Hands-on with Container Apps

The purpose of this repo is to help you quickly get hands-on with Container Apps. It is meant to be consumed either through GitHub codespaces or through a local Dev Container. The idea being that everything you need from tooling to runtimes is already included in the Dev Container so it should be as simple as executing a run command.

• Date: 10th January 2022
• Squad: Cloud Native
• Duration: 30 minutes

Scenario

As a retailer, you want your customers to place online orders, while providing them the best online experience. This includes an API to receive orders that is able to scale out and in based on demand. You want to asynchronously store and process the orders using a queing mechanism that also needs to be auto-scaled. With a microservices architecture, Container Apps offer a simple experience that allows your developers focus on the services, and not infrastructure.

In this sample you will see how to:

1. Deploy the solution and configuration through IaaC, no need to understand Kubernetes
2. Ability to troubleshoot using built-in logging capability with Azure Monitor (Log Analytics)
3. Out of the box Telemetry with Dapr + Azure Monitor (Log Analytics)
4. Ability to split http traffic when deploying a new version
5. Ability to configure scaling to meet usage needs

Pre-requisites

There are two options:

1. Access to GitHub Codespaces
2. VS Code + Docker Desktop on Local Machine

Getting Started

As this is currently a preview service, you will need to install an Azure CLI extension to work with Container Apps.

Run the following command.

az extension add --name containerapp

We will be using the hey load testing tool later on. If you are using Codespaces, the container includes Homebrew, so you can install hey like this:

brew install hey

If you are using an environment other than Codespaces, you can find installation instructions for hey here - https://github.com/rakyll/hey

Setup Solution

Let's start by setting some variables that we will use for creating Azure resources in this demo, and a resource group for those resources to reside in.

# Generate a random name

name=ca-$(cat /dev/urandom | tr -dc '[:lower:]' | fold -w ${1:-5} | head -n 1)

# Set variables for the rest of the demo

resourceGroup=${name}-rg
location=northeurope
containerAppEnv=${name}-env
logAnalytics=${name}-la
appInsights=${name}-ai
storageAccount=$(echo $name | tr -d -)sa

Optional - if using Codespaces or not logged into Azure CLI

# Login into Azure CLI
az login --use-device-code

# Check you are logged into the right Azure subscription. Inspect the name field
az account show

# In case not the right subscription
az account set -s <subscription-id>

# Create Resource Group
az group create --name $resourceGroup --location $location -o table

Deploy version 1 of the application

We'll deploy the first version of the application to Azure. This typically takes around 3 to 5 minutes to complete.

az deployment group create \
  -g $resourceGroup \
  --template-file v1_template.json \
  --parameters @v1_parameters.json \
  --parameters ContainerApps.Environment.Name=$containerAppEnv \
    LogAnalytics.Workspace.Name=$logAnalytics \
    AppInsights.Name=$appInsights \
    StorageAccount.Name=$storageAccount

Now the application is deployed, let's determine the URL we'll need to use to access it and store that in a variable for convenience

storeURL=https://storeapp.$(az containerapp env show -g $resourceGroup -n $containerAppEnv --query 'properties.defaultDomain' -o tsv)/store

Let's see what happens if we call the URL of the store with curl.

Alternatively, you can run echo $storeURL to get the URL for the application and then open that in a browser.

curl $storeURL

The response you should see is [] which means no data was returned. Something's not working, but what?

ContainerApps integrates with Application Insights and Log Analytics. In the Azure Portal, go to the Log Analytics workspace in the resource group we're using for this demo and run the following query to view the logs for the queuereader application.

