Add MakeTombstone transform

README.md

@@ -129,6 +129,18 @@ transforms.ConcatFields.delimiter="-"
 transforms.ConcatFields.field.replace.missing="*"
 ```
 
+### `MakeTombstone`
+
+This transformation converts a record into a tombstone by setting its value and value schema to `null`.
+
+It can be used together with predicates, for example, to create a tombstone event from a delete event produced by a source connector.
+
+Here is an example of this transformation configuration:
+```properties
+transforms=MakeTombstone
+transforms.MakeTombstone.type=io.aiven.kafka.connect.transforms.MakeTombstone
+```
+
 ## License
 
 This project is licensed under the [Apache License, Version 2.0](LICENSE).

src/main/java/io/aiven/kafka/connect/transforms/MakeTombstone.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2020 Aiven Oy
+ *
+ * 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 io.aiven.kafka.connect.transforms;
+
+import java.util.Map;
+
+import org.apache.kafka.common.config.ConfigDef;
+import org.apache.kafka.connect.connector.ConnectRecord;
+import org.apache.kafka.connect.transforms.Transformation;
+
+public class MakeTombstone<R extends ConnectRecord<R>> implements Transformation<R> {
+
+    @Override
+    public R apply(final R record) {
+        return record.newRecord(
+                record.topic(),
+                record.kafkaPartition(),
+                record.keySchema(),
+                record.key(),
+                null,
+                null,
+                record.timestamp(),
+                record.headers()
+        );
+    }
+
+    @Override
+    public ConfigDef config() {
+        return new ConfigDef();
+    }
+
+    @Override
+    public void close() {
+
+    }
+
+    @Override
+    public void configure(final Map<String, ?> configs) {
+
+    }
+}

src/test/java/io/aiven/kafka/connect/transforms/MakeTombstoneTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2020 Aiven Oy
+ *
+ * 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 io.aiven.kafka.connect.transforms;
+
+import org.apache.kafka.connect.data.Schema;
+import org.apache.kafka.connect.source.SourceRecord;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+class MakeTombstoneTest {
+
+    @Test
+    void shouldMakeTombstone() {
+        final MakeTombstone<SourceRecord> makeTombstone = new MakeTombstone<>();
+        final var record = new SourceRecord(null, null, "some_topic", Schema.STRING_SCHEMA, "dummy value");
+
+        final var actual = makeTombstone.apply(record);
+        assertNull(actual.valueSchema(), "value schema should be null");
+        assertNull(actual.value(), "value should be null");
+    }
+}