JSONL로 구조화된 로깅

import structlog

# Configure structlog for JSONL output
structlog.configure(
    processors=[
        structlog.processors.TimeStamper(fmt="iso"),
        structlog.processors.add_log_level,
        structlog.processors.StackInfoRenderer(),
        structlog.processors.JSONRenderer(),
    ],
    wrapper_class=structlog.BoundLogger,
    context_class=dict,
    logger_factory=structlog.PrintLoggerFactory(),
)

log = structlog.get_logger()

# Each call produces one JSONL line
log.info("user.login", user_id="u-42", ip="10.0.0.1")
# {"event":"user.login","user_id":"u-42","ip":"10.0.0.1","level":"info","timestamp":"2026-02-15T08:30:00Z"}

log.error("db.connection_failed", host="db-primary", retries=3)
# {"event":"db.connection_failed","host":"db-primary","retries":3,"level":"error","timestamp":"2026-02-15T08:30:01Z"}

import pino from 'pino';

// pino outputs JSONL by default
const log = pino({
  level: 'info',
  timestamp: pino.stdTimeFunctions.isoTime,
});

// Each call produces one JSONL line
log.info({ userId: 'u-42', ip: '10.0.0.1' }, 'user.login');
// {"level":30,"time":"2026-02-15T08:30:00.000Z","userId":"u-42","ip":"10.0.0.1","msg":"user.login"}

log.error({ host: 'db-primary', retries: 3 }, 'db.connection_failed');
// {"level":50,"time":"2026-02-15T08:30:01.000Z","host":"db-primary","retries":3,"msg":"db.connection_failed"}

// Child loggers inherit context
const reqLog = log.child({ requestId: 'req-abc-123' });
reqLog.info({ path: '/api/users' }, 'request.start');

package main

import (
    "os"
    "github.com/rs/zerolog"
    "github.com/rs/zerolog/log"
)

func main() {
    // Configure JSONL output to stdout
    zerolog.TimeFieldFormat = zerolog.TimeFormatUnix
    log.Logger = zerolog.New(os.Stdout).With().Timestamp().Logger()

    // Each call produces one JSONL line
    log.Info().
        Str("user_id", "u-42").
        Str("ip", "10.0.0.1").
        Msg("user.login")
    // {"level":"info","user_id":"u-42","ip":"10.0.0.1","time":1739608200,"message":"user.login"}

    log.Error().
        Str("host", "db-primary").
        Int("retries", 3).
        Msg("db.connection_failed")
}

[SERVICE]
    Flush        5
    Daemon       Off
    Log_Level    info
    Parsers_File parsers.conf

[INPUT]
    Name         tail
    Path         /var/log/app/*.jsonl
    Parser       json
    Tag          app.*
    Refresh_Interval 5

[FILTER]
    Name         modify
    Match        app.*
    Add          cluster production-us-east-1
    Add          service my-api

[OUTPUT]
    Name         es
    Match        app.*
    Host         elasticsearch
    Port         9200
    Index        app-logs
    Type         _doc
    Logstash_Format On

# fluentd.conf
<source>
  @type tail
  path /var/log/app/*.jsonl
  pos_file /var/log/fluentd/app.pos
  tag app.logs
  <parse>
    @type json
    time_key timestamp
    time_format %Y-%m-%dT%H:%M:%S%z
  </parse>
</source>

<filter app.logs>
  @type record_transformer
  <record>
    hostname "#{Socket.gethostname}"
    environment production
  </record>
</filter>

<match app.logs>
  @type elasticsearch
  host elasticsearch
  port 9200
  index_name app-logs
  logstash_format true
  <buffer>
    @type memory
    flush_interval 5s
    chunk_limit_size 5m
  </buffer>
</match>