private async Task OnRevoke(string revokeKey)
{
if (string.IsNullOrEmpty(revokeKey))
{
Log.Warn("Error while revoking cache, revokeKey can't be null");
return;
}
try
{
HashSet <string> cacheKeys;
if (RevokeKeyToCacheKeysIndex.TryGetValue(revokeKey, out cacheKeys))
{
lock (cacheKeys)
{
var arrayOfCacheKeys = cacheKeys.ToArray();// To prevent iteration over modified collection.
foreach (var cacheKey in arrayOfCacheKeys)
{
var removed = (AsyncCacheItem)MemoryCache.Remove(cacheKey);
}
}
Revokes.Meter("Succeeded", Unit.Events).Mark();
}
else
{
Revokes.Meter("Discarded", Unit.Events).Mark();
}
}
catch (Exception ex)
{
Revokes.Meter("Failed", Unit.Events).Mark();
Log.Warn("error while revoking cache", exception: ex, unencryptedTags: new { revokeKey });
}
}
/// <summary>
/// For revocable items , move over all revoke ids in cache index and remove them.
/// </summary>
private void ItemRemovedCallback(CacheEntryRemovedArguments arguments)
{
var cachedItem = ((AsyncCacheItem)arguments.CacheItem.Value).CurrentValueTask;
if (cachedItem.Status == TaskStatus.RanToCompletion && (cachedItem.Result as IRevocable)?.RevokeKeys != null)
{
foreach (var revocationKey in ((IRevocable)cachedItem.Result).RevokeKeys)
{
HashSet <string> cacheKeys;
if (RevokeKeyToCacheKeysIndex.TryGetValue(revocationKey, out cacheKeys))
{
lock (cacheKeys)
{
cacheKeys.Remove(arguments.CacheItem.Key);
if (!cacheKeys.Any())
{
RevokeKeyToCacheKeysIndex.TryRemove(revocationKey, out cacheKeys);
}
}
}
}
}
Items.Meter(arguments.RemovedReason.ToString(), Unit.Items);
}
/// <summary>
/// For revocable items , move over all revoke ids in cache index and remove them.
/// </summary>
private void ItemRemovedCallback(CacheEntryRemovedArguments arguments)
{
var cacheItem = arguments.CacheItem.Value as AsyncCacheItem;
var shouldLog = ShouldLog(cacheItem?.GroupName);
if (shouldLog)
{
Log.Info(x => x("Item removed from cache", unencryptedTags: new
{
cacheKey = arguments.CacheItem.Key,
removeReason = arguments.RemovedReason.ToString(),
cacheGroup = cacheItem?.GroupName,
cacheData = cacheItem?.LogData
}));
}
var cachedItem = ((AsyncCacheItem)arguments.CacheItem.Value).CurrentValueTask;
if (cachedItem.Status == TaskStatus.RanToCompletion &&
(cachedItem.Result as IRevocable)?.RevokeKeys != null &&
!MemoryCache.Contains(arguments.CacheItem.Key)) //We want to remove items from reverseIndex only if they are not in MemoryCache
{ //In MemoryCache.Set flow, we get here, but item is still in cache - so we skip removal
foreach (var revokeKey in ((IRevocable)cachedItem.Result).RevokeKeys)
{
if (RevokeKeyToCacheKeysIndex.TryGetValue(revokeKey, out HashSet <string> cacheKeys))
{
lock (cacheKeys)
{
cacheKeys.Remove(arguments.CacheItem.Key);
Log.Info(x => x("RevokeKey removed from reverse index", unencryptedTags: new
{
cacheKey = arguments.CacheItem.Key,
revokeKey = revokeKey,
removeReason = arguments.RemovedReason.ToString(),
cacheGroup = cacheItem?.GroupName,
cacheData = cacheItem?.LogData
}));
if (!cacheKeys.Any())
{
if (RevokeKeyToCacheKeysIndex.TryRemove(revokeKey, out _) && shouldLog)
{
Log.Info(x => x("Reverse index for cache item was removed", unencryptedTags: new
{
cacheKey = arguments.CacheItem.Key,
removeReason = arguments.RemovedReason.ToString(),
cacheGroup = cacheItem?.GroupName,
cacheData = cacheItem?.LogData
}));
}
}
}
}
}
}
Items.Meter(arguments.RemovedReason.ToString(), Unit.Items).Mark();
}
private Task OnRevoke(string revokeKey)
{
var shouldLog = GetRevokeConfig().LogRequests;
if (string.IsNullOrEmpty(revokeKey))
{
Log.Warn("Error while revoking cache, revokeKey can't be null");
return(Task.FromResult(false));
}
try
{
if (shouldLog)
{
Log.Info(x => x("Revoke request received", unencryptedTags: new { revokeKey }));
}
if (RevokeKeyToCacheKeysIndex.TryGetValue(revokeKey, out HashSet <string> cacheKeys))
{
lock (cacheKeys)
{
var arrayOfCacheKeys = cacheKeys.ToArray();// To prevent iteration over modified collection.
