Transform messages with Lua custom filter codev3.12+
Configure the Kafka Consume plugin to transform messages with Lua custom filter code. In this example, the Kafka Consume plugin normalizes messages to a table and decodes them into JSON when possible.
Prerequisites
-
You have a Kafka cluster
-
You have a Kafka topic in the cluster
Environment variables
-
BOOTSTRAP_SERVER_HOST: The bootstrap server host. -
KAFKA_TOPIC: The name of the Kafka topic to consume from.
Add this section to your kong.yaml configuration file:
_format_version: "3.0"
plugins:
- name: kafka-consume
config:
bootstrap_servers:
- host: ${{ env "DECK_BOOTSTRAP_SERVER_HOST" }}
port: 9092
topics:
- name: ${{ env "DECK_KAFKA_TOPIC" }}
mode: server-sent-events
message_by_lua_functions:
- |
return function(message)
local json = require("cjson.safe")
local m = type(message) == "table" and message or { value = message }
if type(m.value) == "string" then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
Make the following request:
curl -i -X POST http://localhost:8001/plugins/ \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '
{
"name": "kafka-consume",
"config": {
"bootstrap_servers": [
{
"host": "'$BOOTSTRAP_SERVER_HOST'",
"port": 9092
}
],
"topics": [
{
"name": "'$KAFKA_TOPIC'"
}
],
"mode": "server-sent-events",
"message_by_lua_functions": [
"return function(message)\n local json = require(\"cjson.safe\")\n local m = type(message) == \"table\" and message or { value = message }\n if type(m.value) == \"string\" then\n m.decoded = json.decode(m.value) or nil\n end\n m.processed_by_lua = true\n return m\nend\n"
]
}
}
'
Make the following request:
curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/plugins/ \
--header "accept: application/json" \
--header "Content-Type: application/json" \
--header "Authorization: Bearer $KONNECT_TOKEN" \
--data '
{
"name": "kafka-consume",
"config": {
"bootstrap_servers": [
{
"host": "'$BOOTSTRAP_SERVER_HOST'",
"port": 9092
}
],
"topics": [
{
"name": "'$KAFKA_TOPIC'"
}
],
"mode": "server-sent-events",
"message_by_lua_functions": [
"return function(message)\n local json = require(\"cjson.safe\")\n local m = type(message) == \"table\" and message or { value = message }\n if type(m.value) == \"string\" then\n m.decoded = json.decode(m.value) or nil\n end\n m.processed_by_lua = true\n return m\nend\n"
]
}
}
'
Make sure to replace the following placeholders with your own values:
-
region: Geographic region where your Kong Konnect is hosted and operates. -
controlPlaneId: Theidof the control plane. -
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account.
See the Konnect API reference to learn about region-specific URLs and personal access tokens.
echo "
apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
name: kafka-consume
namespace: kong
annotations:
kubernetes.io/ingress.class: kong
labels:
global: 'true'
config:
bootstrap_servers:
- host: '$BOOTSTRAP_SERVER_HOST'
port: 9092
topics:
- name: '$KAFKA_TOPIC'
mode: server-sent-events
message_by_lua_functions:
- |
return function(message)
local json = require('cjson.safe')
local m = type(message) == 'table' and message or { value = message }
if type(m.value) == 'string' then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
plugin: kafka-consume
" | kubectl apply -f -
Prerequisite: Configure your Personal Access Token
terraform {
required_providers {
konnect = {
source = "kong/konnect"
}
}
}
provider "konnect" {
personal_access_token = "$KONNECT_TOKEN"
server_url = "https://us.api.konghq.com/"
}
Add the following to your Terraform configuration to create a Konnect Gateway Plugin:
resource "konnect_gateway_plugin_kafka_consume" "my_kafka_consume" {
enabled = true
config = {
bootstrap_servers = [
{
host = var.bootstrap_server_host
port = 9092
} ]
topics = [
{
name = var.kafka_topic
} ]
mode = "server-sent-events"
message_by_lua_functions = [<<EOF
return function(message)
local json = require("cjson.safe")
local m = type(message) == "table" and message or { value = message }
if type(m.value) == "string" then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
EOF]
}
control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
}
This example requires the following variables to be added to your manifest. You can specify values at runtime by setting TF_VAR_name=value.
variable "kafka_topic" {
type = string
}
Add this section to your kong.yaml configuration file:
_format_version: "3.0"
plugins:
- name: kafka-consume
route: routeName|Id
config:
bootstrap_servers:
- host: ${{ env "DECK_BOOTSTRAP_SERVER_HOST" }}
port: 9092
topics:
- name: ${{ env "DECK_KAFKA_TOPIC" }}
mode: server-sent-events
message_by_lua_functions:
- |
return function(message)
local json = require("cjson.safe")
local m = type(message) == "table" and message or { value = message }
if type(m.value) == "string" then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
Make sure to replace the following placeholders with your own values:
-
routeName|Id: Theidornameof the route the plugin configuration will target.
