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https://issues.apache.org/jira/browse/AVRO-3027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17289942#comment-17289942
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Yevhen Cherkes commented on AVRO-3027:
--------------------------------------
Hi, I have created a [PR1103|https://github.com/apache/avro/pull/1103], could
someone please review it?
> .net consumer Backward compatibility issue.
> --------------------------------------------
>
> Key: AVRO-3027
> URL: https://issues.apache.org/jira/browse/AVRO-3027
> Project: Apache Avro
> Issue Type: Bug
> Components: csharp
> Affects Versions: 1.10.1
> Environment: .Net core 3.1
> Reporter: Yevhen Cherkes
> Priority: Major
> Attachments: CompatibilityTests.zip
>
>
> We are facing the following exception on the .net core consumer's side:
> (*Java*-based consumers work with no issues for this particular case.)
> {code:java}
> No matching schema for
> {"type":"record","name":"InnerType1","namespace":"com.mycorp.mynamespace","fields":[
> {"name":"value","type":"string"}
> ]} in
> {"type":["null",{"type":"record","name":"InnerType2","namespace":"com.mycorp.mynamespace","fields":[
> {"name":"value","type":"string"}
> ]}]}
> at Avro.Generic.DefaultReader.findBranch(UnionSchema us, Schema s)
> at Avro.Generic.DefaultReader.ReadUnion(Object reuse, UnionSchema
> writerSchema, Schema readerSchema, Decoder d)
> at Avro.Generic.DefaultReader.Read(Object reuse, Schema writerSchema, Schema
> readerSchema, Decoder d)
> at Avro.Specific.SpecificDefaultReader.ReadRecord(Object reuse, RecordSchema
> writerSchema, Schema readerSchema, Decoder dec)
> {code}
> We have 2 versions of the schema on a topic:
> Schema v1:
> {code:json}
> {
> "fields": [
> {
> "name": "InnerComplexValue",
> "type": [
> "null",
> {
> "fields": [
> {
> "name": "value",
> "type": "string"
> }
> ],
> "name": "InnerType1",
> "namespace": "com.mycorp.mynamespace",
> "type": "record"
> }
> ]
> }
> ],
> "name": "RootType",
> "namespace": "com.mycorp.mynamespace",
> "type": "record"
> }
> {code}
> Schema v2:
> {code:json}
> {
> "fields": [
> {
> "name": "InnerComplexValue",
> "type": [
> "null",
> {
> "fields": [
> {
> "name": "value",
> "type": "string"
> }
> ],
> "name": "InnerType2",
> "namespace": "com.mycorp.mynamespace",
> "type": "record"
> }
> ]
> }
> ],
> "name": "RootType",
> "namespace": "com.mycorp.mynamespace",
> "type": "record"
> }
> {code}
> InnerType1 -> InnerType2 is the only change.
> The schema for a topic is configured with *Backward* compatibility.
> An updated version of a Schema is saved with no errors.
> Then we generated a specific record RootType with avrogen tool.
> Reproduction code:
>
> {code:c#}
> var base64 = "AhR0ZXN0IHZhbHVl";
> using var stream = new MemoryStream(Convert.FromBase64String(base64));
> var schema_v1 =
> Schema.Parse("{\"type\":\"record\",\"name\":\"RootType\",\"namespace\":\"com.mycorp.mynamespace\",\"fields\":"
> +
>
> "[{\"name\":\"InnerComplexValue\",\"type\":[\"null\",{\"type\":\"record\",\"name\":\"InnerType1\""
> +
>
> ",\"fields\":[{\"name\":\"value\",\"type\":\"string\"}]}]}]}");
> var schema_v2 =
> Schema.Parse("{\"type\":\"record\",\"name\":\"RootType\",\"namespace\":\"com.mycorp.mynamespace\",\"fields\":"
> +
>
> "[{\"name\":\"InnerComplexValue\",\"type\":[\"null\",{\"type\":\"record\",\"name\":\"InnerType2\""
> +
>
> ",\"fields\":[{\"name\":\"value\",\"type\":\"string\"}]}]}]}");
> var specificRecord = Deserialize<RootType>(stream, schema_v1, schema_v2);
> {code}
> Full sources see in attachments.
> Method Deserialize was taken from the
> [SpecificTests.cs#L408-L417|https://github.com/apache/avro/blob/master/lang/csharp/src/apache/test/Specific/SpecificTests.cs#L408-L417]
>
> Probably, the reason is in a different Schema resolution code:
> java:
> [https://github.com/apache/avro/blob/master/lang/java/avro/src/main/java/org/apache/avro/Resolver.java#L647-L659]
> .net:
> [https://github.com/apache/avro/blob/master/lang/csharp/src/apache/main/Schema/RecordSchema.cs#L310-L312]
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