if (shouldLog && arrayOfCacheKeys.Length == 0)
{
Log.Info(x => x("There is no CacheKey to Revoke", unencryptedTags: new { revokeKey }));
}
foreach (var cacheKey in arrayOfCacheKeys)
{
if (shouldLog)
{
Log.Info(x => x("Revoking cacheKey", unencryptedTags: new { revokeKey, cacheKey }));
}
var unused = (AsyncCacheItem)MemoryCache.Remove(cacheKey);
}
}
Revokes.Meter("Succeeded", Unit.Events).Mark();
}
else
{
if (shouldLog)
{
Log.Info(x => x("Key is not cached. No revoke is needed", unencryptedTags: new { revokeKey }));
}
Revokes.Meter("Discarded", Unit.Events).Mark();
}
}
catch (Exception ex)
{
Revokes.Meter("Failed", Unit.Events).Mark();
Log.Warn("error while revoking cache", exception: ex, unencryptedTags: new { revokeKey });
}
return(Task.FromResult(true));
}
/// <summary>
/// For revocable items , move over all revoke ids in cache index and remove them.
/// </summary>
private void ItemRemovedCallback(CacheEntryRemovedArguments arguments)
{
var cacheItem = arguments.CacheItem.Value as AsyncCacheItem;
var shouldLog = ShouldLog(cacheItem?.GroupName);
if (shouldLog)
{
Log.Info(x => x("Item removed from cache", unencryptedTags: new
{
cacheKey = arguments.CacheItem.Key,
removeReason = arguments.RemovedReason.ToString(),
cacheGroup = cacheItem?.GroupName,
cacheData = cacheItem?.LogData
}));
}
var cachedItem = ((AsyncCacheItem)arguments.CacheItem.Value).CurrentValueTask;
if (cachedItem.Status == TaskStatus.RanToCompletion && (cachedItem.Result as IRevocable)?.RevokeKeys != null)
{
foreach (var revokeKey in ((IRevocable)cachedItem.Result).RevokeKeys)
{
if (RevokeKeyToCacheKeysIndex.TryGetValue(revokeKey, out HashSet <string> cacheKeys))
{
lock (cacheKeys)
{
cacheKeys.Remove(arguments.CacheItem.Key);
Log.Info(x => x("RevokeKey removed from reverse index", unencryptedTags: new
{
cacheKey = arguments.CacheItem.Key,
revokeKey = revokeKey,
removeReason = arguments.RemovedReason.ToString(),
cacheGroup = cacheItem?.GroupName,
cacheData = cacheItem?.LogData
}));
if (!cacheKeys.Any())
{
if (RevokeKeyToCacheKeysIndex.TryRemove(revokeKey, out _) && shouldLog)
{
Log.Info(x => x("Reverse index for cache item was removed", unencryptedTags: new
{
cacheKey = arguments.CacheItem.Key,
removeReason = arguments.RemovedReason.ToString(),
cacheGroup = cacheItem?.GroupName,
cacheData = cacheItem?.LogData
}));
}
}
}
}
}
}
}
private Task <object> GetOrAdd(string key, Func <Task <object> > factory, CacheItemPolicyEx policy, string[] metricsKeys, Type taskResultType)
{
Func <bool, Task <object> > wrappedFactory = async removeOnException =>
{
try
{
var result = await factory().ConfigureAwait(false);
//Can happen if item removed before task is completed
if (MemoryCache.Contains(key))
{
var revocableResult = result as IRevocable;
if (revocableResult?.RevokeKeys != null)
{
foreach (var revokeKey in revocableResult.RevokeKeys)
{
var cacheKeys = RevokeKeyToCacheKeysIndex.GetOrAdd(revokeKey, k => new HashSet <string>());
lock (cacheKeys)
{
cacheKeys.Add(key);
}
