schema registry

[streamsend-io]

The SR container starts, connects & creates the __schemas topic.
On subsequent start, server startup validates the __schemas topic and then fails with

schema-registry  | [2024-09-25 07:18:13,444] ERROR Server died unexpectedly:  (io.confluent.kafka.schemaregistry.rest.SchemaRegistryMain)
schema-registry  | java.lang.NullPointerException: Cannot invoke "org.apache.kafka.clients.admin.ConfigEntry.value()" because the return value of "org.apache.kafka.clients.admin.Config.get(String)" is null

This is the docker-override.yml to recreate this issue:

---
services:
  schema-registry:
    image: confluentinc/cp-schema-registry:latest
    ports:
      - 8081:8081
    container_name: schema-registry
    depends_on:
      - tansu
    environment:
      SCHEMA_REGISTRY_HOST_NAME: schema-registry
      SCHEMA_REGISTRY_KAFKASTORE_BOOTSTRAP_SERVERS: "tansu:9092"
      SCHEMA_REGISTRY_CUB_KAFKA_TIMEOUT: 300
      SCHEMA_REGISTRY_KAFKASTORE_TOPIC_REPLICATION_FACTOR: 1

[shortishly]

The NullPointerException was being caused by Tansu returning a config value of null, which is allowed by the protocol but the Java client doesn't like, so the fix was to return "" instead. SR starts up, and is running fetches, but I've not checked beyond that. I've updated the justfile to incorporate the SR compose, and will merge this onto main shortly.