https://github.com/dv8fromtheworld/lambdaedge-variable-injector
A simple custom resource for adding environment variable support to Lambda@Edge.
https://github.com/dv8fromtheworld/lambdaedge-variable-injector
aws aws-cloudformation-custom-resource aws-custom-resource cloudformation custom-resource lambda lambda-at-edge
Last synced: 2 months ago
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A simple custom resource for adding environment variable support to Lambda@Edge.
- Host: GitHub
- URL: https://github.com/dv8fromtheworld/lambdaedge-variable-injector
- Owner: DV8FromTheWorld
- Created: 2021-05-08T15:30:30.000Z (about 4 years ago)
- Default Branch: master
- Last Pushed: 2021-05-11T22:20:42.000Z (about 4 years ago)
- Last Synced: 2025-02-01T05:15:51.034Z (4 months ago)
- Topics: aws, aws-cloudformation-custom-resource, aws-custom-resource, cloudformation, custom-resource, lambda, lambda-at-edge
- Language: JavaScript
- Homepage:
- Size: 7.81 KB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Lambda@Edge Environment Variable Injector
A simple custom resource for adding environment variable support to Lambda@Edge.
## Why
Per the [official documentation](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-requirements-limits.html)
environment variables are not supported in AWS Lambda@Edge. There are [some](https://stackoverflow.com/a/58101487)
[possible](https://stackoverflow.com/a/54829145) [workarounds](https://aws.amazon.com/blogs/networking-and-content-delivery/leveraging-external-data-in-lambdaedge/),
however each requires leveraging of external AWS constructs to enable environment-variable-like data passing or requires
maintaining or building multiple versions of your code to simulate what environment varaibles are _meant_ to do.
This solution aims to allow the developer to use environments variables as expected in normal lambdas:
- Defined in Cloudformation
- Retrieved from the language standardized environment constructs
- Node: `process.env[KEY]`
- Python: `os.environ[KEY]`
## How
This custom resource retrieves your Node or Python lambda's payload zip from S3, injects a file into the payload
that contains your defined Environment Variables, re-zips the contents and uploads to S3. It then exposes the
S3 bucket and S3 key of the uploaded modified payload in cloudformation (via `Fn::GetAtt`) for use in lambda definitions.
## Example
```yaml
Resources:
InjectEnvVariables:
Type: Custom::InjectEnvironmentVariables
Properties:
ServiceToken: !Sub 'arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:your-global-lambda-edge-variable-injector'
LambdaBucket: 'your-asset-bucket'
LambdaKey: 'path/to/your/lambda/payload.zip'
PayloadLanguage: 'node'
EnvironmentVariables:
IsSomeone: "Getting"
TheBest: "TheBest, TheBest, TheBest"
Of: "You"
LambdaAtEdge:
Type: AWS::Serverless::Function
Properties:
Handler: index.handler
CodeUri:
Bucket: !GetAtt InjectEnvVariables.LambdaBucket
Key: !GetAtt InjectEnvVariables.LambdaKey
Runtime: 'nodejs14.x'
```
Thus, when `LambdaAtEdge` does `require('./env.js`), the provided environment variables will be loaded into `process.env`
| | |
| ------------------------ | ------------------------------ |
| `process.env.IsSomeone` | `"Getting"` |
| `process.env.TheBest` | `"TheBest, TheBest, TheBest"` |
| `process.env.Of` | `"You"` |
## API
### `OutputBucket`
Defines the S3 bucket which the modified payload zip will be uploaded to. This value will override the `OUTPUT_BUCKET`
environment variable set on the Custom Resource lambda itself if one was set on the global declaration of the resource.
If there was no `OUTPUT_BUCKET` environment variable set on the global declaration then this parameter **is required**.
- Type: `string`
- Required: `conditionally`
### `LambdaBucket`
Defines the source S3 bucket where the payload zip resides. This value should correspond to what you would have put
for [Lambda.Code.S3Bucket](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-lambda-function-code.html#cfn-lambda-function-code-s3bucket).
- Type: `string`
- Required: `yes`
### `LambdaKey`
Defines the source S3 key of the zip file. This value should correspond to what you would have put
for [Lambda.Code.S3Key](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-lambda-function-code.html#cfn-lambda-function-code-s3key).
- Type: `string`
- Required: `yes`
### `PayloadLanguage`
Defines what language is being used in provided lambda payload.
- Type: `string`
- Required: `yes`
- Allowed Values:
- `"node"`
- `"python"`
### `EnvironmentVariables`
An object defining the environment variables that should be made available to the lambda. This value should
correspond to what you would have put for [Lambda.Environment.Variables](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-lambda-function-environment.html#cfn-lambda-function-environment-variables).
- Type: `object`
- Required: `yes`
### `EnvironmentFile`
_Optional_
Defines the name of the environment variable file that is injected into the lambda payload. This value **should include**
the language-specific file extension (`.js` / `.py`).
- Type: `string`
- Required: `no`
- Default:
- Node: `env.js`
- Python: `env.py`