Kafka Bridge

The technical documentation of the kafka-bridge microservice, which acts as a communication bridge between two Kafka brokers.

Kafka-bridge is a microservice that connects two Kafka brokers and forwards messages between them. It is used to connect the local broker of the edge computer with the remote broker on the server.

How it works

This microservice has two ways of operation:

  • High Integrity: This mode is used for topics that are critical for the user. It is garanteed that no messages are lost. This is achieved by committing the message only after it has been successfully inserted into the database. Ususally all the topics are forwarded in this mode, except for processValue, processValueString and raw messages.
  • High Throughput: This mode is used for topics that are not critical for the user. They are forwarded as fast as possible, but it is possible that messages are lost, for example if the database struggles to keep up. Usually only the processValue, processValueString and raw messages are forwarded in this mode.

Kubernetes resources

  • Deployment: united-manufacturing-hub-kafkabridge
  • Secret:
    • Local broker: united-manufacturing-hub-kafkabridge-secrets-local
    • Remote broker: united-manufacturing-hub-kafkabridge-secrets-remote

Configuration

You can configure the kafka-bridge microservice by setting the following values in the _000_commonConfig.kafkaBridge section of the Helm chart values file.

  kafkaBridge:
    enabled: true
    remotebootstrapServer: ""
    topicmap:
      - bidirectional: false
        name: HighIntegrity
        send_direction: to_remote
        topic: ^ia\..+\..+\..+\.((addMaintenanceActivity)|(addOrder)|(addParentToChild)|(addProduct)|(addShift)|(count)|(deleteShiftByAssetIdAndBeginTimestamp)|(deleteShiftById)|(endOrder)|(modifyProducedPieces)|(modifyState)|(productTag)|(productTagString)|(recommendation)|(scrapCount)|(startOrder)|(state)|(uniqueProduct)|(scrapUniqueProduct))$
      - bidirectional: false
        name: HighThroughput
        send_direction: to_remote
        topic: ^ia\..+\..+\..+\.(processValue).*$

Topic Map schema

The topic map is a list of objects, each object represents a topic (or a set of topics) that should be forwarded. The following JSON schema describes the structure of the topic map:

