ElastiCache Redis 복제 그룹 및 클러스터 모드

Redis 복제 그룹 개요

# Create a replication group with 1 primary and 2 read replicas
aws elasticache create-replication-group \
  --replication-group-id web-cache \
  --replication-group-description 'Web application cache' \
  --num-cache-clusters 3 \
  --cache-node-type cache.r7g.large \
  --engine redis \
  --engine-version '7.0' \
  --automatic-failover-enabled \
  --multi-az-enabled \
  --cache-subnet-group-name my-multi-az-subnet-group

Primary Endpoint와 Reader Endpoint 비교

# Get primary and reader endpoints
aws elasticache describe-replication-groups \
  --replication-group-id web-cache \
  --query 'ReplicationGroups[].{
    Primary:NodeGroups[].PrimaryEndpoint.Address,
    Reader:ReaderEndpoint.Address
  }'

# Application connection pattern:
# write_client = redis.Redis(host='primary-endpoint', port=6379)
# read_client = redis.Redis(host='reader-endpoint', port=6379)

자동 장애 조치 과정

# Test failover manually (triggers primary failover)
aws elasticache test-failover \
  --replication-group-id web-cache \
  --node-group-id 0001

# Monitor failover events
aws elasticache describe-events \
  --source-identifier web-cache \
  --source-type replication-group \
  --duration 60 \
  --query 'Events[].{Time:Date,Message:Message}'

Multi-AZ 복제본 배치

# Create replication group with explicit AZ placement
aws elasticache create-replication-group \
  --replication-group-id ha-redis \
  --replication-group-description 'Multi-AZ Redis' \
  --num-cache-clusters 3 \
  --cache-node-type cache.r7g.xlarge \
  --engine redis \
  --automatic-failover-enabled \
  --multi-az-enabled \
  --preferred-cache-cluster-a-zs us-east-1a us-east-1b us-east-1c \
  --cache-subnet-group-name multi-az-subnets

Redis Cluster Mode란 무엇인가요?

# Create a Redis Cluster Mode Enabled replication group
# with 3 shards, each with 1 primary and 2 replicas
aws elasticache create-replication-group \
  --replication-group-id clustered-redis \
  --replication-group-description 'Cluster mode: 3 shards x 3 nodes' \
  --num-node-groups 3 \
  --replicas-per-node-group 2 \
  --cache-node-type cache.r7g.large \
  --engine redis \
  --automatic-failover-enabled \
  --multi-az-enabled \
  --cache-subnet-group-name multi-az-subnets

Hash 슬롯과 키 분배

# Python cluster-aware client example
# pip install redis[hiredis]

# from redis.cluster import RedisCluster
# cluster_client = RedisCluster(
#   host='clustered-redis.abc123.clustercfg.use1.cache.amazonaws.com',
#   port=6379,
#   decode_responses=True
# )

# The client automatically resolves slot-to-node mapping
# cluster_client.set('user:1', 'Alice')   # routes to correct shard
# cluster_client.get('user:1')            # routes to correct shard

Cluster Mode와 Non-Cluster Mode 비교

# Scale out a cluster-mode Redis by adding shards
aws elasticache modify-replication-group-shard-configuration \
  --replication-group-id clustered-redis \
  --node-group-count 5 \
  --apply-immediately \
  --resharding-configuration \
    NodeGroupId=0004,PreferredAvailabilityZones=us-east-1a,us-east-1b,us-east-1c \
    NodeGroupId=0005,PreferredAvailabilityZones=us-east-1a,us-east-1b,us-east-1c

# No downtime — slots are migrated incrementally

리전 간 복제를 위한 Global Datastore

# Create a Global Datastore (adds a secondary region to an existing cluster)
aws elasticache create-global-replication-group \
  --global-replication-group-id-suffix my-global-cache \
  --primary-replication-group-id prod-redis

# Add a secondary cluster in another region
aws elasticache create-replication-group \
  --replication-group-id prod-redis-eu \
  --replication-group-description 'EU secondary' \
  --global-replication-group-id ldgnf-my-global-cache \
  --region eu-west-1

대규모 Redis 게시/구독

# Keyspace notification (fires when a key expires)
# Enable in parameter group: notify-keyspace-events Ex

# Subscriber in Python:
# pubsub = redis_client.pubsub()
# pubsub.psubscribe('__keyevent@0__:expired')
# for message in pubsub.listen():
#     if message['type'] == 'pmessage':
#         expired_key = message['data']
#         print(f'Key expired: {expired_key}')

복제 지연 모니터링

# Monitor replication lag for all replicas
aws cloudwatch get-metric-statistics \
  --namespace AWS/ElastiCache \
  --metric-name ReplicationLag \
  --dimensions Name=ReplicationGroupId,Value=web-cache \
  --statistic Maximum \
  --period 60 \
  --start-time $(date -u -d '1 hour ago' +%Y-%m-%dT%H:%M:%SZ) \
  --end-time $(date -u +%Y-%m-%dT%H:%M:%SZ)

# Alert if ReplicationLag > 10 seconds

복제 그룹 확장

# Scale up node type with maintenance window
aws elasticache modify-replication-group \
  --replication-group-id web-cache \
  --cache-node-type cache.r7g.xlarge \
  --apply-immediately false

# Add a read replica
aws elasticache increase-replica-count \
  --replication-group-id web-cache \
  --new-replica-count 4 \
  --apply-immediately

빠른 확인

단원 요약