Tutorial: Scale a container app
Azure Container Apps manages automatic horizontal scaling through a set of declarative scaling rules. As a container app scales out, new instances of the container app are created on-demand. These instances are known as replicas.
In this tutorial, you add an HTTP scale rule to your container app and observe how your application scales.
Prerequisites
Requirement | Instructions |
---|---|
Azure account | If you don't have an Azure account, you can create one for free. You need the Contributor permission on the Azure subscription to proceed. Refer to Assign Azure roles using the Azure portal for details. |
GitHub Account | Get one for free. |
Azure CLI | Install the Azure CLI. |
Setup
To sign in to Azure from the CLI, run the following command and follow the prompts to complete the authentication process.
az login
To ensure you're running the latest version of the CLI, run the upgrade command.
az upgrade
Next, install or update the Azure Container Apps extension for the CLI.
If you receive errors about missing parameters when you run az containerapp
commands in Azure CLI or cmdlets from the Az.App
module in Azure PowerShell, be sure you have the latest version of the Azure Container Apps extension installed.
az extension add --name containerapp --upgrade
Note
Starting in May 2024, Azure CLI extensions no longer enable preview features by default. To access Container Apps preview features, install the Container Apps extension with --allow-preview true
.
az extension add --name containerapp --upgrade --allow-preview true
Now that the current extension or module is installed, register the Microsoft.App
and Microsoft.OperationalInsights
namespaces.
Note
Azure Container Apps resources have migrated from the Microsoft.Web
namespace to the Microsoft.App
namespace. Refer to Namespace migration from Microsoft.Web to Microsoft.App in March 2022 for more details.
az provider register --namespace Microsoft.App
az provider register --namespace Microsoft.OperationalInsights
Create and deploy the container app
Create and deploy your container app with the containerapp up
command. This command creates a:
- Resource group
- Container Apps environment
- Log Analytics workspace
If any of these resources already exist, the command uses the existing resources rather than creating new ones.
Lastly, the command creates and deploys the container app using a public container image.
az containerapp up \
--name my-container-app \
--resource-group my-container-apps \
--location centralus \
--environment 'my-container-apps' \
--image mcr.microsoft.com/k8se/quickstart:latest \
--target-port 8080 \
--ingress external \
--query properties.configuration.ingress.fqdn \
Note
Make sure the value for the --image
parameter is in lower case.
By setting --ingress
to external
, you make the container app available to public requests.
The up
command returns the fully qualified domain name (FQDN) for the container app. Copy this FQDN to a text file. You'll use it in the Send requests section. Your FQDN looks like the following example:
https://my-container-app.icydune-96848328.centralus.azurecontainerapps.io
Add scale rule
Add an HTTP scale rule to your container app by running the az containerapp update
command.
az containerapp update \
--name my-container-app \
--resource-group my-container-apps \
--scale-rule-name my-http-scale-rule \
--scale-rule-http-concurrency 1
This command adds an HTTP scale rule to your container app with the name my-http-scale-rule
and a concurrency setting of 1
. If your app receives more than one concurrent HTTP request, the runtime creates replicas of your app to handle the requests.
The update
command returns the new configuration as a JSON response to verify your request was a success.
Start log output
You can observe the effects of your application scaling by viewing the logs generated by the Container Apps runtime. Use the az containerapp logs show
command to start listening for log entries.
az containerapp logs show \
--name my-container-app \
--resource-group my-container-apps \
--type=system \
--follow=true
The show
command returns entries from the system logs for your container app in real time. You can expect a response like the following example:
{
"TimeStamp":"2023-08-01T16:49:03.02752",
"Log":"Connecting to the container 'my-container-app'..."
