Pre-Migration Assessment for Spring Boot to Azure Container Apps
Local State Assessment
| Issue | Impact | Solution |
|---|---|---|
| Singleton patterns | Multiple instances may run during updates | Refactor to stateless design |
| In-memory sessions | Lost during restarts/scaling | Migrate to Azure Cache for Redis |
| Local caching | Not shared across replicas | Use Azure Cache for Redis with Spring Data Redis |
| File-based state | Lost on restart | Migrate to Azure Cosmos DB, Azure SQL, or Azure Storage |
State Migration Options:
- Azure Cache for Redis: Session data, distributed caching
- Azure Cosmos DB: NoSQL data, document storage
- Azure SQL/MySQL/PostgreSQL: Relational data
- Azure Storage Blobs: Unstructured data, serialized objects
File System Usage
| Pattern | Container Apps Solution |
|---|---|
| Temporary files | Ephemeral storage (automatic, deleted on restart) |
| Shared persistent data | Azure Files storage mounts |
| Static content serving | Azure Blob Storage + Azure CDN |
| User uploads | Azure Blob Storage with Azure Function triggers |
Platform Compatibility
Supported Java Versions
- For Spring Boot 2.x source apps: Java 8 or 11 supported for assessment
- For Spring Boot 3.x target apps: Java 17 or 21 required (verify with
java -version)
Spring Boot Version Requirements
- Recommended target: Spring Boot 3.x (requires Java 17+)
- Supported source: Spring Boot 2.x on Java 8/11 → plan upgrade to Java 17+ and follow Spring Boot 3.0 Migration Guide
Spring Cloud Compatibility
- Verify Spring Cloud version matches Spring Boot 3.x requirements
- See Spring Cloud versions
External Resources Inventory
Inventory all external dependencies. See spring-dependency-patterns.md for configuration examples (databases, message brokers, caches).
Identity Providers
| Provider | Configuration |
|---|---|
| OAuth2 | Spring Security reference docs |
| Auth0 | Auth0 Spring Security documentation |
| PingFederate | Spring Security SAML 2.0/OIDC docs, PingIdentity docs |
| Microsoft Entra ID | Update redirect URIs to new Container Apps FQDN |
Scheduled Jobs Assessment
| Job Type | Container Apps Solution |
|---|---|
| Unix cron jobs | Azure Container Apps Jobs (ephemeral) |
| Spring Batch tasks | Azure Container Apps Jobs |
| Quartz scheduler | Long-running app (handle scale-out race conditions) |
| Scheduled @Scheduled methods | Long-running app (handle multiple instances) |
Configuration & Secrets
Port Configuration
- Default: 8080
- Change via
server.portorSERVER_PORTenvironment variable - Configure in Container Apps ingress settings
Secrets Checklist
- Inventory all secrets in application.properties/application.yml
- Document database passwords, API keys, connection strings
- Plan migration to Azure Key Vault
- Update app to use Key Vault references or environment variables
Certificates
- Run
keytool -list -v -keystore <path>to document SSL certificates - Plan migration to Azure Key Vault or Container Apps managed certificates
Deployment Architecture
Document current state:
- Number of instances
- CPU per instance (vCPU)
- RAM per instance (GiB)
- Regional distribution
- Uptime requirements/SLA
Container Apps Limits:
- Max 4 vCPU per container
- Max 8 GiB RAM per container
- Max 300 replicas per revision
Assessment Checklist
- Identified all local state and planned migration to external storage
- Reviewed file system usage and selected storage solution
- Verified Java version compatibility (17+ for Spring Boot 3.x target; 8/11 for source assessment only)
- Confirmed Spring Boot 3.x or planned upgrade
- Inventoried databases (MySQL, PostgreSQL, MongoDB, Cosmos DB)
- Inventoried message brokers (ActiveMQ, IBM MQ, Azure Service Bus)
- Inventoried external caches (Redis)
- Documented identity providers (OAuth2, SAML, Entra ID)
- Identified scheduled jobs and selected execution model
- Listed all configuration secrets for Key Vault migration
- Documented SSL certificates
- Recorded current deployment architecture (instances, CPU, RAM)
- Reviewed logging configuration (console vs. file)
- Identified APM tools (Application Insights, custom agents)
Complexity Guidelines
Low Complexity:
- Stateless Spring Boot app with external database
- No scheduled jobs or simple @Scheduled tasks
- Standard Java version (11, 17, 21)
- OAuth2/SAML authentication
Medium Complexity:
- In-memory session state requiring Redis migration
- File system writes requiring Azure Files or Blob Storage
- Spring Boot 2.x requiring upgrade to 3.x
- Message broker integration (ActiveMQ, Service Bus)
- Scheduled jobs requiring Jobs configuration
High Complexity:
- Multiple stateful components (local cache, sessions, file storage)
- Custom JVM agents or APM integrations
- Java 8 requiring upgrade to 11+
- Complex scheduled jobs with coordination requirements
- Multi-region deployment with traffic distribution
- Custom identity provider federation