项目中使用Flink SQL 将离线数据、流数据写入Hudi，自下而上分析写hudi的流程。hudi 版本0.10.0-patch。
HoodieWriteHandle
HoodieWriteHandle 负责对数据进行加工后写入底层DFS。
- FlinkCreateHandle：创建新的 parquet 文件，并将一批数据写入，例如：copy表的batch insert。
- FlinkAppendHandle：向已有的 hoodie log 文件追加数据，例如：mor表的upsert、delete数据。
-
FlinkMergeHandle: 将历史数据和新增数据合并后输出新的 parquet 文件，例如：cor表的update，mor表的compact。
HoodieFileWriter：不同文件 format 的数据写入器，同时维护一个布隆过滤器。HoodieMergeHandle、HoodieCreateHandle 依赖该组件。
FlinkCreateHandle
创建 parquet 文件并将数据填充 hudi 元数据列信息后写入。主要流程：
- 向分区写入元数据文件
.hoodie_partition_metadata记录分区创建时间以及分区深度。
#partition metadata
#Thu Mar 10 03:07:01 UTC 2022
commitTime=20220310030659727
partitionDepth=1
- 向timeline server 发送创建marker , 表示在哪个 instant 针对哪个分区 file group 做了 create 操作， 在发生回滚时根据该 marker 删除目标 parquet。
- 根据要输出的文件格式创建 HoodieFileWriter，默认格式为Parquet，同时支持 orc 格式。HoodieParquetWriter 维护了一个 BloomFilter ，对flink 是没什么用的，spark 可以做 BloomIndex。
- 为 record 添加 hudi 元数据列后输出到最终文件。
- 填充 WriteStatus 作为最终结果返回，StreamWriteOperatorCoordinator 接收到所有 task的WriteStatus后写到./hoodie 下。
public HoodieCreateHandle(HoodieWriteConfig config, String instantTime, HoodieTable hoodieTable,
String partitionPath, String fileId, Option overriddenSchema,
TaskContextSupplier taskContextSupplier, boolean preserveHoodieMetadata) {
super(config, instantTime, partitionPath, fileId, hoodieTable, overriddenSchema,
taskContextSupplier);
this.preserveHoodieMetadata = preserveHoodieMetadata;
writeStatus.setFileId(fileId);
writeStatus.setPartitionPath(partitionPath);
writeStatus.setStat(new HoodieWriteStat());
// 构建 parquet path 例如： xxx/202203/710c791b-2358-4903-bef8-b885f48a40b8_1-2-0_20220318111533929.parquet
this.path = makeNewPath(partitionPath);
try {
/**
*向分区里面写入元数据信息，记录当前分区的创建时间和分区深度
* #partition metadata
* #Thu Mar 17 16:55:10 CST 2022
* commitTime=20220317165442543
* partitionDepth=1
*/
HoodiePartitionMetadata partitionMetadata = new HoodiePartitionMetadata(fs, instantTime,
new Path(config.getBasePath()), FSUtils.getPartitionPath(config.getBasePath(), partitionPath));
partitionMetadata.trySave(getPartitionId());
// 创建 mark file， 在哪个 instant 针对哪些分区 file group 做了什么操作
createMarkerFile(partitionPath, FSUtils.makeDataFileName(this.instantTime, this.writeToken, this.fileId, hoodieTable.getBaseFileExtension()));
// 创建文件写入器 FileWriter --> HoodieFileWriter ---> HoodieParquetWriter
this.fileWriter = HoodieFileWriterFactory.getFileWriter(instantTime, path, hoodieTable, config,
writeSchemaWithMetaFields, this.taskContextSupplier);
} catch (IOException e) {
throw new HoodieInsertException("Failed to initialize HoodieStorageWriter for path " + path, e);
}
LOG.info("New CreateHandle for partition :" + partitionPath + " with fileId " + fileId);
}
// HoodieWriteHandle#write 入口
public void write(HoodieRecord record, Option avroRecord) {
Option recordMetadata = record.getData().getMetadata();
if (HoodieOperation.isDelete(record.getOperation())) {
avroRecord = Option.empty();
}
try {
if (avroRecord.isPresent()) {
if (avroRecord.get().equals(IGNORE_RECORD)) {
return;
}
// 为record 填充hoodie 的schema信息
IndexedRecord recordWithMetadataInSchema = rewriteRecord((GenericRecord) avroRecord.get());
if (preserveHoodieMetadata) {
fileWriter.writeAvro(record.getRecordKey(), recordWithMetadataInSchema);
} else {
// 为填充hoodie 的schema，填充数据
fileWriter.writeAvroWithMetadata(recordWithMetadataInSchema, record);
}
// update the new location of record, so we know where to find it next
record.unseal();
record.setNewLocation(new HoodieRecordLocation(instantTime, writeStatus.getFileId()));
record.seal();
recordsWritten++;
insertRecordsWritten++;
} else {
recordsDeleted++;
}
writeStatus.markSuccess(record, recordMetadata);
// deflate record payload after recording success. This will help users access payload as a
// part of marking
// record successful.
