Application Gateway Metric - Healthy vs Unhealthy host Count

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Application Gateway Metric - Healthy vs Unhealthy host Count

Rajesh Swarnkar 41

Unhealthy host count chart shows 1 then it falls to 0 and again up to 1. Does that mean the Number of unreachable host was 1 then it fell to 0 (all OK), then again it gone into unhealth? Is this interpreation correct?
I mean, What is the meaning of Unhealthy host count showing value 1? How to interpret it against the healthy host count?

Tchimwa Sougang 946 Reputation points Microsoft Employee

2022-11-11T06:56:13.833+00:00

@Rajesh Swarnkar Thank you for your question. Yes, your explanation is correct!
Rajesh Swarnkar 41 Reputation points

2022-11-16T03:46:16.953+00:00

Yes, your explanation is correct!
Roman Sheydvasser 0 Reputation points

2025-06-24T19:31:15.81+00:00

I ran into a similar issue and wanted to share what helped in case others find this thread.

If you're seeing constant values like 1 healthy and 0 unhealthy hosts (or vice versa), it might be due to the aggregation type you're using when querying the metric. Azure emits HealthyHostCount and UnhealthyHostCount per backend pool, and when these metrics are aggregated using avg (like in the example above) or max, the result will often look like a constant 1 or 0.

Switching to sum aggregation allows you to see fluctuations more clearly over time. This is particularly helpful when using dashboards in tools like Datadog, Grafana, or Azure Monitor.

Hope this helps someone avoid the confusion I ran into!

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Tchimwa Sougang 946 Reputation points Microsoft Employee

2022-11-11T06:56:13.833+00:00

@Rajesh Swarnkar Thank you for your question. Yes, your explanation is correct!
Rajesh Swarnkar 41 Reputation points

2022-11-16T03:46:16.953+00:00

Yes, your explanation is correct!
Roman Sheydvasser 0 Reputation points

2025-06-24T19:31:15.81+00:00

I ran into a similar issue and wanted to share what helped in case others find this thread.

If you're seeing constant values like 1 healthy and 0 unhealthy hosts (or vice versa), it might be due to the aggregation type you're using when querying the metric. Azure emits HealthyHostCount and UnhealthyHostCount per backend pool, and when these metrics are aggregated using avg (like in the example above) or max, the result will often look like a constant 1 or 0.

Switching to sum aggregation allows you to see fluctuations more clearly over time. This is particularly helpful when using dashboards in tools like Datadog, Grafana, or Azure Monitor.

Hope this helps someone avoid the confusion I ran into!

Answer 1

KapilAnanth-MSFT 49,616 Microsoft Employee Moderator

Hi @Rajesh Swarnkar ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.
I understand that you would like to know more about Application Gateway Metric .

You are right.

The Healthy host count and unhealthy host count represent the number of backend hosts that were healthy (getting an accepted health probe response) and unhealthy (getting a non-accepted health probe response or no response at all) respectively.

Let us know should you require any more information on the above.

Thanks,
Kapil

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Mahesh Kumar Babu Kummara 50 Reputation points

2023-09-05T12:50:15.7466667+00:00

hi Kapil,

Could you please let me know what needs to be done if the unhealthy host count is getting to 0?
KapilAnanth-MSFT 49,616 Reputation points Microsoft Employee Moderator

2023-09-11T10:33:05.3733333+00:00

Mahesh Kumar Babu Kummara ,

If the unhealthy host count is getting to 0, that means all the hosts are healthy and thus, you do not have to do anything further.

Hope that clarifies your query.

Thanks,

Kapil

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Application Gateway Metric - Healthy vs Unhealthy host Count

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