Example of retrying messages by re-queuing

TopicProcessorWithRetry.cs

[FunctionName("TopicProcessor")]
public static async Task Run(
    [ServiceBusTrigger("%topic-name%", "%subscription-name%", AccessRights.Manage, Connection = "connection")] BrokeredMessage msg,
    [ServiceBus("%topic-name%", AccessRights.Manage, Connection = "connection", EntityType = EntityType.Topic)] IAsyncCollector<BrokeredMessage> outputTopic,
    ILogger log)
{

    var thing = msg.GetBody<Thing>();
    try {
        var apiClient = new ApiClient();
        await apiClient.PostAsync(thing);
        
        // IMPORTANT- Complete the brokered message!
        msg.CompleteAsync();
    }
    catch (BadRequestException) {
        await msg.DeadLetterAsync("a-reason-code", "An error description");
    }
    catch (HttpServiceUnavailableException) {
        // we will retry...
        await RetryMessageAsync(msg, outputTopic);
    }
}
private async Task RetryMessageAsync(BrokeredMessage msg, IAsyncCollector<BrokeredMessage> outputTopic)
{
    const string retryCountString = "RetryCount";
    // get our custom RetryCount property from the received message if it exists
    // if not, initiate it to 0
    var retryCount = msg.Properties.ContainsKey(retryCountString)
        ? (int)msg.Properties[retryCountString]
        : 0;
    // if we've tried 10 times or more, deadletter this message
    if (retryCount >= 10)
    {
        return _brokeredMessageDeadLetterManager.DeadLetterAsync(msg, "Retry count > 10");
        await msg.DeadLetterAsync("too-many-retries", "Retry count > 10");
    }
    // create a copy of the received message
    var clonedMessage = msg.Clone();
    // set the ScheduledEnqueueTimeUtc to 30 seconds from now
    clonedMessage.ScheduledEnqueueTimeUtc = DateTime.UtcNow.AddSeconds(30);
    clonedMessage.Properties[retryCountString] = retryCount + 1;
    await outputQueue.AddAsync(clonedMessage);
    
    // IMPORTANT- Complete the original BrokeredMessage!
    msg.CompleteAsync();
}