Serverless架构下Lambda Layers导入模块失败，报Runtime.ImportModuleError

需求与初始目录结构 #

计划在Serverless应用中基于不同目录的requirements.txt创建3个Lambda Layers，初始目录结构如下：

app-directory/
├── lambda functions codes ...
├── layers/
│   ├── layer_A/
│   │   └── requirements.txt
│   ├── layer_B/
│   │   └── requirements.txt
│   └── layer_C/
│       └── requirements.txt
└── serverless.yml

第一次尝试 #

操作步骤 #

1. 创建虚拟环境并安装依赖：

   python3.9 -m venv python
   pip install -r layers/layer_A/requirements.txt
   

   依赖安装到python/lib/python3.9/site-packages/后，压缩python目录。
2. 在serverless.yml中配置Layers：

   layers:
     layerA:
       path: layers/layer_A
       compatibleRuntimes:
         - python3.9
   
     layerB:
       path: layers/layer_B
       compatibleRuntimes:
         - python3.9
   
     layerC:
       path: layers/layer_C
       compatibleRuntimes:
         - python3.9
   

3. 函数中引用Layers：

   migrations:
     handler: src.migrations.lambda_handler
     layers:
       - !Ref LayerALambdaLayer
       - !Ref LayerBLambdaLayer
       - !Ref LayercLambdaLayer
   

执行结果 #

执行sls deploy和sls invoke stage test --function migrations后，出现导入错误：

{
    "errorMessage": "Unable to import module 'src.migrations.handler': No module named 'alembic'",
    "errorType": "Runtime.ImportModuleError",
    "requestId": "59a33572-9439-4590-b547-de6084e784b3",
    "stackTrace": []
}

Environment: darwin, node 20.8.0, framework 3.35.2 (local) 3.38.0v (global), plugin 7.0.5, SDK 4.4.0
Credentials: Local, "default" profile
Docs:        docs.serverless.com
Support:     forum.serverless.com
Bugs:        github.com/serverless/serverless/issues

Error:
Invoked function failed

第二次尝试 #

操作步骤 #

1. 单独创建存放requirements的目录，编写bash脚本自动安装依赖并压缩：

   #!/bin/bash
   
   set -e
   
   LAYER_TARGET_DIR="layers"
   LAYER_REQUIREMENTS_DIR="layers_requirements"
   RUNTIME="python3.9"
   
   for LAYER_PATH in $LAYER_TARGET_DIR/*/; do
     LAYER=$(basename $LAYER_PATH)
   
     printf "Processing $LAYER layer\n"
     if [ -f "$LAYER_PATH/python.zip" ]; then
       echo "Existing python.zip found in $LAYER layer. Deleting...\n"
       rm -rf "$LAYER_PATH/python.zip"
     fi
   
     printf "Installing dependencies for $LAYER layer\n"
     mkdir $LAYER_TARGET_DIR/$LAYER/python
     pip3 install -r $LAYER_REQUIREMENTS_DIR/$LAYER/requirements.txt -t $LAYER_TARGET_DIR/$LAYER/python/
     printf "Dependencies installed for $LAYER layer\n"
       
     printf "Zipping the python folder\n"
     cd $LAYER_TARGET_DIR/$LAYER
     zip -r9 python.zip python
     cd - > /dev/null
   
     rm -rf $LAYER_TARGET_DIR/$LAYER/python
   
     printf "$LAYER layer processing complete"
   done
   
   printf "\nAll layers processed\n--------------------------------------\n"
   

2. 执行脚本后目录结构变为：

   ├── lambda functions codes ...
   ├── layers_requirements/
   │   ├── layer_A/
   │   │   └── requirements.txt
   │   ├── layer_B/
   │   │   └── requirements.txt
   │   └── layer_C/
   │       └── requirements.txt
   ├── layers/
   │   ├── layer_A/
   │   │   └── python.zip
   │   ├── layer_B/
   │   │   └── python.zip
   │   └── layer_C/
   │       └── python.zip
   └── serverless.yml
   

执行结果 #

仍出现相同的No module named 'alembic'导入错误。

疑问 #

已核对目录结构符合AWS要求，请问是否配置有误或遗漏了什么？

内容的提问来源于stack exchange，提问作者b33