ELK 스택 기반 로그 수집·분석 파이프라인: Elasticsearch·Fluentd·Kibana 프로덕션 구축과 최적화

# elasticsearch-master.yml
cluster.name: prod-logs
node.name: master-01
node.roles: [ master ]
network.host: 0.0.0.0
discovery.seed_hosts:
  - master-01
  - master-02
  - master-03
cluster.initial_master_nodes:
  - master-01
  - master-02
  - master-03

# JVM 힙 설정 (jvm.options)
-Xms4g
-Xmx4g

# elasticsearch-data-hot.yml
cluster.name: prod-logs
node.name: data-hot-01
node.roles: [ data_hot, data_content ]
node.attr.data: hot
network.host: 0.0.0.0
discovery.seed_hosts:
  - master-01
  - master-02
  - master-03

# JVM 힙 설정
-Xms16g
-Xmx16g

# elasticsearch-data-warm.yml
cluster.name: prod-logs
node.name: data-warm-01
node.roles: [ data_warm ]
node.attr.data: warm
network.host: 0.0.0.0
discovery.seed_hosts:
  - master-01
  - master-02
  - master-03

# JVM 힙 설정
-Xms8g
-Xmx8g

# 인덱스 템플릿으로 샤드 설정
curl -X PUT "localhost:9200/_index_template/logs-template" \
  -H 'Content-Type: application/json' \
  -d '{
  "index_patterns": ["logs-*"],
  "template": {
    "settings": {
      "number_of_shards": 3,
      "number_of_replicas": 1,
      "refresh_interval": "30s",
      "codec": "best_compression",
      "routing.allocation.require.data": "hot"
    },
    "mappings": {
      "dynamic": "strict",
      "properties": {
        "@timestamp": { "type": "date" },
        "level": { "type": "keyword" },
        "service": { "type": "keyword" },
        "message": { "type": "text" },
        "trace_id": { "type": "keyword" },
        "host": { "type": "keyword" }
      }
    }
  }
}'

{
  "policy": {
    "phases": {
      "hot": {
        "min_age": "0ms",
        "actions": {
          "rollover": {
            "max_primary_shard_size": "50gb",
            "max_age": "1d"
          },
          "set_priority": {
            "priority": 100
          }
        }
      },
      "warm": {
        "min_age": "3d",
        "actions": {
          "shrink": {
            "number_of_shards": 1
          },
          "forcemerge": {
            "max_num_segments": 1
          },
          "allocate": {
            "require": {
              "data": "warm"
            }
          },
          "set_priority": {
            "priority": 50
          }
        }
      },
      "cold": {
        "min_age": "30d",
        "actions": {
          "allocate": {
            "require": {
              "data": "cold"
            }
          },
          "set_priority": {
            "priority": 0
          }
        }
      },
      "delete": {
        "min_age": "90d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

# ILM 정책 생성
curl -X PUT "localhost:9200/_ilm/policy/logs-lifecycle" \
  -H 'Content-Type: application/json' \
  -d @ilm-policy.json

# ILM 정책을 인덱스 템플릿에 연결
curl -X PUT "localhost:9200/_index_template/logs-template" \
  -H 'Content-Type: application/json' \
  -d '{
  "index_patterns": ["logs-*"],
  "template": {
    "settings": {
      "index.lifecycle.name": "logs-lifecycle",
      "index.lifecycle.rollover_alias": "logs"
    }
  }
}'

# 부트스트랩 인덱스 생성
curl -X PUT "localhost:9200/logs-000001" \
  -H 'Content-Type: application/json' \
  -d '{
  "aliases": {
    "logs": {
      "is_write_index": true
    }
  }
}'

<!-- /etc/fluentd/fluent.conf -->
<system>
  log_level info
  workers 4
</system>

<!-- Input: 애플리케이션 로그 수집 -->
<source>
  @type tail
  path /var/log/app/*.log
  pos_file /var/log/fluentd/app.log.pos
  tag app.logs
  read_from_head true
  <parse>
    @type json
    time_key timestamp
    time_format %Y-%m-%dT%H:%M:%S.%NZ
  </parse>
</source>

<!-- Input: Kubernetes 로그 수집 -->
<source>
  @type tail
  path /var/log/containers/*.log
  pos_file /var/log/fluentd/containers.log.pos
  tag kubernetes.*
  <parse>
    @type cri
  </parse>
</source>

<!-- Filter: Kubernetes 메타데이터 추가 -->
<filter kubernetes.**>
  @type kubernetes_metadata
  @id filter_kube_metadata
  skip_labels false
  skip_container_metadata false
</filter>

