Bertram Beyer created AVRO-3235:
-----------------------------------
Summary: Avro Schema Evolution with Enum – Deserialization Crashes
Key: AVRO-3235
URL: https://issues.apache.org/jira/browse/AVRO-3235
Project: Apache Avro
Issue Type: Bug
Components: java
Affects Versions: 1.10.2
Reporter: Bertram Beyer
Originally posted on Stack Overflow in June 2020
https://stackoverflow.com/questions/62596990/avro-schema-evolution-with-enum-deserialization-crashes/
I defined two versions of a record in two separate AVCS schema files. I used
the namespace to distinguish versions *SimpleV1.avsc*
{code:json}
{
"type" : "record",
"name" : "Simple",
"namespace" : "test.simple.v1",
"fields" : [
{
"name" : "name",
"type" : "string"
},
{
"name" : "status",
"type" : {
"type" : "enum",
"name" : "Status",
"symbols" : [ "ON", "OFF" ]
},
"default" : "ON"
}
]
}
{code}
*Example JSON*
{code:java}
{"name":"A","status":"ON"}
{code}
Version 2 just has an additional description field with default value.
*SimpleV2.avsc*
{code:java}
{
"type" : "record",
"name" : "Simple",
"namespace" : "test.simple.v2",
"fields" : [
{
"name" : "name",
"type" : "string"
},
{
"name" : "description",
"type" : "string",
"default" : ""
},
{
"name" : "status",
"type" : {
"type" : "enum",
"name" : "Status",
"symbols" : [ "ON", "OFF" ]
},
"default" : "ON"
}
]
}
{code}
*Example JSON*
{code:java}
{"name":"B","description":"b","status":"ON"}
{code}
Both schemas were serialized to Java classes. In my example I was going to test
backward compatibility. A record written by V1 shall be read by a reader using
V2. I wanted to see that default values are inserted. This is working as long
as I do not use enums.
{code:java}
public class EnumEvolutionExample {
public static void main(String[] args) throws IOException {
Schema schemaV1 = new org.apache.avro.Schema.Parser().parse(new
File("./src/main/resources/SimpleV1.avsc"));
//works as well
//Schema schemaV1 = test.simple.v1.Simple.getClassSchema();
Schema schemaV2 = new org.apache.avro.Schema.Parser().parse(new
File("./src/main/resources/SimpleV2.avsc"));
test.simple.v1.Simple simpleV1 = test.simple.v1.Simple.newBuilder()
.setName("A")
.setStatus(test.simple.v1.Status.ON)
.build();
SchemaPairCompatibility schemaCompatibility =
SchemaCompatibility.checkReaderWriterCompatibility(
schemaV2,
schemaV1);
//Checks that writing v1 and reading v2 schemas is compatible
Assert.assertEquals(SchemaCompatibilityType.COMPATIBLE,
schemaCompatibility.getType());
byte[] binaryV1 = serealizeBinary(simpleV1);
//Crashes with: AvroTypeException: Found test.simple.v1.Status,
expecting test.simple.v2.Status
test.simple.v2.Simple v2 = deSerealizeBinary(binaryV1, new
test.simple.v2.Simple(), schemaV1);
}
public static byte[] serealizeBinary(SpecificRecord record) {
DatumWriter<SpecificRecord> writer = new
SpecificDatumWriter<>(record.getSchema());
byte[] data = new byte[0];
ByteArrayOutputStream stream = new ByteArrayOutputStream();
Encoder binaryEncoder = EncoderFactory.get()
.binaryEncoder(stream, null);
try {
writer.write(record, binaryEncoder);
binaryEncoder.flush();
data = stream.toByteArray();
} catch (IOException e) {
System.out.println("Serialization error " + e.getMessage());
}
return data;
}
public static <T extends SpecificRecord> T deSerealizeBinary(byte[] data, T
reuse, Schema writer) {
Decoder decoder = DecoderFactory.get().binaryDecoder(data, null);
DatumReader<T> datumReader = new SpecificDatumReader<>(writer,
reuse.getSchema());
try {
T datum = datumReader.read(null, decoder);
return datum;
} catch (IOException e) {
System.out.println("Deserialization error" + e.getMessage());
}
return null;
}
}
{code}
The checkReaderWriterCompatibility method confirms that schemas are compatible.
But when I deserialize I’m getting the following exception
{code:java}
Exception in thread "main" org.apache.avro.AvroTypeException: Found
test.simple.v1.Status, expecting test.simple.v2.Status
at org.apache.avro.io.ResolvingDecoder.doAction(ResolvingDecoder.java:309)
at org.apache.avro.io.parsing.Parser.advance(Parser.java:86)
at org.apache.avro.io.ResolvingDecoder.readEnum(ResolvingDecoder.java:260)
at
org.apache.avro.generic.GenericDatumReader.readEnum(GenericDatumReader.java:267)
at
org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:181)
at
org.apache.avro.specific.SpecificDatumReader.readField(SpecificDatumReader.java:136)
at
org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:247)
at
org.apache.avro.specific.SpecificDatumReader.readRecord(SpecificDatumReader.java:123)
at
org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:179)
at
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:160)
at
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:153)
at test.EnumEvolutionExample.deSerealizeBinary(EnumEvolutionExample.java:70)
at test.EnumEvolutionExample.main(EnumEvolutionExample.java:45)
{code}
I don’t understand why Avro thinks it got a v1.Status. Namespaces are not part
of the encoding.
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