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Stable

This component is complete and can be used. The interfaces will be supported until the function is removed from the project via the deprecation process. There will be ongoing extensions to this function, but it will be done to ensure backward compatibility as far as possible. If there is a need to break backward compatibility, this will be discussed and reviewed in the community, with a documented timeline.

Kafka Open Metadata Topic Connector

The Kafka Open Metadata Topic Connector implements an Apache Kafka connector for a topic that exchanges Java Objects as JSON payloads.

Default Configuration

Producer

(see Apache Kafka producer configurations for more information and options)

Property Name Property Value
bootstrap.servers localhost:9092
acks all
retries 1
batch.size 16384
linger.ms 0
buffer.memory 33554432
max.request.size 10485760
key.serializer org.apache.kafka.common.serialization.StringSerializer
value.serializer org.apache.kafka.common.serialization.StringSerializer
bring.up.retries 10
bring.up.minSleepTime 5000

Consumer

(see Apache Kafka consumer configurations for more information and options)

Property Name Property Value
bootstrap.servers localhost:9092
enable.auto.commit true
auto.commit.interval.ms 1000
session.timeout.ms 30000
max.partition.fetch.bytes 10485760
key.deserializer org.apache.kafka.common.serialization.StringDeserializer
value.deserializer org.apache.kafka.common.serialization.StringDeserializer
bring.up.retries 10
bring.up.minSleepTime 5000

Security

By default kafka security is not configured. The exact configuration may depend on the specific kafka service being used. Service specific notes are below. They may work for other providers, and feedback is welcome so that this documentation can be updated accordingly.

Example: IBM Event Streams on IBM Cloud

There are 2 key pieces of information that are provided in the documentation for your configured cloud service

  • List of brokers - try to specify at least 3. The hosts in the examples below will need updating
  • API key - referred to as MYAPIKEY below

Given these, configure kafka properties for both provider and consumer as follows:

"broker.list: "broker-5-uniqueid.kafka.svcnn.region.eventstreams.cloud.ibm.com:9093, broker-3-uniqueid.kafka.svcnn.region.eventstreams.cloud.ibm.com:9093, broker-2-uniqueid.kafka.svcnn.region.eventstreams.cloud.ibm.com:9093, broker-0-uniqueid.kafka.svcnn.region.eventstreams.cloud.ibm.com:9093, broker-1-uniqueid.kafka.svcnn.region.eventstreams.cloud.ibm.com:9093, broker-4-uniqueid.kafka.svcnn.region.eventstreams.cloud.ibm.com:9093"
"security.protocol":"SASL_SSL",
"ssl.protocol":"TLSv1.2",
"ssl.enabled.protocols":"TLSv1.2",
"ssl.endpoint.identification.algorithm":"HTTPS",
"sasl.jaas.config":"org.apache.kafka.common.security.plain.PlainLoginModule required username='token' password='MYAPIKEY';",
"sasl.mechanism":"PLAIN"
An example of a use of this configuration can be found in the virtual data connector helm charts. See odpi-egeria-vdc helm chart

Handling Kafka Cluster Bring Up Issues

It's strongly recommended that you ensure Kafka is started before starting any Egeria servers, for example in Kubernetes you may add an init container into a pod running Egeria to validate Kafka is ok, before the main container is launched. The Helm charts that are provided by the Egeria team typically take this approach. You should also ensure that you have a highly available Kafka deployment with multiple brokers.

However in some environments users have encountered issues where the Kafka Cluster hasn't become fully available. To mitigate this, the Egeria Kafka Topic Connector provides a mechanism that verifies that the Kafka Cluster brokers are available before attempting to connect.

This mechanism is controlled by two properties.

  • bring.up.retries
  • bring.up.minSleepTime

bring.up.retries defaults to 10 and specifies the number of times the Egeria KafkaTopicConnector will retry verification before reporting a failure.

bring.up.minSleepTime is set to 5000ms by default and is the minimum amount of time to wait before attempting a verification retry. If a Kafka verification attempt takes longer than this value the KafkaTopicConnector does not pause before retring the verification.

Different Kafka issues will result in differing overall times. For example, if the Kafka brokers are not resolveable (typical if waiting for a Kubernetes service to start), the Kafka library API calls will immediately fail, and so the connector will impose the minimum delay of 5s, each iteration will therefore take 5s by default. If instead the network address is uncontactable, the Kafka client library will typically wait for 60s. As this is greater than 5s, no additional wait will be added.

If any capabilities of Egeria require Kafka and the topic connector cannot initialize, then the initialization of that capability will fail. For example attempting to start a server which is a member of a Cohort will fail if the Kafka Cluster is not accessible.

Topic Creation

Many enterprise Kafka services do not allow automatic topic creation.

You will need to manually create topics of the following form

BASE_TOPIC_NAME is the value used for topicURLRoot when configuring the egeria event bus. For example, the default value is egeria.

Cohort topics

For each cohort being used (such as cocoCohort): * BASE_TOPIC_NAME.omag.openmetadata.repositoryservices.cohort.COHORT_NAME.OMRSTopic

OMAS Topics

These need to be done FOR EACH SERVER configured to run one or more OMASs. (For example for Coco Pharmaceuticals this might include cocoMDS1, cocoMDS2, cocoMDS3 etc).

FOR EACH OMAS configured (eg Asset Consumer OMAS, Data Platform OMAS, Governance Engine OMAS etc)

  • BASE_TOPIC_NAME.omag.server.SERVER_NAME.omas.OMAS_NAME.InTopic
  • BASE_TOPIC_NAME.omag.server.SERVER_NAME.omas.OMAS_NAME.OutTopic

One way to configure is to initially run against a kafka service which allows auto topic creation, then make note of the kafka topics that have been created - so that they can be replicated on the restricted setup.

In addition review the Egeria Audit Log for any events beginning OCF-KAFKA-TOPIC-CONNECTOR so that action may be taken if for example topics are found to be missing.