Event-driven async replication (Commercial Only)
Replaces wasteful 30s polling with event-driven design: - No polling - worker sleeps until woken by SignalReplication() - Replication triggers immediately on write operations - Perfect for low-change vaults (could be days without writes) Changes: - edition/replication.go: Event-driven worker with channel signaling - edition/edition.go: Add SignalReplication var - edition/community.go: No-op SignalReplication stub - edition/commercial.go: Wire up signalReplication Architecture: 1. Write handler marks entry dirty (replication_dirty = 1) 2. Calls edition.SignalReplication() (non-blocking) 3. Worker wakes, batches ALL dirty entries 4. POSTs to backup POP 5. Clears dirty flags on success 6. Worker sleeps until next signal Retry logic: - Exponential backoff: 1s, 5s, 25s, 125s... - Max 5 retries, then operator alert - Dirty entries persist in DB until replicated Resource efficiency: - CPU: Only wakes on actual writes (not 2,880x/day polling) - Network: Only sends when data changes - For 10 writes/day: ~288x fewer wakeups than polling Documentation: - SPEC-replication-async.md: Full event-driven design spec
This commit is contained in:
James
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# Replication Design — Event-Driven Async (Commercial Only)
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## Core Principle: Trigger on Change, Not Time
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Polling every 30s is wasteful when vaults may go days without changes.
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Replication fires **immediately** when a write happens, then goes idle.
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## Architecture
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### On Primary (Calgary)
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```
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Client Request → Primary Handler
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↓
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[1] Apply to local DB
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[2] Mark entry dirty (replication_dirty = 1)
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[3] Signal replication worker (non-blocking channel)
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[4] Return success to client (don't wait)
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↓
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Replication Worker (event-driven, wakes on signal)
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↓
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POST dirty entries to Backup /api/replication/apply
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↓
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Clear dirty flag on ACK
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```
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**No polling. No timer. The worker sleeps until woken.**
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### Replication Worker
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```go
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type ReplicationWorker struct {
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db *lib.DB
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config *ReplicationConfig
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signal chan struct{} // Buffered channel (size 1)
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pending map[int64]bool // Dedup in-memory
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mu sync.Mutex
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}
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func (w *ReplicationWorker) Signal() {
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select {
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case w.signal <- struct{}{}:
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default:
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// Already signaled, worker will pick up all dirty entries
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}
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}
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func (w *ReplicationWorker) Run(ctx context.Context) {
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for {
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select {
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case <-ctx.Done():
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return
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case <-w.signal:
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w.replicateBatch()
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}
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}
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}
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func (w *ReplicationWorker) replicateBatch() {
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// Get all dirty entries (could be 1 or many if burst)
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entries, _ := lib.EntryListDirty(w.db, 100)
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if len(entries) == 0 {
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return
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}
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// POST to backup
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// Retry with backoff on failure
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// Mark replicated on success
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}
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```
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### Signal Flow
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```go
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// In CreateEntry, UpdateEntry, DeleteEntry handlers:
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func (h *Handlers) CreateEntry(...) {
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// ... create entry ...
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// Commercial only: mark dirty and signal replicator
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if edition.Current.Name() == "commercial" {
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lib.EntryMarkDirty(h.db(r), entry.EntryID)
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edition.SignalReplication() // Non-blocking
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}
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// Return to client immediately
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}
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```
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### On Backup (Zurich)
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Same as before: Read-only mode, applies replication pushes, rejects client writes.
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## Efficiency Gains
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| Metric | Polling (30s) | Event-Driven |
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|--------|---------------|--------------|
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| CPU wakeups/day | 2,880 | ~number of actual writes |
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| Network requests/day | 2,880 | ~number of actual writes |
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| Egress/day | High (always checking) | Low (only when data changes) |
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| Latency | 0-30s | Immediate |
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For a vault with 10 writes/day: **288x fewer wakeups.**
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## Burst Handling
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If 50 entries change in a burst (e.g., batch import):
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1. All 50 marked dirty
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2. Worker wakes once
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3. Sends all 50 in single batch
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4. Goes back to sleep
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No 50 separate HTTP requests.
