1# Container Apps Revision Management
2 
3Revisions are immutable snapshots of a Container App version. Use them for blue/green deployments, canary releases, and instant rollback.
4 
5## Revision Modes
6 
7| Mode | Behavior | Use Case |
8|------|----------|----------|
9| `Single` | New revision replaces old immediately | Simple apps, dev/test |
10| `Multiple` | Multiple revisions run simultaneously with traffic splitting | Production blue/green, canary |
11 
12## Setting Revision Mode (Bicep)
13 
14```bicep
15resource containerApp 'Microsoft.App/containerApps@2024-03-01' = {
16  name: appName
17  location: location
18  properties: {
19    configuration: {
20      activeRevisionsMode: 'Multiple'
21      ingress: {
22        external: true
23        targetPort: 8080
24        traffic: [
25          { latestRevision: true, weight: 100 }
26        ]
27      }
28    }
29  }
30}
31```
32 
33> 💡 **Tip:** In Bicep/ARM deployments, you typically can't predictably target a specific new revision name. Use `latestRevision: true` in Bicep for initial deployment, then configure traffic splitting or labels via CLI after the new revision is created.
34 
35> ⚠️ **Warning:** For blue/green workflows, you must first pin traffic to a named revision before deploying a new one. With `latestRevision: true, weight: 100`, new revisions automatically receive all traffic — there is no validation window.
36 
37## Traffic Splitting Patterns
38 
39### Blue/Green Deployment
40 
41Pin traffic to the current revision, deploy a new one, validate, then switch:
42 
43```bash
44# Deploy new revision and capture its name from the update output
45NEW_REV=$(az containerapp update -n $APP -g $RG --image $NEW_IMAGE \
46  --query properties.latestRevisionName -o tsv)
47 
48# Test the new revision directly via its revision-specific URL
49az containerapp revision list -n $APP -g $RG -o table
50 
51# Switch 100% traffic to the new revision
52az containerapp ingress traffic set -n $APP -g $RG \
53  --revision-weight "$NEW_REV=100"
54```
55 
56### Canary Release
57 
58Gradually shift traffic to validate the new revision under load:
59 
60| Phase | Current | Canary | Duration |
61|-------|---------|--------|----------|
62| 1 | 90% | 10% | 15 min |
63| 2 | 50% | 50% | 30 min |
64| 3 | 0% | 100% | — |
65 
66```bash
67# List revisions to identify current stable and new canary
68az containerapp revision list -n $APP -g $RG -o table
69 
70STABLE_REV=<stable-revision-name>
71CANARY_REV=<canary-revision-name>
72 
73az containerapp ingress traffic set -n $APP -g $RG \
74  --revision-weight "$STABLE_REV=90" "$CANARY_REV=10"
75```
76 
77### Label-Based Routing
78 
79Use labels instead of revision names for stable references:
80 
81```bash
82# Assign labels
83az containerapp revision label add -n $APP -g $RG \
84  --label stable --revision "$APP--v1"
85az containerapp revision label add -n $APP -g $RG \
86  --label canary --revision "$APP--v2"
87 
88# Route by label
89az containerapp ingress traffic set -n $APP -g $RG \
90  --label-weight stable=80 canary=20
91```
92 
93> 💡 **Tip:** Label-based routing lets you swap revision targets without changing traffic rules.
94 
95## Rollback
96 
97Revert instantly by redirecting all traffic to a known-good revision (e.g., one labeled `stable`):
98 
99```bash
100# List active revisions and identify the known-good one
101az containerapp revision list -n $APP -g $RG -o table
102 
103# Roll back using label-based routing (preferred)
104az containerapp ingress traffic set -n $APP -g $RG \
105  --label-weight stable=100
106 
107# Or roll back to a specific revision by name
108az containerapp ingress traffic set -n $APP -g $RG \
109  --revision-weight "<known-good-revision-name>=100"
110```
111 
112## Revision Lifecycle
113 
114| Action | Command |
115|--------|---------|
116| List revisions | `az containerapp revision list -n $APP -g $RG` |
117| Show revision details | `az containerapp revision show -n $APP -g $RG --revision $REV` |
118| Activate a revision | `az containerapp revision activate -n $APP -g $RG --revision $REV` |
119| Deactivate a revision | `az containerapp revision deactivate -n $APP -g $RG --revision $REV` |
120| Restart a revision | `az containerapp revision restart -n $APP -g $RG --revision $REV` |
121 
122> ⚠️ **Warning:** Deactivated revisions cannot receive traffic. Reactivate before routing traffic to them.
123 
124## Terraform Traffic Config
125 
126```hcl
127resource "azurerm_container_app" "app" {
128  name                         = var.app_name
129  container_app_environment_id = azurerm_container_app_environment.env.id
130  resource_group_name          = azurerm_resource_group.rg.name
131  revision_mode                = "Multiple"
132 
133  ingress {
134    external_enabled = true
135    target_port      = 8080
136    traffic_weight {
137      label           = "stable"
138      revision_suffix = "v1"
139      percentage      = 80
140    }
141    traffic_weight {
142      label           = "canary"
143      revision_suffix = "v2"
144      percentage      = 20
145    }
146  }
147}
148```
149 
150## Recommendations
151 
152| Scenario | Revision Mode | Traffic Strategy |
153|----------|---------------|------------------|
154| Dev/Test | Single | N/A — auto-replace |
155| Prod API | Multiple | Blue/green with instant swap |
156| High-risk change | Multiple | Canary (10% → 50% → 100%) |
157| Feature flags | Multiple | Label-based routing |
158