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EnumerableAsyncProcessor

Process Multiple Asynchronous Tasks in Various Ways - One at a time / Batched / Rate limited / Concurrently

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Installation

Install via Nuget Install-Package EnumerableAsyncProcessor

Why I built this

Because I've come across situations where you need to fine tune the rate at which you do things. Maybe you want it fast. Maybe you want it slow. Maybe you want it at a safe balance. Maybe you just don't want to write all the boilerplate code that comes with managing asynchronous operations!

Rate Limited Parallel Processor

Types

Type Source Object Return Object Method 1 Method 2
RateLimitedParallelAsyncProcessor ❌ ❌ .WithExecutionCount(int) .ForEachAsync(delegate)
RateLimitedParallelAsyncProcessor<TInput> ✔ ❌ .WithItems(IEnumerable<TInput>) .ForEachAsync(delegate)
ResultRateLimitedParallelAsyncProcessor<TOutput> ❌ ✔ .WithExecutionCount(int) .SelectAsync(delegate)
ResultRateLimitedParallelAsyncProcessor<TInput, TOutput> ✔ ✔ .WithItems(IEnumerable<TInput>) .SelectAsync(delegate)

How it works
Processes your Asynchronous Tasks in Parallel, but honouring the limit that you set. As one finishes, another will start.

E.g. If you set a limit of 100, only 100 should ever run at any one time

This is a hybrid between Parallel Processor and Batch Processor (see below) - Trying to address the caveats of both. Increasing the speed of batching, but not overwhelming the system by using full parallelisation.

Usage

var ids = Enumerable.Range(0, 5000).ToList();

// SelectAsync for if you want to return something
var results = await ids
        .SelectAsync(id => DoSomethingAndReturnSomethingAsync(id), CancellationToken.None)
        .ProcessInParallel(levelOfParallelism: 100);

// ForEachAsync for when you have nothing to return
await ids
        .ForEachAsync(id => DoSomethingAsync(id), CancellationToken.None) 
        .ProcessInParallel(levelOfParallelism: 100);

Timed Rate Limited Parallel Processor (e.g. Limit RPS)

Types

Type Source Object Return Object Method 1 Method 2
TimedRateLimitedParallelAsyncProcessor ❌ ❌ .WithExecutionCount(int) .ForEachAsync(delegate)
TimedRateLimitedParallelAsyncProcessor<TInput> ✔ ❌ .WithItems(IEnumerable<TInput>) .ForEachAsync(delegate)
ResultTimedRateLimitedParallelAsyncProcessor<TOutput> ❌ ✔ .WithExecutionCount(int) .SelectAsync(delegate)
ResultTimedRateLimitedParallelAsyncProcessor<TInput, TOutput> ✔ ✔ .WithItems(IEnumerable<TInput>) .SelectAsync(delegate)

How it works
Processes your Asynchronous Tasks in Parallel, but honouring the limit that you set over the timespan that you set. As one finishes, another will start, unless you've hit the maximum allowed for the current timespan duration.

E.g. If you set a limit of 100, and a timespan of 1 second, only 100 operation should ever run at any one time over the course of a second. If the operation finishes sooner than a second (or your provided timespan), it'll wait and then start the next operation once that timespan has elapsed.

This is useful in scenarios where, for example, you have an API but it has a request per second limit

Usage

var ids = Enumerable.Range(0, 5000).ToList();

// SelectAsync for if you want to return something
var results = await ids
        .SelectAsync(id => DoSomethingAndReturnSomethingAsync(id), CancellationToken.None)
        .ProcessInParallel(levelOfParallelism: 100, TimeSpan.FromSeconds(1));

// ForEachAsync for when you have nothing to return
await ids
        .ForEachAsync(id => DoSomethingAsync(id), CancellationToken.None) 
        .ProcessInParallel(levelOfParallelism: 100, TimeSpan.FromSeconds(1));

Caveats

  • If your operations take longer than your provided TimeSpan, you probably won't get your desired throughput. This processor ensures you don't go over your rate limit, but will not increase parallel execution if you're below it.

One At A Time

Types

Type Source Object Return Object Method 1 Method 2
OneAtATimeAsyncProcessor ❌ ❌ .WithExecutionCount(int) .ForEachAsync(delegate)
OneAtATimeAsyncProcessor<TInput> ✔ ❌ .WithItems(IEnumerable<TInput>) .ForEachAsync(delegate)
ResultOneAtATimeAsyncProcessor<TOutput> ❌ ✔ .WithExecutionCount(int) .SelectAsync(delegate)
ResultOneAtATimeAsyncProcessor<TInput, TOutput> ✔ ✔ .WithItems(IEnumerable<TInput>) .SelectAsync(delegate)

How it works
Processes your Asynchronous Tasks One at a Time. Only one will ever progress at a time. As one finishes, another will start

Usage

var ids = Enumerable.Range(0, 5000).ToList();

// SelectAsync for if you want to return something
var results = await ids
        .SelectAsync(id => DoSomethingAndReturnSomethingAsync(id), CancellationToken.None)
        .ProcessOneAtATime();

// ForEachAsync for when you have nothing to return
await ids
        .ForEachAsync(id => DoSomethingAsync(id), CancellationToken.None) 
        .ProcessOneAtATime();

