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What is a Schema Payload Validation Policy Interceptor?

Avoid outages from missing or badly formatted records, ensure all messages adhere to a schema.

This interceptor also supports validating payload against specific constraints for AvroSchema and Protobuf.

This is similar to the validations provided by JsonSchema, such as:

  • Number: minimum, maximum, exclusiveMinimum, exclusiveMaximum, multipleOf
  • String: minLength, maxLength, pattern, format
  • Collections: maxItems, minItems

This interceptor also supports validating payload against specific custom constraints expression, which uses a simple language familiar with devs is CEL (Common Expression Language)

This interceptor also supports validating payload against specific custom metadata.rules object in the schema using CEL, too.

View the full demo in realtime​

You can either follow all the steps manually, or watch the recording

Review the docker compose environment​

As can be seen from docker-compose.yaml the demo environment consists of the following services:

  • gateway1
  • gateway2
  • kafka-client
  • kafka1
  • kafka2
  • kafka3
  • schema-registry
cat docker-compose.yaml

Starting the docker environment​

Start all your docker processes, wait for them to be up and ready, then run in background

  • --wait: Wait for services to be running|healthy. Implies detached mode.
  • --detach: Detached mode: Run containers in the background
docker compose up --detach --wait

Creating topic topic-avro on gateway1​

Creating on gateway1:

  • Topic topic-avro with partitions:1 and replication-factor:1
kafka-topics \
    --bootstrap-server localhost:6969 \
    --replication-factor 1 \
    --partitions 1 \
    --create --if-not-exists \
    --topic topic-avro

Review the example avro schema​

Review the example avro schema

cat user-schema.avsc

Let's register it to the Schema Registry​

curl -s \
  http://localhost:8081/subjects/topic-avro/versions \
  -X POST \
  -H "Content-Type: application/vnd.schemaregistry.v1+json" \
  --data "{\"schemaType\": \"AVRO\", \"schema\": $(cat user-schema.avsc | jq tostring)}"

Review invalid payload​

Review invalid payload

cat invalid-payload.json

Let's send invalid data​

cat invalid-payload.json | jq -c | \
    kafka-avro-console-producer \
        --bootstrap-server localhost:6969 \
        --topic topic-avro \
        --property schema.registry.url=http://localhost:8081 \
        --property value.schema.id=1

Let's consume it back​

That's pretty bad, you are going to propagate wrong data within your system!

kafka-avro-console-consumer \
    --bootstrap-server localhost:6969 \
    --topic topic-avro \
    --from-beginning \
    --timeout-ms 3000

Adding interceptor guard-schema-payload-validate​

Add Schema Payload Validation Policy Interceptor

step-11-guard-schema-payload-validate-interceptor.json:

{
  "kind" : "Interceptor",
  "apiVersion" : "gateway/v2",
  "metadata" : {
    "name" : "guard-schema-payload-validate"
  },
  "spec" : {
    "comment" : "Adding interceptor: guard-schema-payload-validate",
    "pluginClass" : "io.conduktor.gateway.interceptor.safeguard.SchemaPayloadValidationPolicyPlugin",
    "priority" : 100,
    "config" : {
      "schemaRegistryConfig" : {
        "host" : "http://schema-registry:8081"
      },
      "topic" : "topic-.*",
      "schemaIdRequired" : true,
      "validateSchema" : true,
      "action" : "BLOCK"
    }
  }
}
curl \
    --silent \
    --request PUT "http://localhost:8888/gateway/v2/interceptor" \
    --header "Content-Type: application/json" \
    --user "admin:conduktor" \
    --data @step-11-guard-schema-payload-validate-interceptor.json | jq

Listing interceptors​

Listing interceptors on gateway1

curl \
    --silent \
    --request GET "http://localhost:8888/gateway/v2/interceptor" \
    --user "admin:conduktor" | jq

Review the avro schema with validation rules​

Review the avro schema with validation rules

cat user-schema-with-validation-rules.avsc

Let's update the schema with our validation rules​

curl -s \
  http://localhost:8081/subjects/topic-avro/versions \
  -X POST \
  -H "Content-Type: application/vnd.schemaregistry.v1+json" \
  --data "{\"schemaType\": \"AVRO\", \"schema\": $(cat user-schema-with-validation-rules.avsc | jq tostring)}"

