In order to deploy your Chalice app, a zip file is created that contains your application and all third party packages your application requires. This file is used by AWS Lambda and is referred to as a deployment package.
Chalice will automatically create this deployment package for you, and offers several features to make this easier to manage. Chalice allows you to clearly separate application specific modules and packages you are writing from 3rd party package dependencies.
You have two options to structure application specific code/config:
- app.py - This file includes all your route information and is always included in the deployment package.
- chalicelib/ - This directory (if it exists) is included in the
deployment package. This is where you can add config files and additional
application modules if you prefer not to have all your app code in the
See :doc:`multifile` for more info on the
chalicelib/ directory. Both the
app.py and the
chalicelib/ directory are intended for code that you
3rd Party Packages
There are two options for handling python package dependencies:
- requirements.txt - During the packaging process, Chalice will
install any packages it finds or can build compatible wheels for.
Specifically all pure python packages as well as all packages that upload
wheel files for the
manylinux1_x86_64platform will be automatically installable.
- vendor/ - The contents of this directory are automatically added to the top level of the deployment package.
Chalice will also check for an optional
vendor/ directory in the project
root directory. The contents of this directory are automatically included in
the top level of the deployment package (see :ref:`package-examples` for
specific examples). The
vendor/ directory is helpful in these scenarios:
- You need to include custom packages or binary content that is not accessible
pip. These may be internal packages that aren't public.
- Wheel files are not available for a package you need from pip.
- A package is installable with
requirements.txtbut has optional c extensions. Chalice can build the dependency without the c extensions, but if you want better performance you can vendor a version that is compiled.
As a general rule of thumb, code that you write goes in either
chalicelib/, and dependencies are either specified in
or placed in the
Suppose I have the following app structure:
. ├── app.py ├── chalicelib │ ├── __init__.py │ └── utils.py ├── requirements.txt └── vendor └── internalpackage └── __init__.py
requirements.txt file had one requirement:
$ cat requirements.txt sortedcontainers==1.5.4
Then the final deployment package directory structure would look like this:
. ├── app.py ├── chalicelib │ ├── __init__.py │ └── utils.py ├── internalpackage │ └── __init__.py └── sortedcontainers └── __init__.py
This directory structure is then zipped up and sent to AWS Lambda during the deployment process.
Since the original version of this example was written, cryptography has released version 2.0 which does have manylinux1 wheels available. This means if you want to use cryptography in a Chalice app all you need to do is add
cryptography>=2.0in your requirements.txt file.
This example will use version 1.9 of Cryptography because it is a good example of a library with C extensions and no wheel files.
Below shows an example of how to use the
cryptography 1.9 package
in a Chalice app for the
python3.6 lambda environment.
Suppose you are on a Mac or Windows and want to deploy a Chalice app that
depends on the
cryptography==1.9 package. If you simply add it to your
requirements.txt file and try to deploy it with
chalice deploy you will
get the following warning during deployment:
$ cat requirements.txt cryptography==1.9 $ chalice deploy Updating IAM policy. Updating lambda function... Creating deployment package. Could not install dependencies: cryptography==1.9 You will have to build these yourself and vendor them in the chalice vendor folder. Your deployment will continue but may not work correctly if missing dependencies are not present. For more information: http://chalice.readthedocs.io/en/latest/topics/packaging.html
This happened because the
cryptography version 1.9 does not have wheel
files available on PyPi, and has C extensions. Since we are not on the same
platform as AWS Lambda, the compiled C extensions Chalice built were not
compatible. To get around this we are going to leverage the
directory, and build the
cryptography package on a compatible linux system.
You can do this yourself by building
cryptography on an Amazon Linux
instance running in EC2. All of the following commands were run inside a
python 3.6 virtual environment.
Download the source first:
$ pip download cryptography==1.9
This will download all the requirements into the current working directory. The directory should have the following contents:
This is a complete set of dependencies required for the cryptography package. Most of these packages have wheels that were downloaded, which means they can simply be put in the
requirements.txtand Chalice will take care of downloading them. That leaves
pycparseras the only two that did not have a wheel file available for download.
Next build the
cryptographysource package into a wheel file:
$ pip wheel cryptography-1.9.tar.gz
This will take a few seconds and build a wheel file for both
pycparser. The directory should now have two additional wheel files:
cryptographywheel file has been built with a compatible architecture for Lambda (
linux_x86_64) and the
pycparserhas been built for
anyarchitecture which means it can also be automatically packaged by Chalice if it is listed in the
cryptographywheel file from the Amazon Linux instance and unzip it into the
vendor/directory in the root directory of your Chalice app.
You should now have a project directory that looks like this:
$ tree . ├── app.py ├── requirements.txt └── vendor ├── cryptography │ ├── ... Lots of files │ └── cryptography-1.9.dist-info ├── DESCRIPTION.rst ├── METADATA ├── RECORD ├── WHEEL ├── entry_points.txt ├── metadata.json └── top_level.txt
requirements.txtfile should look like this:
$ cat requirements.txt cffi==1.10.0 six==1.10.0 asn1crypto==0.22.0 idna==2.5 pycparser==2.17
app.pyfile you can now import
cryptography, and these dependencies will all get included when the
chalice deploycommand is run.