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DP-2429 | Introduce incremental schema evolution (#60)
* introduced incremental schema evolution * reset schema when evolution fails
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22 changes: 22 additions & 0 deletions
22
connector/src/main/java/com/celonis/kafka/connect/schema/SchemaEvolution.java
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|---|---|---|
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| /* | ||
| * Copyright 2023 Celonis SE | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.celonis.kafka.connect.schema; | ||
|
|
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| import org.apache.kafka.connect.data.Schema; | ||
|
|
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| public interface SchemaEvolution { | ||
| Schema evolve(Schema currentSchema, Schema recordSchema) throws SchemaEvolutionException; | ||
| } |
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22
connector/src/main/java/com/celonis/kafka/connect/schema/SchemaEvolutionException.java
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|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| /* | ||
| * Copyright 2023 Celonis SE | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.celonis.kafka.connect.schema; | ||
|
|
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| public final class SchemaEvolutionException extends RuntimeException { | ||
| public SchemaEvolutionException(String message) { | ||
| super(message); | ||
| } | ||
| } |
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36
connector/src/main/java/com/celonis/kafka/connect/schema/SchemaUtils.java
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| /* | ||
| * Copyright 2023 Celonis SE | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.celonis.kafka.connect.schema; | ||
|
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| import org.apache.kafka.connect.data.Schema; | ||
| import org.apache.kafka.connect.data.SchemaBuilder; | ||
|
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| import java.util.Optional; | ||
|
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| public class SchemaUtils { | ||
| public static SchemaBuilder withMetadata(SchemaBuilder builder, Schema schema) { | ||
| Optional.ofNullable(schema.parameters()) | ||
| .filter(params -> !params.isEmpty()) | ||
| .ifPresent(builder::parameters); | ||
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| Optional.ofNullable(schema.name()).ifPresent(builder::name); | ||
| Optional.ofNullable(schema.doc()).ifPresent(builder::doc); | ||
| Optional.ofNullable(schema.defaultValue()).ifPresent(builder::defaultValue); | ||
| Optional.ofNullable(schema.version()).ifPresent(builder::version); | ||
|
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| return builder; | ||
| } | ||
| } |
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76
connector/src/main/java/com/celonis/kafka/connect/schema/StructSchemaAlignment.java
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|---|---|---|
| @@ -0,0 +1,76 @@ | ||
| /* | ||
| * Copyright 2023 Celonis SE | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.celonis.kafka.connect.schema; | ||
|
|
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| import org.apache.kafka.connect.data.Schema; | ||
| import org.apache.kafka.connect.data.Struct; | ||
|
|
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| import java.util.Collection; | ||
| import java.util.Map; | ||
| import java.util.stream.Collectors; | ||
|
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| public final class StructSchemaAlignment { | ||
| /** | ||
| * Align an object to the schema accumulated by incrementally calling SchemaEvolution#evolve. | ||
| * | ||
| * <p>NOTE: this is needed in order to avoid the unnecessarily frequent flush of output Parquet | ||
| * files due JSON schema inference producing different records for what effectively is the same | ||
| * data (see `EmsOutputRecordSink#put) | ||
| * | ||
| * @param evolvedSchema the schema this value should align to. Must be a superset of the supplied | ||
| * struct schema. | ||
| * @param value the current SinKRecord input struct | ||
| * @return a struct with the evolved schema | ||
| */ | ||
| public static Struct alignTo(Schema evolvedSchema, Struct value) { | ||
| return (Struct) align(evolvedSchema, value); | ||
| } | ||
|
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| private static Object align(Schema evolvedSchema, Object value) { | ||
| switch (evolvedSchema.type()) { | ||
| case ARRAY: | ||
| final var collection = (Collection<?>) value; | ||
| return collection.stream() | ||
| .map(item -> align(evolvedSchema.valueSchema(), item)) | ||
| .collect(Collectors.toList()); | ||
|
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| case MAP: | ||
| final var map = (Map<?, ?>) value; | ||
| return map.entrySet().stream() | ||
| .collect( | ||
| Collectors.toMap( | ||
| entry -> align(evolvedSchema.keySchema(), entry.getKey()), | ||
| entry -> align(evolvedSchema.valueSchema(), entry.getValue()))); | ||
|
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| case STRUCT: | ||
| final var structValue = (Struct) value; | ||
| if (structValue.schema() == evolvedSchema) return structValue; | ||
| final var newStruct = new Struct(evolvedSchema); | ||
|
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| for (final var evolvedField : evolvedSchema.fields()) { | ||
| if (structValue.schema().field(evolvedField.name()) != null) { | ||
| newStruct.put( | ||
| evolvedField.name(), | ||
| align(evolvedField.schema(), structValue.get(evolvedField.name()))); | ||
