C#•4mo ago

Parallel list

I'm trying to write to a list in parallel due to vendor SDK performance issues with sequential operations. I have the following code. Is this a proper approach?

c#
    private readonly ConcurrentQueue<DRT> _recordQueue = new ConcurrentQueue<DRT>();
private readonly SemaphoreSlim _flushLock = new SemaphoreSlim(1, 1);

    public async Task Execute() {
      try {
        // external/irrelevant to the list question
        await PerformWorkerSetup();
        IEnumerable<SRT> sourceRecords = ExtractRecords();
        //

        await TransformRecords(sourceRecords);
        await FlushRecords(1);
      } catch (Exception ex) {
        Log.Error(ex.Message);
      }
    }

    public async Task TransformRecordsParallel(IEnumerable<SRT> sourceRecords) {
      IEnumerable<Task> tasks = sourceRecords.Select(async (record) => {
        _recordQueue.Enqueue(this.FormatRecord(record));
        await FlushRecords(Config.Threshold);
      });

      await Task.WhenAll(tasks);
    }

    public async Task FlushRecords(int threshold) {
      if (_recordQueue.Count >= threshold) {
        await _flushLock.WaitAsync();

        try {
          IList<DRT> recordList = new List<DRT>();

          // Pull records out of the bag for processing.
          while (recordList.Count <= threshold && _recordQueue.TryDequeue(out DRT record)) {
            recordList.Add(record);
          }

          // write the recordList to file or SQL
        } catch {
          throw;
        } finally {
          _flushLock.Release();
        }
      }
    }

c#
    private readonly ConcurrentQueue<DRT> _recordQueue = new ConcurrentQueue<DRT>();
private readonly SemaphoreSlim _flushLock = new SemaphoreSlim(1, 1);

    public async Task Execute() {
      try {
        // external/irrelevant to the list question
        await PerformWorkerSetup();
        IEnumerable<SRT> sourceRecords = ExtractRecords();
        //

        await TransformRecords(sourceRecords);
        await FlushRecords(1);
      } catch (Exception ex) {
        Log.Error(ex.Message);
      }
    }

    public async Task TransformRecordsParallel(IEnumerable<SRT> sourceRecords) {
      IEnumerable<Task> tasks = sourceRecords.Select(async (record) => {
        _recordQueue.Enqueue(this.FormatRecord(record));
        await FlushRecords(Config.Threshold);
      });

      await Task.WhenAll(tasks);
    }

    public async Task FlushRecords(int threshold) {
      if (_recordQueue.Count >= threshold) {
        await _flushLock.WaitAsync();

        try {
          IList<DRT> recordList = new List<DRT>();

          // Pull records out of the bag for processing.
          while (recordList.Count <= threshold && _recordQueue.TryDequeue(out DRT record)) {
            recordList.Add(record);
          }

          // write the recordList to file or SQL
        } catch {
          throw;
        } finally {
          _flushLock.Release();
        }
      }
    }

3 Replies

Moods•4mo ago

Task.WhenAll is fine yeah(btw unless I'm blind TransformRecordsParallel is never called in your code)

Moods•4mo ago

there is also https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.parallel.foreachasync?view=net-8.0

Parallel.ForEachAsync Method (System.Threading.Tasks)

Executes a for-each operation on an IEnumerable in which iterations may run in parallel.

engineertdogOP•4mo ago

Whoops, I forgot that function. Basically it's a user-defined choice of parallel vs sequential.

c#
    public async Task TransformRecords(IEnumerable<SRT> sourceRecords) {
      if (Config.Parallel == "") {
        await TransformRecordsSequential(sourceRecords);
      } else {
        await TransformRecordsParallel(sourceRecords);
      }
    }

c#
    public async Task TransformRecords(IEnumerable<SRT> sourceRecords) {
      if (Config.Parallel == "") {
        await TransformRecordsSequential(sourceRecords);
      } else {
        await TransformRecordsParallel(sourceRecords);
      }
    }

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