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Support for Rate-Limiting in the PnP Framework + unifiqation of the t…
…hrottling implementation for all http requests made
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| using PnP.Framework.Diagnostics; | ||
| using System; | ||
| using System.Collections.Generic; | ||
| using System.Linq; | ||
| using System.Net.Http; | ||
| using System.Threading; | ||
| using System.Threading.Tasks; | ||
|
|
||
| namespace PnP.Framework.Http | ||
| { | ||
| public class RateLimiter | ||
| { | ||
| internal const string RATELIMIT_LIMIT = "RateLimit-Limit"; | ||
| internal const string RATELIMIT_REMAINING = "RateLimit-Remaining"; | ||
| internal const string RATELIMIT_RESET = "RateLimit-Reset"; | ||
|
|
||
| /// <summary> | ||
| /// Lock for controlling Read/Write access to the variables. | ||
| /// </summary> | ||
| private readonly ReaderWriterLockSlim readerWriterLock = new ReaderWriterLockSlim(); | ||
|
|
||
| /// <summary> | ||
| /// Maximum number of requests per window | ||
| /// </summary> | ||
| private int limit; | ||
|
|
||
| /// <summary> | ||
| /// The time, in <see cref="TimeSpan.Seconds"/>, when the current window gets reset | ||
| /// </summary> | ||
| private int reset; | ||
|
|
||
| /// <summary> | ||
| /// The timestamp when current window will be reset, in <see cref="TimeSpan.Ticks"/>. | ||
| /// </summary> | ||
| private long nextReset; | ||
|
|
||
| /// <summary> | ||
| /// The remaining requests in the current window. | ||
| /// </summary> | ||
| private int remaining; | ||
|
|
||
| /// <summary> | ||
| /// Minimum % of requests left before the next request will get delayed until the current window is reset. Defaults to 10, set to 0 to disable rate limiting | ||
| /// </summary> | ||
| internal int MinimumCapacityLeft { get; set; } = 10; | ||
|
|
||
| /// <summary> | ||
| /// Default constructor | ||
| /// </summary> | ||
| public RateLimiter() | ||
| { | ||
| readerWriterLock.EnterWriteLock(); | ||
| try | ||
| { | ||
| _ = Interlocked.Exchange(ref limit, -1); | ||
| _ = Interlocked.Exchange(ref remaining, -1); | ||
| _ = Interlocked.Exchange(ref reset, -1); | ||
| _ = Interlocked.Exchange(ref nextReset, DateTime.UtcNow.Ticks); | ||
| } | ||
| finally | ||
| { | ||
| readerWriterLock.ExitWriteLock(); | ||
| } | ||
| } | ||
|
|
||
| internal async Task WaitAsync(CancellationToken cancellationToken) | ||
| { | ||
| cancellationToken.ThrowIfCancellationRequested(); | ||
|
|
||
| // We're not using the rate limiter | ||
| if (MinimumCapacityLeft == 0) | ||
| { | ||
| return; | ||
| } | ||
|
|
||
| long delayInTicks = 0; | ||
| float capacityLeft = 0; | ||
| readerWriterLock.EnterReadLock(); | ||
| try | ||
| { | ||
| // Remaining = 0 means the request is throttled and there's a retry-after header that will be used | ||
| if (limit > 0 && remaining > 0) | ||
| { | ||
| // Calculate percentage requests left in the current window | ||
| capacityLeft = (float)remaining / limit * 100; | ||
|
|
||
| // If getting below the minimum required capacity then lets wait until the current window is reset | ||
| if (capacityLeft <= MinimumCapacityLeft) | ||
| { | ||
| delayInTicks = nextReset - DateTime.UtcNow.Ticks; | ||
| } | ||
| } | ||
| } | ||
| finally | ||
| { | ||
| readerWriterLock.ExitReadLock(); | ||
| } | ||
|
|
||
| if (delayInTicks > 0) | ||
| { | ||
| Log.Info(Constants.LOGGING_SOURCE, $"Delaying request for {new TimeSpan(delayInTicks).Seconds} seconds because remaining request capacity for the current window is at {capacityLeft}%, so below the {MinimumCapacityLeft}% threshold."); | ||
|
|
||
| await Task.Delay(new TimeSpan(delayInTicks), cancellationToken).ConfigureAwait(false); | ||
| } | ||
| } | ||
|
|
||
| internal void UpdateWindow(HttpResponseMessage response) | ||
| { | ||
| int rateLimit = -1; | ||
| int rateRemaining = -1; | ||
| int rateReset = -1; | ||
|
|
||
| // We're not using the rate limiter | ||
| if (MinimumCapacityLeft == 0) | ||
| { | ||
| return; | ||
| } | ||
|
|
||
| if (response != null) | ||
| { | ||
| if (response.Headers.TryGetValues(RATELIMIT_LIMIT, out IEnumerable<string> limitValues)) | ||
| { | ||
| string rateString = limitValues.First(); | ||
| _ = int.TryParse(rateString, out rateLimit); | ||
| } | ||
|
|
||
| if (response.Headers.TryGetValues(RATELIMIT_REMAINING, out IEnumerable<string> remainingValues)) | ||
| { | ||
| string rateString = remainingValues.First(); | ||
| _ = int.TryParse(rateString, out rateRemaining); | ||
| } | ||
|
|
||
| if (response.Headers.TryGetValues(RATELIMIT_RESET, out IEnumerable<string> resetValues)) | ||
| { | ||
| string rateString = resetValues.First(); | ||
| _ = int.TryParse(rateString, out rateReset); | ||
| } | ||
|
|
||
| readerWriterLock.EnterWriteLock(); | ||
| try | ||
| { | ||
| _ = Interlocked.Exchange(ref limit, rateLimit); | ||
| _ = Interlocked.Exchange(ref remaining, rateRemaining); | ||
| _ = Interlocked.Exchange(ref reset, rateReset); | ||
|
|
||
| if (rateReset > -1) | ||
| { | ||
| // Track when the current window get's reset | ||
| _ = Interlocked.Exchange(ref nextReset, DateTime.UtcNow.Ticks + TimeSpan.FromSeconds(rateReset).Ticks); | ||
| } | ||
| } | ||
| finally | ||
| { | ||
| readerWriterLock.ExitWriteLock(); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| } | ||
| } |
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