Terraform+AWS自动扩缩容实例缺失初始化文件问题求助

刚接触Terraform和AWS自动扩缩容，配置了Launch Template和Auto Scaling Group管理EC2实例，但自动扩缩容创建的新实例是空的，没有初始实例部署的文件、软件和文件夹。启动模板的user_data脚本（main.sh）依赖这些文件，但新实例无法正常运行脚本。

当前main.tf核心配置如下：

# Autoscaling Group for EC2 instances, using Launch Template
resource "aws_autoscaling_group" "sample_asg" {
  desired_capacity    = 1
  max_size            = 5
  min_size            = 1
  vpc_zone_identifier = aws_subnet.sample_main[*].id

  launch_template {
    id      = aws_launch_template.sample_template.id
    version = "$Latest"
  }
}

# Launch Template for configuring EC2 instances
resource "aws_launch_template" "sample_template" {
  # Configuration details omitted for brevity
  user_data  = filebase64("../scripts/main.sh") # This user_data script will only work from one of the files and folders that were copied over from the very first instance that used this launch template
}

# The very first EC2 Instance resource using the Launch Template
resource "aws_instance" "sample_gen_server" {
  launch_template {
    id      = aws_launch_template.sample_template.id
    version = "$Latest"
  }
}

# Null resource for setting up the first instance environment. I expect that auto scaled instances should have this folder I just created now
resource "null_resource" "setup_instance" {
  provisioner "remote-exec" {
    inline = [
      "sudo mkdir -p apps/sample-gen-server",
      "sudo chown -R ubuntu:ubuntu apps/sample-gen-server",
    ]
    connection {
      type        = "ssh"
      user        = "ubuntu"
      private_key = file("../sample-key.pem")
      host        = aws_instance.sample_gen_server.public_ip
    }
  }

  provisioner "local-exec" {
    command = local.folder_sync_command
  }

  provisioner "remote-exec" {
    inline = [
      "chmod +x apps/sample-gen-server/scripts/setup_instance.sh",
      "apps/sample-gen-server/scripts/setup_instance.sh",
    ]
    connection {
      type        = "ssh"
      user        = "ubuntu"
      private_key = file("../sample-key.pem")
      host        = aws_instance.sample_gen_server.public_ip
    }
  }

  depends_on = [aws_instance.sample_gen_server]
}

# Null resource for installing dependencies for the first instance, then I expect that auto scaled instances should have all of the files, folders and software I am installing using the script in install_deps.sh
resource "null_resource" "install_dependencies" {
  provisioner "remote-exec" {
    inline = [
      "chmod +x apps/sample-gen-server/scripts/install_deps.sh",
      "apps/sample-gen-server/scripts/install_deps.sh",
    ]
    connection {
      type        = "ssh"
      user        = "ubuntu"
      private_key = file("../sample-key.pem")
      host        = aws_instance.sample_gen_server.public_ip
    }
  }
  triggers = {
    always_run = "${timestamp()}"
  }
  depends_on = [null_resource.sync_app_folder]
}

问题本质：ASG通过Launch Template创建的每个实例都是全新的、基于基础AMI启动的独立实例，不会继承手动配置的初始实例的任何内容。用null_resource给第一个实例做的配置，只会作用于那个单独的实例，和ASG创建的新实例完全无关。

方案1：将所有配置逻辑整合到Launch Template的user_data脚本 #

把原本通过null_resource执行的环境搭建、文件同步、依赖安装操作，全部写到main.sh里，让每个新实例启动时自动完成配置：

1. 修改main.sh，包含以下步骤：
   • 创建必要目录
   • 从S3或Git仓库拉取应用文件（替代本地同步）
   • 安装依赖
   • 启动应用服务

示例main.sh内容：

#!/bin/bash
set -e

# 创建目录并设置权限
sudo mkdir -p apps/sample-gen-server
sudo chown -R ubuntu:ubuntu apps/sample-gen-server

# 从Git拉取应用文件（私有仓库需提前配置SSH密钥或访问令牌）
cd apps/sample-gen-server
git clone https://github.com/your-repo/sample-gen-server.git .

# 安装依赖
chmod +x scripts/install_deps.sh
./scripts/install_deps.sh

# 启动应用服务
chmod +x scripts/setup_instance.sh
./scripts/setup_instance.sh

2. 确保Launch Template的user_data正确引用这个脚本，无需单独创建第一个实例，直接用ASG管理所有实例即可。

方案2：创建自定义AMI #

将配置好的第一个实例制作成自定义AMI，让Launch Template基于这个AMI创建实例：

1. 在AWS控制台或用Terraform的aws_ami资源，将配置完成的aws_instance.sample_gen_server创建为自定义AMI。
2. 修改Launch Template，指定使用这个自定义AMI：

resource "aws_launch_template" "sample_template" {
  image_id      = aws_ami.custom_ubuntu.id # 自定义AMI的ID
  user_data     = filebase64("../scripts/main.sh") # 仅保留启动应用的逻辑，无需重复配置环境
  # 其他配置...
}

3. 注意：后续如果应用或依赖更新，需要重新制作AMI并更新Launch Template，否则新实例还是旧版本。

方案3：使用配置管理工具（如Ansible、Chef） #

通过user_data脚本在实例启动时触发配置管理工具，拉取最新配置并执行：

1. 在main.sh中安装Ansible（或其他工具），然后拉取Playbook执行：

#!/bin/bash
set -e

# 安装Ansible
sudo apt update && sudo apt install -y ansible

# 从Git拉取Playbook
git clone https://github.com/your-repo/ansible-playbooks.git /tmp/playbooks

# 执行配置Playbook
ansible-playbook /tmp/playbooks/configure-app.yml

这种方式适合配置复杂、需要频繁更新的场景，能保持实例配置的一致性和灵活性。

• 永远不要依赖手动配置单个实例来给ASG提供模板，ASG的每个实例都是独立的，必须通过Launch Template/AMI/user_data来统一配置。
• 如果涉及敏感数据（如密钥、令牌），不要硬编码在脚本里，使用AWS Secrets Manager或Parameter Store来安全获取。

内容的提问来源于stack exchange，提问作者ololo