How to fix frequent DNS resolution fails in Azure functions?

Question

How to fix frequent DNS resolution fails in Azure functions?

Jannes Wübbena (Geo++) 20

Since 4 days (08th of March), our daily running Azure functions script that synchronizes a couple of data sources via public REST apis is experiencing DNS problems every day. The error messages are as follows:

Result: Failure Exception: ConnectionError: HTTPSConnectionPool(host='api.personio.de', port=443): Max retries exceeded with url: /v1/company/attendances (Caused by NameResolutionError("

Anonymous

2024-03-12T16:17:50.7666667+00:00

Hi Jannes - could you please provide a few more details. For example is it consumption functions you are using , elastic premium, or functions hosting elsewhere (e.g. AKS/K8S) is your function or the host attached to a VNet? The language and high level config etc may also be helpful.
Tom Wilson 5 Reputation points

2024-09-24T17:12:11.16+00:00
I can provide some details of our similar issue, remarkably unable to resolve graph.microft.com :

consumption plan

python 3.11 Azure Function (on a timer trigger, if that matters)

no vNet setup, just the defaults

Error is Failed to resolve 'graph.microsoft.com' ([Errno -3] Temporary failure in name resolution)

We do not seem to have problems with any other DNS requests, but it's hard to know since this error shuts down the app run

This is intermittent maddenly. It can go for days without a problem but then today, we have a string of failed run, all with this message.

This has been going on for some time and we've been living with it, but it would sure boost our confidence in this system if our MS Azure function would reliably resolve the Microsoft Graph API endpoint!

1 answer

Your answer

Anonymous

2024-03-12T16:17:50.7666667+00:00

Hi Jannes - could you please provide a few more details. For example is it consumption functions you are using , elastic premium, or functions hosting elsewhere (e.g. AKS/K8S) is your function or the host attached to a VNet? The language and high level config etc may also be helpful.
Tom Wilson 5 Reputation points

2024-09-24T17:12:11.16+00:00

I can provide some details of our similar issue, remarkably unable to resolve graph.microft.com :

consumption plan

python 3.11 Azure Function (on a timer trigger, if that matters)

no vNet setup, just the defaults

Error is Failed to resolve 'graph.microsoft.com' ([Errno -3] Temporary failure in name resolution)

We do not seem to have problems with any other DNS requests, but it's hard to know since this error shuts down the app run

This is intermittent maddenly. It can go for days without a problem but then today, we have a string of failed run, all with this message.

This has been going on for some time and we've been living with it, but it would sure boost our confidence in this system if our MS Azure function would reliably resolve the Microsoft Graph API endpoint!

Answer 1

Tom Wilson 5

Solution: Stop using the "Default (Azure provided)" DNS service

This worked for us so I am posting it as an answer.

From the Azure portal, select your Azure Function, and go to the Networking page (that's on the left side menu now, but they "improve" the interface all the time so it might be somewhere else)
Under "Outbound traffic configuration" go to "Outbound DNS"
Change from "Default (Azure provided)" to "Custom" and add the DNS server addresess of your choice. We used the well-known Google servers at 8.8.8.8 and 4.4.4.4.
Don't forget to save this setting, and you will likely have to restart your Azure Function

This worked for us immediately, and the usually-intermittent (but today, consistent) DNS errors disappeared. For details on our rig, please see my comment on the original question.

Ahmed Ibrahem 0 Reputation points

2024-12-23T12:47:33.0533333+00:00

I am encountering an issue that occurs intermittently with the Flex Consumption Plan. I did not face these errors with the standard Consumption Plan, but I had to upgrade due to timeout constraints. Unfortunately, this issue severely limits and renders our work built on Azure Functions useless.

I have tried overriding the DNS providers as suggested in other solutions, but the issue persists. Additionally, I have attempted to use the network debugging features, but they do not work in this case, as I encounter a Kudu error. I have also tried multiple regions in Europe, but I keep running into this issue in all of them.
Abha BARANWAL 0 Reputation points

2025-12-08T18:06:28.7933333+00:00

Hi.. I am facing the same issue. Please share what worked for you.
Charles Beuzet 0 Reputation points

2025-12-12T15:08:24.0166667+00:00

Hi, same issue here
Matthew King 0 Reputation points

2026-01-07T07:56:35.3766667+00:00

I switched from flex consumption plan to consumption plan and this resolved the issue for me. I achieved this by deleting the func app in the portal, created a new one in the portal (I recommend this as allows more configurability over creating it in VSCode) on the consumption plan, then redeployed the functions to the app. It ran fine. Unsure why the flex consumption plan is throwing DNS errors but mine was encountered using pagination on an REST API endpoint. Hope this helps and that MS resolves this issue.
Abha BARANWAL 0 Reputation points

2026-01-08T06:08:52.16+00:00

Thank you. Though the strange part is that I am getting this error for consumption plan and have switched to flex consumption, which seems to have resolved it for now.
Matthew King 0 Reputation points

2026-01-08T06:14:58.8433333+00:00

That is strange. I would be keen to learn more from MS to understand why this is happening in some cases on some plans and not on others, it looks like it something they are managing so would be good to get guidance as to why this is actually happening.
Scott Jenkins 5 Reputation points

2026-01-08T14:31:58.37+00:00

I have the same issue on both the flex and consumption plan. Code has been running for 3 years, on 12/7 started failing graph calls due to name resolution issues. I have multiple apps making graph calls and only 1 is impacted.
Manu 5 Reputation points

2026-02-09T14:03:15.9466667+00:00

We are still experiencing this error, even after switching to customs dns configs.
Sigita Lapina 5 Reputation points

2026-02-17T09:44:18.3133333+00:00

Same issuea here too. NameResolutionError("<urllib3.connection.HTTPSConnection object at 0x7fb8d407ea10>: Failed to resolve 'graph.microsoft.com' ([Errno -3] Temporary failure in name resolution)")