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Move parallelism level for the importing process from the record level to the data chunk level #2728

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Merged
merged 6 commits into from
Jun 9, 2025
Merged

Move parallelism level for the importing process from the record level to the data chunk level #2728

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a27b52f
Move parallelism level for importing process from record level to dat…
thongdk8 Jun 3, 2025
ad37da6
Merge branch 'master' into data-loader/ref/move-parallelism-to-datach…
thongdk8 Jun 3, 2025
11ab70b
Merge branch 'master' into data-loader/ref/move-parallelism-to-datach…
thongdk8 Jun 4, 2025
5b8e63a
Update data-loader/core/src/main/java/com/scalar/db/dataloader/core/d…
thongdk8 Jun 5, 2025
eb33df4
Merge branch 'master' into data-loader/ref/move-parallelism-to-datach…
ypeckstadt Jun 5, 2025
59040c7
Merge branch 'master' into data-loader/ref/move-parallelism-to-datach…
ypeckstadt Jun 9, 2025
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168 changes: 75 additions & 93 deletions ...ore/src/main/java/com/scalar/db/dataloader/core/dataimport/processor/ImportProcessor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,11 +25,11 @@
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.Phaser;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import lombok.RequiredArgsConstructor;
Expand Down Expand Up @@ -62,41 +62,77 @@ public abstract class ImportProcessor {
* @param reader the {@link BufferedReader} used to read the source file
*/
public void process(int dataChunkSize, int transactionBatchSize, BufferedReader reader) {
ExecutorService dataChunkExecutor = Executors.newSingleThreadExecutor();
ExecutorService dataChunkReaderExecutor = Executors.newSingleThreadExecutor();
ExecutorService dataChunkProcessorExecutor =
Executors.newFixedThreadPool(params.getImportOptions().getMaxThreads());
BlockingQueue<ImportDataChunk> dataChunkQueue =
new LinkedBlockingQueue<>(params.getImportOptions().getDataChunkQueueSize());

// Semaphore controls concurrent task submissions, small buffer to be two times of threads
Semaphore taskSemaphore = new Semaphore(params.getImportOptions().getMaxThreads() * 2);
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@brfrn169 brfrn169 Jun 5, 2025

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Instead of using a Semaphore, I think we can use an ExecutorService with a bounded blocking queue, as shown below:

    ExecutorService dataChunkProcessorExecutor =
        new ThreadPoolExecutor(
            params.getImportOptions().getMaxThreads(),
            params.getImportOptions().getMaxThreads(),
            0L,
            TimeUnit.MILLISECONDS,
            new ArrayBlockingQueue<>(params.getImportOptions().getMaxThreads() * 2),
            Executors.defaultThreadFactory(),
            new ThreadPoolExecutor.CallerRunsPolicy());

What do you think?

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@thongdk8 thongdk8 Jun 5, 2025

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Ah yes, we can use bounded blocking queue like you mentioned, but as it is using CallerRunsPolicy so when the thread pool is completely saturated (all threads busy + queue full), CallerRunsPolicy runs the task in the calling thread (main thread in our case) instead of the pool threads, that is not what we expect as all the processing tasks are executed in the pool is more natural I think.
There are other policies as well, but seems there is no suitable one unless we create a custom one, so I think using semaphore with a fixed pool here is ok. WDYT?

// Phaser tracks task completion (start with 1 for the main thread)
Phaser phaser = new Phaser(1);

try {
CompletableFuture<Void> readerFuture =
CompletableFuture.runAsync(
() -> readDataChunks(reader, dataChunkSize, dataChunkQueue), dataChunkExecutor);
() -> readDataChunks(reader, dataChunkSize, dataChunkQueue), dataChunkReaderExecutor);

while (!(dataChunkQueue.isEmpty() && readerFuture.isDone())) {
ImportDataChunk dataChunk = dataChunkQueue.poll(100, TimeUnit.MILLISECONDS);
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@komamitsu komamitsu Jun 4, 2025

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This is not related to this PR, but why we need to wake up every 100 ms? I just think longer timeout or using take() might be better.

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@thongdk8 thongdk8 Jun 4, 2025 •
edited
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The queue is buffered, so the timeout of 100ms would be fine I think.
We can replace it with take, but it seems a bit unsafe since the take will block the loop (deadlock) and you would never get a chance to recheck the while conditions unless a new item arrives. For example, if the queue is empty but the reader is on going for exiting its job (the reader future is going to be done), although this case is hard to be happenned, but still has a posibility. WDYT?

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@komamitsu komamitsu Jun 4, 2025

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Yeah, you're correct. I didn't consider the exit condition. Let's keep it as is.

if (dataChunk != null) {
processDataChunk(dataChunk, transactionBatchSize);
// Acquire semaphore permit (blocks if no permits available)
taskSemaphore.acquire();
// Register with phaser before submitting
phaser.register();

dataChunkProcessorExecutor.submit(
() -> {
try {
processDataChunk(dataChunk, transactionBatchSize);
} finally {
// Always release semaphore and arrive at phaser
taskSemaphore.release();
phaser.arriveAndDeregister();
}
});
}
}

readerFuture.join();
// Wait for all tasks to complete
phaser.arriveAndAwaitAdvance();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new RuntimeException(
CoreError.DATA_LOADER_DATA_CHUNK_PROCESS_FAILED.buildMessage(e.getMessage()), e);
} finally {
dataChunkExecutor.shutdown();
try {
if (!dataChunkExecutor.awaitTermination(60, TimeUnit.SECONDS)) {
dataChunkExecutor.shutdownNow();
}
} catch (InterruptedException e) {
dataChunkExecutor.shutdownNow();
Thread.currentThread().interrupt();
}
shutdownExecutorGracefully(dataChunkReaderExecutor);
shutdownExecutorGracefully(dataChunkProcessorExecutor);
notifyAllDataChunksCompleted();
}
}

