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add RateLimitingService + tests + sample
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| **Rate-limiting pattern** | ||
| **Rate-limiting pattern** | ||
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| Rate limiting involves restricting the number of requests that can be made by a client. | ||
| A client is identified with an access token, which is used for every request to a resource. | ||
| To prevent abuse of the server, APIs enforce rate-limiting techniques. | ||
| Based on the client, the rate-limiting application can decide whether to allow the request to go through or not. | ||
| The client makes an API call to a particular resource; the server checks whether the request for this client is within the limit. | ||
| If the request is within the limit, then the request goes through. | ||
| Otherwise, the API call is restricted. | ||
| Based on RateLimiting service from [ocelot repo](https://github.com/ThreeMammals/Ocelot). | ||
| You can see an example of using in the [SimpleSample](https://github.com/DAKnyazev/rate-limiter/tree/master/Samples/SimpleSample) project. | ||
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| Some examples of request-limiting rules (you could imagine any others) | ||
| * X requests per timespan; | ||
| * a certain timespan passed since the last call; | ||
| * for US-based tokens, we use X requests per timespan, for EU-based - certain timespan passed since the last call. | ||
| ## Usage | ||
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| The goal is to design a class(-es) that manage rate limits for every provided API resource by a set of provided *configurable and extendable* rules. For example, for one resource you could configure the limiter to use Rule A, for another one - Rule B, for a third one - both A + B, etc. Any combinations of rules should be possible, keep this fact in mind when designing the classes. | ||
| To access rate limiting counter you need to resolve service 'IRateLimitingService' | ||
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| We're more interested in the design itself than in some smart and tricky rate limiting algorithm. There is no need to use neither database (in-memory storage is fine) nor any web framework. Do not waste time on preparing complex environment, reusable class library covered by a set of tests is more than enough. | ||
| ### With memory cache | ||
| ```csharp | ||
| .AddRateLimitingServiceWithMemoryCache(); | ||
| ``` | ||
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| There is a Test Project set up for you to use. You are welcome to create your own test project and use whatever test runner you would like. | ||
| ### With distributed cache | ||
| ```csharp | ||
| .AddRateLimitingServiceWithDistributedCache(); | ||
| ``` | ||
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| You are welcome to ask any questions regarding the requirements - treat us as product owners/analysts/whoever who knows the business. | ||
| Should you have any questions or concerns, submit them as a [GitHub issue](https://github.com/crexi-dev/rate-limiter/issues). | ||
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| You should [fork](https://help.github.com/en/github/getting-started-with-github/fork-a-repo) the project, and [create a pull request](https://help.github.com/en/github/collaborating-with-issues-and-pull-requests/creating-a-pull-request-from-a-fork) once you are finished. | ||
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| Good luck! | ||
| ### With custom cache | ||
| ```csharp | ||
| .AddRateLimitingServiceCore() | ||
| .AddSingleton<IRateLimitStorageService, CustomRateLimitStorageService>(); | ||
| ``` | ||
| You need to implement IRateLimitStorageService by yourself. |
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| using System; | ||
| using FluentAssertions; | ||
| using Moq; | ||
| using RateLimiter.Extensions; | ||
| using RateLimiter.Models; | ||
| using RateLimiter.Services; | ||
| using RateLimiter.Services.Interfaces; | ||
| using Xunit; | ||
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| namespace RateLimiter.Tests; | ||
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| public class RateLimitingServiceTests | ||
| { | ||
| private const long MaxRequestsPerPeriod = 3; | ||
| private static readonly TimeSpan Period = TimeSpan.FromSeconds(5); | ||
| private static readonly DateTime Now = DateTime.Now; | ||
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| private readonly IRateLimitingService _rateLimitingService; | ||
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| private readonly Mock<IRateLimitStorageService> _rateLimitStorageServiceMock; | ||