Let's asserts number of registered schemas​

curl -s http://localhost:8081/subjects/topic-avro/versions

Let's produce the same invalid payload again​

The payload has been rejected with useful errors

org.apache.kafka.common.errors.PolicyViolationException: Request parameters do not satisfy the configured policy. 
Topic 'topic-avro' has invalid avro schema payload: hobbies must have 2 items, age must be greater than or equal to 18, email should end with 'example.com', name is too short (1 < 3), name does not match expression 'size(name) >= 3 && size(name) <= 50', email does not match format 'email', email does not match expression 'email.contains('foo')', street is too long (56 > 15), street does not match expression 'size(street) >= 5 && size(street) <= 15', city is too short (0 < 2), address does not match expression 'size(address.street) >= 5 && address.street.contains('paris') || address.city == 'paris'', hobbies has too few items (1 < 2), hobbies does not match expression 'size(hobbies) >= 2', name does not match expression 'size(name) <= 4', age is greater than 10, name does not match expression 'size(name) <= 4', age is greater than 10
cat invalid-payload.json | jq -c | \
    kafka-avro-console-producer \
        --bootstrap-server localhost:6969 \
        --topic topic-avro \
        --property schema.registry.url=http://localhost:8081 \
        --property value.schema.id=2

Check in the audit log that message was denied​

Check in the audit log that message was denied in cluster kafka1

kafka-console-consumer \
    --bootstrap-server localhost:9092,localhost:9093,localhost:9094 \
    --topic _conduktor_gateway_auditlogs \
    --from-beginning \
    --timeout-ms 3000 \| jq 'select(.type=="SAFEGUARD" and .eventData.plugin=="io.conduktor.gateway.interceptor.safeguard.SchemaPayloadValidationPolicyPlugin")'

returns 1 event

{
  "id" : "25cb4ba1-37a6-42a8-baad-68be330f1ce9",
  "source" : "krn://cluster=p0KPFA_mQb2ixdPbQXPblw",
  "type" : "SAFEGUARD",
  "authenticationPrincipal" : "passthrough",
  "userName" : "anonymous",
  "connection" : {
    "localAddress" : null,
    "remoteAddress" : "/172.29.0.1:58384"
  },
  "specVersion" : "0.1.0",
  "time" : "2024-11-17T20:22:11.698055963Z",
  "eventData" : {
    "interceptorName" : "guard-schema-payload-validate",
    "level" : "error",
    "plugin" : "io.conduktor.gateway.interceptor.safeguard.SchemaPayloadValidationPolicyPlugin",
    "message" : "Request parameters do not satisfy the configured policy. Request parameters do not satisfy the configured policy. Topic 'topic-avro' has invalid avro schema payload: hobbies must have 2 items, age must be greater than or equal to 18, email should end with 'example.com', name is too short (1 < 3), name does not match expression 'size(name) >= 3 && size(name) <= 50', email does not match format 'email', email does not match expression 'email.contains('foo')', street is too long (56 > 15), street does not match expression 'size(street) >= 5 && size(street) <= 15', city is too short (0 < 2), address does not match expression 'size(address.street) >= 5 && address.street.contains('paris') || address.city == 'paris'', hobbies has too few items (1 < 2), hobbies does not match expression 'size(hobbies) >= 2', name does not match expression 'size(name) <= 4', age is greater than 10, name does not match expression 'size(name) <= 4', age is greater than 10"
  }
}

Let's now produce a valid payload​

cat valid-payload.json | jq -c | \
    kafka-avro-console-producer \
        --bootstrap-server localhost:6969 \
        --topic topic-avro \
        --property schema.registry.url=http://localhost:8081 \
        --property value.schema.id=2

And consume it back​

kafka-avro-console-consumer \
    --bootstrap-server localhost:6969 \
    --topic topic-avro \
    --from-beginning \
    --timeout-ms 3000

Tearing down the docker environment​

Remove all your docker processes and associated volumes

  • --volumes: Remove named volumes declared in the "volumes" section of the Compose file and anonymous volumes attached to containers.
docker compose down --volumes

Conclusion

You can enrich your existing schema to add even more data quality to your systems!