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Add persistent store implementation (replace in-memory store)

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
go
Domain
backend, databases

Research direction

Start with pkg/domain/environment/repository.go, pkg/infra/store/memory.go, and its memory_test.go to understand the five-method contract, copy semantics, and error behavior. Then inspect cmd/waggle/main.go:59 for wiring and configuration. Done means a persistent implementation, parallel table-driven coverage, context handling, and updated default wiring satisfy the listed acceptance criteria.

Written by the indexing model from the issue text.

Description

enhancement

Summary

Waggle currently uses an in-memory MemoryStore (pkg/infra/store/memory.go) that implements the environment.Repository interface. All environment state is lost on restart. We need a persistent store so environments can survive server restarts and support operational use cases like auditing.

Current Architecture (DDD)

The codebase follows Domain-Driven Design with clean separation:

  • Domain interface: pkg/domain/environment/repository.go defines Repository with 5 methods: Save, FindByID, FindAll, Delete, Count
  • Current adapter: pkg/infra/store/memory.go implements Repository with a map[string]*Environment + sync.RWMutex
  • Service layer: pkg/service/environment.go depends on the Repository interface (not the concrete store)
  • Wiring: cmd/waggle/main.go:59 instantiates store.NewMemoryStore() and injects it

The service layer calls Save() after every state transition (Creating, Running, Error, Destroying) and Delete() on destroy. FindByID() and FindAll() are read-only. All methods accept context.Context.

Critical contract: copy semantics

The MemoryStore returns copies on both Save() and FindByID() to prevent aliasing bugs. The persistent store must maintain equivalent isolation — a mutated *Environment returned from FindByID() must not affect the stored state until Save() is called again.

Approach

New adapter in pkg/infra/store/

Add a new file (e.g., bolt.go or sqlite.go) implementing environment.Repository. The implementation choice depends on requirements:

Option Pros Cons
bbolt (embedded KV) Zero config, single file, no external deps No SQL, limited query flexibility
SQLite (embedded SQL) SQL queries, mature, well-understood CGO dependency (unless modernc)

For a single-binary MCP server, bbolt or modernc SQLite (pure Go) are good fits — no external database to manage.

Serialization

The Environment struct needs to be serialized/deserialized. Options:

  • JSON (simple, human-readable, already used in MCP responses)
  • Protobuf (compact, schema-versioned — overkill for now)
Wiring change

Only cmd/waggle/main.go needs to change:

// Before
repo := store.NewMemoryStore()

// After (example with bbolt)
repo, err := store.NewBoltStore(cfg.DataDir + "/waggle.db")
if err != nil {
    return fmt.Errorf("open store: %w", err)
}
defer repo.Close()
Configuration

Add a WAGGLE_STORE_PATH env var (or reuse DataDir) for the database file path. The MemoryStore should remain available for testing and as a fallback.

Acceptance Criteria

  • New Repository implementation in pkg/infra/store/ with persistent storage
  • Implements all 5 methods: Save, FindByID, FindAll, Delete, Count
  • Returns environment.ErrNotFound for missing entities (matching MemoryStore contract)
  • Copy semantics maintained (returned *Environment is independent of stored state)
  • Context respected for cancellation/timeout on all operations
  • MemoryStore kept for tests (not deleted)
  • Wiring in main.go updated to use persistent store by default
  • Configuration via environment variable for store path
  • Table-driven parallel unit tests matching memory_test.go coverage
  • doc.go with SPDX headers if new package created
Dominant language
Go
Stars
4
Forks
1
No merged PRs in 30d

Getting set up

This project ships no dev container, Dockerfile or contributing guide, so setting up is up to you: start from its README, and see our first-contribution guide for the general steps.

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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