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背景

在之前的文章中Apache Hudi初探(二)(与flink的结合)–flink写hudi的操作(JobManager端的提交操作) 有说到写hudi数据会涉及到写hudi真实数据以及写hudi元数据,这篇文章来说一下具体的实现

写hudi真实数据

这里的操作就是在HoodieFlinkWriteClient.upsert方法:

public List<WriteStatus> upsert(List<HoodieRecord<T>> records, String instantTime) {HoodieTable<T, List<HoodieRecord<T>>, List<HoodieKey>, List<WriteStatus>> table =initTable(WriteOperationType.UPSERT, Option.ofNullable(instantTime));table.validateUpsertSchema();preWrite(instantTime, WriteOperationType.UPSERT, table.getMetaClient());final HoodieWriteHandle<?, ?, ?, ?> writeHandle = getOrCreateWriteHandle(records.get(0), getConfig(),instantTime, table, records.listIterator());HoodieWriteMetadata<List<WriteStatus>> result = ((HoodieFlinkTable<T>) table).upsert(context, writeHandle, instantTime, records);if (result.getIndexLookupDuration().isPresent()) {metrics.updateIndexMetrics(LOOKUP_STR, result.getIndexLookupDuration().get().toMillis());}return postWrite(result, instantTime, table);}

• initTable
  初始化HoodieFlinkTable
• preWrite
  在这里几乎没什么操作
• getOrCreateWriteHandle
  创建一个写文件的handle(假如这里创建的是FlinkMergeAndReplaceHandle)，这里会记录已有的文件路径，后续FlinkMergeHelper.runMerge会从这里读取数
  注意该构造函数中的init方法，会创建一个ExternalSpillableMap类型的map来存储即将插入的记录，这在后续upsert中会用到
• HoodieFlinkTable.upsert
  这里进行真正的upsert操作，会调用FlinkUpsertDeltaCommitActionExecutor.execute,最终会调用到BaseFlinkCommitActionExecutor.execute,从而调用到FlinkMergeHelper.newInstance().runMerge

    public void runMerge(HoodieTable<T, List<HoodieRecord<T>>, List<HoodieKey>, List<WriteStatus>> table,..) {final boolean externalSchemaTransformation = table.getConfig().shouldUseExternalSchemaTransformation();HoodieBaseFile baseFile = mergeHandle.baseFileForMerge();if (externalSchemaTransformation || baseFile.getBootstrapBaseFile().isPresent()) {readSchema = baseFileReader.getSchema();gWriter = new GenericDatumWriter<>(readSchema);gReader = new GenericDatumReader<>(readSchema, mergeHandle.getWriterSchemaWithMetaFields());} else {gReader = null;gWriter = null;readSchema = mergeHandle.getWriterSchemaWithMetaFields();}wrapper = new BoundedInMemoryExecutor<>(table.getConfig().getWriteBufferLimitBytes(), new IteratorBasedQueueProducer<>(readerIterator),Option.of(new UpdateHandler(mergeHandle)), record -> {if (!externalSchemaTransformation) {return record;}return transformRecordBasedOnNewSchema(gReader, gWriter, encoderCache, decoderCache, (GenericRecord) record);});wrapper.execute();。。。mergeHandle.close();}

  • externalSchemaTransformation=
    这里有hoodie.avro.schema.external.transformation配置(默认是false)用来把在之前schame下的数据转换为新的schema下的数据
  • wrapper.execute()
    这里会最终调用到upsertHandle.write(record)，也就是UpdateHandler.consumeOneRecord方法被调用的地方

     public void write(GenericRecord oldRecord) {...if (keyToNewRecords.containsKey(key)) {if (combinedAvroRecord.isPresent() && combinedAvroRecord.get().equals(IGNORE_RECORD)) {copyOldRecord = true;} else if (writeUpdateRecord(hoodieRecord, oldRecord, combinedAvroRecord)) {copyOldRecord = false;}writtenRecordKeys.add(key); }}
    