}
}
}
AwaitingResult.Decrement(metricsKeys);
return(result);
}
catch
{
if (removeOnException)
{
MemoryCache.Remove(key); // Do not cache exceptions.
}
AwaitingResult.Decrement(metricsKeys);
Failed.Mark(metricsKeys);
throw;
}
};
var newItem = new AsyncCacheItem();
Task <object> resultTask;
// Taking a lock on the newItem in case it actually becomes the item in the cache (if no item with that key
// existed). For another thread, it will be returned into the existingItem variable and will block on the
// second lock, preventing concurrent mutation of the same object.
lock (newItem.Lock)
{
if (typeof(IRevocable).IsAssignableFrom(taskResultType))
{
policy.RemovedCallback += ItemRemovedCallback;
}
// Surprisingly, when using MemoryCache.AddOrGetExisting() where the item doesn't exist in the cache,
// null is returned.
var existingItem = (AsyncCacheItem)MemoryCache.AddOrGetExisting(key, newItem, policy);
if (existingItem == null)
{
Misses.Mark(metricsKeys);
AwaitingResult.Increment(metricsKeys);
newItem.CurrentValueTask = wrappedFactory(true);
newItem.NextRefreshTime = DateTime.UtcNow + policy.RefreshTime;
resultTask = newItem.CurrentValueTask;
}
else
{
// This lock makes sure we're not mutating the same object as was added to the cache by an earlier
// thread (which was the first to add from 'newItem', for subsequent threads it will be 'existingItem').
lock (existingItem.Lock)
{
resultTask = existingItem.CurrentValueTask;
// Start refresh if an existing refresh ins't in progress and we've passed the next refresh time.
if (existingItem.RefreshTask == null && DateTime.UtcNow >= existingItem.NextRefreshTime)
{
existingItem.RefreshTask = ((Func <Task>)(async() =>
{
try
{
var getNewValue = wrappedFactory(false);
await getNewValue.ConfigureAwait(false);
existingItem.CurrentValueTask = getNewValue;
existingItem.NextRefreshTime = DateTime.UtcNow + policy.RefreshTime;
existingItem.RefreshTask = null;
MemoryCache.Set(new CacheItem(key, existingItem), policy);
}
catch
{
existingItem.NextRefreshTime = DateTime.UtcNow + policy.FailedRefreshDelay;
existingItem.RefreshTask = null;
}
})).Invoke();
}
}
if (resultTask.GetAwaiter().IsCompleted)
{
Hits.Mark(metricsKeys);
}
else
{
JoinedTeam.Mark(metricsKeys);
}
}
}
return(resultTask);
}
private Task <object> GetOrAdd(string key, Func <Task <object> > factory, CacheItemPolicyEx policy, string groupName, string logData, string[] metricsKeys, Type taskResultType)
{
var shouldLog = ShouldLog(groupName);
async Task <object> WrappedFactory(bool removeOnException)
{
try
{
if (shouldLog)
{
Log.Info(x => x("Cache item is waiting for value to be resolved", unencryptedTags: new
{
cacheKey = key,
cacheGroup = groupName,
cacheData = logData
}));
}
var result = await factory().ConfigureAwait(false);
if (shouldLog)
{
Log.Info(x => x("Cache item value is resolved", unencryptedTags: new
{
cacheKey = key,
cacheGroup = groupName,
cacheData = logData,
value = GetValueForLogging(result)
}));
}
