Web App for Containers: sidecar containers can't see the environment variables

Question

Web App for Containers: sidecar containers can't see the environment variables

Carol Lai 0

I have a Web App for Containers. I use the Deployment Center on Azure Portal to configure the containers. I use the advanced sidecar container support to add a main container and 2 sidecar containers. All three containers use the same image that is stored in Azure Container Registry.

When I first start this Web App, everything run well. All containers can see the environment variables defined under settings. Then if I stop and restart a few times. The main container still see the environment variables, but the sidecar containers will not be able to see the environment variables anymore.

I'm not sure how to fix this problem.

Carol Lai 0 Reputation points

2025-02-26T14:38:55.6766667+00:00

I follow this tutorial here. It says to set environment variables for the sidecar container in the environment variables in settings.
https://learn.microsoft.com/en-us/azure/app-service/tutorial-sidecar?tabs=portal#4-configure-environment-variables
So I added all the variables that are needed for the three containers on the environment variables panel.

If I don't put the variables on that panel, where can I put the variables at? Unlike Container App that can set variables per container, web app for containers only has this panel for the variables.
Bhargavi Naragani 7,940 Reputation points Microsoft External Staff Moderator

2025-02-28T06:35:32.4+00:00

Hi @Carol Lai,

Apologies for the inconvenience caused. We received your feedback that the answer provided on the thread was not helpful.

It's unexpected that your sidecar containers are no longer able to access the environment variables after a few restarts, particularly since you've placed them in the Web App settings as you're supposed to. Under normal circumstances, those settings should apply to all of your containers, including the main one and the sidecars. But sometimes the settings aren't propagated properly.

Double-verify that environment variables are defined at the Web App level (Configuration => Application settings in the Azure Portal) and ensure that the variables are selected as Application Setting and that they are not isolated to a specific container.

Occasionally, restarts or redeployments may cause inconsistent propagation. If the Web App settings panel is not functioning reliably, you can specify environment variables within the container definition in the Deployment Center YAML or through an ARM template. Navigate to Web App => Logs and see if any errors are present when the sidecars attempt to start.

Incomplete environment variables can be associated with startup problems. Rather than stopping and restarting, use the Restart button within the Azure Portal instead. If this persists, you can try triggering a redeployment from the Deployment Center, which tends to reset environment variable propagation.

As you already followed Azure App Service - Sidecar Containers tutorial, if issue continues, refer this: Configure environment variables in Azure App Service.

I have provided a detailed answer which has clear steps for which you are looking for. If you wish, you may re-surveying for the engagement you received on the thread. Your feedback is very important to us.

Looking forward to your reply. Much appreciate your feedback!
Bhargavi Naragani 7,940 Reputation points Microsoft External Staff Moderator

2025-03-03T03:30:38.91+00:00

Hi @Carol Lai,
We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Bhargavi Naragani 7,940 Reputation points Microsoft External Staff Moderator

2025-03-03T23:32:52.5333333+00:00

Hi @Carol Lai,
If this answer was helpful and pointed you in the right direction, please consider clicking "Accept Answer"—it may benefit other community members reading this thread. If you have any further questions, feel free to let us know.
Carol Lai 0 Reputation points

2025-03-25T17:59:16.9933333+00:00

The newer version of the advanced sidecar container panel now has a flag as shown. Once I checked that flag and all the environment variables that are defined on the Environment Variables panel can be seen in the sidecar containers.

4 answers

Your answer

Carol Lai 0 Reputation points

2025-02-26T14:38:55.6766667+00:00

I follow this tutorial here. It says to set environment variables for the sidecar container in the environment variables in settings.
https://learn.microsoft.com/en-us/azure/app-service/tutorial-sidecar?tabs=portal#4-configure-environment-variables
So I added all the variables that are needed for the three containers on the environment variables panel.

If I don't put the variables on that panel, where can I put the variables at? Unlike Container App that can set variables per container, web app for containers only has this panel for the variables.
Bhargavi Naragani 7,940 Reputation points Microsoft External Staff Moderator

2025-02-28T06:35:32.4+00:00

Hi @Carol Lai,

Apologies for the inconvenience caused. We received your feedback that the answer provided on the thread was not helpful.

It's unexpected that your sidecar containers are no longer able to access the environment variables after a few restarts, particularly since you've placed them in the Web App settings as you're supposed to. Under normal circumstances, those settings should apply to all of your containers, including the main one and the sidecars. But sometimes the settings aren't propagated properly.