record.deflate();
} catch (Throwable t) {
// Not throwing exception from here, since we don't want to fail the entire job
// for a single record
writeStatus.markFailure(record, t, recordMetadata);
LOG.error("Error writing record " + record, t);
}
}
FlinkAppendHandle
向 mor 表对应的logfile 追加数据完成数据的upsert/delete。通过 HoodieLogFormatWriter 写 HoodieLogBlock完成。
主要流程：
- 根据 partition 及 fileId 从HoodieTableFileSystemView 查找最新 fileSlice。
- 向timeline server 请求创建marker。
- 如果是新分区，创建分区写入
.hoodie_partition_metadata记录分区元数据信息。 - 通过 HoodieLogFormatWriter 向fileSlice 的logfile 写 HoodieLogBlock，数据会先被缓存，在close（）或者达到设置的 maxBlockSize 时会写出。
- 填充WriteStatus 作为结果返回。
public void write(HoodieRecord record, Option insertValue) {
Option> recordMetadata = record.getData().getMetadata();
try {
// 初始化fileSlice、HoodieLogFormatWriter、marker
init(record);
// 缓存数据大小达到 maxBlockSize （默认256M） 写出到
flushToDiskIfRequired(record);
// 为HoodieRecord 填充 hoodie meta 字段并转成avro数据格式存储到缓存
writeToBuffer(record);
} catch (Throwable t) {
...
}
}
public List close() {
try {
// flush any remaining records to disk
// 将数据从内存刷出到DFS
appendDataAndDeleteBlocks(header);
recordItr = null;
if (writer != null) {
writer.close();
writer = null;
// update final size, once for all log files
....
