Migration hooks provide powerful custom automation capabilities that enable running custom code at specific points during the migration process. This chapter covers comprehensive hook development, deployment, and integration with migration workflows.

Overview: Enabling Custom Automation

What are Migration Hooks?

Migration hooks are Kubernetes resources that define custom automation to be executed during VM migration:

• Pre-migration Hooks: Execute before VM conversion begins
• Post-migration Hooks: Execute after VM migration completes
• Custom Logic: Handle migration-specific requirements unique to your environment
• Ansible-Based: Leverage Ansible playbooks for automation logic

Hook Execution Model

Hooks run as Kubernetes Jobs in the konveyor-forklift namespace:

1. Job Creation: Hook container is scheduled as a Kubernetes Job
2. Context Injection: Migration context is made available via mounted files
3. Playbook Execution: Ansible playbook runs with access to migration data
4. Result Handling: Job completion status determines hook success/failure

Common Use Cases

• Pre-migration: Application quiescing, backup creation, dependency checks
• Post-migration: Health validation, configuration updates, service restoration
• Integration: External system notifications, monitoring updates, compliance logging
• Troubleshooting: Debug information collection, state preservation

Hook Architecture and Context

Default Hook Image

The default hook runtime is based on Ansible Runner with Kubernetes integration:

• Default Image: quay.io/kubev2v/hook-runner (verified from command code)
• Based On: Ansible Runner with python-openshift and oc binary
• Capabilities: Full Ansible automation with Kubernetes API access
• Extensibility: Custom images supported for specialized requirements

Accessing Migration Context

Hooks receive migration context through mounted files:

plan.yml

Contains complete migration plan information:

• Plan metadata and configuration
• VM list and specifications
• Mapping configurations
• Provider references

workload.yml

Contains current VM (workload) specific data:

• VM properties and configuration
• IP addresses and network information
• Disk and storage details
• Migration-specific metadata

Hook Parameters

Hook creation supports comprehensive configuration verified from the command code:

Parameter	Flag	Description	Default
Image	--image, -i	Container image URL	quay.io/kubev2v/hook-runner
Playbook	--playbook	Ansible playbook content or @file	None
Service Account	--service-account	Kubernetes ServiceAccount	Default
Deadline	--deadline	Hook timeout in seconds	No timeout

How-To: Creating Hooks

Basic Hook Creation

# Create hook with inline playbook
kubectl mtv create hook --name simple-notification \
  --playbook "$(cat << 'EOF'
- hosts: localhost
  tasks:
  - name: Send notification
    debug:
      msg: "Migration hook executed for {{ workload.vm.name }}"
EOF
)"

Hook Creation with File Playbook

# Create playbook file
cat > database-backup.yml << 'EOF'
- name: Database Backup Hook
  hosts: localhost
  tasks:
  - name: Load migration context
    include_vars:
      file: plan.yml
      name: plan
  
  - name: Load workload context  
    include_vars:
      file: workload.yml
      name: workload
  
  - name: Create database backup
    shell: |
      mysqldump -h {{ workload.vm.ipaddress }} -u backup_user \
      --all-databases > /backup/{{ workload.vm.name }}-$(date +%Y%m%d).sql
    when: workload.vm.name is match('.*database.*')
EOF

# Create hook using file
kubectl mtv create hook --name database-backup \
  --playbook @database-backup.yml \
  --service-account migration-hooks-sa \
  --deadline 1800

Advanced Hook with Custom Image

# Create hook with custom image and extended capabilities
kubectl mtv create hook --name advanced-validation \
  --image registry.company.com/migration/custom-hook:v1.2 \
  --playbook @advanced-validation.yml \
  --service-account admin-hooks-sa \
  --deadline 3600

Detailed Hook Examples

Example 1: Database Backup Hook (Pre-migration)

Create the Playbook

# Save as db-backup-hook.yml
- name: Database Backup Pre-Migration Hook
  hosts: localhost
  tasks:
  - name: Load migration plan context
    include_vars:
      file: plan.yml
      name: plan

  - name: Load VM workload context
    include_vars:
      file: workload.yml
      name: workload

  - name: Create backup directory
    file:
      path: /backup/{{ plan.metadata.name }}
      state: directory
      mode: '0755'

  - name: Check if VM is database server
    set_fact:
      is_database: "{{ workload.vm.name | regex_search('(database|db|sql|mysql|postgres)', ignorecase=True) | bool }}"

