# Deployments

Source: https://docs.ops0.com/docs/kubernetes/deployments

Manage Kubernetes Deployments with scaling, rolling restarts, and rollout controls.

## Deployment List

View all deployments in a cluster with status, replicas, and availability.

| Column | Description |
|--------|-------------|
| **Name** | Deployment name |
| **Namespace** | Kubernetes namespace |
| **Replicas** | Desired / Current / Available |
| **Strategy** | RollingUpdate or Recreate |
| **Age** | Time since creation |

## Deployment Details

Click a deployment to view:
- Deployment strategy and settings
- ReplicaSet history
- Pod template spec
- Rollout status
- Conditions and events

## Scaling Deployments

**Via UI**:
1. Open deployment detail panel
2. Use replica slider or enter count
3. Click "Scale" to apply
4. Watch rollout progress

**Scaling Behavior**:
- New pods created gradually
- Old pods terminated after new ones are ready
- Max surge / max unavailable controls

## Restarting Deployments

Perform a rolling restart without changing configuration:

1. Click "Restart" on deployment
2. Confirm action
3. Pods restart one-by-one

**Use Cases**:
- Force pull latest image (imagePullPolicy: Always)
- Clear in-memory cache
- Apply ConfigMap/Secret changes

## Rollout History

View previous ReplicaSets and revisions:

| Revision | Change Cause | Created | Replicas |
|----------|--------------|---------|----------|
| 3 | Update to v1.2.3 | 2h ago | 3 |
| 2 | Update to v1.2.2 | 1d ago | 3 |
| 1 | Initial deployment | 5d ago | 2 |

## Rollback Deployments

Revert to a previous revision:

1. Click "Rollback" on deployment
2. Select revision number
3. Confirm rollback
4. Watch rollout to previous version

## Rollout Status

Monitor ongoing rollouts:

- Progress percentage
- Pods updated / total
- Conditions (Progressing, Available, ReplicaFailure)

## Deployment Strategies

### RollingUpdate (Default)

Gradually replace old pods with new ones:

- `maxSurge`: Max extra pods during update
- `maxUnavailable`: Max pods down during update

### Recreate

Terminate all old pods before creating new ones:

- Causes downtime
- Use for stateful apps that can't run multiple versions

## Troubleshooting

| Issue | Cause | Solution |
|-------|-------|----------|
| **Rollout stuck** | ImagePullBackOff or CrashLoop | Check pod events and logs |
| **Replicas not scaling** | Resource quota exceeded | Increase namespace quota or reduce requests |
| **Old ReplicaSets not deleted** | RevisionHistoryLimit | Set limit in deployment spec |

---

## Example: Scaling a Deployment

### Before Scaling

```
Deployment: api-gateway
Namespace:  production
Replicas:   3/3
Strategy:   RollingUpdate (maxSurge: 1, maxUnavailable: 0)
```

### Scaling to 5 Replicas

1. Open deployment detail
2. Move slider to 5
3. Click "Scale"

**Rollout Process**:
```
10:30:00  Scaling api-gateway from 3 to 5 replicas
10:30:01  Creating pod api-gateway-7d9f8c6b4d-4th-pod
10:30:02  Creating pod api-gateway-7d9f8c6b4d-5th-pod
10:30:15  Pod 4/5 Running and Ready
10:30:18  Pod 5/5 Running and Ready
10:30:18  Deployment successfully scaled to 5 replicas
```

### After Scaling

```
Deployment: api-gateway
Namespace:  production
Replicas:   5/5
Pods:       api-gateway-7d9f8c6b4d-2xkjp (Running)
            api-gateway-7d9f8c6b4d-9vwrt (Running)
            api-gateway-7d9f8c6b4d-kp3mn (Running)
            api-gateway-7d9f8c6b4d-4th-pod (Running)
            api-gateway-7d9f8c6b4d-5th-pod (Running)
```

---

## Example: Rolling Restart

### Scenario

ConfigMap updated with new database connection pool size. Pods need restart to pick up changes.

### Restart Workflow

1. Click "Restart" on deployment
2. Confirm: "This will perform a rolling restart of all pods"
3. Rollout begins

**Restart Process**:
```
10:45:00  Updating pod template with restart annotation
10:45:01  Terminating pod api-gateway-7d9f8c6b4d-2xkjp
10:45:02  Creating new pod api-gateway-new-rs-abc123
10:45:15  New pod Running and Ready
10:45:16  Terminating pod api-gateway-7d9f8c6b4d-9vwrt
10:45:17  Creating new pod api-gateway-new-rs-def456
...
10:47:00  All 5 pods restarted successfully
```

### Result

All pods running with new ReplicaSet, ConfigMap changes applied.