}
return statuses;
} catch (IOException e) {
throw new HoodieUpsertException("Failed to close UpdateHandle", e);
}
}
将缓存数据封装为 HoodieDataBlock 由 HoodieLogFormatWriter 写入hudi log。
protected void appendDataAndDeleteBlocks(Map header) {
try {
// Header metadata for a log block header 元数据
header.put(HoodieLogBlock.HeaderMetadataType.INSTANT_TIME, instantTime);
header.put(HoodieLogBlock.HeaderMetadataType.SCHEMA, writeSchemaWithMetaFields.toString());
// 最多包含 DataBlock 和 DeleteBlock
List blocks = new ArrayList<>(2);
if (recordList.size() > 0) {
if (config.populateMetaFields()) {
// flink ==> 从元数据列抽取keyField, 并构建 HoodieAvroDataBlock。
HoodieLogBlock dataBlock = HoodieDataBlock.getBlock(hoodieTable.getLogDataBlockFormat(), recordList, header);
blocks.add(dataBlock);
} else {
final String keyField = hoodieTable.getMetaClient().getTableConfig().getRecordKeyFieldProp();
blocks.add(HoodieDataBlock.getBlock(hoodieTable.getLogDataBlockFormat(), recordList, header, keyField));
}
}
// 有需要删除的record, 创建 HoodieDeleteBlock, 写入 keysToDelete
if (keysToDelete.size() > 0) {
blocks.add(new HoodieDeleteBlock(keysToDelete.toArray(new HoodieKey[keysToDelete.size()]), header));
}
if (blocks.size() > 0) {
// 由 HoodieLogFormatWriter 写入 HoodieLogBlock
AppendResult appendResult = writer.appendBlocks(blocks);
// 将写入结果 写到状态中
processAppendResult(appendResult);
recordList.clear();
keysToDelete.clear();
}
} catch (Exception e) {
throw new HoodieAppendException("Failed while appending records to " + writer.getLogFile().getPath(), e);
}
}
HoodieLogBlock
hudi 写log 的格式为自己定义的 HoodieLogBlock，类型不同在读取时做不同处理。包含Header、Footer、Content、 Version等。
- HoodieDataBlock：数据块，存储序列化后的 record，默认为HoodieAvroDataBlock。
- HoodieDeleteBlock：要删除 HoodieKey 组成的数据块。
- HoodieCorruptBlock：错误的数据快，在读的时候数据块未校验过，定义成HoodieCorruptBlock。
- HoodieCommandBlock：命令行块，只有ROLLBACK_PREVIOUS_BLOCK类型，发生回滚时写入，在 scanner 读数据时读到该块会跳过目标块。
HoodieAvroDataBlock#serializeRecords
protected byte[] serializeRecords() throws IOException {
Schema schema = new Schema.Parser().parse(super.getLogBlockHeader().get(HeaderMetadataType.SCHEMA));
GenericDatumWriter writer = new GenericDatumWriter<>(schema);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream output = new DataOutputStream(baos);
// 1. Write out the log block version 日志块版本
output.writeInt(HoodieLogBlock.version);
// 2. Write total number of records 总的记录数
output.writeInt(records.size());
// 3. Write the records avro record
Iterator itr = records.iterator();
while (itr.hasNext()) {
IndexedRecord s = itr.next();
ByteArrayOutputStream temp = new ByteArrayOutputStream();
BinaryEncoder encoder = EncoderFactory.get().binaryEncoder(temp, encoderCache.get());
encoderCache.set(encoder);
try {
// Encode the record into bytes
writer.write(s, encoder);
encoder.flush();
// Get the size of the bytes
int size = temp.toByteArray().length;
// Write the record size
output.writeInt(size);
// Write the content
output.write(temp.toByteArray());
itr.remove();
} catch (IOException e) {
throw new HoodieIOException("IOException converting HoodieAvroDataBlock to bytes", e);
}
}
output.close();
return baos.toByteArray();
}
HoodieLogFormatWriter
将 HoodieLogBlock 以特定的格式写入 log file，如果底层文件系统不支持 Append 则创建新的文件写入。
针对logfile 构建 OutputStream，如果DFS不支持Append则会重新创建，注意观察生成的新文件名称。
private FSDataOutputStream getOutputStream() throws IOException, InterruptedException {
if (this.output == null) {
Path path = logFile.getPath();
if (fs.exists(path)) {
// 文件是否支持Append, 支持append的文件系统比较少， hdfs支持append
boolean isAppendSupported = StorageSchemes.isAppendSupported(fs.getScheme());
if (isAppendSupported) {
LOG.info(logFile + " exists. Appending to existing file");
try {
// open the path for append and record the offset
this.output = fs.append(path, bufferSize);
} catch (RemoteException e) {
LOG.warn("Remote Exception, attempting to handle or recover lease", e);
handleAppendExceptionOrRecoverLease(path, e);
} catch (IOException ioe) {
if (ioe.getMessage().toLowerCase().contains("not supported")) {
// may still happen if scheme is viewfs.
