Azure Load Balancer: Behaviour when one of a couple health probes fails

Question

I have a load balancer in front of a set of VMs. Additionally i got several health probes with corresponding balancer rules set up.

E.g. A rule (with probe) for port 80 (http), onr for 443 (https) and one for 25 (smtp).

My question is: If on VM B the 25-Port Probe fails (a couple of times so it recognizes the port on that vm as unhealthy), does the load balancer still route Port 80/443 Requests to that VM or does it generally say that VM B is unhealthy and no further traffic will be routed to that VM until its healthy again?

Thanks in advance!

Does those rules use the same probe? if not, I think other ports will work fine. — Jason Ye
Yes, they are completely different probes. Each Rule has its own probe. — Eiren
we can enable diagnostics for azure load balancer, in this way, we can check probe logs, please check my answer. — Jason Ye

Jason Ye Jason Ye · Accepted Answer · 2017-06-23T06:21:13

For example, if your port 80 is down, and other ports are health, port 80 will not effect other service.
But if your VM CPU usage over 80%, all probe to this VM will not health.
To monitor Azure Load Balancer probe status, we can enable diagnostics.
The result like this:

{
    "records":[
    {
        "time": "2016-01-26T10:37:46.6024215Z",
        "systemId": "32077926-b9c4-42fb-94c1-762e528b5b27",
        "category": "LoadBalancerProbeHealthStatus",
        "resourceId": "/SUBSCRIPTIONS/XXXXXXXXXXXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXX/RESOURCEGROUPS/RG7/PROVIDERS/MICROSOFT.NETWORK/LOADBALANCERS/WWEBLB",
        "operationName": "LoadBalancerProbeHealthStatus",
        "properties": {
            "publicIpAddress": "40.83.190.158",
            "port": "81",
            "totalDipCount": 2,
            "dipDownCount": 1,
            "healthPercentage": 50.000000
        }
    },
    {
        "time": "2016-01-26T10:37:46.6024215Z",
        "systemId": "32077926-b9c4-42fb-94c1-762e528b5b27",
        "category": "LoadBalancerProbeHealthStatus",
        "resourceId": "/SUBSCRIPTIONS/XXXXXXXXXXXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXX/RESOURCEGROUPS/RG7/PROVIDERS/MICROSOFT.NETWORK/LOADBALANCERS/WWEBLB",
        "operationName": "LoadBalancerProbeHealthStatus",
        "properties": {
            "publicIpAddress": "40.83.190.158",
            "port": "81",
            "totalDipCount": 2,
            "dipDownCount": 0,
            "healthPercentage": 100.000000
        }
    }]
}

Please refer to this link to enable it.

Azure Load Balancer: Behaviour when one of a couple health probes fails

1 Answers