| } | ||
| } | ||
|
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| return newStruct; | ||
| default: | ||
| return value; | ||
| } | ||
| } | ||
| } |
127 changes: 127 additions & 0 deletions
127
connector/src/main/java/com/celonis/kafka/connect/schema/StructSchemaEvolution.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,127 @@ | ||
| /* | ||
| * Copyright 2023 Celonis SE | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.celonis.kafka.connect.schema; | ||
|
|
||
| import org.apache.kafka.connect.data.Schema; | ||
| import org.apache.kafka.connect.data.SchemaBuilder; | ||
|
|
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| import java.util.Objects; | ||
|
|
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| /** | ||
| * StructSchemaEvolution is responsible for the recursively merging existing schema and schema from | ||
| * new record. And thus evolving the schema with each new record received from connector. | ||
| */ | ||
| public class StructSchemaEvolution implements SchemaEvolution { | ||
|
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| /** | ||
| * Merge top level Kafka Connect Structs | ||
| * | ||
| * @param currentSchema existing schema, must be of type Struct | ||
| * @param recordSchema schema of new record, must be of type Struct | ||
| * @return Schema after merging existing and new schema recursively | ||
| */ | ||
| @Override | ||
| public Schema evolve(Schema currentSchema, Schema recordSchema) throws SchemaEvolutionException { | ||
| if (currentSchema == recordSchema) return currentSchema; | ||
|
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| // RecordTransformer ensures that the top level schema are of type Struct. | ||
| return mergeSchemas(null, currentSchema, recordSchema); | ||
| } | ||
|
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| /** | ||
| * Merge a Kafka Connect Schemas | ||
| * | ||
| * @param fieldName current field name, `null` when the recursion starts | ||
| * @param currentSchema existing schema, (Accepted types MAP, ARRAY, STRUCT) | ||
| * @param recordSchema schema of new record, (Accepted types MAP, ARRAY, STRUCT) | ||
| * @return Schema after merging existing and new schemas recursively | ||
| */ | ||
| private Schema mergeSchemas(String fieldName, Schema currentSchema, Schema recordSchema) { | ||
| // validationsFirst | ||
| validateSchemasTypes(fieldName, currentSchema, recordSchema); | ||
|
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| switch (currentSchema.type()) { | ||
| case STRUCT: | ||
| return mergeStructs(currentSchema, recordSchema); | ||
| case ARRAY: | ||
| return SchemaBuilder.array( | ||
| mergeSchemas(fieldName, currentSchema.valueSchema(), recordSchema.valueSchema())) | ||
| .build(); | ||
| case MAP: | ||
| var keySchema = | ||
| mergeSchemas(fieldName, currentSchema.keySchema(), recordSchema.keySchema()); | ||
| var valueSchema = | ||
| mergeSchemas(fieldName, currentSchema.valueSchema(), recordSchema.valueSchema()); | ||
| return SchemaBuilder.map(keySchema, valueSchema).build(); | ||
| default: | ||
| return currentSchema; | ||
| } | ||
| } | ||
|
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| private Schema mergeStructs(Schema currentSchema, Schema recordSchema) | ||
| throws SchemaEvolutionException { | ||
| SchemaBuilder result = SchemaUtils.withMetadata(SchemaBuilder.struct(), currentSchema); | ||
|
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| // First currentSchemaFields | ||
| currentSchema.fields().stream() | ||
| .forEach( | ||
| currentSchemaField -> { | ||
| final var recordSchemaField = recordSchema.field(currentSchemaField.name()); | ||
| if (recordSchemaField == null) { | ||
| // If not present in recordSchema, just add it | ||
| result.field(currentSchemaField.name(), currentSchemaField.schema()); | ||
| } else { | ||
| // Recursively evolve otherwise | ||
| result.field( | ||
| currentSchemaField.name(), | ||
| mergeSchemas( | ||
| currentSchemaField.name(), | ||
| currentSchemaField.schema(), | ||
| recordSchemaField.schema())); | ||
| } | ||
| }); | ||
|
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| // Just add remaining record schema fields as they are | ||
| recordSchema.fields().stream() | ||
| .filter(rf -> currentSchema.field(rf.name()) == null) | ||
| .forEach(rf -> result.field(rf.name(), rf.schema())); | ||
|
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| return result.build(); | ||
| } | ||
|
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| private void validateSchemasTypes(String fieldName, Schema currentSchema, Schema recordSchema) { | ||
| if (bothPrimitives(currentSchema, recordSchema) && !sameLogicalType(currentSchema, recordSchema) | ||
| || !currentSchema.type().equals(recordSchema.type())) { | ||
|
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| throw new SchemaEvolutionException( | ||
| String.format( | ||
| "New schema has field '%s' with a different type! " | ||
| + "previous type: %s, current type: %s", | ||
| fieldName, currentSchema, recordSchema)); | ||
| } | ||
| } | ||
|
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| private boolean bothPrimitives(Schema s1, Schema s2) { | ||
| return s1.type().isPrimitive() && s2.type().isPrimitive(); | ||
| } | ||
|
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| private boolean sameLogicalType(Schema s1, Schema s2) { | ||
| return Objects.equals(s1.type(), s2.type()) | ||
| && Objects.equals(s1.name(), s2.name()) | ||
| && Objects.equals(s1.version(), s2.version()) | ||
| && Objects.equals(s1.parameters(), s2.parameters()); | ||
| } | ||
| } |
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