架构注册表中的向后兼容性问题和不确定性 [英] Backward Comaptibility issue and uncertainity in Schema Registry
问题描述
我有一个用例，其中有一个JSON，我想生成模式并从JSON中记录并发布记录. 我已经配置了值序列化程序，并且Schema设置是向后兼容的.
I have a use case where I have a JSON and I want to generate schema and record out of the JSON and publish a record. I have configured the value serializer and Schema setting is Backward compatible.
第一个JSON
字符串json ="{\ n" +
String json = "{\n" +
" \"id\": 1,\n" +
" \"name\": \"Headphones\",\n" +
" \"price\": 1250.0,\n" +
" \"tags\": [\"home\", \"green\"]\n" +
"}\n"
;
已注册版本1模式.
在Avro控制台使用者中收到的消息.
Received message in avro console consumer.
第二个JSON.
字符串json ="{\ n" +
String json = "{\n" +
" \"id\": 1,\n" +
" \"price\": 1250.0,\n" +
" \"tags\": [\"home\", \"green\"]\n" +
"}\n"
;
成功注册架构. 已发送邮件.
Registered schema Successfully. Sent message.
现在尝试发送成功发送的JSON 1
Now tried sending the JSON 1 sent successfully
模式3:
字符串json ="{\ n" +
String json = "{\n" +
" \"id\": 1,\n" +
" \"name\": \"Headphones\",\n" +
" \"tags\": [\"home\", \"green\"]\n" +
"}\n"
;
在这种情况下出现错误. 由以下原因引起:io.confluent.kafka.schemaregistry.client.rest.exceptions.RestClientException:正在注册的架构与早期的架构不兼容.错误代码:409
Got error for this case. Caused by: io.confluent.kafka.schemaregistry.client.rest.exceptions.RestClientException: Schema being registered is incompatible with an earlier schema; error code: 409
如何注册从第二个JSON生成的架构，并且 第三个被拒绝了?虽然我没有任何默认键 删除字段?是架构注册表始终接受第一个 进化? (第2个模式超过第1个)
How is that schema generated from 2nd JSON was registered and the third one was rejected? Although I didn't have any Default key for the deleted field? Is it that the Schema Registry always accepts the 1st evolution? (2nd schema over 1st)
架构注册表中的架构
版本1模式
{ 字段":[
{ "fields": [
{
"doc": "Type inferred from '1'",
"name": "id",
"type": "int"
},
{
"doc": "Type inferred from '\"Headphones\"'",
"name": "name",
"type": "string"
},
{
"doc": "Type inferred from '1250.0'",
"name": "price",
"type": "double"
},
{
"doc": "Type inferred from '[\"home\",\"green\"]'",
"name": "tags",
"type": {
"items": "string",
"type": "array"
}
}
],
"name": "myschema",
"type": "record" }
版本2:
{ 字段":[
{ "fields": [
{
"doc": "Type inferred from '1'",
"name": "id",
"type": "int"
},
{
"doc": "Type inferred from '1250.0'",
"name": "price",
"type": "double"
},
{
"doc": "Type inferred from '[\"home\",\"green\"]'",
"name": "tags",
"type": {
"items": "string",
"type": "array"
}
}
],
"name": "myschema",
"type": "record" }
推荐答案
Let's go over the backwards compatibility rules... https://docs.confluent.io/current/schema-registry/avro.html#compatibility-types
首先，默认设置不是可传递的，因此版本3仅查看版本2.
First, the default isn't transitive, so version 3 only will look at version 2.
向后规则指出您可以删除字段或添加可选字段(默认情况下).我假设您的模式生成器工具不知道如何使用可选选项，因此只允许您删除而不允许添加.
The backwards rule states you can delete fields or add optional fields (those with a default). I assume your schema generator tool doesn't know how to use optionals, so you're only allowed to delete, not add.
在版本1和版本2之间，您已经删除了有效的名称字段.
Between version 1 and 2, you've deleted the name field, which is valid.
在版本2和传入版本3之间，它认为您正在尝试发布一个新的架构，该架构会取消价格(可以这样做)，但是会添加一个必填名称字段，这是不允许的.
Between version 2 and the incoming 3, it thinks you're trying to post a new schema which removes price (this is okay}, but adds a required name field, which is not allowed.
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