/**
* Shuts down the given `ExecutorService` gracefully. This method attempts to cleanly shut down
* the executor by first invoking `shutdown` and waiting for termination for up to 60 seconds. If
* the executor does not terminate within this time, it forces a shutdown using `shutdownNow`. If
* interrupted, it forces a shutdown and interrupts the current thread.
*
* @param es the `ExecutorService` to be shut down gracefully
*/
private void shutdownExecutorGracefully(ExecutorService es) {
es.shutdown();
try {
if (!es.awaitTermination(60, TimeUnit.SECONDS)) {
es.shutdownNow();
}
} catch (InterruptedException e) {
es.shutdownNow();
Thread.currentThread().interrupt();
}
}

/**
* Reads and processes data in chunks from the provided reader.
*
Expand Down Expand Up @@ -373,46 +409,26 @@ private ImportDataChunkStatus processDataChunkWithTransactions(
Instant startTime = Instant.now();
List<ImportTransactionBatch> transactionBatches =
splitIntoTransactionBatches(dataChunk, transactionBatchSize);
ExecutorService transactionBatchExecutor =
Executors.newFixedThreadPool(params.getImportOptions().getMaxThreads());
List<Future<?>> transactionBatchFutures = new ArrayList<>();
AtomicInteger successCount = new AtomicInteger(0);
AtomicInteger failureCount = new AtomicInteger(0);
try {
for (ImportTransactionBatch transactionBatch : transactionBatches) {
Future<?> transactionBatchFuture =
transactionBatchExecutor.submit(
() -> processTransactionBatch(dataChunk.getDataChunkId(), transactionBatch));
transactionBatchFutures.add(transactionBatchFuture);
}

waitForFuturesToComplete(transactionBatchFutures);
transactionBatchFutures.forEach(
batchResult -> {
try {
ImportTransactionBatchResult importTransactionBatchResult =
(ImportTransactionBatchResult) batchResult.get();
importTransactionBatchResult
.getRecords()
.forEach(
batchRecords -> {
if (batchRecords.getTargets().stream()
.allMatch(
targetResult ->
targetResult
.getStatus()
.equals(ImportTargetResultStatus.SAVED))) {
successCount.incrementAndGet();
} else {
failureCount.incrementAndGet();
}
});
} catch (InterruptedException | ExecutionException e) {
throw new RuntimeException(e);
}
});
} finally {
transactionBatchExecutor.shutdown();
for (ImportTransactionBatch transactionBatch : transactionBatches) {
ImportTransactionBatchResult importTransactionBatchResult =
processTransactionBatch(dataChunk.getDataChunkId(), transactionBatch);

importTransactionBatchResult
.getRecords()
.forEach(
batchRecords -> {
if (batchRecords.getTargets().stream()
.allMatch(
targetResult ->
targetResult.getStatus().equals(ImportTargetResultStatus.SAVED))) {
successCount.incrementAndGet();
} else {
failureCount.incrementAndGet();
}
});
}
Instant endTime = Instant.now();
int totalDuration = (int) Duration.between(startTime, endTime).toMillis();
Expand Down Expand Up @@ -440,32 +456,14 @@ private ImportDataChunkStatus processDataChunkWithoutTransactions(ImportDataChun
Instant startTime = Instant.now();
AtomicInteger successCount = new AtomicInteger(0);
AtomicInteger failureCount = new AtomicInteger(0);
ExecutorService recordExecutor =
Executors.newFixedThreadPool(params.getImportOptions().getMaxThreads());
List<Future<?>> recordFutures = new ArrayList<>();
try {
for (ImportRow importRow : dataChunk.getSourceData()) {
Future<?> recordFuture =
recordExecutor.submit(
() -> processStorageRecord(dataChunk.getDataChunkId(), importRow));
recordFutures.add(recordFuture);
}
waitForFuturesToComplete(recordFutures);
recordFutures.forEach(
r -> {
try {
ImportTaskResult result = (ImportTaskResult) r.get();
boolean allSaved =
result.getTargets().stream()
.allMatch(t -> t.getStatus().equals(ImportTargetResultStatus.SAVED));
if (allSaved) successCount.incrementAndGet();
else failureCount.incrementAndGet();
} catch (InterruptedException | ExecutionException e) {
throw new RuntimeException(e);
}
});
} finally {
recordExecutor.shutdown();

for (ImportRow importRow : dataChunk.getSourceData()) {
ImportTaskResult result = processStorageRecord(dataChunk.getDataChunkId(), importRow);
boolean allSaved =
result.getTargets().stream()
.allMatch(t -> t.getStatus().equals(ImportTargetResultStatus.SAVED));
if (allSaved) successCount.incrementAndGet();
else failureCount.incrementAndGet();
}
Instant endTime = Instant.now();
int totalDuration = (int) Duration.between(startTime, endTime).toMillis();
Expand All @@ -480,20 +478,4 @@ private ImportDataChunkStatus processDataChunkWithoutTransactions(ImportDataChun
.status(ImportDataChunkStatusState.COMPLETE)
.build();
}

/**
* Waits for all futures in the provided list to complete. Any exceptions during execution are
* logged but not propagated.
*
* @param futures the list of {@link Future} objects to wait for
*/
private void waitForFuturesToComplete(List<Future<?>> futures) {
for (Future<?> future : futures) {
try {
future.get();
} catch (Exception e) {
LOGGER.error(e.getMessage());
}
}
}
}
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