internal void SetCursor(TimedQueueCacheCursor cursor, LinkedListNode <TimedQueueCacheItem> item)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, SetCursor: {0} to item {1}", Id.ToString(), cursor, item.Value.Batch);
cursor.Set(item);
// add to bucket
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(1);
}
internal void ResetCursor(TimedQueueCacheCursor cursor, StreamSequenceToken token)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, ResetCursor: {0} to token {1}", Id.ToString(), cursor, token);
if (cursor.IsSet)
{
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(-1);
}
cursor.Reset(token);
}
private void UpdateCursor(TimedQueueCacheCursor cursor, LinkedListNode <TimedQueueCacheItem> item)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, UpdateCursor: {0} to item {1}", Id.ToString(), cursor, item.Value.Batch);
// remove from previous bucket
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(-1);
cursor.Set(item);
// add to next bucket
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(1);
}
//public virtual IQueueCacheCursor GetCacheCursor(Guid streamGuid, string streamNamespace, StreamSequenceToken token)
public virtual IQueueCacheCursor GetCacheCursor(IStreamIdentity streamIdentity, StreamSequenceToken token)
{
if (token != null && !(token is EventSequenceToken))
{
// Null token can come from a stream subscriber that is just interested to
// start consuming from latest (the most recent event added to the cache).
throw new ArgumentOutOfRangeException(nameof(token), "token must be of type EventSequenceToken");
}
var cursor = new TimedQueueCacheCursor(this, streamIdentity.Guid, streamIdentity.Namespace, _logger);
InitializeCursor(cursor, token);
return(cursor);
}
internal void InitializeCursor(TimedQueueCacheCursor cursor, StreamSequenceToken sequenceToken)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, InitializeCursor: {1} to sequenceToken {2}", Id.ToString(), cursor, sequenceToken);
if (_cachedMessages.Count == 0) // nothing in cache
{
Log(_logger, "TimedQueueCache for QueueId:{0}, InitializeCursor: The TimedQueueCache is empty", Id.ToString());
ResetCursor(cursor, sequenceToken);
return;
}
// if offset is not set, iterate from newest (first) message in cache, but not
// including the first message itself
if (sequenceToken == null)
{
LinkedListNode <TimedQueueCacheItem> firstMessage = _cachedMessages.First;
ResetCursor(cursor, firstMessage.Value.SequenceToken);
return;
}
// Since we do not support finding a sequence of type x.y where y > 0, we round the token down
var flooredToken = FloorSequenceToken(sequenceToken);
if (flooredToken.Newer(FirstItem.SequenceToken)) // sequenceId is too new to be in cache
{
Log(_logger, "TimedQueueCache for QueueId:{0}, initializing with newer token", Id.ToString());
ResetCursor(cursor, flooredToken);
return;
}
// Check to see if offset is too old to be in cache
if (flooredToken.Older(LastItem.SequenceToken))
{
// We don't throw cache misses, we are more tolerant. Starting the cursor
// from the last message and logging the incident
_logger.Info("TimedQueueCache for QueueId:{0}, InitializeCursor: Sequence tried to subscribe with an older token: {0}, started instead from oldest token in cache which is: {1} and was inserted on {2}", Id.ToString(), sequenceToken, LastItem.SequenceToken, LastItem.Timestamp);
SetCursor(cursor, _cachedMessages.Last);
return;
}
// Now the requested sequenceToken is set and is also within the limits of the cache.
var node = FindNodeBySequenceToken(flooredToken);
// return cursor from start.
SetCursor(cursor, node);
}
/// <summary>
/// Acquires the next message in the cache at the provided cursor
/// </summary>
/// <param name="cursor"></param>
/// <param name="batch"></param>
/// <returns></returns>
internal bool TryGetNextMessage(TimedQueueCacheCursor cursor, out IBatchContainer batch)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: {0}", Id.ToString(), cursor);
batch = null;
if (cursor == null)
{
throw new ArgumentNullException(nameof(cursor));
}
//if not set, try to set and then get next
if (!cursor.IsSet)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: cursor was not set on a value, initializing with the cursor sequence token", Id.ToString());
InitializeCursor(cursor, cursor.SequenceToken);
return(cursor.IsSet && TryGetNextMessage(cursor, out batch));
}
// has this message been purged
if (cursor.SequenceToken.Older(LastItem.SequenceToken))
{
Log(_logger, "TimedQueueCache for QueueId:{0}, This is a faulted state, by this point the cursor should point to an item in the cache. The cursor is {1}", Id.ToString(), cursor.ToString());
SetCursor(cursor, _cachedMessages.Last);
}
// Cursor now points to a valid message in the cache. Get it!
