In recent ClickHouse versions (21.3) Avro format for kafka does not work at all.
In ClickHouse 20.3 one Avro formatted kafka message can read, than stall forever.
Reportedly in ClickHouse prior 20.3 Avro formatted kafka messages work Ok while contain only single record
{
public:
    explicit SchemaRegistry(const std::string & base_url_, size_t schema_cache_max_size = 1000)
        : base_url(base_url_), schema_cache(schema_cache_max_size)
    {
        if (base_url.empty())
            throw Exception("Empty Schema Registry URL", ErrorCodes::BAD_ARGUMENTS);
    }
    avro::ValidSchema getSchema(uint32_t id)
    {
        auto [schema, loaded] = schema_cache.getOrSet(
            id,
            [this, id](){ return std::make_shared<avro::ValidSchema>(fetchSchema(id)); }
        );
        return *schema;
    }
private:
    avro::ValidSchema fetchSchema(uint32_t id)