/*
* Copyright © 2014 Cask Data, Inc.
*
* 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 co.cask.cdap.common.stream;
import co.cask.cdap.api.flow.flowlet.StreamEvent;
import co.cask.cdap.api.stream.StreamEventData;
import co.cask.cdap.common.io.BinaryDecoder;
import co.cask.cdap.common.io.BinaryEncoder;
import co.cask.cdap.common.io.Decoder;
import co.cask.cdap.common.io.Encoder;
import co.cask.cdap.internal.io.ByteBufferInputStream;
import co.cask.cdap.internal.io.ReflectionSchemaGenerator;
import co.cask.cdap.internal.io.Schema;
import co.cask.cdap.internal.io.SchemaHash;
import co.cask.cdap.internal.io.UnsupportedTypeException;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Map;
/**
* A utility class for encoding/decoding {@link StreamEvent} into {@code byte[]} that is ready to be
* used by QueueEntry.
*/
public final class StreamEventCodec {
private static final Schema STREAM_EVENT_SCHEMA;
static {
Schema schema;
try {
schema = new ReflectionSchemaGenerator().generate(StreamEvent.class);
} catch (UnsupportedTypeException e) {
schema = null;
}
STREAM_EVENT_SCHEMA = schema;
}
/**
* Encodes the given {@link StreamEvent} into {@code byte[]} that could become
* payload of a QueueEntry.
*
* @param event The {@link StreamEvent} to encode.
* @return Encoded {@code byte[]}.
*/
public byte[] encodePayload(StreamEvent event) {
// TODO: This is a bit hacky to do it directly for now, for performance reason.
ByteBuffer body = event.getBody();
Map<String, String> headers = event.getHeaders();
long timestamp = event.getTimestamp();
// Some assumption on the header size to minimize array copying
// 16 bytes Schema hash + body size + (header size) * (50 bytes key/value pair) + 9 bytes timestamp (vlong encoding)
ByteArrayOutputStream os = new ByteArrayOutputStream(16 + body.remaining() + headers.size() * 50 + 9);
Encoder encoder = new BinaryEncoder(os);
try {
// Write the schema hash
os.write(STREAM_EVENT_SCHEMA.getSchemaHash().toByteArray());
StreamEventDataCodec.encode(event, encoder);
encoder.writeLong(timestamp);
return os.toByteArray();
} catch (IOException e) {
// It should never happens, otherwise something very wrong.
throw Throwables.propagate(e);
}
}
/**
* Reverse of {@link #encodePayload(StreamEvent)}.
*
* @param payload The byte array containing the queue payload.
* @return A {@link StreamEvent} reconstructed from payload.
*/
public StreamEvent decodePayload(byte[] payload) {
ByteBuffer buffer = ByteBuffer.wrap(payload);
SchemaHash schemaHash = new SchemaHash(buffer);
Preconditions.checkArgument(schemaHash.equals(STREAM_EVENT_SCHEMA.getSchemaHash()),
"Schema from payload not matching StreamEvent schema.");
Decoder decoder = new BinaryDecoder(new ByteBufferInputStream(buffer));
try {
StreamEventData data = StreamEventDataCodec.decode(decoder);
// Read the timestamp
long timestamp = decoder.readLong();
return new DefaultStreamEvent(data, timestamp);
} catch (IOException e) {
// It should never happens, otherwise something very wrong.
throw Throwables.propagate(e);
}
}
}