// Capture the current element and advance to the next one.
batch = cursor.NextElement.Value.Batch;
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: retrieved an item from cache.", Id.ToString());
// Advance to next:
if (cursor.NextElement == _cachedMessages.First)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: reached end of cache, resetting the cursor to a future token.", Id.ToString());
// If we are at the end of the cache unset cursor and move offset one forward
ResetCursor(cursor, cursor.SequenceToken);
}
else // move to next
{
UpdateCursor(cursor, cursor.NextElement.Previous);
}
return(true);
}
internal void ResetCursor(TimedQueueCacheCursor cursor, StreamSequenceToken token)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, ResetCursor: {0} to token {1}", Id.ToString(), cursor, token);
if (cursor.IsSet)
{
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(-1);
}
cursor.Reset(token);
}
internal void SetCursor(TimedQueueCacheCursor cursor, LinkedListNode<TimedQueueCacheItem> item)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, SetCursor: {0} to item {1}", Id.ToString(), cursor, item.Value.Batch);
cursor.Set(item);
// add to bucket
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(1);
}
private void UpdateCursor(TimedQueueCacheCursor cursor, LinkedListNode<TimedQueueCacheItem> item)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, UpdateCursor: {0} to item {1}", Id.ToString(), cursor, item.Value.Batch);
// remove from previous bucket
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(-1);
cursor.Set(item);
// add to next bucket
cursor.NextElement.Value.CacheBucket.UpdateNumCursors(1);
}
/// <summary>
/// Acquires the next message in the cache at the provided cursor
/// </summary>
/// <param name="cursor"></param>
/// <param name="batch"></param>
/// <returns></returns>
internal bool TryGetNextMessage(TimedQueueCacheCursor cursor, out IBatchContainer batch)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: {0}", Id.ToString(), cursor);
batch = null;
if (cursor == null) throw new ArgumentNullException(nameof(cursor));
//if not set, try to set and then get next
if (!cursor.IsSet)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: cursor was not set on a value, initializing with the cursor sequence token", Id.ToString());
InitializeCursor(cursor, cursor.SequenceToken);
return cursor.IsSet && TryGetNextMessage(cursor, out batch);
}
// has this message been purged
if (cursor.SequenceToken.Older(LastItem.SequenceToken))
{
Log(_logger, "TimedQueueCache for QueueId:{0}, This is a faulted state, by this point the cursor should point to an item in the cache. The cursor is {1}", Id.ToString(), cursor.ToString());
SetCursor(cursor, _cachedMessages.Last);
}
// Cursor now points to a valid message in the cache. Get it!
// Capture the current element and advance to the next one.
batch = cursor.NextElement.Value.Batch;
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: retrieved an item from cache.", Id.ToString());
// Advance to next:
if (cursor.NextElement == _cachedMessages.First)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, TryGetNextMessage: reached end of cache, resetting the cursor to a future token.", Id.ToString());
// If we are at the end of the cache unset cursor and move offset one forward
ResetCursor(cursor, ((EventSequenceToken)cursor.SequenceToken).NextSequenceNumber());
}
else // move to next
{
UpdateCursor(cursor, cursor.NextElement.Previous);
}
return true;
}
internal void InitializeCursor(TimedQueueCacheCursor cursor, StreamSequenceToken sequenceToken)
{
Log(_logger, "TimedQueueCache for QueueId:{0}, InitializeCursor: {1} to sequenceToken {2}", Id.ToString(), cursor, sequenceToken);
if (_cachedMessages.Count == 0) // nothing in cache
{
Log(_logger, "TimedQueueCache for QueueId:{0}, InitializeCursor: The TimedQueueCache is empty", Id.ToString());
ResetCursor(cursor, sequenceToken);
return;
}
// if offset is not set, iterate from newest (first) message in cache, but not
// including the first message itself
if (sequenceToken == null)
{
LinkedListNode<TimedQueueCacheItem> firstMessage = _cachedMessages.First;
ResetCursor(cursor, ((EventSequenceToken)firstMessage.Value.SequenceToken).NextSequenceNumber());
return;
}
// Since we do not support finding a sequence of type x.y where y > 0, we round the token down
var flooredToken = FloorSequenceToken(sequenceToken);
if (flooredToken.Newer(FirstItem.SequenceToken)) // sequenceId is too new to be in cache
{
Log(_logger, "TimedQueueCache for QueueId:{0}, initializing with newer token", Id.ToString());
ResetCursor(cursor, flooredToken);
return;
}
// Check to see if offset is too old to be in cache
if (flooredToken.Older(LastItem.SequenceToken))
{
// We don't throw cache misses, we are more tolerant. Starting the cursor
// from the last message and logging the incident
_logger.Info("TimedQueueCache for QueueId:{0}, InitializeCursor: Sequence tried to subscribe with an older token: {0}, started instead from oldest token in cache which is: {1} and was inserted on {2}", Id.ToString(), sequenceToken, LastItem.SequenceToken, LastItem.Timestamp);
SetCursor(cursor, _cachedMessages.Last);
return;
}
// Now the requested sequenceToken is set and is also within the limits of the cache.
var node = FindNodeBySequenceToken(flooredToken);
// return cursor from start.
SetCursor(cursor, node);
}
//public virtual IQueueCacheCursor GetCacheCursor(Guid streamGuid, string streamNamespace, StreamSequenceToken token)
public virtual IQueueCacheCursor GetCacheCursor(IStreamIdentity streamIdentity, StreamSequenceToken token)
{
if (token != null && !(token is EventSequenceToken))
{
// Null token can come from a stream subscriber that is just interested to
// start consuming from latest (the most recent event added to the cache).
throw new ArgumentOutOfRangeException(nameof(token), "token must be of type EventSequenceToken");
}
var cursor = new TimedQueueCacheCursor(this, streamIdentity.Guid, streamIdentity.Namespace, _logger);
InitializeCursor(cursor, token);
return cursor;
}
