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Does Azure (Standard) load-balancing require two or more nodes in backend pool?

Troy Martin-1E 1 Reputation point
2020-08-19T21:19:21.997+00:00

I'm configuring/testing Azure (Standard) load balancer, currently with a backend pool that has a single VM; in the future, additional VMs will be added.

With only a single VM in the BP, I assumed my app can still be configured to use the LB. However, I'm finding that the app is not able to connect to the VM in the BP e.g. winhttp timeout (12002).

The only reason I can think of as to why the LB is not sending traffic to the VM is because maybe there is an unwritten requirement that a backend pool is required to have at least two VMs/nodes. I cannot find documentation that confirms or denies.

Of course I can just test myself by adding a second VM to the BP, but not quite ready to do that yet. So thought I'd ask

FYI - the LB has two backend pools: #1 has two VMs for that component of the app, #2 has one VM for that component of the app.

1 works fine; the LB is spreading the load across both VMs. #2 does not work

Just really wanting to know if Azure LB can work when the backend pool has a single node, or are two or more nodes required.

Any thoughts/details on this topic?

Azure Load Balancer
Azure Load Balancer
An Azure service that delivers high availability and network performance to applications.
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  1. GitaraniSharma-MSFT 49,401 Reputation points Microsoft Employee
    2020-08-20T01:42:53.063+00:00

    Hello @Troy Martin-1E ,

    Azure load balancer can work even when the backend pool has a single node. There is no prerequisite to have 2 or more nodes for it to work.

    The error_winhttp_timeout 12002 that you are receiving seems to be a timeout error returned as a result of TCP/IP time-out behavior, regardless of time-out values set in Windows HTTP Services.
    You may need to refer to the below articles and check your configuration for further troubleshooting:
    https://learn.microsoft.com/en-us/windows/win32/winhttp/error-messages
    https://learn.microsoft.com/en-us/iis/extensions/troubleshooting-application-request-routing/troubleshooting-502-errors-in-arr

    You may also refer to TCP Idle Timeout on Azure Load Balancer.

    Kindly let us know if you need any further assistance on this issue from our end.

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