Category: Quick Post

Quick Post! – Using NetScaler responder policies/actions and backup vServers to notify users of Service Downtime

NetScaler, as I am sure you are aware, is a superbly powerful Application Delivery Controller. One of the most useful features is the use of Responder Policies/Actions, and Backup vServers to indicate that a service is down or to provide access to an alternative service for end users.

Let’s say – you have a load balancer configured that balances two Web Servers, which you then present for users to access. This load balancer could be configured with monitoring to check the health of the Web Servers, and also to ensure that the servers are loaded evenly with requests.

But – what happens when both servers are down? Maybe you have scheduled patching, or there is a fault. Leaving users with a blank page or one that times out is never ideal, and letting them know there is a fault is always best. This is especially relevant if the users are accessing pages of a commercial nature – for example, “The Online shop will be back open at 2pm” is a lot better than a blank page.

Both of the options below take less than 10 minutes configuration on a NetScaler – so if you need to get a page up quickly… these are very useful!

To do this – we can go down one of the two routes below:

Option 1

Use the Redirect URL option on the vServer – this redirects client requests to the custom URL when the service is down. So for example this could be a custom page on elsewhere, which explains that there is an issue.

This could be used for Scheduled patching for example – for times when we know the site will be down, we just add the URL to the vServer and any users who visit during the maintenance window will see the redirected page.

Option 2

Another option, is to use the Backup vServer feature within NetScaler – this is great because it can be used to direct traffic to a backup Data Center if our primary is unavailable. But also – we can use this feature to put up a NetScaler generated page informing the user that there is a problem with the backend service.

To do this – we need to create a new vServer to use for Maintenance. Create this with the following basic settings:

Then create a service for this – any local service bound to 127.0.0.1 will do. Assign a basic monitor so that the service shows as up.

Next – go to AppExpert, and then Responder, and create a Responder Action. Fill out the details as below – note: you will need to create a new HTML Page, this is the 2nd and 3rd screenshots below:

HTML Page:

Click on Done, and then Click Create for the Responder Action.

We can then go back to the vServer and assign this under the Policies option. Select the options as per the screenshot below and press Continue:

Next we are presented with the below screen, click on the Plus sign next to “Select Policy”:

Fill out the details as per the below:

Click on “Create” and then click on “Bind”. Finally, click “Done”. We can now apply this vServer as a backup vServer to others – so that if those vServers are down, this page will be shown to users.

This is configured on a per vServer basis as per the below:

Now when accessing the page, and with the services down – the following page is shown:

Obviously, you can customise the page a little more than I have – but hopefully this will help. It’s a quick step to setup and gives some extra information to users when there is scheduled work or an unexpected fault.

Testing out Project Honolulu

Recently I have been testing out something new – Project Honolulu from Microsoft. I first heard about this on Twitter (thanks to Eric @XenAppBlog), and was interested in what it could offer straight away. Project Honolulu is a new way to manage Windows Server – using a web based method, that does not rely on the traditional Server Manager GUI. Functionality is similar, and offers the usual range of configuration options, as well the ability to manage roles and features as you would normally expect.

You can download Project Honolulu here. Windows Server 2016 is supported natively, but for 2012R2 Support, you will need to install WMF5.0 (KB3134758).

Project Honolulu has a number of ways to deploy – but I went with a simple install on a single server within my lab. Once this is completed (it’s an easy next next next done install), you are presented with the following screen, which opens up in your default browser:

From here – we can add server connections. Note: Standalone, Failover Cluster, and Hyper-Converged systems are supported:

After I’d added a few servers from my lab, the main screen appeared as below. You can also import servers from a text file – so an export from AD is possible too:

From here, we can see the status of the servers I have added and then drill down further into the options by clicking on a server name. The overview screen gives the usual range of information we’d expect to see:

Particularly nice – is the metric display, which gives an overview of CPU, Memory, Ethernet, and Disk Activity. This is realtime data – but useful for monitoring key servers/clusters, perhaps on an Ops display board or large screen etc.:

As well as a range of metrics available, we have a range of management tools we can take advantage of. Particularly interesting is the ability to manage elements like Network Adaptors, Services, and Roles/Features, as well as to view Event Log entries and the Registry:

Management of Services is also a very useful feature – allowing services to be stopped and started (I wish it had a restart button though!) from the Web Console. This is particularly useful for Managed Service Providers – when the 2am call comes in that a failure has occurred, instead of a VPN into an RDP Session into another RDP Session, you can fire up a Web Interface and restart the service from there (NAT rules and an SSL cert required of course…) :

You’ll notice here that I’ve highlighted a couple of Citrix Services too – Project Honolulu allows you to manage all services running on a supported machine. So this is great for managing 3rd Party applications and services too. The lightweight nature of the system also means that this can be added to existing systems with ease (a single installer and a list of servers).

I’m really interested to see where this Project will go – in particular, it makes the use of Server Core much more accessible, because a familiar and common interface can be used for management of multiple servers. It also allows simple management of basic server configurations, as well as Service management for Microsoft and Third Party applications. Any environment could probably benefit from a single interface that allows basic configuration and Service restarts… the key questions is… where will this Project go next?

I’d really like to see support for more configuration changes, for example, customisable PowerShell options (e.g. this button in the interface runs this remote command) or support for a PowerShell session via the Web Interface. Also it would be great to see support for Third Party software – for example, additional modules that could be included to provide web based management of other software items on the server.