<!-- Filter: 불필요한 로그 제거 -->
<filter **>
  @type grep
  <exclude>
    key log
    pattern /healthcheck|readiness|liveness/
  </exclude>
</filter>

<!-- Filter: 로그 레벨 기반 태깅 -->
<filter app.logs>
  @type record_transformer
  enable_ruby true
  <record>
    hostname "#{Socket.gethostname}"
    environment "production"
  </record>
</filter>

<!-- Output: Elasticsearch로 전송 -->
<match **>
  @type elasticsearch
  host elasticsearch-coordinating
  port 9200
  logstash_format true
  logstash_prefix fluentd-logs
  logstash_dateformat %Y.%m.%d
  include_tag_key true
  tag_key @fluentd_tag

  <buffer tag, time>
    @type file
    path /var/log/fluentd/buffer
    timekey 1h
    timekey_wait 10m
    chunk_limit_size 64MB
    total_limit_size 8GB
    flush_mode interval
    flush_interval 30s
    flush_thread_count 4
    retry_max_interval 30
    retry_forever true
    overflow_action block
  </buffer>
</match>

# fluent-bit-configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: fluent-bit-config
  namespace: logging
data:
  fluent-bit.conf: |
    [SERVICE]
        Flush         5
        Log_Level     info
        Daemon        off
        Parsers_File  parsers.conf
        HTTP_Server   On
        HTTP_Listen   0.0.0.0
        HTTP_Port     2020
        storage.path  /var/log/flb-storage/
        storage.sync  normal
        storage.checksum off
        storage.backlog.mem_limit 5M

    [INPUT]
        Name              tail
        Tag               kube.*
        Path              /var/log/containers/*.log
        Parser            cri
        DB                /var/log/flb_kube.db
        Mem_Buf_Limit     5MB
        Skip_Long_Lines   On
        Refresh_Interval  10
        storage.type      filesystem

    [FILTER]
        Name                kubernetes
        Match               kube.*
        Kube_URL            https://kubernetes.default.svc:443
        Kube_CA_File        /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
        Kube_Token_File     /var/run/secrets/kubernetes.io/serviceaccount/token
        Kube_Tag_Prefix     kube.var.log.containers.
        Merge_Log           On
        Keep_Log            Off
        K8S-Logging.Parser  On
        K8S-Logging.Exclude On

    [FILTER]
        Name    grep
        Match   *
        Exclude log healthcheck

    [OUTPUT]
        Name            forward
        Match           *
        Host            fluentd-aggregator.logging.svc.cluster.local
        Port            24224
        Retry_Limit     False

  parsers.conf: |
    [PARSER]
        Name        cri
        Format      regex
        Regex       ^(?<time>[^ ]+) (?<stream>stdout|stderr) (?<logtag>[^ ]*) (?<log>.*)$
        Time_Key    time
        Time_Format %Y-%m-%dT%H:%M:%S.%L%z

# fluent-bit-daemonset.yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluent-bit
  namespace: logging
spec:
  selector:
    matchLabels:
      app: fluent-bit
  template:
    metadata:
      labels:
        app: fluent-bit
    spec:
      serviceAccountName: fluent-bit
      tolerations:
        - key: node-role.kubernetes.io/master
          effect: NoSchedule
      containers:
        - name: fluent-bit
          image: fluent/fluent-bit:3.2
          resources:
            requests:
              cpu: 100m
              memory: 128Mi
            limits:
              cpu: 500m
              memory: 256Mi
          volumeMounts:
            - name: varlog
              mountPath: /var/log
            - name: config
              mountPath: /fluent-bit/etc/
            - name: storage
              mountPath: /var/log/flb-storage/
      volumes:
        - name: varlog
          hostPath:
            path: /var/log
        - name: config
          configMap:
            name: fluent-bit-config
        - name: storage
          emptyDir: {}

# Kibana API로 인덱스 패턴 생성
curl -X POST "localhost:5601/api/saved_objects/index-pattern" \
  -H 'kbn-xsrf: true' \
  -H 'Content-Type: application/json' \
  -d '{
  "attributes": {
    "title": "fluentd-logs-*",
    "timeFieldName": "@timestamp"
  }
}'

# 벌크 인덱싱 최적화 설정
curl -X PUT "localhost:9200/logs-000001/_settings" \
  -H 'Content-Type: application/json' \
  -d '{
  "index": {
    "refresh_interval": "30s",
    "translog.durability": "async",
    "translog.sync_interval": "30s",
    "translog.flush_threshold_size": "1gb"
  }
}'