  - name: Create database backup
    shell: |
      BACKUP_FILE="/backup/{{ plan.metadata.name }}/{{ workload.vm.name }}-backup-$(date +%Y%m%d_%H%M%S).sql"
      mysqldump -h {{ workload.vm.ipaddress }} -u {{ backup_user }} -p{{ backup_password }} \
        --single-transaction --routines --triggers --all-databases > "${BACKUP_FILE}"
      echo "Backup created: ${BACKUP_FILE}"
    environment:
      backup_user: "{{ lookup('kubernetes.core.k8s', api_version='v1', kind='Secret', namespace='migration', resource_name='db-credentials')['data']['username'] | b64decode }}"
      backup_password: "{{ lookup('kubernetes.core.k8s', api_version='v1', kind='Secret', namespace='migration', resource_name='db-credentials')['data']['password'] | b64decode }}"
    when: is_database

  - name: Store backup location in ConfigMap
    kubernetes.core.k8s:
      api_version: v1
      kind: ConfigMap
      name: "{{ plan.metadata.name }}-backups"
      namespace: migration-backups
      definition:
        data:
          "{{ workload.vm.name }}": "/backup/{{ plan.metadata.name }}/{{ workload.vm.name }}-backup-{{ ansible_date_time.epoch }}.sql"
    when: is_database

  - name: Log backup completion
    debug:
      msg: "Database backup completed for {{ workload.vm.name }}"
    when: is_database

Create the Hook

# Create database credentials secret
kubectl create secret generic db-credentials \
  --from-literal=username=backup_user \
  --from-literal=password=secure_backup_password \
  -n migration

# Create the hook
kubectl mtv create hook --name database-backup-pre \
  --playbook @db-backup-hook.yml \
  --service-account migration-admin \
  --deadline 1800

Example 2: Application Health Check Hook (Post-migration)

Create the Playbook

# Save as health-check-hook.yml
- name: Post-Migration Health Check
  hosts: localhost
  tasks:
  - name: Load migration contexts
    include_vars:
      file: "{{ item }}"
      name: "{{ item | basename | regex_replace('\\.yml$', '') }}"
    loop:
      - plan.yml
      - workload.yml

  - name: Wait for VM to be ready
    kubernetes.core.k8s_info:
      api_version: kubevirt.io/v1
      kind: VirtualMachine
      name: "{{ workload.vm.name }}"
      namespace: "{{ plan.spec.targetNamespace | default('default') }}"
      wait: true
      wait_condition:
        type: Ready
        status: 'True'
      wait_timeout: 600

  - name: Check application endpoints
    uri:
      url: "http://{{ workload.vm.ipaddress }}:{{ item.port }}{{ item.path }}"
      method: GET
      status_code: 200
      timeout: 30
    register: health_checks
    loop:
      - { port: 8080, path: "/health" }
      - { port: 8080, path: "/ready" }
      - { port: 9090, path: "/metrics" }
    ignore_errors: true

  - name: Validate service responses
    assert:
      that:
        - item.status == 200
      fail_msg: "Health check failed for {{ item.url }}"
      success_msg: "Health check passed for {{ item.url }}"
    loop: "{{ health_checks.results }}"
    when: item.status is defined

  - name: Update monitoring configuration
    kubernetes.core.k8s:
      api_version: v1
      kind: ConfigMap
      name: monitoring-targets
      namespace: monitoring
      definition:
        data:
          "{{ workload.vm.name }}": |
            - targets: ['{{ workload.vm.ipaddress }}:9090']
              labels:
                instance: '{{ workload.vm.name }}'
                environment: '{{ plan.metadata.labels.environment | default("production") }}'

  - name: Send notification
    uri:
      url: "{{ notification_webhook }}"
      method: POST
      body_format: json
      body:
        text: "Migration completed for {{ workload.vm.name }} - Health checks passed"
        vm: "{{ workload.vm.name }}"
        plan: "{{ plan.metadata.name }}"
        status: "healthy"
    vars:
      notification_webhook: "{{ lookup('kubernetes.core.k8s', api_version='v1', kind='Secret', namespace='migration', resource_name='notification-config')['data']['webhook_url'] | b64decode }}"

Create the Hook

# Create notification webhook secret
kubectl create secret generic notification-config \
  --from-literal=webhook_url=https://hooks.slack.com/services/YOUR/WEBHOOK/URL \
  -n migration

