AWS Lambda Ruby环境Postgres Layer构建失败求助

尝试为运行Ruby的AWS Lambda构建Postgres Layer，参考相关帖子操作未成功。已添加RUN bundle config cache_all true和RUN bundle package尝试解决，也试过RUN env ARCHFLAGS="-arch aarch64" gem install pg，均无效。

使用的Dockerfile #

FROM public.ecr.aws/lambda/ruby:3.2

RUN yum install -y amazon-linux-extras \
    && amazon-linux-extras enable postgresql14 \
    && yum group install "Development Tools" -y

RUN yum install -y postgresql postgresql-devel

ADD Gemfile Gemfile.lock ${LAMBDA_TASK_ROOT}

ENV GEM_HOME=${LAMBDA_TASK_ROOT}

RUN bundle config cache_all true
RUN bundle config set path 'vendor/bundle'

RUN bundle install
RUN bundle package

构建脚本 #

#!/bin/sh -e

DIST_DIR="pg"
rm -rf $DIST_DIR
mkdir -p "$DIST_DIR/lib"
mkdir -p "$DIST_DIR/ruby/gems"

cd "$SOURCE_DIR" >/dev/null || exit

docker build -t ruby-builder -f Dockerfile .
CONTAINER=$(docker run -d ruby-builder)

# 复制Amazon Linux 2所需的libpq相关二进制文件
docker cp \
  $CONTAINER:/usr/lib64/libpq.so.5.14 \
  $DIST_DIR/lib/libpq.so.5

docker cp \
  $CONTAINER:/usr/lib64/libldap_r-2.4.so.2.10.7 \
  $DIST_DIR/lib/libldap_r-2.4.so.2

docker cp \
  $CONTAINER:/usr/lib64/liblber-2.4.so.2.10.7 \
  $DIST_DIR/lib/liblber-2.4.so.2

docker cp \
  $CONTAINER:/usr/lib64/libsasl2.so.3.0.0 \
  $DIST_DIR/lib/libsasl2.so.3

docker cp \
  $CONTAINER:/usr/lib64/libssl3.so \
  $DIST_DIR/lib/

docker cp \
  $CONTAINER:/usr/lib64/libsmime3.so \
  $DIST_DIR/lib/

docker cp \
  $CONTAINER:/usr/lib64/libnss3.so \
  $DIST_DIR/lib/

docker cp \
  $CONTAINER:/usr/lib64/libnssutil3.so \
  $DIST_DIR/lib/

docker cp \
  $CONTAINER:/var/task/vendor/bundle/ruby/3.2.0 \
  $DIST_DIR/ruby/gems/3.2.0

docker stop $CONTAINER
docker rm $CONTAINER

生成的目录结构 #

.
├── lib
└── ruby
    └── gems
        └── 3.2.0
            ├── bin
            ├── build_info
            ├── cache
            ├── doc
            ├── extensions
            │   └── aarch64-linux
            │       └── 3.2.0
            ├── gems
            │   ├── bundler-2.4.17
            │   │   ├── exe
            │   │   └── lib
            │   └── pg-1.5.4
            │       ├── certs
            │       ├── ext
            │       ├── lib
            │       ├── misc
            │       ├── rakelib
            │       ├── sample
            │       └── translation
            ├── plugins
            └── specifications

测试Lambda函数 #

require 'json'
require 'pg'

def lambda_handler(event:, context:)
    { statusCode: 200, body: {postgres_client_version: PG.library_version}.to_json }
end

报错信息 #

Test Event Name
test

Response
{
  "errorMessage": "cannot load such file -- pg",
  "errorType": "Init<LoadError>",
  "stackTrace": [
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "/var/task/lambda_function.rb:2:in `<top (required)>'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'"
  ]
}

Function Logs
Ignoring pg-1.5.4 because its extensions are not built. Try: gem pristine pg --version 1.5.4
Init error when loading handler lambda_function.lambda_handler
{
  "errorMessage": "cannot load such file -- pg",
  "errorType": "Init<LoadError>",
  "stackTrace": [
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "/var/task/lambda_function.rb:2:in `<top (required)>'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'"
  ]
}
INIT_REPORT Init Duration: 324.56 ms    Phase: init Status: error   Error Type: Runtime.ExitError
Ignoring pg-1.5.4 because its extensions are not built. Try: gem pristine pg --version 1.5.4
Init error when loading handler lambda_function.lambda_handler
{
  "errorMessage": "cannot load such file -- pg",
  "errorType": "Init<LoadError>",
  "stackTrace": [
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "/var/task/lambda_function.rb:2:in `<top (required)>'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'",
    "<internal:/var/lang/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require'"
  ]
}
INIT_REPORT Init Duration: 2500.61 ms   Phase: invoke   Status: error   Error Type: Runtime.ExitError
START RequestId: 2ab0555b-bde9-4cb1-a0d4-ee0d2fe2d0b1 Version: $LATEST
Unknown application error occurred
Runtime.Unknown
END RequestId: 2ab0555b-bde9-4cb1-a0d4-ee0d2fe2d0b1
REPORT RequestId: 2ab0555b-bde9-4cb1-a0d4-ee0d2fe2d0b1  Duration: 2520.07 ms    Billed Duration: 2521 ms    Memory Size: 128 MB Max Memory Used: 16 MB

解决思路建议 #

• 验证扩展编译状态：从报错信息看，pg的原生扩展未正确构建。在Dockerfile的bundle install步骤后添加命令，检查扩展目录是否生成.so文件：

  RUN ls -la ${LAMBDA_TASK_ROOT}/vendor/bundle/ruby/3.2.0/extensions/aarch64-linux/3.2.0/pg-1.5.4/
  

  如果没有.so文件，说明编译过程存在问题。
• 直接用gem安装pg：跳过bundle，直接指定架构参数安装pg，确保原生扩展适配Lambda的aarch64环境：

  RUN env ARCHFLAGS="-arch aarch64" gem install pg -v 1.5.4 --install-dir ${LAMBDA_TASK_ROOT}/vendor/bundle/ruby/3.2.0
  

• 修正Layer的gem路径识别：AWS Lambda Ruby层需要确保GEM_PATH包含Layer的gem目录。可以在Layer中添加ruby/lib/ruby/site_ruby/3.2.0/rubygems/defaults/operating_system.rb文件，内容如下：

  Gem.default_path << '/opt/ruby/gems/3.2.0'
  

  或者在Lambda函数开头显式设置环境变量：

  ENV['GEM_PATH'] = '/opt/ruby/gems/3.2.0'
  

• 检查系统依赖库的完整性：复制libpq相关文件时，保留原始软链接而非仅复制具体版本文件，避免链接错误。可以修改构建脚本中的复制命令：

  docker cp $CONTAINER:/usr/lib64/libpq.so* $DIST_DIR/lib/
  

• 容器内预测试pg加载：构建完Docker镜像后，进入容器运行irb并执行require 'pg'，确认pg能正常加载，排除构建过程中的问题。

内容的提问来源于stack exchange，提问作者Alvaro