# jvm.options 설정
# 전체 RAM의 50% 이하, 최대 31GB (Compressed OOPs 한계)
-Xms16g
-Xmx16g

# G1GC 설정 (Elasticsearch 8.x 기본)
-XX:+UseG1GC
-XX:G1HeapRegionSize=16m
-XX:InitiatingHeapOccupancyPercent=30
-XX:+ParallelRefProcEnabled

# GC 로그 활성화
-Xlog:gc*,gc+age=trace,safepoint:file=logs/gc.log:utctime,pid,tags:filecount=32,filesize=64m

# forcemerge로 세그먼트 병합 (읽기 전용 인덱스에서 수행)
curl -X POST "localhost:9200/logs-2026.03.01/_forcemerge?max_num_segments=1"

# 인덱스 압축 확인
curl -X GET "localhost:9200/_cat/indices/logs-*?v&h=index,store.size,pri.store.size,docs.count&s=index"

# 디스크 워터마크 설정
curl -X PUT "localhost:9200/_cluster/settings" \
  -H 'Content-Type: application/json' \
  -d '{
  "persistent": {
    "cluster.routing.allocation.disk.watermark.low": "85%",
    "cluster.routing.allocation.disk.watermark.high": "90%",
    "cluster.routing.allocation.disk.watermark.flood_stage": "95%"
  }
}'

# 매핑 필드 수 제한 설정
curl -X PUT "localhost:9200/_index_template/logs-template" \
  -H 'Content-Type: application/json' \
  -d '{
  "index_patterns": ["logs-*"],
  "template": {
    "settings": {
      "index.mapping.total_fields.limit": 1000
    },
    "mappings": {
      "dynamic": "strict"
    }
  }
}'

# Circuit breaker 설정
curl -X PUT "localhost:9200/_cluster/settings" \
  -H 'Content-Type: application/json' \
  -d '{
  "persistent": {
    "indices.breaker.total.limit": "70%",
    "indices.breaker.fielddata.limit": "40%",
    "indices.breaker.request.limit": "40%"
  }
}'

# elasticsearch.yml - 보안 설정
xpack.security.enabled: true
xpack.security.transport.ssl.enabled: true
xpack.security.transport.ssl.verification_mode: certificate
xpack.security.transport.ssl.keystore.path: /etc/elasticsearch/certs/elastic-certificates.p12
xpack.security.transport.ssl.truststore.path: /etc/elasticsearch/certs/elastic-certificates.p12

xpack.security.http.ssl.enabled: true
xpack.security.http.ssl.keystore.path: /etc/elasticsearch/certs/http.p12

# 미할당 샤드 확인
curl -X GET "localhost:9200/_cat/shards?v&h=index,shard,prirep,state,unassigned.reason&s=state"

# 미할당 원인 진단
curl -X GET "localhost:9200/_cluster/allocation/explain?pretty"

# 수동 샤드 할당 (디스크 공간 부족 시)
curl -X POST "localhost:9200/_cluster/reroute" \
  -H 'Content-Type: application/json' \
  -d '{
  "commands": [
    {
      "allocate_stale_primary": {
        "index": "logs-2026.03.10",
        "shard": 0,
        "node": "data-hot-02",
        "accept_data_loss": true
      }
    }
  ]
}'

# 스레드 풀 상태 확인
curl -X GET "localhost:9200/_cat/thread_pool/write?v&h=node_name,active,rejected,queue,completed"

# 벌크 큐 크기 조정
curl -X PUT "localhost:9200/_cluster/settings" \
  -H 'Content-Type: application/json' \
  -d '{
  "persistent": {
    "thread_pool.write.queue_size": 1000
  }
}'

# read-only 해제 (디스크 확보 후)
curl -X PUT "localhost:9200/_all/_settings" \
  -H 'Content-Type: application/json' \
  -d '{
  "index.blocks.read_only_allow_delete": null
}'

# 오래된 인덱스 수동 삭제
curl -X DELETE "localhost:9200/logs-2026.01.*"

# 디스크 사용량 확인
curl -X GET "localhost:9200/_cat/allocation?v"

# metricbeat.yml - Elasticsearch 모니터링
metricbeat.modules:
  - module: elasticsearch
    xpack.enabled: true
    period: 10s
    hosts:
      - 'https://es-node-01:9200'
      - 'https://es-node-02:9200'
    username: 'monitoring_user'
    password: 'secure_password'
    ssl.certificate_authorities:
      - /etc/metricbeat/certs/ca.crt

  - module: kibana
    xpack.enabled: true
    period: 10s
    hosts:
      - 'https://kibana:5601'

output.elasticsearch:
  hosts:
    - 'https://monitoring-es:9200'
  username: 'metricbeat_writer'
  password: 'secure_password'