/// <summary>
/// Gets the next queue request from the queues.
/// </summary>
/// <returns>a subclass of <see cref="BaseQueueRequest" /> representing the next request from the queues</returns>
protected virtual BaseQueueRequest GetNextQueueRequest()
{
//Order for queue orchestration is as follows:
//
// 1) ShardCreationRequests:make the databases that are necessary to handle the rest of the activity
// 2) ShardMapPublishing: Determine all of the shardlet moves that will be necessary and actually update the shard map in the published store
// 3) ShardletMoves: Move all of the shardlets to their new homes
// 4) ShardDeletionRequest: Delete retired shards (which should have been emptied by the steps above);
// 5) ShardSyncRequest: Apply a SQL statement to a specific shard.
BaseQueueRequest returnItem = GetNextQueuedRequest <ShardCreationRequest>();
if (returnItem != null)
{
return(returnItem);
}
returnItem = GetNextQueuedRequest <ShardMapPublishingRequest>();
if (returnItem != null)
{
WaitForEmptyQueue <ShardCreationRequest>();
return(returnItem);
}
returnItem = GetNextQueuedRequest <ShardletMoveRequest>();
if (returnItem != null)
{
WaitForEmptyQueue <ShardMapPublishingRequest>();
if (ShardletMoveDelayInMilliseconds > 0)
{
Thread.Sleep(ShardletMoveDelayInMilliseconds);
}
return(returnItem);
}
returnItem = GetNextQueuedRequest <ShardDeletionRequest>();
if (returnItem != null)
{
WaitForEmptyQueue <ShardletMoveRequest>();
return(returnItem);
}
returnItem = GetNextQueuedRequest <ShardSyncRequest>();
if (returnItem != null)
{
WaitForEmptyQueue <ShardDeletionRequest>();
return(returnItem);
}
return(null);
}
private static string GetErrorMessage(string requestName, BaseQueueRequest request)
{
return(string.Format("Error {0}({1}):{2}", requestName, request.QueueId, request.Message));
}
private static string GetCompletionMessage(string requestName, BaseQueueRequest request)
{
return(string.Format("Processing complete for {0}({1})", requestName, request.QueueId));
}
private void SendQueueProcessingEvent(string requestName, BaseQueueRequest itemToProcess)
{
SendQueueProcessingEvent(string.Format("Processing {0} ({1})", requestName, itemToProcess.QueueId));
}
