What this covers

Each change to a container app's template (image, env vars, CPU and memory, scale rules, probes) creates a new immutable revision. Managing the lifecycle means choosing a revision mode, moving traffic between revisions, restarting or deactivating bad ones, and stopping the whole app when you need to. Most "it worked yesterday" problems are revision problems, so this is also the first thing to check when troubleshooting.

Exam weight: Develop containerized solutions on Azure (20–25%)

Skills measured

"Deploy applications to Azure Container Apps, including environment configuration and revision management"
"Monitor and troubleshoot solutions on AKS and Container Apps by inspecting logs, events, and end-to-end connectivity"

Key concepts

Revision-scope vs application-scope changes

Change	Creates a new revision?
Image, env vars, CPU/memory, probes, scale rules (`properties.template`)	Yes
Ingress, secrets, registries, Dapr, revision mode (`properties.configuration`)	No. Applies to all revisions

A new revision gets a name suffix: auto-generated, or set with --revision-suffix v2.

Revision modes

Single (default): the newest healthy revision gets 100% of traffic, and the old one is deactivated once the new one is ready. That gives zero-downtime replacement.
Multiple: several revisions stay active. You split traffic by weight (for example 80/20) and can use labels for stable test URLs (<app>---<label>.<env-domain>).

Lifecycle states and operations

Operation	Effect
`revision activate` / `deactivate`	Starts or stops replicas of one revision (Multiple mode). A deactivated revision is kept but runs nothing
`revision restart`	Restarts the replicas of a revision, for example to pick up a changed secret
`containerapp stop` / `start`	Stops or starts the whole app. A stopped app isn't billed for compute
Scale to zero	`--min-replicas 0` means no replicas while idle. The log stream then says the revision is scaled to zero

Revision status combines Provisioning status (Provisioning, Provisioned, Failed) with Running status (Running, Processing, Degraded, Activating). Up to 100 inactive revisions are kept for rollback.

How it works

In Single mode a failed revision never takes traffic, so the previous one keeps serving. In Multiple mode you decide when traffic moves.

Hands-on

Azure portal

Open the container app and select Application > Revisions and replicas.
Select Choose revision mode and switch to Multiple to keep revisions side by side.
Enter traffic percentages per active revision and select Save.
Select a revision, then Restart or Deactivate. On Overview, use Stop or Start for the whole app.

Azure CLI

Azure CLI / Bash

az containerapp update -n quote-api -g quote-api-rg \
  --image quoteapiacr.azurecr.io/quote-api:v2 --revision-suffix v2

az containerapp revision set-mode -n quote-api -g quote-api-rg --mode multiple
az containerapp ingress traffic set -n quote-api -g quote-api-rg \
  --revision-weight quote-api--v1=80 quote-api--v2=20

az containerapp revision list -n quote-api -g quote-api-rg -o table
az containerapp revision restart -n quote-api -g quote-api-rg --revision quote-api--v2
az containerapp revision deactivate -n quote-api -g quote-api-rg --revision quote-api--v1
az containerapp revision label add -n quote-api -g quote-api-rg --label blue --revision quote-api--v2

az containerapp stop -n quote-api -g quote-api-rg
az containerapp start -n quote-api -g quote-api-rg

Python

from azure.identity import DefaultAzureCredential
from azure.mgmt.appcontainers import ContainerAppsAPIClient

client = ContainerAppsAPIClient(DefaultAzureCredential(), "<subscription-id>")
rg, app = "<resource-group>", "quote-api"

for rev in client.container_apps_revisions.list_revisions(rg, app):
    print(rev.name, rev.active, rev.traffic_weight, rev.running_state, rev.provisioning_state)

client.container_apps_revisions.restart_revision(rg, app, "quote-api--v2")

Exam traps

Goal	Use
Replace the app with zero downtime, no canary	Single revision mode
Canary or A/B test at 10%	Multiple mode plus `ingress traffic set`
Stable URL to test a revision before it gets traffic	Revision label
Pick up a rotated secret	`revision restart` (secrets don't create revisions)
Roll back	Reactivate the old revision and move its weight to 100

Quick review

Revisions are immutable snapshots of the template.
Single mode is the default: the newest healthy revision gets 100%.
Multiple mode gives weighted traffic splitting and labels.
Deactivate stops replicas but keeps the revision for rollback.
revision restart refreshes secrets on running replicas.
containerapp stop stops the whole app and its compute billing.
A degraded new revision never takes traffic in Single mode.

Manage the container app lifecycle