public virtual bool IsResponseCacheable(ResponseCachingContext context)
{
var responseCacheControlHeader = context.HttpContext.Response.Headers[HeaderNames.CacheControl];
// Only cache pages explicitly marked with public
if (!HeaderUtilities.ContainsCacheDirective(responseCacheControlHeader, CacheControlHeaderValue.PublicString))
{
context.Logger.ResponseWithoutPublicNotCacheable();
return(false);
}
// Check response no-store
if (HeaderUtilities.ContainsCacheDirective(responseCacheControlHeader, CacheControlHeaderValue.NoStoreString))
{
context.Logger.ResponseWithNoStoreNotCacheable();
return(false);
}
// Check no-cache
if (HeaderUtilities.ContainsCacheDirective(responseCacheControlHeader, CacheControlHeaderValue.NoCacheString))
{
context.Logger.ResponseWithNoCacheNotCacheable();
return(false);
}
var response = context.HttpContext.Response;
// Do not cache responses with Set-Cookie headers
if (!StringValues.IsNullOrEmpty(response.Headers[HeaderNames.SetCookie]))
{
context.Logger.ResponseWithSetCookieNotCacheable();
return(false);
}
// Do not cache responses varying by *
var varyHeader = response.Headers[HeaderNames.Vary];
if (varyHeader.Count == 1 && string.Equals(varyHeader, "*", StringComparison.OrdinalIgnoreCase))
{
context.Logger.ResponseWithVaryStarNotCacheable();
return(false);
}
// Check private
if (HeaderUtilities.ContainsCacheDirective(responseCacheControlHeader, CacheControlHeaderValue.PrivateString))
{
context.Logger.ResponseWithPrivateNotCacheable();
return(false);
}
// Check response code
if (response.StatusCode != StatusCodes.Status200OK)
{
context.Logger.ResponseWithUnsuccessfulStatusCodeNotCacheable(response.StatusCode);
return(false);
}
// Check response freshness
if (!context.ResponseDate.HasValue)
{
if (!context.ResponseSharedMaxAge.HasValue &&
!context.ResponseMaxAge.HasValue &&
context.ResponseTime.Value >= context.ResponseExpires)
{
context.Logger.ExpirationExpiresExceeded(context.ResponseTime.Value, context.ResponseExpires.Value);
return(false);
}
}
else
{
var age = context.ResponseTime.Value - context.ResponseDate.Value;
// Validate shared max age
if (age >= context.ResponseSharedMaxAge)
{
context.Logger.ExpirationSharedMaxAgeExceeded(age, context.ResponseSharedMaxAge.Value);
return(false);
}
else if (!context.ResponseSharedMaxAge.HasValue)
{
// Validate max age
if (age >= context.ResponseMaxAge)
{
context.Logger.ExpirationMaxAgeExceeded(age, context.ResponseMaxAge.Value);
return(false);
}
else if (!context.ResponseMaxAge.HasValue)
{
// Validate expiration
if (context.ResponseTime.Value >= context.ResponseExpires)
{
context.Logger.ExpirationExpiresExceeded(context.ResponseTime.Value, context.ResponseExpires.Value);
return(false);
}
}
}
}
return(true);
}
public virtual bool AllowCacheStorage(ResponseCachingContext context)
{
// Check request no-store
return(!HeaderUtilities.ContainsCacheDirective(context.HttpContext.Request.Headers[HeaderNames.CacheControl], CacheControlHeaderValue.NoStoreString));
}
// BaseKey<delimiter>H<delimiter>HeaderName=HeaderValue<delimiter>Q<delimiter>QueryName=QueryValue1<subdelimiter>QueryValue2
public string CreateStorageVaryByKey(ResponseCachingContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
var varyByRules = context.CachedVaryByRules;
if (varyByRules == null)
{
throw new InvalidOperationException($"{nameof(CachedVaryByRules)} must not be null on the {nameof(ResponseCachingContext)}");
}
if ((StringValues.IsNullOrEmpty(varyByRules.Headers) && StringValues.IsNullOrEmpty(varyByRules.QueryKeys)))
{
return(varyByRules.VaryByKeyPrefix);
}
var request = context.HttpContext.Request;
var builder = _builderPool.Get();
try
{
// Prepend with the Guid of the CachedVaryByRules
builder.Append(varyByRules.VaryByKeyPrefix);
// Vary by headers
if (varyByRules?.Headers.Count > 0)
{
// Append a group separator for the header segment of the cache key
builder.Append(KeyDelimiter)
.Append('H');
for (var i = 0; i < varyByRules.Headers.Count; i++)
{
var header = varyByRules.Headers[i];
var headerValues = context.HttpContext.Request.Headers[header];
builder.Append(KeyDelimiter)
.Append(header)
.Append("=");
var headerValuesArray = headerValues.ToArray();
Array.Sort(headerValuesArray, StringComparer.Ordinal);
for (var j = 0; j < headerValuesArray.Length; j++)
{
builder.Append(headerValuesArray[j]);
}
}
}
// Vary by query keys
if (varyByRules?.QueryKeys.Count > 0)
{
// Append a group separator for the query key segment of the cache key
builder.Append(KeyDelimiter)
.Append('Q');
if (varyByRules.QueryKeys.Count == 1 && string.Equals(varyByRules.QueryKeys[0], "*", StringComparison.Ordinal))
{
// Vary by all available query keys
var queryArray = context.HttpContext.Request.Query.ToArray();
// Query keys are aggregated case-insensitively whereas the query values are compared ordinally.