# Create the hook
kubectl mtv create hook --name health-check-post \
  --playbook @health-check-hook.yml \
  --service-account migration-monitor \
  --deadline 900

Example 3: Shell Script Hook Integration

Create Shell Script Hook

# Save as shell-script-hook.yml
- name: Shell Script Integration Hook
  hosts: localhost
  tasks:
  - name: Load migration context
    include_vars:
      file: workload.yml
      name: workload

  - name: Execute custom shell script
    script: |
      #!/bin/bash
      
      VM_NAME="{{ workload.vm.name }}"
      VM_IP="{{ workload.vm.ipaddress }}"
      PLAN_NAME="{{ plan.metadata.name | default('unknown') }}"
      
      echo "Processing VM: $VM_NAME (IP: $VM_IP) in plan: $PLAN_NAME"
      
      # Custom application-specific logic
      if [[ "$VM_NAME" == *"web"* ]]; then
        echo "Configuring web server post-migration..."
        # Update load balancer configuration
        curl -X POST "http://load-balancer.internal/api/servers" \
          -H "Content-Type: application/json" \
          -d "{\"name\":\"$VM_NAME\",\"ip\":\"$VM_IP\",\"status\":\"active\"}"
      fi
      
      if [[ "$VM_NAME" == *"database"* ]]; then
        echo "Validating database connectivity..."
        # Test database connection
        timeout 30 bash -c "until nc -z $VM_IP 3306; do sleep 1; done"
        echo "Database is responding on $VM_IP:3306"
      fi
      
      # Update external monitoring
      curl -X POST "http://monitoring.internal/api/targets" \
        -H "Authorization: Bearer $MONITORING_TOKEN" \
        -d "host=$VM_IP&name=$VM_NAME&plan=$PLAN_NAME"
    environment:
      MONITORING_TOKEN: "{{ lookup('kubernetes.core.k8s', api_version='v1', kind='Secret', namespace='migration', resource_name='monitoring-token')['data']['token'] | b64decode }}"
    register: script_result

  - name: Log script execution results
    debug:
      var: script_result.stdout_lines

Create and Use the Hook

# Create monitoring token secret
kubectl create secret generic monitoring-token \
  --from-literal=token=your-monitoring-api-token \
  -n migration

# Create the hook
kubectl mtv create hook --name shell-integration \
  --playbook @shell-script-hook.yml \
  --service-account migration-integration \
  --deadline 600

Adding Hooks via Plan Creation Flags

Plan-Level Hook Integration

Plan creation supports adding hooks to all VMs in the plan:

# Add pre-hook to all VMs in the plan
kubectl mtv create plan --name hooked-migration \
  --source vsphere-prod \
  --pre-hook database-backup-pre \
  --vms "database-01,database-02,app-server-01"

# Add both pre and post hooks
kubectl mtv create plan --name comprehensive-hooks \
  --source vsphere-prod \
  --pre-hook preparation-hook \
  --post-hook validation-hook \
  --vms "where name ~= '.*prod.*'"

# Combined with other migration settings
kubectl mtv create plan --name production-with-hooks \
  --source vsphere-prod \
  --target-namespace production \
  --migration-type warm \
  --network-mapping prod-network-map \
  --storage-mapping prod-storage-map \
  --pre-hook backup-and-quiesce \
  --post-hook health-and-notify \
  --vms @production-vms.yaml

Hook Execution Order

When multiple hooks are configured:

1. Pre-hooks execute: Before VM conversion begins
2. Migration proceeds: VM conversion and data transfer
3. Post-hooks execute: After VM migration completes

Managing Hooks via PlanVM Configuration

Per-VM Hook Configuration

Individual VMs can have specific hooks using the PlanVMS format:

# vm-specific-hooks.yaml
- name: database-primary
  targetName: db-prod-01
  hooks:
  - step: PreHook
    hook:
      name: database-backup-pre
      namespace: migration-hooks
  - step: PostHook
    hook:
      name: database-health-check
      namespace: migration-hooks

- name: web-server-01
  targetName: web-prod-01
  hooks:
  - step: PreHook
    hook:
      name: web-drain-connections
      namespace: migration-hooks
  - step: PostHook
    hook:
      name: web-health-check
      namespace: migration-hooks

