serverless-package-python-functions

• Installation
• What's it?
• Why do I need it?
• How does it work?

Installation

$ npm install --save serverless-package-python-functions

# serverless.yml
plugins:
  - serverless-package-python-functions

What is it?

A Serverless Framework plugin for packaging Python Lambda functions with only the dependencies they need.

Why do I need it?

This plugin makes it easy to manage function-level and service-level dependencies for your awesome Python Serverless project

Let's consider the following project structure

your-awesome-project/
├── common_files
│   ├── common1.py
│   └── common2.py
├── function1
│   ├── lambda.py
│   └── requirements.txt # with simplejson library
├── function2
│   ├── lambda.py
│   └── requirements.txt
├── requirements.txt # with requests library
└── serverless.yml

This project has:

• two functions, function1 and function2, each with their own requirements.txt files. function1's requirements.txt lists the simplejson pip package
• Code common to both function1 and function2 in a directory named common_files
• A top-level requirements.txt file with pip dependencies common to both functions, e.g requests library

This plugin will package your functions into individual zip files that look like:

├── lambda.py # function-level code
├── requirements.txt
├── common1.py # service-level code
├── common2.py
├── simplejson # function-level dependencies
├── simplejson-3.10.0.dist-info
├── requests # service-level dependencies
└── requests-2.13.0.dist-info

So that the below code

import common1, common2, requests, simplejson

in function1/lambda.py works like works like a charm!

The plugin also supports packaging your dependencies using a Docker Image that replicates your cloud providers environment, allowing you easily work with platform-dependent libraries like numpy.

How does it work?

The plugin handles the creation of the artifact zip files for your Serverless functions.

When serverless deploy is run, the plugin will:

1. create a build directory for each function
2. copy the appropriate function-level and service-level code you specify into each function's build directory
3. Download the appropriate function-level and service-level pip dependencies into each function's build directory
4. Create zip files of each functions build directory

The Serverless framework will then pickup each zip file and upload it to your provider.

Here's a simple serverless.yml configuration for this plugin, assuming the project structure above one of the functions we add -${opt:stage} to the name in order to append the stage to the function name

service: your-awesome-project
package:
    individually: true
    
plugins:
  - serverless-package-python-functions
custom:
  pkgPyFuncs: # plugin configuration
    buildDir: _build
    requirementsFile: 'requirements.txt'
    globalRequirements:
      - ./requirements.txt
    globalIncludes:
      - ./common_files
    cleanup: true
functions:
  function1:
    name: function1-${opt:stage}
    handler: lambda.handler
    package:
      include:
        - function1
      artifact: ${self:custom.pkgPyFuncs.buildDir}/function1.zip
  function2:
    name: function2
    handler: lambda.handler
    package:
      include:
        - function2
      artifact: ${self:custom.pkgPyFuncs.buildDir}/function2.zip

The plugin configurations are simple:

At the function level, you:

• Specify name to give your function a name. The plugin uses the function's name as the name of the zip artifact
• Use include to specify what function-level files you want to include in your artifact. Simply specifying the path to the function's folder will include every file in the folder in the function's zip artifact
• Use artifact to tell Serverless where to find the zip artifact. The plugin creates the zip artifact for the function at buildDir/name.zip, so using ${self:custom.pkgPyFuncs.buildDir}/[function-name-here].zip is advised.

At the package level, you may need to:

• Specify the individually parameter as true to ensure that zip artifacts are generated properly. You may need this if you are getting file not found errors about your zip artifact.

Now, you may be wondering, doesn't the Serverless documentation say:

Serverless won't zip your service if [artifact] is configured and therefore exclude and include will be ignored. Either you use artifact or include / exclude.

Yes, that is correct and is actually awesome! Since Serverless ignores include/exclude silently when artifact is specified, it allows this plugin take advantage of the include property to provide you with a familiar interface for specifying function-level dependencies. So while this plugin uses include to determine what goes in your artifact, all Serverless cares about is the artifact that this plugin creates when it executes.

The last thing that your keen eye may have noticed from the example serverless.yml above is that handler is specified simply as lambda.handler not ${self:custom.pkgPyFuncs.buildDir}/function/lambda.hadler or function/lambda.handler. This is because the plugin zips your artifacts such that /path/to/function is the root of the zip file. Combined with the fact that it uses pip install -t to download pip dependencies directly to the top level of the zip file, this makes imports significantly simpler for your project. Furthermore, since pip install -t downloads the actual pip package files into a folder, this plugin works without the need for virtualenv