Make the following request:
curl -i -X POST http://localhost:8001/routes/{routeName|Id}/plugins/ \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '
{
"name": "kafka-consume",
"config": {
"bootstrap_servers": [
{
"host": "'$BOOTSTRAP_SERVER_HOST'",
"port": 9092
}
],
"topics": [
{
"name": "'$KAFKA_TOPIC'"
}
],
"mode": "server-sent-events",
"message_by_lua_functions": [
"return function(message)\n local json = require(\"cjson.safe\")\n local m = type(message) == \"table\" and message or { value = message }\n if type(m.value) == \"string\" then\n m.decoded = json.decode(m.value) or nil\n end\n m.processed_by_lua = true\n return m\nend\n"
]
}
}
'
Make sure to replace the following placeholders with your own values:
-
routeName|Id: Theidornameof the route the plugin configuration will target.
Make the following request:
curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/routes/{routeId}/plugins/ \
--header "accept: application/json" \
--header "Content-Type: application/json" \
--header "Authorization: Bearer $KONNECT_TOKEN" \
--data '
{
"name": "kafka-consume",
"config": {
"bootstrap_servers": [
{
"host": "'$BOOTSTRAP_SERVER_HOST'",
"port": 9092
}
],
"topics": [
{
"name": "'$KAFKA_TOPIC'"
}
],
"mode": "server-sent-events",
"message_by_lua_functions": [
"return function(message)\n local json = require(\"cjson.safe\")\n local m = type(message) == \"table\" and message or { value = message }\n if type(m.value) == \"string\" then\n m.decoded = json.decode(m.value) or nil\n end\n m.processed_by_lua = true\n return m\nend\n"
]
}
}
'
Make sure to replace the following placeholders with your own values:
-
region: Geographic region where your Kong Konnect is hosted and operates. -
controlPlaneId: Theidof the control plane. -
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account. -
routeId: Theidof the route the plugin configuration will target.
See the Konnect API reference to learn about region-specific URLs and personal access tokens.
echo "
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
name: kafka-consume
namespace: kong
annotations:
kubernetes.io/ingress.class: kong
config:
bootstrap_servers:
- host: '$BOOTSTRAP_SERVER_HOST'
port: 9092
topics:
- name: '$KAFKA_TOPIC'
mode: server-sent-events
message_by_lua_functions:
- |
return function(message)
local json = require('cjson.safe')
local m = type(message) == 'table' and message or { value = message }
if type(m.value) == 'string' then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
plugin: kafka-consume
" | kubectl apply -f -
Next, apply the KongPlugin resource by annotating the httproute or ingress resource:
kubectl annotate -n kong httproute konghq.com/plugins=kafka-consume
kubectl annotate -n kong ingress konghq.com/plugins=kafka-consume
Prerequisite: Configure your Personal Access Token
terraform {
required_providers {
konnect = {
source = "kong/konnect"
}
}
}
provider "konnect" {
personal_access_token = "$KONNECT_TOKEN"
server_url = "https://us.api.konghq.com/"
}
Add the following to your Terraform configuration to create a Konnect Gateway Plugin:
resource "konnect_gateway_plugin_kafka_consume" "my_kafka_consume" {
enabled = true
config = {
bootstrap_servers = [
{
host = var.bootstrap_server_host
port = 9092
} ]
topics = [
{
name = var.kafka_topic
} ]
mode = "server-sent-events"
message_by_lua_functions = [<<EOF
return function(message)
local json = require("cjson.safe")
local m = type(message) == "table" and message or { value = message }
if type(m.value) == "string" then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
EOF]
}
control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
route = {
id = konnect_gateway_route.my_route.id
}
}
This example requires the following variables to be added to your manifest. You can specify values at runtime by setting TF_VAR_name=value.
variable "kafka_topic" {
type = string
}
Add this section to your kong.yaml configuration file:
_format_version: "3.0"
plugins:
- name: kafka-consume
consumer: consumerName|Id
config:
bootstrap_servers:
- host: ${{ env "DECK_BOOTSTRAP_SERVER_HOST" }}
port: 9092
topics:
- name: ${{ env "DECK_KAFKA_TOPIC" }}
mode: server-sent-events
message_by_lua_functions:
- |
return function(message)
local json = require("cjson.safe")
local m = type(message) == "table" and message or { value = message }
if type(m.value) == "string" then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
Make sure to replace the following placeholders with your own values:
-
consumerName|Id: Theidornameof the consumer the plugin configuration will target.
