Spring Boot Multitenancy – Day 1: Wiring the Skeleton

Summary:

Thread-safety, routing, and resolver strategy — Day 1 of building a Spring Boot multitenancy starter from scratch. A lot of thinking, a lot of tests, and the first structure is now alive.

After Day 0’s fire, Day 1 was all about grounding the idea into structure. This was the first time the code felt “real.”

My focus: building it the way Spring Boot would — if it handled multitenancy natively.

Day 1 of My Spring Boot Multitenancy Starter: Contexts, Filters, and Auto-Config

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🎯 Goal

Scaffold the foundational skeleton of a plug-and-play Spring Boot multitenancy starter — just like how Spring Boot itself feels.

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🧱 What I Built Today

🧠 Core Concepts Implemented

• Thread-safe TenantContextHolder using ThreadLocal

• Pluggable TenantResolver interface (subdomain strategy default)

• TenantFilter to set/clear context per request

• TenantDefinition (record) to hold metadata like tenantId, creds, etc.

• TenantRegistry + InMemoryTenantRegistry to register and fetch tenants

• TenantRoutingDataSource to delegate dynamically

• DataSourceFactory to build isolated HikariDataSources per tenant

• Custom YAML props via HikariTenantPoolProperties

• Spring Boot AutoConfig:

  • MultitenancyAutoConfiguration

  • TenantRegistryAutoConfig

  • TenantDataSourceAutoConfig

• @EnableMultitenancy annotation to wire everything

🧪 Tests Added

• ✅ TenantContextTest — validate isolation

• ✅ TenantContextLeakTest — simulate misuse

• ✅ TenantContextConcurrencyTest — 100-thread stress test

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🧠 What I Learned Today

🔹 Java Concurrency

Built a cheat-sheet on:

• ThreadLocal

• ExecutorService, CountDownLatch, AtomicBoolean

🔹 Maven Structuring

• Local publish using mvn install

• Clean starter module structure

• IDE tricks for IntelliJ Maven + .iml

🔹 Spring Boot Internals

• @ImportAutoConfiguration flow

• AutoConfiguration.imports mechanism

• Clean starter design, Spring-style

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📁 Folder Structure

multi-tenant-springboot-starter/
├── pom.xml
├── starter/
│ ├── pom.xml
│ └── src/main/java/org/nirvikalpa/...
│ └── src/test/java/org/nirvikalpa/...
├── demo/ # coming tomorrow

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🧭 Next Steps (Day 2 Plan)

• Build a tenant onboarding workflow

• Wire demo app to consume the starter

• Expose /health per-tenant endpoint

• Reflect in Ego Log #002

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🔗 Repo: Github Link

Thanks for following my journey.
This is more than code — it's my architectural diary.