126 lines
4.8 KiB
C#
126 lines
4.8 KiB
C#
// Copyright (C) 2018, The Duplicati Team
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// http://www.duplicati.com, info@duplicati.com
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//
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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using Duplicati.Library.Logging;
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using Duplicati.Library.Utility;
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Net.Http.Headers;
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using System.Text;
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using System.Threading;
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using System.Threading.Tasks;
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namespace Duplicati.Library
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{
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public class RetryAfterHelper
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{
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private static readonly string LOGTAG = Log.LogTagFromType<RetryAfterHelper>();
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// Whenever a response includes a Retry-After header, we'll update this timestamp with when we can next
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// send a request. And before sending any requests, we'll make sure to wait until at least this time.
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// Since this may be read and written by multiple threads, it is stored as a long and updated using Interlocked.Exchange.
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private long retryAfter = DateTimeOffset.MinValue.UtcTicks;
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public void SetRetryAfter(RetryConditionHeaderValue retryAfter)
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{
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if (retryAfter != null)
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{
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DateTimeOffset? delayUntil = null;
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if (retryAfter.Delta.HasValue)
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{
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delayUntil = DateTimeOffset.UtcNow + retryAfter.Delta.Value;
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}
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else if (retryAfter.Date.HasValue)
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{
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delayUntil = retryAfter.Date.Value;
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}
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if (delayUntil.HasValue)
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{
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// Set the retry timestamp to the UTC version of the timestamp.
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long newRetryAfter = delayUntil.Value.UtcTicks;
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// Update the persisted retry after timestamp
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long replacedRetryAfter;
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long currentRetryAfter;
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do
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{
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currentRetryAfter = Interlocked.Read(ref this.retryAfter);
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if (newRetryAfter < currentRetryAfter)
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{
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// If the current retry after is already past the new value, then no need to update it again.
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break;
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}
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else
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{
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replacedRetryAfter = Interlocked.CompareExchange(ref this.retryAfter, newRetryAfter, currentRetryAfter);
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}
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}
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while (replacedRetryAfter != currentRetryAfter);
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}
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}
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}
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public void WaitForRetryAfter()
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{
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this.WaitForRetryAfterAsync(CancellationToken.None).Await();
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}
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public async Task WaitForRetryAfterAsync(CancellationToken cancelToken)
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{
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TimeSpan delay = this.GetDelayTime();
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if (delay > TimeSpan.Zero)
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{
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Log.WriteProfilingMessage(
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LOGTAG,
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"RetryAfterWait",
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"Waiting for {0} to respect Retry-After header",
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delay);
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await Task.Delay(delay).ConfigureAwait(false);
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}
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}
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private TimeSpan GetDelayTime()
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{
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// Make sure this is thread safe in case multiple calls are made concurrently to this backend
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// This is done by reading the value into a local value which is then parsed and operated on locally.
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long retryAfterTicks = Interlocked.Read(ref this.retryAfter);
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DateTimeOffset delayUntil = new DateTimeOffset(retryAfterTicks, TimeSpan.Zero);
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TimeSpan delay;
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DateTimeOffset now = DateTimeOffset.UtcNow;
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// Make sure delayUntil is in the future and delay until then if so
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if (delayUntil >= now)
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{
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delay = delayUntil - now;
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}
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else
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{
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// If the date given was in the past then don't wait at all
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delay = TimeSpan.Zero;
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}
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return delay;
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}
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}
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}
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