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Drop ETag and use Last-Modified header #890

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merged 2 commits into from Feb 13, 2019
Merged

Drop ETag and use Last-Modified header #890

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77e4a01
Drop ETag and use Last-Modified since performance is much better
cvium Feb 13, 2019
a5ca457
Remove int conversion
cvium Feb 13, 2019
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100 changes: 23 additions & 77 deletions Emby.Server.Implementations/HttpServer/HttpResultFactory.cs
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Expand Up @@ -422,27 +422,27 @@ private static string SerializeToXmlString(object from)
/// <summary>
/// Pres the process optimized result.
/// </summary>
private object GetCachedResult(IRequest requestContext, IDictionary<string, string> responseHeaders, Guid cacheKey, string cacheKeyString, DateTime? lastDateModified, TimeSpan? cacheDuration, string contentType)
private object GetCachedResult(IRequest requestContext, IDictionary<string, string> responseHeaders, StaticResultOptions options)
{
bool noCache = (requestContext.Headers.Get("Cache-Control") ?? string.Empty).IndexOf("no-cache", StringComparison.OrdinalIgnoreCase) != -1;
AddCachingHeaders(responseHeaders, options.CacheDuration, noCache, options.DateLastModified);

if (!noCache)
{
if (IsNotModified(requestContext, cacheKey))
DateTime.TryParse(requestContext.Headers.Get("If-Modified-Since"), out var ifModifiedSinceHeader);

if (IsNotModified(ifModifiedSinceHeader, options.CacheDuration, options.DateLastModified))
{
AddAgeHeader(responseHeaders, lastDateModified);
AddExpiresHeader(responseHeaders, cacheKeyString, cacheDuration);
AddAgeHeader(responseHeaders, options.DateLastModified);

var result = new HttpResult(Array.Empty<byte>(), contentType ?? "text/html", HttpStatusCode.NotModified);
var result = new HttpResult(Array.Empty<byte>(), options.ContentType ?? "text/html", HttpStatusCode.NotModified);

AddResponseHeaders(result, responseHeaders);

return result;
}
}

AddCachingHeaders(responseHeaders, cacheKeyString, cacheDuration);

return null;
}

Expand Down Expand Up @@ -487,9 +487,6 @@ public Task<object> GetStaticFileResult(IRequest requestContext, StaticFileResul
options.DateLastModified = _fileSystem.GetLastWriteTimeUtc(path);
}

var cacheKey = path + options.DateLastModified.Value.Ticks;

options.CacheKey = cacheKey.GetMD5();
options.ContentFactory = () => Task.FromResult(GetFileStream(path, fileShare));

options.ResponseHeaders = options.ResponseHeaders ?? new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
Expand Down Expand Up @@ -520,7 +517,6 @@ private Stream GetFileStream(string path, FileShareMode fileShare)
return GetStaticResult(requestContext, new StaticResultOptions
{
CacheDuration = cacheDuration,
CacheKey = cacheKey,
ContentFactory = factoryFn,
ContentType = contentType,
DateLastModified = lastDateModified,
Expand All @@ -534,14 +530,10 @@ public async Task<object> GetStaticResult(IRequest requestContext, StaticResultO
options.ResponseHeaders = options.ResponseHeaders ?? new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

var contentType = options.ContentType;
var etag = requestContext.Headers.Get("If-None-Match");
var cacheKey = etag != null ? new Guid(etag.Trim('\"')) : Guid.Empty;
if (!cacheKey.Equals(Guid.Empty))
if (!string.IsNullOrEmpty(requestContext.Headers.Get("If-Modified-Since")))
{
var key = cacheKey.ToString("N");

// See if the result is already cached in the browser
var result = GetCachedResult(requestContext, options.ResponseHeaders, cacheKey, key, options.DateLastModified, options.CacheDuration, contentType);
var result = GetCachedResult(requestContext, options.ResponseHeaders, options);

if (result != null)
{
Expand All @@ -553,6 +545,8 @@ public async Task<object> GetStaticResult(IRequest requestContext, StaticResultO
var isHeadRequest = options.IsHeadRequest || string.Equals(requestContext.Verb, "HEAD", StringComparison.OrdinalIgnoreCase);
var factoryFn = options.ContentFactory;
var responseHeaders = options.ResponseHeaders;
AddCachingHeaders(responseHeaders, options.CacheDuration, false, options.DateLastModified);
AddAgeHeader(responseHeaders, options.DateLastModified);

var rangeHeader = requestContext.Headers.Get("Range");

Expand All @@ -566,21 +560,10 @@ public async Task<object> GetStaticResult(IRequest requestContext, StaticResultO
};