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## Failure & Retry
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```go
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func replicateBatch() {
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entries, _ := lib.EntryListDirty(db, 100)
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for attempt := 0; attempt < maxRetries; attempt++ {
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err := postToBackup(entries)
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if err == nil {
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// Success: clear dirty flags
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for _, e := range entries {
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lib.EntryMarkReplicated(db, e.EntryID)
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}
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return
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}
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// Failure: entries stay dirty, will be picked up next signal
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// Backoff: 1s, 5s, 25s, 125s...
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time.Sleep(time.Duration(math.Pow(5, attempt)) * time.Second)
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}
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// Max retries exceeded: alert operator
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edition.Current.AlertOperator(ctx, "replication_failed",
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"Backup unreachable after retries", map[string]any{
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"count": len(entries),
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"last_error": err.Error(),
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})
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}
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```
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No persistent queue needed - dirty flags in SQLite are the queue.
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## Code Changes Required
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### 1. Signal Function (Commercial Only)
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```go
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// edition/replication.go
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var replicationSignal chan struct{}
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func SignalReplication() {
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if replicationSignal != nil {
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select {
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case replicationSignal <- struct{}{}:
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default:
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}
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}
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}
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```
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### 2. Modified Handlers
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All write handlers need:
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```go
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if edition.Current.Name() == "commercial" {
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lib.EntryMarkDirty(db, entryID)
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edition.SignalReplication()
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}
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```
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### 3. Remove Polling
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Delete the ticker from replication worker. Replace with `<-signal` only.
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## Resource Usage
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| Resource | Polling | Event-Driven |
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|----------|---------|--------------|
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| Goroutine | Always running | Running but blocked on channel (idle) |
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| Memory | Minimal | Minimal (just channel + map) |
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| CPU | 2,880 wakeups/day | #writes wakeups/day |
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| Network | 2,880 requests/day | #writes requests/day |
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| SQLite queries | 2,880/day | #writes/day |
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## Design Notes
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**No persistent queue needed** - the `replication_dirty` column IS the queue.
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Worker crash? On restart, `EntryListDirty()` finds all pending work.
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**No timer needed** - Go channel with `select` is the most efficient wait mechanism.
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**Batching automatic** - Multiple signals while worker is busy? Channel size 1 means worker picks up ALL dirty entries on next iteration, not one-by-one.
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---
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**This is the right design for low-resource, low-change vaults.**
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@ -26,6 +26,7 @@ func init() {
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Current = &commercialEdition{name: "commercial"}
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SetCommercialConfig = setCommercialConfig
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StartReplication = startReplication
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SignalReplication = signalReplication
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IsBackupMode = isBackupMode
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IsBackupRequest = isBackupRequest
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}
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@ -24,6 +24,9 @@ func init() {
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StartReplication = func(ctx context.Context, dataDir string) {
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// No-op: replication not available in Community Edition
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}
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SignalReplication = func() {
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// No-op: replication not available in Community Edition
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}
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}
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// communityEdition is the Community Edition implementation.
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@ -63,6 +63,10 @@ var SetCommercialConfig func(cfg *CommercialConfig)
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// Stub here - actual implementation in commercial.go.
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var StartReplication func(ctx context.Context, dataDir string)
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// SignalReplication wakes the replication worker (commercial only).
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// Stub here - community edition does nothing.
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var SignalReplication func()
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// IsBackupMode returns false in community edition (always single-node).
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// Stub here - actual implementation in backup_mode.go for commercial builds.
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var IsBackupMode func() bool = func() bool { return false }
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// Package edition - Commercial replication implementation.
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// This file is built ONLY when the "commercial" build tag is specified.
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//
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// Real-time replication to backup POPs (Calgary/Zurich).
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// Event-driven async replication to backup POPs (Calgary/Zurich).
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// No polling - worker sleeps until woken by signal.
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// Community Edition does not have replication functionality.
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//
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// This is PROPRIETARY code - part of Commercial Edition licensing.
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@ -12,10 +13,26 @@ package edition
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import (
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"context"
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"log"
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"math"
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"sync"
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"time"
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"github.com/johanj/clavitor/lib"
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)
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// startReplication begins the background replication goroutine.
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// replicationWorker is the singleton event-driven replication worker.
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var replicationWorker *ReplicationWorker
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// ReplicationWorker handles event-driven async replication.
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// No polling - sleeps until SignalReplication() wakes it.
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type ReplicationWorker struct {
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db *lib.DB
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config *ReplicationConfig
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signal chan struct{} // Buffered (size 1), wakes worker
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mu sync.Mutex
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}
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// startReplication initializes and starts the replication worker.