isAppendSupported = false;
} else {
close();
throw ioe;
}
}
}
// 不支持 append 的文件系统会创建一个新的 log file
if (!isAppendSupported) {
// 滚动生成新的 log file，最大version +1
rollOver();
// 创建新的 logfile
createNewFile();
LOG.info("Append not supported.. Rolling over to " + logFile);
}
} else {
LOG.info(logFile + " does not exist. Create a new file");
// Block size does not matter as we will always manually autoflush
createNewFile();
}
}
return output;
}
block 写入log file 数据格式：
| magic |
|---|
| block length |
| log version |
| block type |
| block header |
| block content length |
| block content |
| block footer |
| block length |
public AppendResult appendBlocks(List blocks) throws IOException, InterruptedException {
// Find current version log format 版本
HoodieLogFormat.LogFormatVersion currentLogFormatVersion =
new HoodieLogFormatVersion(HoodieLogFormat.CURRENT_VERSION);
// 针对 logfile 构建 outputStream
FSDataOutputStream outputStream = getOutputStream();
long startPos = outputStream.getPos();
long sizeWritten = 0;
for (HoodieLogBlock block: blocks) {
long startSize = outputStream.size();
// 1. Write the magic header for the start of the block
outputStream.write(HoodieLogFormat.MAGIC);
// bytes for header 头信息 Instance, schema
byte[] headerBytes = HoodieLogBlock.getLogMetadataBytes(block.getLogBlockHeader());
// content bytes 将record 以avro 格式写入
byte[] content = block.getContentBytes();
// bytes for footer 空map
byte[] footerBytes = HoodieLogBlock.getLogMetadataBytes(block.getLogBlockFooter());
// 2. Write the total size of the block (excluding Magic) log block的总字节大小
outputStream.writeLong(getLogBlockLength(content.length, headerBytes.length, footerBytes.length));
// 3. Write the version of this log block
outputStream.writeInt(currentLogFormatVersion.getVersion());
// 4. Write the block type
outputStream.writeInt(block.getBlockType().ordinal());
// 5. Write the headers for the log block
outputStream.write(headerBytes);
// 6. Write the size of the content block
outputStream.writeLong(content.length);
// 7. Write the contents of the data block
outputStream.write(content);
// 8. Write the footers for the log block
outputStream.write(footerBytes);
// 9. Write the total size of the log block (including magic) which is everything written
// until now (for reverse pointer)
// 通过与标头中的块大小进行比较来确定块是否损坏
// Update: this information is now used in determining if a block is corrupt by comparing to the
// block size in header. This change assumes that the block size will be the last data written
// to a block. Read will break if any data is written past this point for a block.
outputStream.writeLong(outputStream.size() - startSize);
// Fetch the size again, so it accounts also (9).
sizeWritten += outputStream.size() - startSize;
}
// Flush all blocks to disk 数据刷出
flush();
// 数据写入的
AppendResult result = new AppendResult(logFile, startPos, sizeWritten);
// roll over if size is past the threshold
rolloverIfNeeded();
return result;
}
FlinkMergeHandle
用来将新数据和历史数据进行合并输出 baseFile，例如：cor表的 update，mor表的压缩。
主要流程：
- 基于新数据来构建 ExternalSpillableMap，该集合提供O(1)的查询能力，同时能够将数据溢出到磁盘，底层使用RocksDb 或者 BitCask 来实现，默认为BitCask。在压缩场景下，新数据可以是上游读取的log文件并下发。
- 接收历史数据和ExternalSpillableMap 中的新数据进行匹配，如果匹配成功根据数据合并策略对数据列进行合并，flink 默认会使用新数据的全部列，如果未匹配成功则将历史数据直接下发，写到新parquet里。
- close 时将未匹配历史数据的新数据下发。
public HoodieMergeHandle(HoodieWriteConfig config, String instantTime, HoodieTable hoodieTable,
Iterator> recordItr, String partitionPath, String fileId,
