Description and usage of ConsumeKafka_1_0 processor:

Consumes messages from Apache Kafka specifically built against the Kafka 1.0 Consumer API. The complementary NiFi processor for sending messages is PublishKafka_1_0.

Tags:

Kafka, Get, Ingest, Ingress, Topic, PubSub, Consume, 1.0

Properties:

In the list below, the names of required properties appear in bold. Any other properties (not in bold) are considered optional. The table also indicates any default values, and whether a property supports the Expression Language Guide.

Name	Default Value	Allowable Values	Description
Kafka Brokers	localhost:9092		A comma-separated list of known Kafka Brokers in the format <host>:<port> Supports Expression Language: true (will be evaluated using variable registry only)
Security Protocol	PLAINTEXT	* PLAINTEXT * SSL * SASL_PLAINTEXT * SASL_SSL	Protocol used to communicate with brokers. Corresponds to Kafka's 'security.protocol' property.
Kerberos Service Name			The Kerberos principal name that Kafka runs as.This can be defined either in Kafka's JAAS config or in Kafka's config. Corresponds to Kafka's 'security.protocol' property.It is ignored unless one of the SASL options of the <Security Protocol> are selected. Supports Expression Language: true (will be evaluated using variable registry only)
Kerberos Credentials Service		Controller Service API: KerberosCredentialsService Implementation: KeytabCredentialsService	Specifies the Kerberos Credentials Controller Service that should be used for authenticating with Kerberos
Kerberos Principal			The Kerberos principal that will be used to connect to brokers. If not set, it is expected to set a JAAS configuration file in the JVM properties defined in the bootstrap.conf file. This principal will be set into 'sasl.jaas.config' Kafka's property. Supports Expression Language: true (will be evaluated using variable registry only)
Kerberos Keytab			The Kerberos keytab that will be used to connect to brokers. If not set, it is expected to set a JAAS configuration file in the JVM properties defined in the bootstrap.conf file. This principal will be set into 'sasl.jaas.config' Kafka's property. Supports Expression Language: true (will be evaluated using variable registry only)
SSL Context Service		Controller Service API: SSLContextService Implementations: StandardRestrictedSSLContextService StandardSSLContextService	Specifies the SSL Context Service to use for communicating with Kafka.
Topic Name(s)			The name of the Kafka Topic(s) to pull from. More than one can be supplied if comma separated. Supports Expression Language: true (will be evaluated using variable registry only)
Topic Name Format	names	* names * pattern	Specifies whether the Topic(s) provided are a comma separated list of names or a single regular expression
Honor Transactions	true	* true * false	Specifies whether or not NiFi should honor transactional guarantees when communicating with Kafka. If false, the Processor will use an "isolation level" of read_uncomitted. This means that messages will be received as soon as they are written to Kafka but will be pulled, even if the producer cancels the transactions. If this value is true, NiFi will not receive any messages for which the producer's transaction was canceled, but this can result in some latency since the consumer must wait for the producer to finish its entire transaction instead of pulling as the messages become available.
Group ID			A Group ID is used to identify consumers that are within the same consumer group. Corresponds to Kafka's 'group.id' property. Supports Expression Language: true (will be evaluated using variable registry only)
Offset Reset	latest	* earliest * latest * none	Allows you to manage the condition when there is no initial offset in Kafka or if the current offset does not exist any more on the server (e.g. because that data has been deleted). Corresponds to Kafka's 'auto.offset.reset' property.
Key Attribute Encoding	utf-8	* UTF-8 Encoded * Hex Encoded	FlowFiles that are emitted have an attribute named 'kafka.key'. This property dictates how the value of the attribute should be encoded.
Message Demarcator			Since KafkaConsumer receives messages in batches, you have an option to output FlowFiles which contains all Kafka messages in a single batch for a given topic and partition and this property allows you to provide a string (interpreted as UTF-8) to use for demarcating apart multiple Kafka messages. This is an optional property and if not provided each Kafka message received will result in a single FlowFile which time it is triggered. To enter special character such as 'new line' use CTRL+Enter or Shift+Enter depending on the OS Supports Expression Language: true (will be evaluated using variable registry only)
Message Header Encoding	UTF-8		Any message header that is found on a Kafka message will be added to the outbound FlowFile as an attribute. This property indicates the Character Encoding to use for deserializing the headers.
Headers to Add as Attributes (Regex)			A Regular Expression that is matched against all message headers. Any message header whose name matches the regex will be added to the FlowFile as an Attribute. If not specified, no Header values will be added as FlowFile attributes. If two messages have a different value for the same header and that header is selected by the provided regex, then those two messages must be added to different FlowFiles. As a result, users should be cautious about using a regex like ".*" if messages are expected to have header values that are unique per message, such as an identifier or timestamp, because it will prevent NiFi from bundling the messages together efficiently.
Max Poll Records	10000		Specifies the maximum number of records Kafka should return in a single poll.
Max Uncommitted Time	1 secs		Specifies the maximum amount of time allowed to pass before offsets must be committed. This value impacts how often offsets will be committed. Committing offsets less often increases throughput but also increases the window of potential data duplication in the event of a rebalance or JVM restart between commits. This value is also related to maximum poll records and the use of a message demarcator. When using a message demarcator we can have far more uncommitted messages than when we're not as there is much less for us to keep track of in memory.

