The solution to process the message on another thread, and acknowledge the call right away is good only for a bot on an App Service.
But as for a Functions Bot doing so will finish the Azure Function if I immediately return from this method.
I tried it. The Azure Function stops running, and the real response to the chat never comes. So it's not a solution at all for the Function Bots.
I ended up with this code for a Functions Bot, which resolves this problem.
Using Azure Queues
public static class Functions
{
[FunctionName("messages")]
[return: Queue("somequeue")]
public static async Task<MessagePayload> Messages([HttpTrigger
(WebHookType = "genericJson")]HttpRequestMessage req) =>
// return from this Azure Function immediately to avoid timeout warning message
// in the chat.
// just put the request into "somequeue".
// We can't pass the whole request via the Queue, so pass only what we need for
// the message to be processed by Bot Framework
new MessagePayload
{
RequestUri = req.RequestUri,
Content = await req.Content.ReadAsStringAsync(),
AuthScheme = req.Headers.Authorization.Scheme,
AuthParameter = req.Headers.Authorization.Parameter
};
// Do the actual message processing in another Azure Function, which is
// triggered by a message enqueued in the Azure Queue "somequeue"
[FunctionName("processTheMessage")]
public static async Task ProcessTheMessage([QueueTrigger("somequeue")]
MessagePayload payload, TraceWriter logger)
{
// we don't want the queue to process this message 5 times if it fails,
// so we won't throw any exceptions here at all, but we'll handle them properly.
try
{
// recreate the request
var request = new HttpRequestMessage
{
Content = new StringContent(payload.Content),
RequestUri = payload.RequestUri
};
request.Headers.Authorization = new
AuthenticationHeaderValue(payload.AuthScheme, payload.AuthParameter);
// initialize dependency injection container, services, etc.
var initializer = new SomeInitializer(logger);
initializer.Initialize();
// handle the request in a usual way and reply back to the chat
await initializer.HandleRequestAsync(request);
}
catch (Exception ex)
{
try
{
// TODO: handle the exception
}
catch (Exception anotherException)
{
// swallow any exceptions in the exceptions handler?
}
}
}
}
[Serializable]
public class MessagePayload
{
public string Content { get; set; }
public string AuthParameter { get; set; }
public string AuthScheme { get; set; }
public Uri RequestUri { get; set; }
}
(Be sure to use different Azure Queues for local development with Bot Framework emulator and for a cloud-deployed Function App. Otherwise, the messages sent to your bot from real customers may be processed locally while you are debugging on your machine)
Using an HTTP request
Of course, the same can be done without using an Azure Queue with a direct call to another Azure Function's public URL - https://<my-bot>.azurewebsites.net/api/processTheMessage?code=<function-secret>
. This call has to be done on another thread, without waiting for the result in the messages
function.
[FunctionName("messages")]
public static async Task Run([HttpTrigger(WebHookType = "genericJson")]
HttpRequestMessage req)
{
// return from this Azure Function immediately to avoid timeout warning message
// in the chat.
using (var client = new HttpClient())
{
string secret = ConfigurationManager.AppSettings["processMessageHttp_secret"];
// change the RequestUri of the request to processMessageHttp Function's
// public URL, providing the secret code, stored in app settings
// with key 'processMessageHttp_secret'
req.RequestUri = new Uri(req.RequestUri.AbsoluteUri.Replace(
req.RequestUri.PathAndQuery, $"/api/processMessageHttp?code={secret}"));
// don't 'await' here. Simply send.
#pragma warning disable CS4014
client.SendAsync(req);
#pragma warning restore CS4014
// wait a little bit to ensure the request is sent. It will not
// send the request at all without this line, because it would
// terminate this Azure Function immediately
await Task.Delay(500);
}
}
[FunctionName("processMessageHttp")]
public static async Task ProcessMessageHttp([HttpTrigger(WebHookType = "genericJson")]
HttpRequestMessage req,
Microsoft.Extensions.Logging.ILogger log)
{
// first and foremost: initialize dependency
// injection container, logger, services, set default culture/language, etc.
var initializer = FunctionAppInitializer.Initialize(log);
// handle the request in a usual way and reply back to the chat
await initializer.HandleRequest(req);
}