Keep Azure WCF http relay alive

Question

I have set up a relay successfully on an existing service by adding an endpoint to my local WCF service

endpoint:

<endpoint address="https://xxxx.servicebus.windows.net/brokers" binding="basicHttpRelayBinding" contract="Services.WebServices.IBrokerService" behaviorConfiguration="clients" bindingConfiguration="HttpRelayConfiguration"/>

behaviour:

<endpointBehaviors>
            <behavior name="clients">
                <transportClientEndpointBehavior>
                    <tokenProvider>
                        <sharedAccessSignature keyName="RootManageSharedAccessKey" key="dsfsdfsdfsdfds"/>
                    </tokenProvider>
                </transportClientEndpointBehavior>
            </behavior>
        </endpointBehaviors>

binding:

<basicHttpRelayBinding>
            <binding name="HttpRelayConfiguration"/>                
        </basicHttpRelayBinding>

Its working great but if I don't access the underlying WCF service through the browser for a while azure doesn't pick up the relay.

What is the easiest way to ensure that the relay is always available when the underlying WCF service is up and running?

Answer 1

First, the "Azure Service bus Relay" is now referenced as Azure Relay (repository GitHub), based on Azure Service Bus Messaging.

For your WCF service remains continuously available, you might consider implementing a keep-alive mechanism. This can be achieved by periodically sending requests to an existing endpoint on the underlying WCF service, such as the WSDL, rather than adding a separate "ping" method. This is based on the observation that merely accessing the WCF service keeps the Azure Relay alive.

For testing, create a simple client that will call this "Ping" method at regular intervals, using for instance a System.Timers.Timer:

using System;
using System.ServiceModel;
using System.Timers;

namespace KeepAliveClient
{
    class Program
    {
        static void Main(string[] args)
        {
            Timer timer = new Timer(60000); // Set interval to 60,000 milliseconds (1 minute)
            timer.Elapsed += TimerElapsed;
            timer.Start();

            Console.WriteLine("Press [Enter] to exit the application.");
            Console.ReadLine();
        }

        private static void TimerElapsed(object sender, ElapsedEventArgs e)
        {
            try
            {
                // Create a proxy to your WCF service
                ChannelFactory<Services.WebServices.IBrokerService> factory = 
                    new ChannelFactory<Services.WebServices.IBrokerService>("YourWSDLorEndpointHere");

                Services.WebServices.IBrokerService proxy = factory.CreateChannel();

                // Call the Ping method
                string response = proxy.Ping();

                if (response == "Alive")
                {
                    Console.WriteLine("Service is alive.");
                }
                else
                {
                    Console.WriteLine("Unexpected response.");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error: {ex.Message}");
            }
        }
    }
}

Do replace "YourWSDLorEndpointHere" with the actual WSDL or another endpoint URL of your WCF service.

---

Alternatively, you can set up an Azure Automation Runbook to accomplish the same task. The Runbook can contain a PowerShell script to access the WSDL or another endpoint at regular intervals.

Within your Azure Automation account, create a new PowerShell Runbook.

# Define the URI to the WSDL or another endpoint on the WCF service
$uri = "https://YourWSDLorEndpointHere"

# Make the web request
$response = Invoke-WebRequest -Uri $uri -Method GET

# Check the response
if ($response.StatusCode -eq 200) {
    Write-Host "Service is alive."
} else {
    Write-Host "Service is not responding as expected."
}

Once your Runbook is tested and published, schedule it to run at regular intervals to keep your relay alive.