Make the following request:
curl -i -X POST http://localhost:8001/consumers/{consumerName|Id}/plugins/ \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '
{
"name": "kafka-consume",
"config": {
"bootstrap_servers": [
{
"host": "'$BOOTSTRAP_SERVER_HOST'",
"port": 9092
}
],
"topics": [
{
"name": "'$KAFKA_TOPIC'"
}
],
"mode": "server-sent-events",
"message_by_lua_functions": [
"return function(message)\n local json = require(\"cjson.safe\")\n local m = type(message) == \"table\" and message or { value = message }\n if type(m.value) == \"string\" then\n m.decoded = json.decode(m.value) or nil\n end\n m.processed_by_lua = true\n return m\nend\n"
]
}
}
'
Make sure to replace the following placeholders with your own values:
-
consumerName|Id: Theidornameof the consumer the plugin configuration will target.
Make the following request:
curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/consumers/{consumerId}/plugins/ \
--header "accept: application/json" \
--header "Content-Type: application/json" \
--header "Authorization: Bearer $KONNECT_TOKEN" \
--data '
{
"name": "kafka-consume",
"config": {
"bootstrap_servers": [
{
"host": "'$BOOTSTRAP_SERVER_HOST'",
"port": 9092
}
],
"topics": [
{
"name": "'$KAFKA_TOPIC'"
}
],
"mode": "server-sent-events",
"message_by_lua_functions": [
"return function(message)\n local json = require(\"cjson.safe\")\n local m = type(message) == \"table\" and message or { value = message }\n if type(m.value) == \"string\" then\n m.decoded = json.decode(m.value) or nil\n end\n m.processed_by_lua = true\n return m\nend\n"
]
}
}
'
Make sure to replace the following placeholders with your own values:
-
region: Geographic region where your Kong Konnect is hosted and operates. -
controlPlaneId: Theidof the control plane. -
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account. -
consumerId: Theidof the consumer the plugin configuration will target.
See the Konnect API reference to learn about region-specific URLs and personal access tokens.
echo "
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
name: kafka-consume
namespace: kong
annotations:
kubernetes.io/ingress.class: kong
config:
bootstrap_servers:
- host: '$BOOTSTRAP_SERVER_HOST'
port: 9092
topics:
- name: '$KAFKA_TOPIC'
mode: server-sent-events
message_by_lua_functions:
- |
return function(message)
local json = require('cjson.safe')
local m = type(message) == 'table' and message or { value = message }
if type(m.value) == 'string' then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
plugin: kafka-consume
" | kubectl apply -f -
Next, apply the KongPlugin resource by annotating the KongConsumer resource:
kubectl annotate -n kong CONSUMER_NAME konghq.com/plugins=kafka-consume
Prerequisite: Configure your Personal Access Token
terraform {
required_providers {
konnect = {
source = "kong/konnect"
}
}
}
provider "konnect" {
personal_access_token = "$KONNECT_TOKEN"
server_url = "https://us.api.konghq.com/"
}
Add the following to your Terraform configuration to create a Konnect Gateway Plugin:
resource "konnect_gateway_plugin_kafka_consume" "my_kafka_consume" {
enabled = true
config = {
bootstrap_servers = [
{
host = var.bootstrap_server_host
port = 9092
} ]
topics = [
{
name = var.kafka_topic
} ]
mode = "server-sent-events"
message_by_lua_functions = [<<EOF
return function(message)
local json = require("cjson.safe")
local m = type(message) == "table" and message or { value = message }
if type(m.value) == "string" then
m.decoded = json.decode(m.value) or nil
end
m.processed_by_lua = true
return m
end
EOF]
}
control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
consumer = {
id = konnect_gateway_consumer.my_consumer.id
}
}
This example requires the following variables to be added to your manifest. You can specify values at runtime by setting TF_VAR_name=value.
variable "kafka_topic" {
type = string
}