Migrate to Fedimint v0.9.0 - Smooth Operator

[okjodom]

Smooth operator has landed with lots of benefits for clients, including streamlined client rpcs and gateway autoselection! This task is for migrating from v0.8.0 to v0.9.0. Ref: https://github.com/fedimint/fedimint/releases/tag/v0.9.0

[okjodom]

Fedimint v0.9.0 Migration Plan for fmcd

Executive Summary

This document outlines the migration plan for fmcd to fully leverage Fedimint v0.9.0 features. The codebase has already been updated to use v0.9.0 dependencies and implements gateway auto-selection, but several important features remain to be implemented.

Current Implementation Status

✅ Completed

• Dependencies: All Fedimint crates updated to v0.9.0
• Gateway Auto-Selection: Implemented in commit 1066e18
  • Invoice creation and payment support optional gateway_id
  • Auto-selects best available gateway when not specified
• LNURL Support: Full implementation with Lightning Address support
• Core Architecture: Restructured as dual library/binary crate
• Crypto Provider Initialization: Implemented in src/bin/main.rs:109
  • Required for v0.9.0 TLS connections
  • Calls fedimint_core::rustls::install_crypto_provider().await

❌ Not Yet Implemented

• Client RPC interface
• Enhanced gateway monitoring
• Event log trimming
• Config backup/recovery features
• Network performance optimizations

Priority Implementation Tasks

🔴 Priority 1: Critical Breaking Changes (Immediate)

1.1 Crypto Provider Initialization ✅ COMPLETED

Status: ✅ IMPLEMENTED (2025-11-09)
Urgency: CRITICAL - Application won't work without this

Implementation:

// In src/bin/main.rs:109
fedimint_core::rustls::install_crypto_provider().await;

Files modified:

• ✅ /home/okj/minmoto/fmcd/src/bin/main.rs (line 109)
• ✅ /home/okj/minmoto/fmcd/flake.nix (updated to Rust 1.91.0+ for v0.9.0 compatibility)

Testing:

• Verify TLS connections work in production
• Test federation joins with v0.9.0
• Test gateway communications

Notes:

• Function is async, requires .await
• Must be called before any TLS operations
• Nix flake updated to use latest stable Rust (required for fedimint v0.9.0 if-let-guard feature)

---

🟡 Priority 2: Major Features (This Week)

2.1 Client RPC Interface

Status: NOT IMPLEMENTED
Complexity: High
Time Estimate: 2-3 days

Implementation Steps:

1. Create new module: src/api/rpc/mod.rs
2. Implement JSON-RPC 2.0 server using existing core methods
3. Add RPC-specific types and error handling
4. Expose endpoints:
   • Federation management (join, leave, list)
   • Lightning operations (invoice, pay, list)
   • Mint operations (issue, spend, balance)
   • On-chain operations (deposit, withdraw)

Files to create:

• /home/okj/minmoto/fmcd/src/api/rpc/mod.rs
• /home/okj/minmoto/fmcd/src/api/rpc/handlers.rs
• /home/okj/minmoto/fmcd/src/api/rpc/types.rs

Dependencies to add:

jsonrpsee = { version = "0.20", features = ["server", "macros"] }

---

🟢 Priority 3: Enhancements (Next Sprint)

3.1 Trimable Event Log

Status: NOT IMPLEMENTED
Complexity: Medium
Time Estimate: 1 day

Implementation Steps:

1. Add configuration for max log size/age
2. Implement log rotation mechanism
3. Add trim operation to EventBus
4. Schedule periodic trim tasks

Files to modify:

• /home/okj/minmoto/fmcd/src/events/mod.rs
• /home/okj/minmoto/fmcd/src/config.rs

3.2 Config Backup and Recovery

Status: NOT IMPLEMENTED
Complexity: Medium
Time Estimate: 1-2 days

Implementation Steps:

1. Add backup endpoint to admin API
2. Implement config export/import functions
3. Add encryption for sensitive data
4. Support dynamic config switching

Files to modify:

• /home/okj/minmoto/fmcd/src/api/rest/admin/mod.rs
• /home/okj/minmoto/fmcd/src/config.rs

3.3 Network Performance Optimizations

Status: NOT IMPLEMENTED
Complexity: Low-Medium
Time Estimate: 1 day

Implementation Steps:

1. Implement connection pooling for WebSocket
2. Add Iroh connection reuse
3. Add configuration for DHT disable
4. Monitor and log connection types

Files to modify:

• /home/okj/minmoto/fmcd/src/core/multimint.rs
• Network client initialization code

---

Implementation Schedule

Week 1 (Immediate)

• Day 1: Crypto provider initialization (1 hour) ✅ COMPLETED 2025-11-09
• Day 1-3: Client RPC interface implementation

Week 2

• Day 1-2: Event log trimming
• Day 3-4: Config backup/recovery
• Day 5: Network optimizations

Week 3

• Testing and bug fixes
• Documentation updates
• Performance benchmarking

Testing Strategy

Unit Tests

• Test crypto provider initialization
• Test RPC endpoint handlers
• Test gateway selection with new metrics
• Test event log trimming logic

Integration Tests

• Test full RPC workflow
• Test gateway failover scenarios
• Test config backup/restore
• Test connection reuse

Performance Tests

• Benchmark RPC vs REST API
• Measure connection reuse benefits
• Test event log performance with trimming

Migration Risks and Mitigations

Risk 1: Crypto Provider Breaking Change ✅ MITIGATED

Impact: HIGH - Application won't start
Mitigation: ✅ Implemented on 2025-11-09, requires production testing

Risk 2: RPC Interface Compatibility

Impact: MEDIUM - External integrations may break
Mitigation: Maintain REST API, document RPC differences

Risk 3: Gateway Selection Changes

Impact: LOW - Already implemented
Mitigation: Monitor gateway selection behavior

Success Criteria

1. Functional:

   • All v0.9.0 critical features implemented
   • No regression in existing functionality
   • All tests passing

2. Performance:

   • Connection establishment 20% faster
   • Gateway selection < 100ms
   • Event processing maintains < 10ms latency

3. Reliability:

   • Zero downtime during migration
   • Graceful handling of gateway failures
   • Successful config backup/restore

Documentation Updates Required

1. Update README with v0.9.0 features
2. Document RPC API endpoints
3. Add gateway configuration guide
4. Update deployment documentation

Next Steps

1. Immediate Action: Implement crypto provider initialization ✅ COMPLETED
2. This Week: Start RPC interface development
3. Testing: Production testing of crypto provider initialization
4. Testing: Set up v0.9.0 test environment
5. Communication: Update team on migration progress

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Appendix: v0.9.0 Feature Reference

Complete v0.9.0 Feature List (from changelog)

• ✅ Gateway auto-selection
• ✅ Reduced default gateway fees
• ❌ Client RPC interface
• ❌ Config backup download
• ❌ Trimable event log
• ❌ Online e-cash validation
• ❌ WebSocket connection reuse
• ❌ Iroh connection optimizations
• ❌ DHT disable option

Breaking Changes Checklist

• Crypto provider initialization ✅ COMPLETED 2025-11-09
• Gateway selection API changes (backward compatible)
• Fee structure updates (handled by federation)