unsecure connections.
Accepted Values
Required
true

Kerberos Principal for Schema Registry

Description
The Kerberos principal used for authenticating to Schema Registry.
Default Value
default
Accepted Values
Required
true

Keystore Filename for Secure HTTP

Description
The fully-qualified filename of a keystore. This keystore is used to establish a secure connection with the HTTP server using mutual TLS.

If the HTTP server does not require client certificate authentication, this property must be completely removed from the configuration JSON.

Default Value
Accepted Values
Required
false

Keystore Key Password for Secure HTTP

Description
The password used to access the key stored in the keystore file configured in the Keystore Filename for Secure HTTP property.

If the HTTP server does not require client certificate authentication, this property must be completely removed from the configuration JSON.

Default Value
Accepted Values
Required
false

Keystore Password for Secure HTTP

Description
The password used to access the contents of the keystore configured in the Keystore Filename for Secure HTTP property.

If the HTTP server does not require client certificate authentication, this property must be completely removed from the configuration JSON.

Default Value
Accepted Values
Required
false

Keystore Type for Secure HTTP

Description
The type of the keystore configured in the Keystore Filename for Secure HTTP property.

If the HTTP server does not require client certificate authentication, this property must be completely removed from the configuration JSON.

Default Value
Accepted Values
BCFKS, PKCS12, JKS
Required
false

Output Grouping for JSON

Description
Specifies how JSON objects are grouped in the connector output.

If set to output-array, the output will consist of an array of JSON objects.

f set to output-oneline, each line of the output data becomes one JSON object. That is, each JSON object occupies one line in the output.

This property is only used if forwarding raw data is disabled (Forward Raw Data is set to false). This is because when forwarding raw data is disabled, the data coming from Kafka gets converted to JSON. However, this property must still be set even if forwarding raw data is enabled.

Default Value
output-oneline
Accepted Values

output-array, output-oneline

Required
true

Remote URL

Description
The remote URL to connect to. Must include scheme, host, port, and path.
Default Value
https://localhost:22000/contentListener
Accepted Values
Required
true

Schema Access Strategy

Description
Specifies the strategy used for determining the schema of the Kafka record. The value you set here depends on the data format set in Kafka Message Data Format.
  • If set to Schema Registry, the schema is read from Schema Registry. This setting can be used with both Avro and JSON formats.
  • If set to Infer Schema, the schema is inferred based on the input file. This setting can only be used if Kafka Message Data Format is JSON.
  • If set to Embedded Schema, the schema embedded in the input is used. This setting can only be used if Kafka Message Data Format is Avro.
  • If set to HWX Content-Encoded Schema Reference, the schema is read from Schema Registry. This setting can only be used if Kafka Message Data Format is Avro. In this case the Avro messages are expected to have a reference to the schema in Schema Registry encoded within the message content.
This property is not used if record processing is disabled (Forward Raw Data is set to true).
Default Value
Schema Registry
Accepted Values
Schema Registry, Infer Schema, Embedded Schema, HWX Content-Encoded Schema Reference
Required
true

Schema Branch

Description
The name of the branch to use when looking up the schema in Schema Registry. Schema Branch and Schema Version cannot be specified at the same time. If one is specified, the other needs to be removed from the configuration. If Schema Registry is not used, this property must be completely removed from the configuration.
Default Value
Accepted Values
Required
false

Schema Name

Description
The schema name to look up in Schema Registry.

If the Schema Access Strategy property is set to Schema Registry, this property must contain a valid schema name.

If Schema Registry is not used, this property must be completely removed from the configuration JSON.

Default Value
Accepted Values
Required
false

Schema Registry URL

Description
The URL of the Schema Registry server. If Schema Registry is not used, use the default value.
Default Value
http://localhost:7788/api/v1
Accepted Values
Required
true

Schema Version

Description
The version of the schema to look up in Schema Registry. If Schema Registry is used and a schema version is not specified, the latest version of the schema is retrieved. Schema Branch and Schema Version cannot be specified at the same time. If one is specified, the other needs to be removed from the configuration. If Schema Registry is not used, this property must be completely removed from the configuration.
Default Value
Accepted Values
Required
false

Time Format

Description
Specifies the format to use when reading time fields from JSON. If Forward Raw Data is set to false, the format defined here also applies to the time fields in the output JSON message.
Default Value
HH:mm:ss
Accepted Values
Required
true

Timestamp Format

Description
Specifies the format to use when reading timestamp fields from JSON. If Forward Raw Data is set to false, the format defined here also applies to the timestamp fields in the output JSON message.
Default Value
HH:mm:ss.SSS
Accepted Values
Required
true

Truststore Filename for Schema Registry

Description
The fully-qualified filename of a truststore. This truststore is used to establish a secure connection with Schema Registry using TLS.
Default Value
The location of the default truststore which is empty and can only be used for unsecure connection.
Accepted Values
Required
true

Truststore Filename for Secure HTTP

Description
The fully-qualified filename of a truststore. This truststore is used to establish a secure connection with the HTTP server using TLS
Default Value
The location of the default truststore which is empty and can only be used for unsecure connections.
Accepted Values
Required
true

Truststore Password for Schema Registry

Description
The password used to access the contents of the truststore configured in the Truststore Filename for Schema Registry property.
Default Value
password
Accepted Values
Required
true

Truststore Password for Secure HTTP

Description
The password used to access the contents of the truststore configured in the Truststore Filename for Secure HTTP property.
Default Value
password
Accepted Values
Required
true

Truststore Type for Schema Registry

Description
The type of the truststore configured in the Truststore Filename for Schema Registry property.
Default Value
JKS
Accepted Values
BCFKS, PKCS12, JKS
Required
true

Truststore Type for Secure HTTP

Description
The type of the truststore configured in the Truststore Filename for Secure HTTP property.
Default Value
JKS
Accepted Values
BCFKS, PKCS12, JKS
Required
true