lambda-promtail

This is a sample deployment for lambda-promtail - Below is a brief explanation of what we have generated for you:

.
├── Makefile                    <-- Make to automate build
├── Dockerfile                  <-- Uses the AWS Lambda Go base image
├── README.md                   <-- This instructions file
├── lambda-promtail             <-- Source code for a lambda function
│   └── main.go                 <-- Lambda function code

Requirements

• AWS CLI already configured with Administrator permission
• Terraform

If you want to modify the lambda-promtail code you will also need:

• Docker installed
• Golang

Setup process

Building and Packaging

The provided Makefile has targets build, and clean.

build builds the lambda-promtail as a Go static binary. To build the container image properly you should run docker build . -f tools/lambda-promtail/Dockerfile from the root of the Loki repository,you can upload this image to your AWS ECR and use via Lambda. clean will remove the built Go binary.

Packaging and deployment

The easiest way to deploy to AWS Lambda using the Golang runtime is to use the lambda-promtail image by uploading it to your ECR.

Alternatively you can build the Go binary and upload it to Lambda as a zip:

GOOS=linux CGO_ENABLED=0 go build main.go
zip function.zip main

To deploy your application for the first time, first make sure you've set the following value in the Terraform file:

• WRITE_ADDRESS

This is the Loki Write API compatible endpoint that you want to write logs to, either promtail or Loki.

The lambda-promtail code picks this value up via an environment variable.

Also, if your deployment requires a VPC configuration, make sure to edit the vpc_config field in main.tf manually. Additonal documentation for the Lambda specific Terraform configuration is here.

Then use Terraform to deploy:

terraform apply -var "<ecr-repo>:<tag>" -var "write_address=https://your-loki-url/loki/api/v1/push" -var "password=<basic-auth-pw>" -var "username=<basic-auth-username>" -var 'log_group_names=["log-group-01", "log-group-02"]'

or CloudFormation:

aws cloudformation create-stack --stack-name lambda-promtail-stack --template-body file://template.yaml --capabilities CAPABILITY_IAM CAPABILITY_NAMED_IAM --region us-east-2 --parameters ParameterKey=WriteAddress,ParameterValue=https://your-loki-url/loki/api/v1/push ParameterKey=Username,ParameterValue=<basic-auth-username> ParameterKey=Password,ParameterValue=<basic-auth-pw> ParameterKey=LambdaPromtailImage,ParameterValue=<ecr-repo>:<tag>

Appendix

Golang installation

Please ensure Go 1.x (where 'x' is the latest version) is installed as per the instructions on the official golang website: https://golang.org/doc/install

For example:

GO_VERSION=go1.16.6.linux-amd64.tar.gz

rm -rf /usr/local/bin/go*
rm -rf /usr/local/go
curl -O https://storage.googleapis.com/golang/$GO_VERSION
tar -zxvf $GO_VERSION
sudo mv go /usr/local/
rm $GO_VERSION
ln -s /usr/local/go/bin/* /usr/local/bin/

A quickstart way would be to use Homebrew, chocolatey or your Linux package manager.

Homebrew (Mac)

Issue the following command from the terminal:

brew install golang

If it's already installed, run the following command to ensure it's the latest version:

brew update
brew upgrade golang

Chocolatey (Windows)

Issue the following command from the powershell:

choco install golang

If it's already installed, run the following command to ensure it's the latest version:

choco upgrade golang

Limitations

• Error handling: If promtail is unresponsive, lambda-promtail will drop logs after retry_count, which defaults to 2.
• AWS CloudWatch quotas state that the event size is limited to 256kb. 256 KB (maximum). This quota can't be changed.