📘 第24课：健康检查

生产部署

💓 容器健康检查

进程在≠服务可用。健康检查让Docker知道应用是否真正可用，而不仅仅是进程还活着。

📝 HEALTHCHECK配置

# Dockerfile中定义 ✅
HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
  CMD curl -f http://localhost:3000/health || exit 1

# docker run指定 ✅
docker run -d --health-cmd="curl -f http://localhost:3000/health" \
  --health-interval=30s \
  --health-timeout=3s \
  --health-retries=3 \
  my-app

# Compose配置 ✅
services:
  app:
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 3s
      start_period: 10s
      retries: 3

📊 健康状态

# 查看健康状态 ✅
docker ps --format "table {{.Names}}\t{{.Status}}"
NAMES    STATUS
api      Up 5 minutes (healthy)
db       Up 5 minutes (healthy)
cache    Up 5 minutes (unhealthy)

# 查看详细健康检查日志 ✅
docker inspect api --format='{{json .State.Health}}' | jq

{
  "Status": "healthy",
  "FailingStreak": 0,
  "Log": [
    {
      "ExitCode": 0,
      "Output": "OK",
      "Start": "2024-01-15T10:30:00Z"
    }
  ]
}

🔧 常见应用健康检查

# HTTP服务 ✅
HEALTHCHECK CMD curl -f http://localhost/health || exit 1

# PostgreSQL ✅
HEALTHCHECK CMD pg_isready -U postgres

# Redis ✅
HEALTHCHECK CMD redis-cli ping

# MySQL ✅
HEALTHCHECK CMD mysqladmin ping -h localhost

# MongoDB ✅
HEALTHCHECK CMD mongosh --eval "db.adminCommand('ping')"

# Alpine镜像（无curl）✅
HEALTHCHECK CMD wget --no-verbose --tries=1 --spider http://localhost/health || exit 1

# TCP端口检查 ✅
HEALTHCHECK CMD nc -z localhost 5432 || exit 1

🔄 健康检查与自动重启

# 配合restart策略自动重启不健康容器 ✅
services:
  app:
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      retries: 3
    restart: unless-stopped

# Swarm模式：自动替换不健康容器
deploy:
  restart_policy:
    condition: on-failure
    delay: 5s
    max_attempts: 3

❓ 常见问题

📚 深度补充：健康检查进阶要点

【运维与部署阶段】生产环境注意事项

常见误区与避坑指南

1. 过度配置：不是所有服务都需要高可用，根据实际需求选择架构复杂度，避免过度工程
2. 忽略日志：日志是排障的关键，确保日志格式统一、级别合理、采集完整
3. 资源超卖：容器资源限制不是摆设，超卖会导致性能下降甚至OOM Kill
4. 安全忽视：默认配置不等于安全配置，生产环境必须加固（非root、只读FS、最小能力）
5. 监控缺失：没有监控等于盲飞，至少要有基础的健康检查和资源监控
6. 手动运维：能自动化的绝不手动，手动操作容易出错且不可追溯
7. 忽略网络策略：默认所有容器互通不安全，应按最小权限原则配置网络

进阶阅读与参考

• Docker官方文档：https://docs.docker.com/
• Docker最佳实践指南：Dev Best Practices
• CIS Docker Benchmark：容器安全基线检查标准
• 12-Factor App方法论：https://12factor.net/
• Google SRE Book：运维可靠性工程实践
• Kubernetes官方文档：https://kubernetes.io/docs/

Docker命令速查卡

# 容器生命周期
docker create/start/stop/restart/rm/pause/unpause
docker logs/top/stats/inspect/exec diff

# 镜像构建
docker build/pull/push/tag/rmi/images/history
docker save/load/import/manifest

# 网络与存储
docker network create/ls/inspect/connect/disconnect/rm/prune
docker volume create/ls/inspect/rm/prune

# Docker Compose
docker compose up/down/ps/logs/build/exec
docker compose config/stop/start/scale/top/cp

# 系统维护
docker system df/prune/info
docker builder prune
docker container/prune/image prune

# K8s常用命令
kubectl get/describe/logs/exec/apply/delete
kubectl rollout status/undo/history
kubectl scale/autoscale/set

本阶段知识脉络

生产环境检查清单

SRE关键指标（SLI/SLO）

实战案例：故障排查流程

# Step 1: 检查容器状态
docker ps -a                          # 查看所有容器
docker inspect <container>            # 查看详细配置

# Step 2: 查看日志
docker logs --tail 100 <container>    # 最近100行日志
docker logs --since 1h <container>    # 最近1小时

# Step 3: 进入容器排查
docker exec -it <container> sh        # 进入容器shell

# Step 4: 检查资源
docker stats --no-stream              # 资源使用概览
docker system df                      # 磁盘使用

# Step 5: 网络排查
docker network ls                     # 网络列表
docker exec <c> ping <target>        # 网络连通性
docker exec <c> nslookup <svc>       # DNS解析

# Step 6: 检查健康状态
docker inspect --format '{{.State.Health}}' <c>
docker inspect --format '{{.State.ExitCode}}' <c>
docker inspect --format '{{.State.OOMKilled}}' <c>

Dockerfile模板：多语言通用

# 通用最佳实践模板
FROM alpine:3.19 AS builder
# ... 构建步骤 ...

FROM alpine:3.19
RUN addgroup -S appgroup && adduser -S appuser -G appgroup
WORKDIR /app
COPY --from=builder /app/output .
USER appuser
HEALTHCHECK --interval=30s --timeout=3s --retries=3 \
  CMD wget -qO- http://localhost:8080/health || exit 1
EXPOSE 8080
CMD ["./app"]

Docker Compose健康检查模板

services:
  app:
    build: .
    healthcheck:
      test: ["CMD", "wget", "-qO-", "http://localhost:8080/health"]
      interval: 30s
      timeout: 5s
      retries: 3
      start_period: 30s
    restart: unless-stopped
    deploy:
      resources:
        limits:
          cpus: '1'
          memory: 512M

性能调优要点