Azure Service Bus relay response slow - wcf

Question

I've a Azure Service Bus Relay hosted in Azure which exposes the end point similar to one below:
https://myTestSB.servicebus.windows.net/MyService/LogIn()
Interestingly when I make a call to this service bus, it makes 4 calls as shown below.
This is causing the slow response.
Could someone
clarify what's happening
on each call? Does first call #1 have to wait for 2, 3 and 4?
1 (Takes long time)
GET https://myTestSB.servicebus.windows.net/MyService/LogIn()?$filter=UserID eq '1234' and Password eq 'secret'
User-Agent: Microsoft ADO.NET Data Services
.....
Status Code: OK 200
...
2
CONNECT https://myTest-sb.accesscontrol.windows.net/WRAPv0.9/
Status Code: OK 200
Connection: Keep-Alive
Proxy-Connection: Keep-Alive
3
POST https://TestSB-sb.accesscontrol.windows.net/WRAPv0.9/
Content-Type: application/x-www-form-urlencoded
Host: TestSB-sb.accesscontrol.windows.net
Content-Length: 307
Expect: 100-continue
Connection: Keep-Alive
Status Code: OK 200
.......
4
CONNECT https://myTestSB.servicebus.windows.net/MyService/LogIn()?$filter=UserID eq '1234' and Password eq 'secret'
Status Code: OK 200
Connection: Keep-Alive
Proxy-Connection: Keep-Alive
It takes 5-10 seconds for logon Service Bus which only takes less than a second on on-premise environment. Not sure why and how Service Bus is adding delay.

Answer 1

By default, the Azure Service Bus Relay typically uses an opt-in authentication via ACS (Access Control Services). In order to consume the relay endpoint - it must first authorize the WCF Channel using an ACS token. The extra calls you are seeing could be removed via configuration if you choose not to use ACS as you are providing your own relay access control.
Disables ACS for Service Bus Relay (Opt-Out)
<bindings>
<netTcpRelayBinding>
<binding name="default">
<security relayClientAuthenticationType="None" />
</binding>
</netTcpRelayBinding>
</bindings>
For more details, see MSDN on securing Azure Service Bus Connections.
As for the latency issue (5-10 seconds) - this all depends on the number of WCF Calls used, where you are in relation to the data center, and how much data is being shared. There are numerous options to tune all the above. Also ensure you have configured your firewall properly for establishing Azure Relay communication.

Answer 2

Myagdi, are you using the WebHttpRelayBinding for both the service and the client? What is the version of the SDK you are using?
Note that when you use the Service Bus Relay there are 2 layers of authentication that occur. The client has to first authenticate to the Service Bus Relay endpoint using ACS, and then perform any application-specific authentication against the on-premises WCF service.
The additional traffic that you are seeing is due to the client acquiring a token from ACS to authenticate to the Service Bus Relay. Now, by default, the lifetime of the token issued by ACS ranges from 20 mins to 3 hours. If you are using our .NET SDK, then in most cases, the client will cache the token for the duration of its lifetime. Hence subsequent requests to the Relay endpoint during this token lifetime should not result in this additional exchange with ACS for token-acquisition.
Also, due to the Service Bus Relay design, the first request from a client to a listener service generally incurs higher latency, due to control communication. The latency is generally lower for subsequent calls.
You can contact me at #santoshc1 if you have additional questions/issues.