| private readonly Mock<IDateTimeProvider> _dateTimeProviderMock; | ||
| private readonly RateLimitRule _rateLimitRule; | ||
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| public RateLimitingServiceTests() | ||
| { | ||
| _rateLimitStorageServiceMock = new Mock<IRateLimitStorageService>(); | ||
| _dateTimeProviderMock = new Mock<IDateTimeProvider>(MockBehavior.Strict); | ||
| _dateTimeProviderMock.SetupGet(x => x.UtcNow).Returns(Now); | ||
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| _rateLimitingService = new RateLimitingService( | ||
| _rateLimitStorageServiceMock.Object, | ||
| _dateTimeProviderMock.Object); | ||
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| _rateLimitRule = new RateLimitRule(Period, MaxRequestsPerPeriod); | ||
| } | ||
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| [Fact] | ||
| public void GetRateLimitCounter_FirstRequest_ShouldReturnDefaultRateLimitCounter() | ||
| { | ||
| // Arrange | ||
| var identity = new ClientRequestIdentity(Guid.NewGuid().ToString(), "/create", "POST"); | ||
| var key = identity.GetStorageKey(Period); | ||
| _rateLimitStorageServiceMock.Setup(x => x.Get(key)).Returns((RateLimitCounter?)null); | ||
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| // Act | ||
| var result = _rateLimitingService.GetRateLimitCounter(identity, _rateLimitRule); | ||
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| // Assert | ||
| result.StartedAt.Should().Be(Now); | ||
| result.ExceededAt.Should().BeNull(); | ||
| result.TotalRequests.Should().Be(1); | ||
| _rateLimitStorageServiceMock.VerifyAll(); | ||
| _rateLimitStorageServiceMock | ||
| .Verify(x => | ||
| x.Set( | ||
| key, | ||
| It.Is<RateLimitCounter>(c => | ||
| c.StartedAt == Now | ||
| && c.ExceededAt.HasValue == false | ||
| && c.TotalRequests == 1), | ||
| Period), | ||
| Times.Once); | ||
| _rateLimitStorageServiceMock.VerifyNoOtherCalls(); | ||
| } | ||
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| [Fact] | ||
| public void GetRateLimitCounter_OneRequestUntilBan_ShouldReturnRateLimitCounterWithMaxRequestsPerPeriod() | ||
| { | ||
| // Arrange | ||
| var identity = new ClientRequestIdentity(Guid.NewGuid().ToString(), "/create", "POST"); | ||
| var key = identity.GetStorageKey(Period); | ||
| var halfOfPeriod = Period / 2; | ||
| var startedAt = Now.Add(-halfOfPeriod); | ||
| var exceededAt = Now.Add(halfOfPeriod); | ||
| _rateLimitStorageServiceMock | ||
| .Setup(x => x.Get(key)) | ||
| .Returns(new RateLimitCounter( | ||
| startedAt, | ||
| exceededAt, | ||
| MaxRequestsPerPeriod - 1)); | ||
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| // Act | ||
| var result = _rateLimitingService.GetRateLimitCounter(identity, _rateLimitRule); | ||
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| // Assert | ||
| result.StartedAt.Should().Be(startedAt); | ||
| result.ExceededAt.Should().Be(exceededAt); | ||
| result.TotalRequests.Should().Be(MaxRequestsPerPeriod); | ||
| _rateLimitStorageServiceMock.VerifyAll(); | ||
| _rateLimitStorageServiceMock | ||
| .Verify(x => | ||
| x.Set( | ||
| key, | ||
| It.Is<RateLimitCounter>(c => | ||
| c.StartedAt == startedAt | ||
| && c.ExceededAt == exceededAt | ||
| && c.TotalRequests == MaxRequestsPerPeriod), | ||
| Period), | ||
| Times.Once); | ||
| _rateLimitStorageServiceMock.VerifyNoOtherCalls(); | ||
| } | ||
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| [Fact] | ||
| public void GetRateLimitCounter_BanExpired_ShouldReturnDefaultRateLimitCounter() | ||
| { | ||
| // Arrange | ||
| var identity = new ClientRequestIdentity(Guid.NewGuid().ToString(), "/create", "POST"); | ||
| var key = identity.GetStorageKey(Period); | ||
| var startedAt = Now.Add(-Period).AddSeconds(-1); | ||
| var exceededAt = Now.Add(-Period).AddMilliseconds(-1); | ||
| _rateLimitStorageServiceMock | ||
| .Setup(x => x.Get(key)) | ||
| .Returns(new RateLimitCounter( | ||
| startedAt, | ||
| exceededAt, | ||
| MaxRequestsPerPeriod)); | ||
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| // Act | ||
| var result = _rateLimitingService.GetRateLimitCounter(identity, _rateLimitRule); | ||
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| // Assert | ||
| result.StartedAt.Should().Be(Now); | ||
| result.ExceededAt.Should().BeNull(); | ||
| result.TotalRequests.Should().Be(1); | ||
| _rateLimitStorageServiceMock.VerifyAll(); | ||
| _rateLimitStorageServiceMock | ||
| .Verify(x => | ||
| x.Set( | ||
| key, | ||
| It.Is<RateLimitCounter>(c => | ||
| c.StartedAt == Now | ||
| && c.ExceededAt.HasValue == false | ||
| && c.TotalRequests == 1), | ||
| Period), | ||
| Times.Once); | ||
| _rateLimitStorageServiceMock.VerifyNoOtherCalls(); | ||
| } | ||
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| [Fact] | ||
| public void GetRateLimitCounter_BanNotExpired_ShouldReturnRateLimitCounterWithBan() | ||