Dynamic Properties:

Dynamic Properties allow the user to specify both the name and value of a property.

Name	Value	Description
The name of a Kafka configuration property.	The value of a given Kafka configuration property.	These properties will be added on the Kafka configuration after loading any provided configuration properties. In the event a dynamic property represents a property that was already set, its value will be ignored and WARN message logged. For the list of available Kafka properties please refer to: http://kafka.apache.org/documentation.html#configuration. Supports Expression Language: true (will be evaluated using variable registry only)

Relationships:

Name	Description
success	FlowFiles received from Kafka. Depending on demarcation strategy it is a flow file per message or a bundle of messages grouped by topic and partition.

Reads Attributes:

None specified.

Writes Attributes:

Name	Description
kafka.count	The number of messages written if more than one
kafka.key	The key of message if present and if single message. How the key is encoded depends on the value of the 'Key Attribute Encoding' property.
kafka.offset	The offset of the message in the partition of the topic.
kafka.timestamp	The timestamp of the message in the partition of the topic.
kafka.partition	The partition of the topic the message or message bundle is from
kafka.topic	The topic the message or message bundle is from

State management:

This component does not store state.

Restricted:

This component is not restricted.

Input requirement:

This component requires an incoming relationship.

System Resource Considerations:

None specified.

Summary

This Processor polls Apache Kafka for data using KafkaConsumer API available with Kafka 1.0. When a message is received from Kafka, this Processor emits a FlowFile where the content of the FlowFile is the value of the Kafka message.

Security Configuration

The Security Protocol property allows the user to specify the protocol for communicating with the Kafka broker. The following sections describe each of the protocols in further detail.

PLAINTEXT

This option provides an unsecured connection to the broker, with no client authentication and no encryption. In order to use this option the broker must be configured with a listener of the form:

PLAINTEXT://host.name:port

SSL

This option provides an encrypted connection to the broker, with optional client authentication. In order to use this option the broker must be configured with a listener of the form:

SSL://host.name:port

In addition, the processor must have an SSL Context Service selected.

If the broker specifies ssl.client.auth=none, or does not specify ssl.client.auth, then the client will not be required to present a certificate. In this case, the SSL Context Service selected may specify only a truststore containing the public key of the certificate authority used to sign the broker’s key.

If the broker specifies ssl.client.auth=required then the client will be required to present a certificate. In this case, the SSL Context Service must also specify a keystore containing a client key, in addition to a truststore as described above.

SASL_PLAINTEXT

This option uses SASL with a PLAINTEXT transport layer to authenticate to the broker. In order to use this option the broker must be configured with a listener of the form:

SSL://host.name:port

In addition, the Kerberos Service Name must be specified in the processor.

SASL_PLAINTEXT - GSSAPI

If the SASL mechanism is GSSAPI, then the client must provide a JAAS configuration to authenticate. The JAAS configuration can be provided by specifying the java.security.auth.login.config system property in NiFi’s bootstrap.conf, such as:

java.arg.16=-Djava.security.auth.login.config=/path/to/kafka_client_jaas.conf

An example of the JAAS config file would be the following:

KafkaClient {
    com.sun.security.auth.module.Krb5LoginModule required
    useKeyTab=true
    storeKey=true
    keyTab="/path/to/nifi.keytab"
    serviceName="kafka"
    principal="nifi@YOURREALM.COM";
};

NOTE: The serviceName in the JAAS file must match the Kerberos Service Name in the processor.

Alternatively, the JAAS configuration when using GSSAPI can be provided by specifying the Kerberos Principal and Kerberos Keytab directly in the processor properties. This will dynamically create a JAAS configuration like above, and will take precedence over the java.security.auth.login.config system property.

SASL_PLAINTEXT - PLAIN

If the SASL mechanism is PLAIN, then client must provide a JAAS configuration to authenticate, but the JAAS configuration must use Kafka’s PlainLoginModule. An example of the JAAS config file would be the following:

KafkaClient {
  org.apache.kafka.common.security.plain.PlainLoginModule required
  username="nifi"
  password="nifi-password";
};

NOTE: It is not recommended to use a SASL mechanism of PLAIN with SASL_PLAINTEXT, as it would transmit the username and password unencrypted.

NOTE: Using the PlainLoginModule will cause it be registered in the JVM’s static list of Providers, making it visible to components in other NARs that may access the providers. There is currently a known issue where Kafka processors using the PlainLoginModule will cause HDFS processors with Keberos to no longer work.

SASL_SSL

This option uses SASL with an SSL/TLS transport layer to authenticate to the broker. In order to use this option the broker must be configured with a listener of the form:

SASL_SSL://host.name:port

See the SASL_PLAINTEXT section for a description of how to provide the proper JAAS configuration depending on the SASL mechanism (GSSAPI or PLAIN).

See the SSL section for a description of how to configure the SSL Context Service based on the ssl.client.auth property.