1# Error Handling Patterns
2 
3> **MANDATORY**: All function implementations MUST include proper error handling with logging.
4 
5## Python
6 
7```python
8import logging
9 
10try:
11    # Your function logic here
12    result = process_data(data)
13    logging.info(f"Success: processed {item_id}")
14except Exception as error:
15    logging.error(f"Error processing {item_id}: {error}")
16    raise  # Re-raise to trigger retry/dead-letter
17```
18 
19## TypeScript
20 
21```typescript
22try {
23    // Your function logic here
24    const result = await processData(data);
25    context.log(`Success: processed ${itemId}`);
26} catch (error) {
27    context.error(`Error processing ${itemId}:`, error);
28    throw error;  // Re-raise to trigger retry/dead-letter
29}
30```
31 
32## JavaScript
33 
34```javascript
35try {
36    // Your function logic here
37    const result = await processData(data);
38    context.log(`Success: processed ${itemId}`);
39} catch (error) {
40    context.error(`Error processing ${itemId}:`, error);
41    throw error;  // Re-raise to trigger retry/dead-letter
42}
43```
44 
45## C# (.NET)
46 
47```csharp
48try
49{
50    // Your function logic here
51    var result = await ProcessDataAsync(data);
52    _logger.LogInformation($"Success: processed {itemId}");
53}
54catch (Exception ex)
55{
56    _logger.LogError(ex, $"Error processing {itemId}");
57    throw;  // Re-raise to trigger retry/dead-letter
58}
59```
60 
61## Java
62 
63```java
64try {
65    // Your function logic here
66    Result result = processData(data);
67    context.getLogger().info("Success: processed " + itemId);
68} catch (Exception e) {
69    context.getLogger().severe("Error processing " + itemId + ": " + e.getMessage());
70    throw e;  // Re-raise to trigger retry/dead-letter
71}
72```
73 
74## PowerShell
75 
76```powershell
77try {
78    # Your function logic here
79    $result = Process-Data -Data $data
80    Write-Host "Success: processed $itemId"
81}
82catch {
83    Write-Error "Error processing $itemId : $_"
84    throw  # Re-raise to trigger retry/dead-letter
85}
86```
87 
88## Key Principles
89 
901. **Always log before throwing** - Enables debugging from logs
912. **Re-throw exceptions** - Allows Functions runtime to handle retry/dead-letter
923. **Include context in logs** - Item ID, operation name, relevant metadata
934. **Use appropriate log levels** - Info for success, Error for failures
94