{
    "$schema": "http://json-schema.org/draft-07/schema",
    "type": "array",
    "title": "Kafka Topic Map",
    "description": "This schema validates valid Kafka topic maps.",
    "default": [],
    "additionalItems": true,
    "items": {
        "$id": "#/items",
        "anyOf": [
            {
                "$id": "#/items/anyOf/0",
                "type": "object",
                "title": "Unidirectional Kafka Topic Map with send direction",
                "description": "This schema validates entries, that are unidirectional and have a send direction.",
                "default": {},
                "examples": [
                    {
                        "name": "HighIntegrity",
                        "topic": "^ia\\..+\\..+\\..+\\.(?!processValue).+$",
                        "bidirectional": false,
                        "send_direction": "to_remote"
                    }
                ],
                "required": [
                    "name",
                    "topic",
                    "bidirectional",
                    "send_direction"
                ],
                "properties": {
                    "name": {
                        "$id": "#/items/anyOf/0/properties/name",
                        "type": "string",
                        "title": "Entry Name",
                        "description": "Name of the map entry, only used for logging & tracing.",
                        "default": "",
                        "examples": [
                            "HighIntegrity"
                        ]
                    },
                    "topic": {
                        "$id": "#/items/anyOf/0/properties/topic",
                        "type": "string",
                        "title": "The topic to listen on",
                        "description": "The topic to listen on, this can be a regular expression.",
                        "default": "",
                        "examples": [
                            "^ia\\..+\\..+\\..+\\.(?!processValue).+$"
                        ]
                    },
                    "bidirectional": {
                        "$id": "#/items/anyOf/0/properties/bidirectional",
                        "type": "boolean",
                        "title": "Is the transfer bidirectional?",
                        "description": "When set to true, the bridge will consume and produce from both brokers",
                        "default": false,
                        "examples": [
                            false
                        ]
                    },
                    "send_direction": {
                        "$id": "#/items/anyOf/0/properties/send_direction",
                        "type": "string",
                        "title": "Send direction",
                        "description": "Can be either 'to_remote' or 'to_local'",
                        "default": "",
                        "examples": [
                            "to_remote",
                            "to_local"
                        ]
                    }
                },
                "additionalProperties": true
            },
            {
                "$id": "#/items/anyOf/1",
                "type": "object",
                "title": "Bi-directional Kafka Topic Map with send direction",
                "description": "This schema validates entries, that are bi-directional.",
                "default": {},
                "examples": [
                    {
                        "name": "HighIntegrity",
                        "topic": "^ia\\..+\\..+\\..+\\.(?!processValue).+$",
                        "bidirectional": true
                    }
                ],
                "required": [
                    "name",
                    "topic",
                    "bidirectional"
                ],
                "properties": {
                    "name": {
                        "$id": "#/items/anyOf/1/properties/name",
                        "type": "string",
                        "title": "Entry Name",
                        "description": "Name of the map entry, only used for logging & tracing.",
                        "default": "",
                        "examples": [
                            "HighIntegrity"
                        ]
                    },
                    "topic": {
                        "$id": "#/items/anyOf/1/properties/topic",
                        "type": "string",
                        "title": "The topic to listen on",
                        "description": "The topic to listen on, this can be a regular expression.",
                        "default": "",
                        "examples": [
                            "^ia\\..+\\..+\\..+\\.(?!processValue).+$"
                        ]
                    },
                    "bidirectional": {
                        "$id": "#/items/anyOf/1/properties/bidirectional",
                        "type": "boolean",
                        "title": "Is the transfer bidirectional?",
                        "description": "When set to true, the bridge will consume and produce from both brokers",
                        "default": false,
                        "examples": [
                            true
                        ]
                    }
                },
                "additionalProperties": true
            }
        ]
    },
    "examples": [
   {
      "name":"HighIntegrity",
      "topic":"^ia\\..+\\..+\\..+\\.(?!processValue).+$",
      "bidirectional":true
   },
   {
      "name":"HighThroughput",
      "topic":"^ia\\..+\\..+\\..+\\.(processValue).*$",
      "bidirectional":false,
      "send_direction":"to_remote"
   }
]
}

Environment variables

Environment variables
Variable nameDescriptionTypeAllowed valuesDefault
DEBUG_ENABLE_FGTRACEEnables the use of the fgtrace library, do not enable in productionstringtrue, falsefalse
KAFKA_GROUP_ID_SUFFIXIdentifier appended to the kafka group ID, usually a serial numberstringAnydefalut
KAFKA_SSL_KEY_PASSWORD_LOCALPassword for the SSL key pf the local brokerstringAny""
KAFKA_SSL_KEY_PASSWORD_REMOTEPassword for the SSL key of the remote brokerstringAny""
KAFKA_TOPIC_MAPA json map of the kafka topics should be forwardedJSONSee below{}
KAKFA_USE_SSLEnables the use of SSL for the kafka connectionstringtrue, falsefalse
LOCAL_KAFKA_BOOTSTRAP_SERVERURL of the local kafka broker, port is requiredstringAny valid URLunited-manufacturing-hub-kafka:9092
LOGGING_LEVELDefines which logging level is used, mostly relevant for developers.stringPRODUCTION, DEVELOPMENTPRODUCTION
MICROSERVICE_NAMEName of the microservice (used for tracing)stringAnyunited-manufacturing-hub-kafka-bridge
REMOTE_KAFKA_BOOTSTRAP_SERVERURL of the remote kafka brokerstringAny valid URL""
SERIAL_NUMBERSerial number of the cluster (used for tracing)stringAnydefalut
Last modified April 17, 2023: build: version 0.9.13 (6cb0a01)