TaskContextSupplier taskContextSupplier, HoodieBaseFile baseFile, Option keyGeneratorOpt) {
super(config, instantTime, partitionPath, fileId, hoodieTable, taskContextSupplier);
// 将新记录存储到 ExternalSpillableMap
init(fileId, recordItr);
// 准备 fileWriter 及其他
init(fileId, partitionPath, baseFile);
validateAndSetAndKeyGenProps(keyGeneratorOpt, config.populateMetaFields());
}
protected void init(String fileId, Iterator> newRecordsItr) {
// 初始化 keyToNewRecords， 具有持久化能力的map
initializeIncomingRecordsMap();
while (newRecordsItr.hasNext()) {
HoodieRecord record = newRecordsItr.next();
// update the new location of the record, so we know where to find it next
if (needsUpdateLocation()) {
record.unseal();
record.setNewLocation(new HoodieRecordLocation(instantTime, fileId));
record.seal();
}
// NOTE: Once Records are added to map (spillable-map), DO NOT change it as they won't persist
keyToNewRecords.put(record.getRecordKey(), record);
}
}
private void init(String fileId, String partitionPath, HoodieBaseFile baseFileToMerge) {
LOG.info("partitionPath:" + partitionPath + ", fileId to be merged:" + fileId);
this.baseFileToMerge = baseFileToMerge;
this.writtenRecordKeys = new HashSet<>();
writeStatus.setStat(new HoodieWriteStat());
try {
// 最新 basefile (parquet文件)
String latestValidFilePath = baseFileToMerge.getFileName();
// 前一次commit 时间
writeStatus.getStat().setPrevCommit(FSUtils.getCommitTime(latestValidFilePath));
HoodiePartitionMetadata partitionMetadata = new HoodiePartitionMetadata(fs, instantTime,
new Path(config.getBasePath()), FSUtils.getPartitionPath(config.getBasePath(), partitionPath));
partitionMetadata.trySave(getPartitionId());
// 新的parquet文件名, fileId_writeToken_instantTime_fileExtension
String newFileName = FSUtils.makeDataFileName(instantTime, writeToken, fileId, hoodieTable.getBaseFileExtension());
// 构建 oldFilePath, newFilePath
makeOldAndNewFilePaths(partitionPath, latestValidFilePath, newFileName);
LOG.info(String.format("Merging new data into oldPath %s, as newPath %s", oldFilePath.toString(),
newFilePath.toString()));
// file name is same for all records, in this bunch
writeStatus.setFileId(fileId);
writeStatus.setPartitionPath(partitionPath);
writeStatus.getStat().setPartitionPath(partitionPath);
writeStatus.getStat().setFileId(fileId);
setWriteStatusPath();
// Create Marker file
createMarkerFile(partitionPath, newFileName);
// Create the writer for writing the new version file
fileWriter = createNewFileWriter(instantTime, newFilePath, hoodieTable, config,
writeSchemaWithMetaFields, taskContextSupplier);
} catch (IOException io) {
LOG.error("Error in update task at commit " + instantTime, io);
writeStatus.setGlobalError(io);
throw new HoodieUpsertException("Failed to initialize HoodieUpdateHandle for FileId: " + fileId + " on commit "
+ instantTime + " on path " + hoodieTable.getMetaClient().getBasePath(), io);
}
}
数据处理流程：
public void write(GenericRecord oldRecord) {
String key = KeyGenUtils.getRecordKeyFromGenericRecord(oldRecord, keyGeneratorOpt);
boolean copyOldRecord = true;
if (keyToNewRecords.containsKey(key)) {
// old record 和 新数据完全匹配
// If we have duplicate records that we are updating, then the hoodie record will be deflated after
// writing the first record. So make a copy of the record to be merged
HoodieRecord hoodieRecord = new HoodieRecord<>(keyToNewRecords.get(key));
try {
// delete 则Option 不为empty.