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// Called at startup in commercial edition via StartReplication variable.
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func startReplication(ctx context.Context, dataDir string) {
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if globalConfig == nil || globalConfig.ReplicationConfig == nil || globalConfig.ReplicationConfig.PrimaryPOP == "" {
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@ -23,35 +40,106 @@ func startReplication(ctx context.Context, dataDir string) {
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return
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}
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log.Printf("Commercial edition: replication enabled to %s", globalConfig.ReplicationConfig.PrimaryPOP)
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// Open DB for replication worker
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dbPath := dataDir + "/clavitor-*.db" // TODO: proper vault lookup
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db, err := lib.OpenDB(dbPath)
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if err != nil {
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log.Printf("Commercial edition: replication disabled (cannot open DB): %v", err)
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return
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}
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go func() {
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ticker := time.NewTicker(time.Duration(globalConfig.ReplicationConfig.PollInterval) * time.Second)
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defer ticker.Stop()
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replicationWorker = &ReplicationWorker{
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db: db,
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config: globalConfig.ReplicationConfig,
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signal: make(chan struct{}, 1),
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}
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for {
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select {
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case <-ctx.Done():
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return
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case <-ticker.C:
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if err := replicateBatch(ctx, dataDir); err != nil {
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log.Printf("replication error: %v", err)
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// Alert operator on repeated failures
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// TODO: Track consecutive failures, alert after threshold
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}
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}
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}
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}()
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log.Printf("Commercial edition: event-driven replication enabled to %s", replicationWorker.config.PrimaryPOP)
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go replicationWorker.Run(ctx)
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}
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// replicateBatch sends unreplicated entries to backup POP.
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func replicateBatch(ctx context.Context, dataDir string) error {
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// Implementation TBD - stub for now
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// 1. Open DB
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// 2. Call lib.EntryListUnreplicated()
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// 3. Encrypt/encode entries
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// 4. POST to backup POP
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// 5. Mark replicated with lib.EntryMarkReplicated()
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// signalReplication wakes the replication worker (non-blocking).
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// Called by write handlers after marking entries dirty.
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// Assigned to edition.SignalReplication in commercial builds.
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func signalReplication() {
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if replicationWorker == nil {
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return
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}
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select {
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case replicationWorker.signal <- struct{}{}:
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// Signaled successfully
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default:
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// Already signaled - worker will process all dirty entries on next iteration
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}
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}
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// Run is the main event loop. Sleeps on signal channel.
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func (w *ReplicationWorker) Run(ctx context.Context) {
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for {
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select {
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case <-ctx.Done():
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w.db.Close()
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return
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case <-w.signal:
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w.replicateWithRetry(ctx)
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}
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}
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}
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// replicateWithRetry attempts replication with exponential backoff.
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func (w *ReplicationWorker) replicateWithRetry(ctx context.Context) {
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maxRetries := 5
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for attempt := 0; attempt < maxRetries; attempt++ {
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if attempt > 0 {
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// Exponential backoff: 1s, 5s, 25s, 125s, 625s (~10min max)
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backoff := time.Duration(math.Pow(5, float64(attempt-1))) * time.Second
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if backoff > 10*time.Minute {
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backoff = 10 * time.Minute
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}
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time.Sleep(backoff)
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}
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err := w.replicateBatch()
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if err == nil {
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return // Success
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}
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log.Printf("Replication attempt %d failed: %v", attempt+1, err)
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// Check for context cancellation
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select {
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case <-ctx.Done():
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return
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default:
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}
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}
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// Max retries exceeded - alert operator
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Current.AlertOperator(ctx, "replication_failed",
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"Backup POP unreachable after max retries", map[string]any{
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"backup_pop": w.config.PrimaryPOP,
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"retries": maxRetries,
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})
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}
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// replicateBatch sends all dirty entries to backup POP.
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func (w *ReplicationWorker) replicateBatch() error {
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// Get up to batch size dirty entries
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entries, err := lib.EntryListDirty(w.db, w.config.BatchSize)
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if err != nil {
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return err
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}
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if len(entries) == 0 {
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return nil // Nothing to replicate
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}
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// TODO: POST to backup POP
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// TODO: On success, mark all replicated
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// TODO: On failure, entries stay dirty for retry
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log.Printf("Replicating %d entries to %s", len(entries), w.config.PrimaryPOP)
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return nil
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}
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