How to check if Message already exists in the queue and if message is processing currently

Question

Hi everyone
I am new to Azure and worked on adding messages to the queue through workerrole1. Worker role 2 pulls them out from queue and processing them and de-queing them.
Worker role1 runs method gets called after every 10 seconds and puts messages in queue
CloudQueueMessage
message = newCloudQueueMessage(oAzureWorker.WorkerInstanceOf
+ "_"+ oAzureWorker.AgentId.ToString()
+ "|"+ ExecutionId.ToString());
                                queue.AddMessage(message);
Worker role2 runs method gets called after every 10 seconds too and checks the queue like this
foreach
(CloudQueueMessagemessage
inqueue.GetMessages(20,
TimeSpan.FromMinutes(5)))
// Process all (20) messages in less than 5 minutes, deleting each message after processing.
// Process message
queue.DeleteMessage(message);
Following are my questions
1) How do I check in worker role1 if the message is already in queue, Because I don't want to queue it back again if its not yet processed and is in the queue already
2) How do I check in worker role1 if the message is currently processing. Because I don't want to queue it back again.
3) How do I make sure that ALL the messages get processed in the order they are inserted. I know Queue is FIFO, but I know if the message gets delayed in processing another instance can pick it up, even if it gets picked up by another instance, I want to
make sure that the order remains.
Right now the instances of both these worker roles are 1, in the future when we increase them, I don't want them to queue the same messages multiple times or queue them if the message is already in process mode.

Answer 1

Hi Sarah,
I agree to the Frank's suggestion. Why you need to burden the worker role 1 to check if the message really sits on the queue or not? You can do this simply in your code before pushing it on queue instead querying queue.
All you need to do on worker role 1 is - push the message on the queue and forget as the entire queue design in azure is designed from asynchronous processing.
About worker role 2 - Use the GetMessage method which hides retrieved message's from other clients and hence makes sure that only one client is processing it at a time. If processing is successful - delete the message. if it is not - the message will be
visible anyways after the mentioned time provided in the GetMessage method.
I agree that when you will increase number of instances of your worker role 1 which might insert duplicates in the queue - in that case - you might need to introduce the shared entity (like database) and let all instances communicate through it to avoid
the duplication of messages on queue. 
Bhushan | http://www.passionatetechie.blogspot.com | http://twitter.com/BhushanGawale