Array.Sort(queryArray, QueryKeyComparer.OrdinalIgnoreCase);
for (var i = 0; i < queryArray.Length; i++)
{
builder.Append(KeyDelimiter)
.AppendUpperInvariant(queryArray[i].Key)
.Append("=");
var queryValueArray = queryArray[i].Value.ToArray();
Array.Sort(queryValueArray, StringComparer.Ordinal);
for (var j = 0; j < queryValueArray.Length; j++)
{
if (j > 0)
{
builder.Append(KeySubDelimiter);
}
builder.Append(queryValueArray[j]);
}
}
}
else
{
for (var i = 0; i < varyByRules.QueryKeys.Count; i++)
{
var queryKey = varyByRules.QueryKeys[i];
var queryKeyValues = context.HttpContext.Request.Query[queryKey];
builder.Append(KeyDelimiter)
.Append(queryKey)
.Append("=");
var queryValueArray = queryKeyValues.ToArray();
Array.Sort(queryValueArray, StringComparer.Ordinal);
for (var j = 0; j < queryValueArray.Length; j++)
{
if (j > 0)
{
builder.Append(KeySubDelimiter);
}
builder.Append(queryValueArray[j]);
}
}
}
}
return(builder.ToString());
}
finally
{
_builderPool.Return(builder);
}
}
public virtual bool IsCachedEntryFresh(ResponseCachingContext context)
{
var age = context.CachedEntryAge.Value;
var cachedCacheControlHeaders = context.CachedResponseHeaders[HeaderNames.CacheControl];
var requestCacheControlHeaders = context.HttpContext.Request.Headers[HeaderNames.CacheControl];
// Add min-fresh requirements
TimeSpan?minFresh;
if (HeaderUtilities.TryParseSeconds(requestCacheControlHeaders, CacheControlHeaderValue.MinFreshString, out minFresh))
{
age += minFresh.Value;
context.Logger.ExpirationMinFreshAdded(minFresh.Value);
}
// Validate shared max age, this overrides any max age settings for shared caches
TimeSpan?cachedSharedMaxAge;
HeaderUtilities.TryParseSeconds(cachedCacheControlHeaders, CacheControlHeaderValue.SharedMaxAgeString, out cachedSharedMaxAge);
if (age >= cachedSharedMaxAge)
{
// shared max age implies must revalidate
context.Logger.ExpirationSharedMaxAgeExceeded(age, cachedSharedMaxAge.Value);
return(false);
}
else if (!cachedSharedMaxAge.HasValue)
{
TimeSpan?requestMaxAge;
HeaderUtilities.TryParseSeconds(requestCacheControlHeaders, CacheControlHeaderValue.MaxAgeString, out requestMaxAge);
TimeSpan?cachedMaxAge;
HeaderUtilities.TryParseSeconds(cachedCacheControlHeaders, CacheControlHeaderValue.MaxAgeString, out cachedMaxAge);
var lowestMaxAge = cachedMaxAge < requestMaxAge ? cachedMaxAge : requestMaxAge ?? cachedMaxAge;
// Validate max age
if (age >= lowestMaxAge)
{
// Must revalidate or proxy revalidate
if (HeaderUtilities.ContainsCacheDirective(cachedCacheControlHeaders, CacheControlHeaderValue.MustRevalidateString) ||
HeaderUtilities.ContainsCacheDirective(cachedCacheControlHeaders, CacheControlHeaderValue.ProxyRevalidateString))
{
context.Logger.ExpirationMustRevalidate(age, lowestMaxAge.Value);
return(false);
}
TimeSpan?requestMaxStale;
var maxStaleExist = HeaderUtilities.ContainsCacheDirective(requestCacheControlHeaders, CacheControlHeaderValue.MaxStaleString);
HeaderUtilities.TryParseSeconds(requestCacheControlHeaders, CacheControlHeaderValue.MaxStaleString, out requestMaxStale);
// Request allows stale values with no age limit
if (maxStaleExist && !requestMaxStale.HasValue)
{
context.Logger.ExpirationInfiniteMaxStaleSatisfied(age, lowestMaxAge.Value);
return(true);
}
// Request allows stale values with age limit
if (requestMaxStale.HasValue && age - lowestMaxAge < requestMaxStale)
{
context.Logger.ExpirationMaxStaleSatisfied(age, lowestMaxAge.Value, requestMaxStale.Value);
return(true);
}
context.Logger.ExpirationMaxAgeExceeded(age, lowestMaxAge.Value);
return(false);
}
else if (!cachedMaxAge.HasValue && !requestMaxAge.HasValue)
{
// Validate expiration
DateTimeOffset expires;
if (HeaderUtilities.TryParseDate(context.CachedResponseHeaders[HeaderNames.Expires].ToString(), out expires) &&
context.ResponseTime.Value >= expires)
{
context.Logger.ExpirationExpiresExceeded(context.ResponseTime.Value, expires);
return(false);
}
}
}
return(true);
}
public IEnumerable <string> CreateLookupVaryByKeys(ResponseCachingContext context)
{
return(new string[] { CreateStorageVaryByKey(context) });
}