- name: cache-server-01
  targetName: cache-prod-01
  hooks:
  - step: PostHook
    hook:
      name: cache-warmup
      namespace: migration-hooks

Using VM-Specific Hooks

# Create plan with VM-specific hooks
kubectl mtv create plan --name vm-specific-hooks \
  --source vsphere-prod \
  --vms @vm-specific-hooks.yaml \
  --network-mapping prod-network-map \
  --storage-mapping prod-storage-map

Hook Management via Plan Patching

Hooks can be added or modified after plan creation using the patch planvm command:

# Add a pre-migration hook to a specific VM
kubectl mtv patch planvm --plan-name existing-plan \
  --vm-name additional-vm \
  --add-pre-hook new-preparation-hook

# Add a post-migration hook to a specific VM
kubectl mtv patch planvm --plan-name existing-plan \
  --vm-name additional-vm \
  --add-post-hook health-check-post

# Remove a specific hook from a VM
kubectl mtv patch planvm --plan-name existing-plan \
  --vm-name additional-vm \
  --remove-hook new-preparation-hook

# Clear all hooks from a VM
kubectl mtv patch planvm --plan-name existing-plan \
  --vm-name additional-vm \
  --clear-hooks

Advanced Hook Development

Custom Hook Images

Building Custom Hook Image

# Custom hook image with additional tools
FROM quay.io/kubev2v/hook-runner:latest

# Install additional packages
USER root
RUN dnf install -y postgresql mysql jq curl wget && \
    dnf clean all

# Install custom Python packages
RUN pip3 install psycopg2-binary pymongo redis

# Add custom scripts
COPY scripts/ /usr/local/bin/
RUN chmod +x /usr/local/bin/*

# Return to ansible user
USER ansible

Using Custom Image

# Build and push custom image
docker build -t registry.company.com/migration/custom-hook:v1.0 .
docker push registry.company.com/migration/custom-hook:v1.0

# Create hook with custom image
kubectl mtv create hook --name custom-database-hook \
  --image registry.company.com/migration/custom-hook:v1.0 \
  --playbook @database-migration-hook.yml \
  --service-account database-migration-sa

Hook Development Best Practices

Error Handling and Logging

# Error handling in hook playbooks
- name: Robust Hook with Error Handling
  hosts: localhost
  tasks:
  - name: Set failure flag
    set_fact:
      hook_failed: false

  - name: Critical operation with error handling
    block:
      - name: Perform critical task
        # Task that might fail
        shell: risky_command_here
        register: result
        
    rescue:
      - name: Handle failure
        set_fact:
          hook_failed: true
          
      - name: Log failure details
        debug:
          msg: "Hook failed: {{ ansible_failed_result.msg }}"
          
      - name: Send failure notification
        # Notification logic here
        
    always:
      - name: Cleanup operations
        # Cleanup logic here

  - name: Fail hook if critical operations failed
    fail:
      msg: "Hook execution failed"
    when: hook_failed

Secret and ConfigMap Access

# Secure credential access in hooks
- name: Secure Credential Management
  hosts: localhost
  tasks:
  - name: Load database credentials
    kubernetes.core.k8s_info:
      api_version: v1
      kind: Secret
      name: database-credentials
      namespace: migration-secrets
    register: db_creds

  - name: Use credentials securely
    # Use credentials from db_creds.resources[0].data
    no_log: true  # Don't log sensitive operations

Timeout and Deadline Management

# Timeout management in hook operations
- name: Hook with Timeout Management
  hosts: localhost
  tasks:
  - name: Operation with timeout
    async: 600  # 10 minute timeout
    poll: 10    # Check every 10 seconds
    # Long running operation here
    
  - name: Wait for background task
    async_status:
      jid: "{{ operation_result.ansible_job_id }}"
    register: job_result
    until: job_result.finished
    retries: 60
    delay: 10

Hook Integration Scenarios

Scenario 1: Enterprise Database Migration

# Complete database migration hook workflow
- name: Enterprise Database Migration Hooks
  hosts: localhost
  vars:
    notification_webhook: "{{ lookup('env', 'NOTIFICATION_WEBHOOK') }}"
    
  tasks:
  # Pre-migration tasks
  - name: Database pre-migration validation
    block:
      - name: Check database connectivity
        # Validate source database accessibility
        