//Can happen if item removed before task is completed
if (MemoryCache.Contains(key))
{
var revocableResult = result as IRevocable;
if (revocableResult?.RevokeKeys != null)
{
foreach (var revokeKey in revocableResult.RevokeKeys)
{
var cacheKeys = RevokeKeyToCacheKeysIndex.GetOrAdd(revokeKey, k => new HashSet <string>());
lock (cacheKeys)
{
cacheKeys.Add(key);
}
Log.Info(x => x("RevokeKey added to reverse index", unencryptedTags: new
{
revokeKey = revokeKey,
cacheKey = key,
cacheGroup = groupName,
cacheData = logData
}));
}
}
}
return(result);
}
catch (Exception exception)
{
Log.Info(x => x("Error resolving value for cache item", unencryptedTags: new
{
cacheKey = key,
cacheGroup = groupName,
cacheData = logData,
removeOnException,
errorMessage = exception.Message
}));
if (removeOnException)
{
MemoryCache.Remove(key); // Do not cache exceptions.
}
throw;
}
}
var newItem = shouldLog ?
new AsyncCacheItem {
GroupName = string.Intern(groupName), LogData = logData
} :
new AsyncCacheItem(); // if log is not needed, then do not cache unnecessary details which will blow up the memory
Task <object> resultTask;
// Taking a lock on the newItem in case it actually becomes the item in the cache (if no item with that key
// existed). For another thread, it will be returned into the existingItem variable and will block on the
// second lock, preventing concurrent mutation of the same object.
lock (newItem.Lock)
{
if (typeof(IRevocable).IsAssignableFrom(taskResultType))
{
policy.RemovedCallback += ItemRemovedCallback;
}
// Surprisingly, when using MemoryCache.AddOrGetExisting() where the item doesn't exist in the cache,
// null is returned.
var existingItem = (AsyncCacheItem)MemoryCache.AddOrGetExisting(key, newItem, policy);
if (existingItem == null)
{
newItem.CurrentValueTask = WrappedFactory(true);
newItem.NextRefreshTime = DateTime.UtcNow + policy.RefreshTime;
resultTask = newItem.CurrentValueTask;
if (shouldLog)
{
Log.Info(x => x("Item added to cache", unencryptedTags: new
{
cacheKey = key,
cacheGroup = groupName,
cacheData = logData
}));
}
}
else
{
// This lock makes sure we're not mutating the same object as was added to the cache by an earlier
// thread (which was the first to add from 'newItem', for subsequent threads it will be 'existingItem').
lock (existingItem.Lock)
{
resultTask = existingItem.CurrentValueTask;
// Start refresh if an existing refresh ins't in progress and we've passed the next refresh time.
if (existingItem.RefreshTask?.IsCompleted != false && DateTime.UtcNow >= existingItem.NextRefreshTime)
{
existingItem.RefreshTask = ((Func <Task>)(async() =>
{
try
{
var getNewValue = WrappedFactory(false);
await getNewValue.ConfigureAwait(false);
existingItem.CurrentValueTask = getNewValue;
existingItem.NextRefreshTime = DateTime.UtcNow + policy.RefreshTime;
MemoryCache.Set(new CacheItem(key, existingItem), policy);
}
catch
{
existingItem.NextRefreshTime = DateTime.UtcNow + policy.FailedRefreshDelay;
}
})).Invoke();
}
}
}
}
return(resultTask);
}