Caveats

  • Slowest method

Batch

Types

Type Source Object Return Object Method 1 Method 2
BatchAsyncProcessor ❌ ❌ .WithExecutionCount(int) .ForEachAsync(delegate)
BatchAsyncProcessor<TInput> ✔ ❌ .WithItems(IEnumerable<TInput>) .ForEachAsync(delegate)
ResultBatchAsyncProcessor<TOutput> ❌ ✔ .WithExecutionCount(int) .SelectAsync(delegate)
ResultBatchAsyncProcessor<TInput, TOutput> ✔ ✔ .WithItems(IEnumerable<TInput>) .SelectAsync(delegate)

How it works
Processes your Asynchronous Tasks in Batches. The next batch will not start until every Task in previous batch has finished

Usage

var ids = Enumerable.Range(0, 5000).ToList();

// SelectAsync for if you want to return something
var results = await ids
        .SelectAsync(id => DoSomethingAndReturnSomethingAsync(id), CancellationToken.None)
        .ProcessInBatches(batchSize: 100);

// ForEachAsync for when you have nothing to return
await ids
        .ForEachAsync(id => DoSomethingAsync(id), CancellationToken.None) 
        .ProcessInBatches(batchSize: 100);

Caveats

  • If even just 1 Task in a batch is slow or hangs, this will prevent the next batch from starting
  • If you set a batch of 100, and 70 have finished, you'll only have 30 left executing. This could slow things down

Parallel

Types

Type Source Object Return Object Method 1 Method 2
ParallelAsyncProcessor ❌ ❌ .WithExecutionCount(int) .ForEachAsync(delegate)
ParallelAsyncProcessor<TInput> ✔ ❌ .WithItems(IEnumerable<TInput>) .ForEachAsync(delegate)
ResultParallelAsyncProcessor<TOutput> ❌ ✔ .WithExecutionCount(int) .SelectAsync(delegate)
ResultParallelAsyncProcessor<TInput, TOutput> ✔ ✔ .WithItems(IEnumerable<TInput>) .SelectAsync(delegate)

How it works
Processes your Asynchronous Tasks as fast as it can. All at the same time if it can

Usage

var ids = Enumerable.Range(0, 5000).ToList();

// SelectAsync for if you want to return something
var results = await ids
        .SelectAsync(id => DoSomethingAndReturnSomethingAsync(id), CancellationToken.None)
        .ProcessInParallel();

// ForEachAsync for when you have nothing to return
await ids
        .ForEachAsync(id => DoSomethingAsync(id), CancellationToken.None) 
        .ProcessInParallel();

Caveats

  • Depending on how many operations you have, you could overwhelm your system. Memory and CPU and Network usage could spike, and cause bottlenecks / crashes / exceptions

Processor Methods

As above, you can see that you can just await on the processor to get the results. Below shows examples of using the processor object and the various methods available.

This is for when you need to Enumerate through some objects and use them in your operations. E.g. Sending notifications to certain ids

    var httpClient = new HttpClient();

    var ids = Enumerable.Range(0, 5000).ToList();

    // This is for when you need to Enumerate through some objects and use them in your operations
    
    var itemProcessor = Enumerable.Range(0, 5000).ToAsyncProcessorBuilder()
        .SelectAsync(NotifyAsync)
        .ProcessInParallel(100);

    // Or
    // var itemProcessor = AsyncProcessorBuilder.WithItems(ids)
    //     .SelectAsync(NotifyAsync, CancellationToken.None)
    //     .ProcessInParallel(100);

// GetEnumerableTasks() returns IEnumerable<Task<TOutput>> - These may have completed, or may still be waiting to finish.
    var tasks = itemProcessor.GetEnumerableTasks();

// Or call GetResultsAsyncEnumerable() to get an IAsyncEnumerable<TOutput> so you can process them in real-time as they finish.
    await foreach (var httpResponseMessage in itemProcessor.GetResultsAsyncEnumerable())
    {
        // Do something
    }

// Or call GetResultsAsync() to get a Task<TOutput[]> that contains all of the finished results 
    var results = await itemProcessor.GetResultsAsync();

// My dummy method
    Task<HttpResponseMessage> NotifyAsync(int id)
    {
        return httpClient.GetAsync($"https://localhost:8080/notify/{id}");
    }

This is for when you need to don't need any objects - But just want to do something a certain amount of times. E.g. Pinging a site to warm up multiple instances

    var httpClient = new HttpClient();

    var itemProcessor = AsyncProcessorBuilder.WithExecutionCount(100)
        .SelectAsync(PingAsync, CancellationToken.None)
        .ProcessInParallel(10);

// GetEnumerableTasks() returns IEnumerable<Task<TOutput>> - These may have completed, or may still be waiting to finish.
    var tasks = itemProcessor.GetEnumerableTasks();

// Or call GetResultsAsyncEnumerable() to get an IAsyncEnumerable<TOutput> so you can process them in real-time as they finish.
    await foreach (var httpResponseMessage in itemProcessor.GetResultsAsyncEnumerable())
    {
        // Do something
    }

// Or call GetResultsAsync() to get a Task<TOutput[]> that contains all of the finished results 
    var results = await itemProcessor.GetResultsAsync();

// My dummy method
    Task<HttpResponseMessage> PingAsync()
    {
        return httpClient.GetAsync("https://localhost:8080/ping");
    }