1# Pre-Migration Assessment for Spring Boot to Azure Container Apps
2 
3## Local State Assessment
4 
5| Issue | Impact | Solution |
6|-------|--------|----------|
7| Singleton patterns | Multiple instances may run during updates | Refactor to stateless design |
8| In-memory sessions | Lost during restarts/scaling | Migrate to Azure Cache for Redis |
9| Local caching | Not shared across replicas | Use Azure Cache for Redis with Spring Data Redis |
10| File-based state | Lost on restart | Migrate to Azure Cosmos DB, Azure SQL, or Azure Storage |
11 
12**State Migration Options:**
13- **Azure Cache for Redis**: Session data, distributed caching
14- **Azure Cosmos DB**: NoSQL data, document storage
15- **Azure SQL/MySQL/PostgreSQL**: Relational data
16- **Azure Storage Blobs**: Unstructured data, serialized objects
17 
18## File System Usage
19 
20| Pattern | Container Apps Solution |
21|---------|------------------------|
22| Temporary files | Ephemeral storage (automatic, deleted on restart) |
23| Shared persistent data | Azure Files storage mounts |
24| Static content serving | Azure Blob Storage + Azure CDN |
25| User uploads | Azure Blob Storage with Azure Function triggers |
26 
27## Platform Compatibility
28 
29### Supported Java Versions
30- **For Spring Boot 2.x source apps**: Java 8 or 11 supported for assessment
31- **For Spring Boot 3.x target apps**: Java 17 or 21 required (verify with `java -version`)
32 
33### Spring Boot Version Requirements
34- **Recommended target**: Spring Boot 3.x (requires Java 17+)
35- **Supported source**: Spring Boot 2.x on Java 8/11 → plan upgrade to Java 17+ and follow [Spring Boot 3.0 Migration Guide](https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.0-Migration-Guide)
36 
37### Spring Cloud Compatibility
38- Verify Spring Cloud version matches Spring Boot 3.x requirements
39- See [Spring Cloud versions](https://spring.io/projects/spring-cloud#overview)
40 
41## External Resources Inventory
42 
43Inventory all external dependencies. See [spring-dependency-patterns.md](spring-dependency-patterns.md) for configuration examples (databases, message brokers, caches).
44 
45### Identity Providers
46 
47| Provider | Configuration |
48|----------|---------------|
49| OAuth2 | Spring Security reference docs |
50| Auth0 | Auth0 Spring Security documentation |
51| PingFederate | Spring Security SAML 2.0/OIDC docs, PingIdentity docs |
52| Microsoft Entra ID | Update redirect URIs to new Container Apps FQDN |
53 
54## Scheduled Jobs Assessment
55 
56| Job Type | Container Apps Solution |
57|----------|------------------------|
58| Unix cron jobs | Azure Container Apps Jobs (ephemeral) |
59| Spring Batch tasks | Azure Container Apps Jobs |
60| Quartz scheduler | Long-running app (handle scale-out race conditions) |
61| Scheduled @Scheduled methods | Long-running app (handle multiple instances) |
62 
63## Configuration & Secrets
64 
65### Port Configuration
66- Default: 8080
67- Change via `server.port` or `SERVER_PORT` environment variable
68- Configure in Container Apps ingress settings
69 
70### Secrets Checklist
711. Inventory all secrets in application.properties/application.yml
722. Document database passwords, API keys, connection strings
733. Plan migration to Azure Key Vault
744. Update app to use Key Vault references or environment variables
75 
76### Certificates
77- Run `keytool -list -v -keystore <path>` to document SSL certificates
78- Plan migration to Azure Key Vault or Container Apps managed certificates
79 
80## Deployment Architecture
81 
82**Document current state:**
83- Number of instances
84- CPU per instance (vCPU)
85- RAM per instance (GiB)
86- Regional distribution
87- Uptime requirements/SLA
88 
89**Container Apps Limits:**
90- Max 4 vCPU per container
91- Max 8 GiB RAM per container
92- Max 300 replicas per revision
93 
94## Assessment Checklist
95 
96- [ ] Identified all local state and planned migration to external storage
97- [ ] Reviewed file system usage and selected storage solution
98- [ ] Verified Java version compatibility (17+ for Spring Boot 3.x target; 8/11 for source assessment only)
99- [ ] Confirmed Spring Boot 3.x or planned upgrade
100- [ ] Inventoried databases (MySQL, PostgreSQL, MongoDB, Cosmos DB)
101- [ ] Inventoried message brokers (ActiveMQ, IBM MQ, Azure Service Bus)
102- [ ] Inventoried external caches (Redis)
103- [ ] Documented identity providers (OAuth2, SAML, Entra ID)
104- [ ] Identified scheduled jobs and selected execution model
105- [ ] Listed all configuration secrets for Key Vault migration
106- [ ] Documented SSL certificates
107- [ ] Recorded current deployment architecture (instances, CPU, RAM)
108- [ ] Reviewed logging configuration (console vs. file)
109- [ ] Identified APM tools (Application Insights, custom agents)
110 
111## Complexity Guidelines
112 
113**Low Complexity:**
114- Stateless Spring Boot app with external database
115- No scheduled jobs or simple @Scheduled tasks
116- Standard Java version (11, 17, 21)
117- OAuth2/SAML authentication
118 
119**Medium Complexity:**
120- In-memory session state requiring Redis migration
121- File system writes requiring Azure Files or Blob Storage
122- Spring Boot 2.x requiring upgrade to 3.x
123- Message broker integration (ActiveMQ, Service Bus)
124- Scheduled jobs requiring Jobs configuration
125 
126**High Complexity:**
127- Multiple stateful components (local cache, sessions, file storage)
128- Custom JVM agents or APM integrations
129- Java 8 requiring upgrade to 11+
130- Complex scheduled jobs with coordination requirements
131- Multi-region deployment with traffic distribution
132- Custom identity provider federation
133