AddResponseHeaders(hasHeaders, options.ResponseHeaders);
// Generate an ETag based on identifying information - TODO read contents from filesystem instead?
var responseId = $"{hasHeaders.ContentType}{options.Path}{hasHeaders.TotalContentLength}";
var hashedId = MD5.Create().ComputeHash(Encoding.Default.GetBytes(responseId));
hasHeaders.Headers["ETag"] = new Guid(hashedId).ToString("N");

return hasHeaders;
}

var stream = await factoryFn().ConfigureAwait(false);
// Generate an etag based on stream content
var streamHash = MD5.Create().ComputeHash(stream);
var newEtag = new Guid(streamHash).ToString("N");

// reset position so the response can re-use it -- TODO is this ok?
stream.Position = 0;

var totalContentLength = options.ContentLength;
if (!totalContentLength.HasValue)
Expand All @@ -603,7 +586,6 @@ public async Task<object> GetStaticResult(IRequest requestContext, StaticResultO
};

AddResponseHeaders(hasHeaders, options.ResponseHeaders);
hasHeaders.Headers["ETag"] = newEtag;
return hasHeaders;
}
else
Expand All @@ -628,7 +610,6 @@ public async Task<object> GetStaticResult(IRequest requestContext, StaticResultO
};

AddResponseHeaders(hasHeaders, options.ResponseHeaders);
hasHeaders.Headers["ETag"] = newEtag;
return hasHeaders;
}
}
Expand All @@ -641,37 +622,28 @@ public async Task<object> GetStaticResult(IRequest requestContext, StaticResultO
/// <summary>
/// Adds the caching responseHeaders.
/// </summary>
private void AddCachingHeaders(IDictionary<string, string> responseHeaders, string cacheKey, TimeSpan? cacheDuration)
private void AddCachingHeaders(IDictionary<string, string> responseHeaders, TimeSpan? cacheDuration,
bool noCache, DateTime? lastModifiedDate)
{
if (cacheDuration.HasValue)
{
responseHeaders["Cache-Control"] = "public, max-age=" + Convert.ToInt32(cacheDuration.Value.TotalSeconds);
}
else if (!string.IsNullOrEmpty(cacheKey))
{
responseHeaders["Cache-Control"] = "public";
}
else
if (noCache)
{
responseHeaders["Cache-Control"] = "no-cache, no-store, must-revalidate";
responseHeaders["pragma"] = "no-cache, no-store, must-revalidate";
return;
}

AddExpiresHeader(responseHeaders, cacheKey, cacheDuration);
}

/// <summary>
/// Adds the expires header.
/// </summary>
private static void AddExpiresHeader(IDictionary<string, string> responseHeaders, string cacheKey, TimeSpan? cacheDuration)
{
if (cacheDuration.HasValue)
{
responseHeaders["Expires"] = DateTime.UtcNow.Add(cacheDuration.Value).ToString("r");
responseHeaders["Cache-Control"] = "public, max-age=" + Convert.ToInt32(cacheDuration.Value.TotalSeconds);
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}
else if (string.IsNullOrEmpty(cacheKey))
else
{
responseHeaders["Expires"] = "-1";
responseHeaders["Cache-Control"] = "public";
}

if (lastModifiedDate.HasValue)
{
responseHeaders["Last-Modified"] = lastModifiedDate.ToString();
}
}

Expand All @@ -687,32 +659,6 @@ private static void AddAgeHeader(IDictionary<string, string> responseHeaders, Da
responseHeaders["Age"] = Convert.ToInt64((DateTime.UtcNow - lastDateModified.Value).TotalSeconds).ToString(CultureInfo.InvariantCulture);
}
}
/// <summary>
/// Determines whether [is not modified] [the specified cache key].
/// </summary>
/// <param name="requestContext">The request context.</param>
/// <param name="cacheKey">The cache key.</param>
/// <param name="lastDateModified">The last date modified.</param>
/// <param name="cacheDuration">Duration of the cache.</param>
/// <returns><c>true</c> if [is not modified] [the specified cache key]; otherwise, <c>false</c>.</returns>
private bool IsNotModified(IRequest requestContext, Guid cacheKey)
{
var ifNoneMatchHeader = requestContext.Headers.Get("If-None-Match");

bool hasCacheKey = !cacheKey.Equals(Guid.Empty);

// Validate If-None-Match
if (hasCacheKey && !string.IsNullOrEmpty(ifNoneMatchHeader))
{
if (Guid.TryParse(ifNoneMatchHeader, out var ifNoneMatch)
&& cacheKey.Equals(ifNoneMatch))
{
return true;
}
}

return false;
}

/// <summary>
/// Determines whether [is not modified] [the specified if modified since].
Expand Down
2 changes: 0 additions & 2 deletions MediaBrowser.Controller/Net/StaticResultOptions.cs
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Expand Up @@ -12,8 +12,6 @@ public class StaticResultOptions
public string ContentType { get; set; }
public TimeSpan? CacheDuration { get; set; }
public DateTime? DateLastModified { get; set; }
public Guid CacheKey { get; set; }

public Func<Task<Stream>> ContentFactory { get; set; }

public bool IsHeadRequest { get; set; }
Expand Down