A receiver can only read from one source, but many programs need to be able to read messages from many sources. In the Qpid Messaging API, a program can ask a session for the “next receiver”; that is, the receiver that is responsible for the next available message. The following example shows how this is done in C++, Python, and .NET C#.
Note that to use this pattern you must enable prefetching for each receiver of interest so that the broker will send messages before a fetch call is made. See Section 2.6, “Receiver Capacity (Prefetch)” for more on this.
Example 2.12. Receiving Messages from Multiple Sources
C++:
Receiver receiver1 = session.createReceiver(address1); receiver1.setCapacity(10); Receiver receiver2 = session.createReceiver(address2); receiver2.setCapacity(10); Message message = session.nextReceiver().fetch(); std::cout << message.getContent() << std::endl; session.acknowledge(); // acknowledge message receipt
Python:
receiver1 = session.receiver(address1) receiver1.capacity = 10 receiver2 = session.receiver(address) receiver2.capacity = 10 message = session.next_receiver().fetch() print message.content session.acknowledge()
.NET C#:
Receiver receiver1 = session.CreateReceiver(address1);
receiver1.Capacity = 10;
Receiver receiver2 = session.CreateReceiver(address2);
receiver2.Capacity = 10;
Message message = new Message();
message = session.NextReceiver().Fetch();
Console.WriteLine("{0}", message.GetContent());
session.Acknowledge();