| { | ||
| // Arrange | ||
| var identity = new ClientRequestIdentity(Guid.NewGuid().ToString(), "/create", "POST"); | ||
| var key = identity.GetStorageKey(Period); | ||
| var startedAt = Now.Add(-Period).AddSeconds(-1); | ||
| var exceededAt = Now.Add(-Period).AddMilliseconds(1); | ||
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| _rateLimitStorageServiceMock | ||
| .Setup(x => x.Get(key)) | ||
| .Returns(new RateLimitCounter( | ||
| startedAt, | ||
| exceededAt, | ||
| MaxRequestsPerPeriod)); | ||
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| // Act | ||
| var result = _rateLimitingService.GetRateLimitCounter(identity, _rateLimitRule); | ||
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| // Assert | ||
| result.StartedAt.Should().Be(startedAt); | ||
| result.ExceededAt.Should().Be(exceededAt); | ||
| result.TotalRequests.Should().Be(MaxRequestsPerPeriod + 1); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| using System; | ||
| using System.Security.Cryptography; | ||
| using System.Text; | ||
| using RateLimiter.Models; | ||
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| namespace RateLimiter.Extensions; | ||
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| internal static class ClientRequestIdentityExtensions | ||
| { | ||
| internal static string GetStorageKey(this ClientRequestIdentity identity, TimeSpan period) | ||
| { | ||
| var key = $"{identity.ClientId}_{period}_{identity.HttpVerb}_{identity.Path}"; | ||
| var idBytes = Encoding.UTF8.GetBytes(key); | ||
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| byte[] hashBytes; | ||
| using (var algorithm = SHA1.Create()) | ||
| { | ||
| hashBytes = algorithm.ComputeHash(idBytes); | ||
| } | ||
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| return BitConverter.ToString(hashBytes).Replace("-", string.Empty); | ||
| } | ||
| } |
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| using RateLimiter.Models; | ||
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| namespace RateLimiter; | ||
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| /// <summary> | ||
| /// A service, providing information about count of requests that clients made to the endpoint | ||
| /// </summary> | ||
| public interface IRateLimitingService | ||
| { | ||
| RateLimitCounter GetRateLimitCounter(ClientRequestIdentity identity, RateLimitRule rule); | ||
| } |
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| @@ -0,0 +1,15 @@ | ||
| namespace RateLimiter.Models; | ||
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| public sealed class ClientRequestIdentity | ||
| { | ||
| public ClientRequestIdentity(string clientId, string path, string httpverb) | ||
| { | ||
| ClientId = clientId; | ||
| Path = path; | ||
| HttpVerb = httpverb; | ||
| } | ||
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| public string ClientId { get; } | ||
| public string Path { get; } | ||
| public string HttpVerb { get; } | ||
| } |
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| @@ -0,0 +1,22 @@ | ||
| using System; | ||
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| namespace RateLimiter.Models; | ||
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| /// <summary> | ||
| /// Stores the initial access time and the numbers of calls made from that point. | ||
| /// </summary> | ||
| public struct RateLimitCounter | ||
| { | ||
| public RateLimitCounter(DateTime startedAt, DateTime? exceededAt, long totalRequests) | ||
| { | ||
| StartedAt = startedAt; | ||
| ExceededAt = exceededAt; | ||
| TotalRequests = totalRequests; | ||
| } | ||
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| public DateTime StartedAt { get; } | ||
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| public DateTime? ExceededAt { get; } | ||
|
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| public long TotalRequests { get; set; } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,20 @@ | ||
| using System; | ||
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| namespace RateLimiter.Models; | ||
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| public sealed class RateLimitRule | ||
| { | ||
| public RateLimitRule(TimeSpan period, long limit) | ||
| { | ||
| Period = period; | ||
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| if (limit < 1) | ||
| throw new ArgumentOutOfRangeException($"{nameof(Limit)} must be positive."); | ||
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| Limit = limit; | ||
| } | ||
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| public TimeSpan Period { get; } | ||
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| public long Limit { get; } | ||
| } |
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