1# Blob Storage with Event Grid Recipe
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3Blob trigger via Event Grid for high-scale, low-latency blob processing.
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5## Template Selection
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7Resource filter: `blob`  
8Discover templates via MCP or CDN manifest where `resource == "blob"` and `language` matches user request.
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10## Why Event Grid?
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12| Aspect | Polling Trigger | Event Grid Source |
13|--------|-----------------|-------------------|
14| **Latency** | 10s-60s | Sub-second |
15| **Scale** | Limited | High-scale |
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17## Troubleshooting
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19### "Unauthorized" or "Forbidden" Errors
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21**Cause:** Missing UAMI credential settings for Storage.  
22**Solution:** Ensure these settings are present in app configuration (prefix must match the connection name used in your function code, default: `AzureWebJobsStorage`):
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24- `<ConnectionName>__blobServiceUri` (e.g., `https://<account>.blob.core.windows.net`)
25- `<ConnectionName>__credential` (value: `managedidentity`)
26- `<ConnectionName>__clientId`
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28See [Blob Storage trigger connections](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-storage-blob-trigger#connections) for identity-based config — refer to the **"Connections"** section on that page for managed identity app settings.
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30### Blob Events Not Triggering
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32**Cause:** Event Grid subscription not created or filtering incorrectly.  
33**Solution:** Verify the Event Grid system topic and subscription exist. Check the blob container prefix filter matches the expected path.
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35## Eval
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37| Path | Description |
38|------|-------------|
39| [eval/summary.md](eval/summary.md) | Evaluation summary |
40| [eval/python.md](eval/python.md) | Python evaluation results |
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