1# Service Bus - Messaging Patterns
2 
3## Point-to-Point (Queue)
4 
5```
6Producer → Queue → Consumer
7```
8 
9Use for: Work distribution, command processing
10 
11## Pub/Sub (Topic + Subscriptions)
12 
13```
14Publisher → Topic → Subscription A → Consumer A
15                 → Subscription B → Consumer B
16```
17 
18Use for: Event broadcasting, multiple consumers
19 
20## SDK Patterns
21 
22### Managed Identity (Recommended)
23 
24#### Node.js
25 
26> **Auth:** `DefaultAzureCredential` is for local development. See [auth-best-practices.md](../../auth-best-practices.md) for production patterns.
27 
28```javascript
29const { ServiceBusClient } = require("@azure/service-bus");
30const { DefaultAzureCredential } = require("@azure/identity");
31 
32const credential = new DefaultAzureCredential();
33const fullyQualifiedNamespace = process.env.SERVICEBUS_NAMESPACE + ".servicebus.windows.net";
34const client = new ServiceBusClient(fullyQualifiedNamespace, credential);
35 
36// Send
37const sender = client.createSender("orders");
38await sender.sendMessages({ body: { orderId: "123" } });
39 
40// Receive
41const receiver = client.createReceiver("orders");
42const messages = await receiver.receiveMessages(10);
43for (const message of messages) {
44  await receiver.completeMessage(message);
45}
46```
47 
48#### Python
49 
50> **Auth:** `DefaultAzureCredential` is for local development. See [auth-best-practices.md](../../auth-best-practices.md) for production patterns.
51 
52```python
53from azure.servicebus import ServiceBusClient, ServiceBusMessage
54from azure.identity import DefaultAzureCredential
55 
56credential = DefaultAzureCredential()
57fully_qualified_namespace = f"{os.environ['SERVICEBUS_NAMESPACE']}.servicebus.windows.net"
58client = ServiceBusClient(fully_qualified_namespace, credential)
59 
60# Send
61sender = client.get_queue_sender("orders")
62with sender:
63    sender.send_messages(ServiceBusMessage('{"orderId": "123"}'))
64 
65# Receive
66receiver = client.get_queue_receiver("orders")
67with receiver:
68    messages = receiver.receive_messages(max_message_count=10, max_wait_time=5)
69    for message in messages:
70        print(message)
71        receiver.complete_message(message)
72```
73 
74#### .NET
75 
76> **Auth:** `DefaultAzureCredential` is for local development. See [auth-best-practices.md](../../auth-best-practices.md) for production patterns.
77 
78```csharp
79using Azure.Identity;
80using Azure.Messaging.ServiceBus;
81 
82var credential = new DefaultAzureCredential();
83var fullyQualifiedNamespace = $"{Environment.GetEnvironmentVariable("SERVICEBUS_NAMESPACE")}.servicebus.windows.net";
84var client = new ServiceBusClient(fullyQualifiedNamespace, credential);
85 
86// Send
87var sender = client.CreateSender("orders");
88await sender.SendMessageAsync(new ServiceBusMessage("{\"orderId\": \"123\"}"));
89 
90// Receive
91var receiver = client.CreateReceiver("orders");
92var messages = await receiver.ReceiveMessagesAsync(maxMessages: 10);
93foreach (var message in messages)
94{
95    await receiver.CompleteMessageAsync(message);
96}
97```
98 
99> 💡 **Required Permissions:**
100> - `Azure Service Bus Data Sender` (69a216fc-b8fb-44d8-bc22-1f3c2cd27a39) - for sending
101> - `Azure Service Bus Data Receiver` (4f6d3b9b-027b-4f4c-9142-0e5a2a2247e0) - for receiving
102 
103### Connection String (Legacy)
104 
105#### Node.js
106 
107```javascript
108const { ServiceBusClient } = require("@azure/service-bus");
109 
110const client = new ServiceBusClient(process.env.SERVICEBUS_CONNECTION_STRING);
111 
112// Send
113const sender = client.createSender("orders");
114await sender.sendMessages({ body: { orderId: "123" } });
115 
116// Receive
117const receiver = client.createReceiver("orders");
118const messages = await receiver.receiveMessages(10);
119for (const message of messages) {
120  await receiver.completeMessage(message);
121}
122```
123 
124#### Python
125 
126```python
127from azure.servicebus import ServiceBusClient, ServiceBusMessage
128 
129client = ServiceBusClient.from_connection_string(
130    os.environ["SERVICEBUS_CONNECTION_STRING"]
131)
132sender = client.get_queue_sender("orders")
133 
134with sender:
135    sender.send_messages(ServiceBusMessage('{"orderId": "123"}'))
136```
137 
138#### .NET
139 
140```csharp
141var client = new ServiceBusClient(
142    Environment.GetEnvironmentVariable("SERVICEBUS_CONNECTION_STRING")
143);
144var sender = client.CreateSender("orders");
145 
146await sender.SendMessageAsync(new ServiceBusMessage("{\"orderId\": \"123\"}"));
147```
148 
149## Dead Letter Handling
150 
151```javascript
152const dlqReceiver = client.createReceiver("orders", {
153    subQueueType: "deadLetter"
154});
155```
156