}
{
"TimeStamp":"2023-08-01T16:49:03.04437",
"Log":"Successfully Connected to container:
'my-container-app' [Revision: 'my-container-app--9uj51l6',
Replica: 'my-container-app--9uj51l6-5f96557ffb-5khg9']"
}
{
"TimeStamp":"2023-08-01T16:47:31.9480811+00:00",
"Log":"Microsoft.Hosting.Lifetime[14]"
}
{
"TimeStamp":"2023-08-01T16:47:31.9481264+00:00",
"Log":"Now listening on: http://[::]:8080"
}
{
"TimeStamp":"2023-08-01T16:47:31.9490917+00:00",
"Log":"Microsoft.Hosting.Lifetime[0]"
}
{
"TimeStamp":"2023-08-01T16:47:31.9491036+00:00",
"Log":"Application started. Press Ctrl+C to shut down."
}
{
"TimeStamp":"2023-08-01T16:47:31.949723+00:00",
"Log":"Microsoft.Hosting.Lifetime[0]"
}
{
"TimeStamp":"2023-08-01T16:47:31.9497292+00:00",
"Log":"Hosting environment: Production"
}
{
"TimeStamp":"2023-08-01T16:47:31.9497325+00:00",
"Log":"Microsoft.Hosting.Lifetime[0]"
}
{
"TimeStamp":"2023-08-01T16:47:31.9497367+00:00",
"Log":"Content root path: /app/"
}
For more information, see az containerapp logs.
Send requests
Open a new bash shell. Run the following command, replacing <YOUR_CONTAINER_APP_FQDN>
with the fully qualified domain name for your container app that you saved from the Create and deploy the container app section.
seq 1 50 | xargs -Iname -P10 curl "<YOUR_CONTAINER_APP_FQDN>"
These commands send 50 requests to your container app in concurrent batches of 10 requests each.
Command or argument | Description |
---|---|
seq 1 50 |
Generates a sequence of numbers from 1 to 50. |
| |
The pipe operator sends the sequence to the xargs command. |
xargs |
Runs curl with the specified URL |
-Iname |
Acts as a placeholder for the output of seq . This argument prevents the return value from being sent to the curl command. |
curl |
Calls the given URL. |
-P10 |
Instructs xargs to run up to 10 processes at a time. |
For more information, see the documentation for:
In the first shell, where you ran the az containerapp logs show
command, the output now contains one or more log entries like the following.
{
"TimeStamp":"2023-08-01 18:09:52 +0000 UTC",
"Type":"Normal",
"ContainerAppName":"my-container-app",
"RevisionName":"my-container-app--9uj51l6",
"ReplicaName":"my-container-app--9uj51l6-5f96557ffb-f795d",
"Msg":"Replica 'my-container-app--9uj51l6-5f96557ffb-f795d' has been scheduled to run on a node.",
"Reason":"AssigningReplica",
"EventSource":"ContainerAppController",
"Count":0
}
View scaling in Azure portal (optional)
- Sign in to the Azure portal.
- In the Search bar at the top, enter my-container-app.
- In the search results, under Resources, select my-container-app.
- In the navigation bar at the left, expand Application and select Scale and replicas.
- In the Scale and Replicas page, select Replicas.
- Your container app now has more than one replica running.
You may need to select Refresh to see the new replicas.
In the navigation bar at the left, expand Monitoring and select Metrics.
In the Metrics page, set Metric to Requests.
Select Apply splitting.
Expand the Values drop-down and check Replica.
Select the blue checkmark icon to finish editing the splitting.
The graph shows the requests received by your container app, split by replica.
By default, the graph scale is set to last 24 hours, with a time granularity of 15 minutes. Select the scale and change it to the last 30 minutes, with a time granularity of one minute. Select the Apply button.
Select on the graph and drag to highlight the recent increase in requests received by your container app.
The following screenshot shows a zoomed view of how the requests received by your container app are divided among replicas.
Clean up resources
If you're not going to continue to use this application, run the following command to delete the resource group along with all the resources created in this tutorial.
Caution
The following command deletes the specified resource group and all resources contained within it. If resources outside the scope of this tutorial exist in the specified resource group, they will also be deleted.
az group delete --name my-container-apps
Tip
Having issues? Let us know on GitHub by opening an issue in the Azure Container Apps repo.