ContainerAppConsoleLogs_CL
| where ContainerAppName_s has "queuereader" and ContainerName_s has "queuereader"
| where Log_s has "null"
| project TimeGenerated, ContainerAppName_s, ContainerName_s, Log_s
| order by TimeGenerated desc

Alternatively, if you prefer to stay in the CLI, you can run the Log Analytics query from there.

workspaceId=$(az monitor log-analytics workspace show -n $logAnalytics -g $resourceGroup --query "customerId" -o tsv)
az monitor log-analytics query -w $workspaceId --analytics-query "ContainerAppConsoleLogs_CL | where ContainerAppName_s has 'queuereader' and ContainerName_s has 'queuereader' | where Log_s has 'null' | project TimeGenerated, ContainerAppName_s, ContainerName_s, Log_s | order by TimeGenerated desc"

You should see a number of log file entries which will likely all contain the same error. Drill down on one of them to reveal more. You should see something like the following:

"Log_s": " Value cannot be null. (Parameter ''DaprPort' config value is required. Please add an environment variable or app setting.')",

Looks like we're missing a configuration value relating to Dapr. So, we've gone ahead and made the necessary changes to our code and packaged that up in version 2 of our application's container. Let's deploy version 2.

Deploy Version 2

We'll repeat the deployment command from earlier, but we've updated our template to use version 2 of the queuereader application.

az deployment group create \
  -g $resourceGroup \
  --template-file v2_template.json \
  --parameters @v2_parameters.json \
  --parameters ContainerApps.Environment.Name=$containerAppEnv \
    LogAnalytics.Workspace.Name=$logAnalytics \
    AppInsights.Name=$appInsights \
    StorageAccount.Name=$storageAccount

This time, we'll store the URL for the HTTP API application in a variable

dataURL=https://httpapi.$(az containerapp env show -g $resourceGroup -n ${name}-env --query 'properties.defaultDomain' -o tsv)/Data

Now let's see what happens if we access that URL

As before, you can type echo $dataURL to get the URL of the HTTP API and then open it in a browser if you prefer

curl $dataURL

The result tells us that demoqueue has no messages:

Queue 'demoqueue' has 0 messages

We can call the HTTP API endpoint to add a test message.

curl -X POST $dataURL?message=test

Ok, let's check our Store URL and see what happens this time

curl $storeURL

[{"id":"f30e1eb6-d9d1-458b-b8d3-327e5597ffc7","message":"57e88c1e-f4a4-4c66-8eb5-128bb235b08d"}]

Ok, that's something but that's not the message we sent. Let's take a look at the application code

DataController.cs

...
  [HttpPost]
  public async Task PostAsync()
  {
      try
      {
          await queueClient.SendMessageAsync(Guid.NewGuid().ToString());

          Ok();
      }
...

It looks like the code is set to send a GUID, not the message itself. Must have been something the developer left in to test things out. Let's modify that code:

DataController.cs (version 2)

  [HttpPost]
  public async Task PostAsync(string message)
  {
      try
      {
          await queueClient.SendMessageAsync(DateTimeOffset.Now.ToString() + " -- " + message);

          Ok();
      }

We've fixed the code so that the message received is now actually being sent and we've packaged this up into a new container ready to be redeployed.

But maybe we should be cautious and make sure this new change is working as expected. Let's perform a controlled rollout of the new version and split the incoming network traffic so that only 20% of requests will be sent to the new version of the application.

To implement the traffic split, the following has been added to the deployment template

  "ingress": {
      "external": true,
      "targetPort": 80,
      "traffic":[
          {
              "revisionName": "[concat('httpapi--', parameters('ContainerApps.HttpApi.CurrentRevisionName'))]",
              "weight": 80
          },
          {
              "latestRevision": true,
              "weight": 20
          }
      ]

Effectively, we're asking for 80% of traffic to be sent to the current version (revision) of the application and 20% to be sent to the new version that's about to be deployed.

Deploy version 3

Once again, let's repeat the deployment command from earlier, now using version 2 of the HTTP API application and with traffic splitting configured

az deployment group create \
  -g $resourceGroup \
  --template-file v3_template.json \
  --parameters @v3_parameters.json \
  --parameters ContainerApps.Environment.Name=$containerAppEnv \
    LogAnalytics.Workspace.Name=$logAnalytics \
    AppInsights.Name=$appInsights \
    StorageAccount.Name=$storageAccount

With the third iteration of our applications deployed, let's try and send another order.

curl -X POST $dataURL?message=secondtest

And let's check the Store application again to see if the messages have been received

curl $storeURL | jq

[
  {
    "id": "b205d410-5150-4ac6-9e26-7079ebcae67b",
    "message": "a39ecc22-cece-4442-851e-25d7329a1f55"
  },
  {
    "id": "318e72bb-8c55-486c-99ec-18a5bd76bc1d",
    "message": "01/03/2022 13:28:33 +00:00 -- secondtest"
  }
]

That's looking better. We can still see the original message, but we can also now see our "test" message with the date and time appended to it.