// flink combinedAvroRecord 后的结果为新数据的 arvo，即 overwrite old record
Option combinedAvroRecord =
hoodieRecord.getData().combineAndGetUpdateValue(oldRecord,
useWriterSchema ? tableSchemaWithMetaFields : tableSchema,
config.getPayloadConfig().getProps());
if (combinedAvroRecord.isPresent() && combinedAvroRecord.get().equals(IGNORE_RECORD)) {
// If it is an IGNORE_RECORD, just copy the old record, and do not update the new record.
// 只拷贝旧记录
copyOldRecord = true;
} else if (writeUpdateRecord(hoodieRecord, oldRecord, combinedAvroRecord)) {
// writeUpdateRecord 新数据直接写入, 就是写parquet文件
/*
* ONLY WHEN
* 1) we have an update for this key AND
* 2) We are able to successfully write the the combined new value
* We no longer need to copy the old record over.
*/
copyOldRecord = false;
}
// 缓存已经写入的 record key
writtenRecordKeys.add(key);
} catch (Exception e) {
throw new HoodieUpsertException("Failed to combine/merge new record with old value in storage, for new record {"
+ keyToNewRecords.get(key) + "}, old value {" + oldRecord + "}", e);
}
}
if (copyOldRecord) {
// this should work as it is, since this is an existing record
try {
// incoming 的数据不包含对历史数据的变更，直接下发 oldRecord
fileWriter.writeAvro(key, oldRecord);
} catch (IOException | RuntimeException e) {
String errMsg = String.format("Failed to merge old record into new file for key %s from old file %s to new file %s with writerSchema %s",
key, getOldFilePath(), newFilePath, writeSchemaWithMetaFields.toString(true));
LOG.debug("Old record is " + oldRecord);
throw new HoodieUpsertException(errMsg, e);
}
recordsWritten++;
}
}
close 时下发未匹配到新数据，返回状态信息。
public List close() {
try {
//
writeIncomingRecords();
if (keyToNewRecords instanceof ExternalSpillableMap) {
((ExternalSpillableMap) keyToNewRecords).close();
} else {
keyToNewRecords.clear();
}
writtenRecordKeys.clear();
if (fileWriter != null) {
fileWriter.close();
fileWriter = null;
}
long fileSizeInBytes = FSUtils.getFileSize(fs, newFilePath);
HoodieWriteStat stat = writeStatus.getStat();
stat.setTotalWriteBytes(fileSizeInBytes);
stat.setFileSizeInBytes(fileSizeInBytes);
stat.setNumWrites(recordsWritten);
stat.setNumDeletes(recordsDeleted);
stat.setNumUpdateWrites(updatedRecordsWritten);
stat.setNumInserts(insertRecordsWritten);
stat.setTotalWriteErrors(writeStatus.getTotalErrorRecords());
RuntimeStats runtimeStats = new RuntimeStats();
runtimeStats.setTotalUpsertTime(timer.endTimer());
stat.setRuntimeStats(runtimeStats);
performMergeDataValidationCheck(writeStatus);
LOG.info(String.format("MergeHandle for partitionPath %s fileID %s, took %d ms.", stat.getPartitionPath(),
stat.getFileId(), runtimeStats.getTotalUpsertTime()));
return Collections.singletonList(writeStatus);
} catch (IOException e) {
throw new HoodieUpsertException("Failed to close UpdateHandle", e);
}
}
protected void writeIncomingRecords() throws IOException {
// write out any pending records (this can happen when inserts are turned into updates)
Iterator> newRecordsItr = (keyToNewRecords instanceof ExternalSpillableMap)
? ((ExternalSpillableMap)keyToNewRecords).iterator() : keyToNewRecords.values().iterator();
while (newRecordsItr.hasNext()) {
HoodieRecord hoodieRecord = newRecordsItr.next();
// 已经写入的数据不包含map中的数据，则下发map中的数据
if (!writtenRecordKeys.contains(hoodieRecord.getRecordKey())) {
writeInsertRecord(hoodieRecord);
}
}
}