How to handle error & retry ?

Retries

The retry behavior is configured at different places because all triggers (binding) do not support the same retry policy.

Trigger/binding	Retry source	Configuration
Azure Cosmos DB	Retry policies	Function-level
Azure Blob Storage	Binding extension	host.json
Azure Event Grid	Binding extension	Event subscription
Azure Event Hubs	Retry policies	Function-level
Azure Queue Storage	Binding extension	host.json
RabbitMQ	Binding extension	Dead letter queue
Azure Service Bus	Binding extension	Dead letter queue
Timer	Retry policies	Function-level
Kafka	Retry policies	Function-level

Here’s an example at the function level for Azure Event Hubs

[FunctionName("EventHubTrigger")]
[FixedDelayRetry(5, "00:00:10")]
public static async Task Run([EventHubTrigger("myHub", Connection = "EventHubConnection")] EventData[] events, ILogger log)
{
// ...
}

Error Codes

With the integration with Azure services, errors might originate from APIs : Azure Functions error handling and retry guidance | Microsoft Learn

See the example for Azure Cosmos Db : HTTP Status Codes for Azure Cosmos DB | Microsoft Learn
See the example for Blob Storage : Azure Blob storage output binding for Azure Functions | Microsoft Learn
etc.