Double-verify that environment variables are defined at the Web App level (Configuration => Application settings in the Azure Portal) and ensure that the variables are selected as Application Setting and that they are not isolated to a specific container.

Occasionally, restarts or redeployments may cause inconsistent propagation. If the Web App settings panel is not functioning reliably, you can specify environment variables within the container definition in the Deployment Center YAML or through an ARM template. Navigate to Web App => Logs and see if any errors are present when the sidecars attempt to start.

Incomplete environment variables can be associated with startup problems. Rather than stopping and restarting, use the Restart button within the Azure Portal instead. If this persists, you can try triggering a redeployment from the Deployment Center, which tends to reset environment variable propagation.

As you already followed Azure App Service - Sidecar Containers tutorial, if issue continues, refer this: Configure environment variables in Azure App Service.

I have provided a detailed answer which has clear steps for which you are looking for. If you wish, you may re-surveying for the engagement you received on the thread. Your feedback is very important to us.

Looking forward to your reply. Much appreciate your feedback!
Bhargavi Naragani 7,940 Reputation points Microsoft External Staff Moderator

2025-03-03T03:30:38.91+00:00

Hi @Carol Lai,
We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Bhargavi Naragani 7,940 Reputation points Microsoft External Staff Moderator

2025-03-03T23:32:52.5333333+00:00

Hi @Carol Lai,
If this answer was helpful and pointed you in the right direction, please consider clicking "Accept Answer"—it may benefit other community members reading this thread. If you have any further questions, feel free to let us know.
Carol Lai 0 Reputation points

2025-03-25T17:59:16.9933333+00:00

The newer version of the advanced sidecar container panel now has a flag as shown. Once I checked that flag and all the environment variables that are defined on the Environment Variables panel can be seen in the sidecar containers.

Answer 1

Deepanshu katara 17,960 MVP Moderator

Hello Carol, Welcome to MS Q&A

Sidecar containers in Kubernetes do not automatically inherit environment variables from the main application container, meaning they cannot directly access the environment variables set for the primary container unless explicitly defined in their own configuration; essentially, each container within a pod has its own set of environment variables, even if they share the same network namespace

Please check this for more details

Sidecar Containers

Kindly let me know if have further questions

Pls accept if it helps

Thanks

Deepanshu

Jason Thorpe 10 Reputation points Microsoft Employee

2025-12-03T21:06:29.8233333+00:00

This question is about is Azure App Service, not Kubernetes (both of which have a similar concept of a sidecar with very different implementations).

Answer 2

Hi @Carol Lai,

I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to accept the answer.

Issue: Web App for Containers: sidecar containers can't see the environment variables

Solution:

The newer version of the advanced sidecar container panel has a flag a shown. Once I checked that flag and all the environment variables that are defined on the Environment Variables panel can be seen in the sidecar containers.
sidecar

If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.

Answer 3

Jason Thorpe 10 Microsoft Employee

[deleted].

Jason Thorpe 10 Reputation points Microsoft Employee

2025-12-03T23:02:05.52+00:00

FWIW, I don't work in azure engineering, and with regard to Azure App Services, I'm just an ordinary user...)

Answer 4

According to the azure app service sidecar documentation, the default value for the inheritAppSettingsAndConnectionStrings sidecar setting is true, so when unset, it the sidecar should inherit the main environment variables. This is the case when using ARM templates, the Azure CLI and the like.

However, when the box is unchecked in the portal, it is set to false, which results in the sidecar * not * inheriting the environment variables. If you make any updates to the sidecar in the portal, the default then becomes inheritAppSettingsAndConnectionStrings=false, but if you update it with the CLI the inheritAppSettingsAndConnectionStrings=undefined which defaults to true.

This effectively means that the portal and automation tools have the opposite defaults * and * that the difference is indistinguishable in the portal (since both undefined and false result in an un-checked checkbox) ! Hence you may have no way of knowing the difference between the two un-checked behaviors, -- and even worse, unrelated changes to the app service in the portal may update the default value from undefined to false.

So in short, good luck to you, and don't trust the inheritAppSettingsAndConnectionStrings setting, so you may want to set environment variables for the sidecar right there in the sidecar settings (which you can do).

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Web App for Containers: sidecar containers can't see the environment variables

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