We configured traffic splitting, so let's see that in action. First we will need to send multiple messages to the application. We can use the load testing tool hey to do that.

hey -m POST -n 25 -c 1 $dataURL?message=hello

curl $storeURL | jq

Let's check the application logs for the Queue Reader application

ContainerAppConsoleLogs_CL
| where ContainerAppName_s has "queuereader" and ContainerName_s has "queuereader"
| where Log_s has "Message"
| project TimeGenerated, Log_s
| order by TimeGenerated desc

Looking through those logs, you should see a mix of messages, with some containing "hello" and others still containing a GUID. It won't be exact, but roughly one out of every five messages should contain "hello".

So, is our app ready for primetime now? Let's change things so that the new app is now receiving all of the traffic, plus we'll also setup some scaling rules. This will allow the container apps to scale up when things are busy, and scale to zero when things are quiet.

Deploy version 4

One final time, we'll now deploy the new configuration with scaling configured. We will also add a simple dashboard for monitoring the messages flow.

az deployment group create \
  -g $resourceGroup \
  --template-file v4_template.json \
  --parameters @v4_parameters.json \
  --parameters ContainerApps.Environment.Name=$containerAppEnv \
    LogAnalytics.Workspace.Name=$logAnalytics \
    AppInsights.Name=$appInsights \
    StorageAccount.Name=$storageAccount

First, let's confirm that all of the traffic is now going to the new application

hey -m POST -n 10 -c 1 $dataURL?message=testscale

Let's check the number of orders in the queue

curl $dataURL

As before, we can check the application log files in Log Analytics to see what messages are being received

ContainerAppConsoleLogs_CL
| where ContainerAppName_s has "queuereader" and ContainerName_s has "queuereader"
| where Log_s has "Message"
| project TimeGenerated, Log_s
| order by TimeGenerated desc

Now let's see scaling in action. To do this, we will generate a large amount of messages which should cause the applications to scale up to cope with the demand.

[Optional] While the scaling script is running, you can also have this operations dashboard open to visually see the messages flowing through queue into the store

dashboardURL=https://dashboardapp.$(az containerapp env show -g $resourceGroup -n ${name}-env --query 'properties.defaultDomain' -o tsv)
echo 'Open the URL in your browser of choice:' $dashboardURL

To demonstrate this, a script that uses the tmux command is provided in the scripts folder of this repository. Run the following commands:

cd scripts
./appwatch.sh $resourceGroup $dataURL

This will split your terminal into four separate views.

• On the left, you will see the output from the hey command. It's going to send 10,000 requests to the application, so there will be a short delay, around 20 to 30 seconds, whilst the requests are sent. Once the hey command finishes, it should report its results.
• On the right at the top, you will see a list of the container app versions (revisions) that we've deployed. One of these will be the latest version that we just deployed. As hey sends more and more messages, you should notice that one of these revisions of the app starts to increase its replica count
• Also on the right, in the middle, you should see the current count of messages in the queue. This will increase to 10,000 and then slowly decrease as the app works it way through the queue.

Once hey has finished generating messages, the number of instances of the HTTP API application should start to scale up and eventually max out at 10 replicas. After the number of messages in the queue reduces to zero, you should see the number of replicas scale down and return to 1.

Tip! To exit from tmux when you're finished, type CTRL-b, then : and then the command kill-session

Cleanup

Deleting the Azure resource group should remove everything associated with this demo.

az group delete -g $resourceGroup --no-wait -y

Contributors

• Kevin Harris - [email protected]
• Mahmoud El Zayet - [email protected]
• Mark Whitby - [email protected]
• Anu Bhattacharya - [email protected]