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A Node.js AWS Lambda script that converts the ELB logs written to S3 into JSON and pushes them to Loggly

More information about AWS Lambda and Loggly

Get the code and prep it for the uploading to AWS

  • Clone the git repo
git clone
cd elb2loggly
  • Optionally, edit elb2loggly.js with proper Loggly customer token and optional log tags. (You can set these as tags on the S3 Bucket that contains the logs.)
  • Install require npm packages.
npm install


npm run bundle

The resulting zip ( is what you will upload to AWS in step 1 below.

Setting up AWS

For all of the AWS setup, I used the AWS console following this example. Below, you will find a high-level description of how to do this. I also found this blog post on how to set things up using the command line tools.

Create and upload the elb2loggly Lamba function in the AWS Console

  1. Create lambda function
  3. Click "Create a Lambda function" button. (Choose "Upload a .ZIP file") * Name: elb2loggly * Upload lambda function (zip file you made above.) * Handler:* elb2loggly.handler * Role:* In the drop down click "S3 execution role". (This will open a new window to create the role.) Before clicking the "Allow" button to save this new Role, click the "> View Policy Document", then edit and change the Aciton from "s3:GetObject" to "s3:Get*" * I left the memory at 128MB. In my testing with ELBs set upload every 5 minutes this worked for me. You may need to bump this up if your ELB logs are larger.
    * Same advice for Timer, I set it to 10 seconds.
  4. Configure Event Source to call elb2loggly when logs added to S3 bucket.
  6. Make sure the elb2loggly lambda function is selected, then click 'Actions->Add event source' * Event source type: S3 * Bucket: Choose the bucket that contains your ELB logs. * Event type: ObjectCreated (All)

Configure the S3 buckets with tags the elb2loggly uses to know where to send logs. (Alternatively, you can hard-code these values in elb2loggly.js.)

Using S3 Management Console click the bucket that contains your ELB logs.

  1. Under Properties -> Tags add the following tag: * Key: loggly-customer-token * Value: your-loggly-customer-token
  2. And optionally this tag (will tag log entries in loggly): * Key: loggly-tag * Value: aws-elb (Or what ever you want.)

Private URL parameters

If your ELB logs contain private URL parameters such as authentication tokens, e.g.:

you can obscure this information when sending the data to loggly. Add an additional tag to your S3 bucket:

  • Key: elb2loggly-private-url-params
  • Value: authToken/10

This will obscure all authToken parameters with an obscure length of 10, e.g.:


  • To remove a parameter totally use a length of 0, e.g. authToken/0
  • To obscure multiple parameters use a double forward slash as a separator in the tag value, e.g. authToken/10//secretParam/0

Configure ELB to log to S3

I'll assume you already have your ELB set up, just not logging.

  1. Goto the EC2 Management Console under 'Load Balancers'
  2. Choose your ELB, and scroll down to Access Logs:, click edit. * Set Interval to 5 minutes * Set S3 Location to the bucket where you want to put your logs.


A Node.js AWS Lambda script that converts the ELB logs written to S3 into JSON and push them to Loggly




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