2nd/10_Wiki/Topics/Architecture/Snapshots.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-snapshots	Snapshots	10_Wiki/Topics	verified	self	State Snapshot V8 Snapshot GC Snapshot Heap Snapshot	none	A	0.9	applied	runtime performance debugging memory state		2026-05-10	pending	language framework javascript v8

Snapshots

매 한 줄

"매 point-in-time 의 state freeze — 매 startup 의 accelerate, 매 leak 의 hunt, 매 recovery 의 enable.". 매 V8 startup snapshot, heap snapshot, filesystem snapshot (ZFS/Btrfs), DB snapshot, state snapshot (Redux time-travel) — 매 same primitive 의 different domain. 매 modern runtime 의 cold-start optimization 의 default tool.

매 핵심

매 종류

• V8 startup snapshot: serialize heap → fast Node.js cold start.
• Heap snapshot (.heapsnapshot): debug memory leak, retainer graph.
• GC snapshot: generational scan checkpoint.
• Filesystem snapshot: ZFS/Btrfs/LVM copy-on-write point-in-time.
• DB snapshot: PITR base, transactional checkpoint.
• State snapshot: Redux DevTools time-travel, game save.

매 properties

• Copy-on-write (efficient diff storage).
• Atomic (consistent point-in-time).
• Restorable (full state reconstruction).
• Immutable (snapshot itself never mutated).

매 응용

1. Node.js bootup --snapshot-blob (200ms → 30ms startup).
2. Chrome DevTools heap profiler — leak hunt.
3. ZFS rollback before risky deploy.
4. Postgres PITR base + WAL replay.
5. Redux DevTools — time-travel debug.
6. AWS EBS snapshot — disaster recovery.
7. Container checkpoint/restore (CRIU).

💻 패턴

Node.js startup snapshot

node --snapshot-blob snapshot.blob --build-snapshot snapshot-init.js
node --snapshot-blob snapshot.blob app.js
# Cold start: 200ms → ~30ms

Chrome heap snapshot programmatic

const v8 = require('v8');
const fs = require('fs');
const stream = v8.getHeapSnapshot();
stream.pipe(fs.createWriteStream('heap.heapsnapshot'));
// Open in Chrome DevTools → Memory tab

ZFS snapshot + rollback

zfs snapshot tank/data@before-deploy
# ... risky operation ...
zfs rollback tank/data@before-deploy   # if failure
zfs destroy tank/data@before-deploy    # if success

Postgres base backup + PITR

pg_basebackup -D /backup/base -F tar -X stream -P
# Recover to point-in-time
restore_command = 'cp /archive/%f %p'
recovery_target_time = '2026-05-10 14:30:00'

Redux state snapshot

import { createStore } from 'redux';
const store = createStore(reducer);

const snapshot = store.getState();  // freeze
// ... actions ...
store.replaceReducer((state = snapshot) => state);  // restore

CRIU container checkpoint

criu dump --tree $PID --images-dir /checkpoints/svc-1 --leave-running
# Later, possibly on different host:
criu restore --images-dir /checkpoints/svc-1

EBS snapshot via AWS SDK

import { EC2Client, CreateSnapshotCommand } from '@aws-sdk/client-ec2';

await client.send(new CreateSnapshotCommand({
  VolumeId: 'vol-0abc',
  Description: 'pre-migration-2026-05-10',
  TagSpecifications: [{ ResourceType: 'snapshot', Tags: [{ Key: 'env', Value: 'prod' }] }],
}));

Heap diff analysis

// Take 2 snapshots, diff in DevTools to find leak
v8.writeHeapSnapshot('/tmp/before.heapsnapshot');
runSuspectCode();
v8.writeHeapSnapshot('/tmp/after.heapsnapshot');
// Load both → "Comparison" view → growing retainer chains

매 결정 기준

상황	Approach
Node.js cold start slow	startup snapshot
Memory leak hunt	heap snapshot diff
Pre-deploy rollback safety	ZFS/EBS snapshot
DB recovery to time T	PITR base + WAL
Container live migration	CRIU checkpoint
Frontend bug repro	Redux time-travel

기본값: heap snapshot for leaks, ZFS/EBS for storage, PITR for DB, CRIU for container.

🔗 Graph

• 부모: State-Management
• 변형: Heap-Snapshot · V8-Snapshot
• 응용: Disaster-Recovery
• Adjacent: Event-Sourcing

🤖 LLM 활용

언제: cold-start optim, leak diag, DR planning, time-travel debug strategy. 언제 X: write-heavy hot path — snapshot overhead 의 measure 필요.

❌ 안티패턴

• Snapshot as backup: 매 same disk 의 snapshot 의 disk failure 의 protect X.
• No retention policy: 매 snapshot accumulate → storage explode.
• Heap snapshot in prod under load: 매 GC pause spike — staging 에서.

🧪 검증 / 중복

• Verified (V8 docs, Chrome DevTools docs, ZFS handbook, Postgres PITR docs).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — snapshot taxonomy, V8/heap/ZFS/PITR/CRIU patterns