    如果keyToNewRecords报班了对应的记录，也就是说会有uodate的操作的话，就插入新的数据，
    writeUpdateRecord 这里进行数据的更新，并用writtenRecordKeys记录插入的记录
  • mergeHandle.close()

     public List<WriteStatus> close() {writeIncomingRecords();...}...protected void writeIncomingRecords() throws IOException {// write out any pending records (this can happen when inserts are turned into updates)Iterator<HoodieRecord<T>> newRecordsItr = (keyToNewRecords instanceof ExternalSpillableMap)? ((ExternalSpillableMap)keyToNewRecords).iterator() : keyToNewRecords.values().iterator();while (newRecordsItr.hasNext()) {HoodieRecord<T> hoodieRecord = newRecordsItr.next();if (!writtenRecordKeys.contains(hoodieRecord.getRecordKey())) {writeInsertRecord(hoodieRecord);}}}
    

    这里的writeIncomingRecords会判断如果writtenRecordKeys没有包含该记录的话，就直接插入数据，而不是更新

总结一下upsert的关键点:

mergeHandle.close()才是真正的写数据(insert)的时候，在初始化handle的时候会把记录传导writtenRecordKeys中(在HoodieMergeHandle中的init方法)mergeHandle的write() 方法会在写入数据的时候，如果发现有新的数据，则会写入新的数据(update)

写hudi元数据

这里的操作是StreamWriteOperatorCoordinator.notifyCheckpointComplete方法

public void notifyCheckpointComplete(long checkpointId) {...final boolean committed = commitInstant(this.instant, checkpointId);...
}...
private boolean commitInstant(String instant, long checkpointId){...doCommit(instant, writeResults);...
}...
private void doCommit(String instant, List<WriteStatus> writeResults) {// commit or rollbacklong totalErrorRecords = writeResults.stream().map(WriteStatus::getTotalErrorRecords).reduce(Long::sum).orElse(0L);long totalRecords = writeResults.stream().map(WriteStatus::getTotalRecords).reduce(Long::sum).orElse(0L);boolean hasErrors = totalErrorRecords > 0;if (!hasErrors || this.conf.getBoolean(FlinkOptions.IGNORE_FAILED)) {HashMap<String, String> checkpointCommitMetadata = new HashMap<>();if (hasErrors) {LOG.warn("Some records failed to merge but forcing commit since commitOnErrors set to true. Errors/Total="+ totalErrorRecords + "/" + totalRecords);}final Map<String, List<String>> partitionToReplacedFileIds = tableState.isOverwrite? writeClient.getPartitionToReplacedFileIds(tableState.operationType, writeResults): Collections.emptyMap();boolean success = writeClient.commit(instant, writeResults, Option.of(checkpointCommitMetadata),tableState.commitAction, partitionToReplacedFileIds);if (success) {reset();this.ckpMetadata.commitInstant(instant);LOG.info("Commit instant [{}] success!", instant);} else {throw new HoodieException(String.format("Commit instant [%s] failed!", instant));}} else {LOG.error("Error when writing. Errors/Total=" + totalErrorRecords + "/" + totalRecords);LOG.error("The first 100 error messages");writeResults.stream().filter(WriteStatus::hasErrors).limit(100).forEach(ws -> {LOG.error("Global error for partition path {} and fileID {}: {}",ws.getGlobalError(), ws.getPartitionPath(), ws.getFileId());if (ws.getErrors().size() > 0) {ws.getErrors().forEach((key, value) -> LOG.trace("Error for key:" + key + " and value " + value));}});// Rolls back instantwriteClient.rollback(instant);throw new HoodieException(String.format("Commit instant [%s] failed and rolled back !", instant));}
}

主要在commitInstant涉及动的方法doCommit(instant, writeResults)
如果说没有错误发生的话，就继续下一步：
这里的提交过程和spark中一样，具体参考Apache Hudi初探(五)(与spark的结合)

其他

在flink和spark中新写入的文件是在哪里分配对一个的fieldId:

//Flink中
BucketAssignFunction 中processRecord getNewRecordLocation 分配新的 fieldId//Spark中
BaseSparkCommitActionExecutor 中execute方法 中 handleUpsertPartition 涉及到的UpsertPartitioner getBucketInfo方法
其中UpsertPartitioner构造函数中 assignInserts 方法涉及到分配新的 fieldId