      - name: Create backup
        # Full database backup
        
      - name: Quiesce applications
        # Stop application connections
        
      - name: Validate backup integrity
        # Verify backup completed successfully

  # Post-migration tasks  
  - name: Database post-migration validation
    block:
      - name: Validate target database startup
        # Ensure database started correctly
        
      - name: Run data integrity checks
        # Verify data migration completeness
        
      - name: Update DNS records
        # Point applications to new database
        
      - name: Resume application connections
        # Allow applications to reconnect
        
      - name: Send completion notification
        # Notify operations team

Scenario 2: Multi-Tier Application Migration

# Coordinated multi-tier application migration
- name: Multi-Tier Application Migration
  hosts: localhost
  tasks:
  - name: Load balancer update
    when: workload.vm.name is match('.*web.*')
    # Remove from load balancer (pre) / Add to load balancer (post)
    
  - name: Session store migration  
    when: workload.vm.name is match('.*cache.*')
    # Handle session data migration
    
  - name: Database coordination
    when: workload.vm.name is match('.*database.*')
    # Database-specific migration logic
    
  - name: Service discovery update
    # Update service registry entries

Scenario 3: Compliance and Auditing

# Compliance and audit trail hooks
- name: Compliance Migration Hook
  hosts: localhost
  tasks:
  - name: Log migration start
    # Create audit trail entry
    
  - name: Validate security compliance
    # Check security configurations
    
  - name: Document configuration changes
    # Record all migration changes
    
  - name: Generate compliance report
    # Create detailed compliance documentation
    
  - name: Store audit evidence
    # Archive all compliance artifacts

Hook Monitoring and Troubleshooting

Hook Execution Monitoring

# Monitor hook job execution
kubectl get jobs -n konveyor-forklift | grep hook

# Check hook pod logs
kubectl logs -n konveyor-forklift job/hook-job-name

# Monitor hook completion
kubectl get jobs -n konveyor-forklift -w

Hook Debugging

# Describe failed hook job
kubectl describe job hook-job-name -n konveyor-forklift

# Get hook pod details
kubectl get pods -n konveyor-forklift -l job-name=hook-job-name

# Access hook execution environment
kubectl exec -it hook-pod-name -n konveyor-forklift -- /bin/bash

# Check hook context files
kubectl exec hook-pod-name -n konveyor-forklift -- cat /tmp/hook/plan.yml
kubectl exec hook-pod-name -n konveyor-forklift -- cat /tmp/hook/workload.yml

Common Hook Issues

Timeout Issues

# Check hook deadline configuration
kubectl describe hook hook-name

# Monitor long-running hooks
kubectl logs -f job/hook-job-name -n konveyor-forklift

Permission Issues

# Verify ServiceAccount permissions
kubectl describe serviceaccount hook-service-account -n konveyor-forklift

# Check RBAC configurations
kubectl auth can-i create configmaps --as=system:serviceaccount:konveyor-forklift:hook-service-account

Playbook Errors

# Validate playbook syntax
ansible-playbook --syntax-check playbook.yml

# Test playbook locally (with mock context)
ansible-playbook -i localhost, playbook.yml

Hook Security and Best Practices

Security Considerations

1. Least Privilege: Use minimal required ServiceAccount permissions
2. Secret Management: Store sensitive data in Kubernetes Secrets
3. Network Isolation: Limit hook network access when possible
4. Image Security: Use trusted, regularly updated hook images

Operational Best Practices

1. Testing: Thoroughly test hooks in non-production environments
2. Idempotency: Design hooks to be safely re-runnable
3. Monitoring: Implement comprehensive hook execution monitoring
4. Documentation: Maintain clear hook documentation and runbooks

Performance Optimization

1. Efficient Playbooks: Minimize unnecessary operations in playbooks
2. Parallel Execution: Use Ansible parallel features where appropriate
3. Resource Limits: Set appropriate resource limits on hook jobs
4. Cleanup: Implement proper cleanup for temporary resources

Next Steps

After mastering migration hooks:

1. Advanced Plan Management: Learn dynamic plan modification in Chapter 18: Advanced Plan Patching
2. Execute Migrations: Manage complete migration lifecycle in Chapter 19: Plan Lifecycle Execution
3. Troubleshooting: Master debugging techniques in Chapter 20: Debugging and Troubleshooting
4. Best Practices: Learn operational excellence in Chapter 21: Best Practices and Security

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Previous: Chapter 16: Migration Process Optimization
Next: Chapter 18: Advanced Plan Patching