jpaolin / aws-lambda-s3-wkhtmltopdf

Convert HTML to PDF using Webkit (QtWebKit) on AWS Lambda

aws-lambda-s3-wkhtmltopdf

Convert S3-website HTML to PF using Webkit (QtWebKit) on AWS Lambda.

Required permissions

Permissions required to properly function.

• s3:PutObject - Upload the output PDF to the bucket
• s3:PutObjectTagging - Set tags on the uploaded PDF

Note that s3:GetObject is not used. The html page is loaded directly from the s3-website URL which requires public read.

Optional permissions

CloudWatch logging permissions. If you Create new role from template(s), these logging permissions will be automatically granted

• logs:CreateLogGroup
• logs:CreateLogStream
• logs:PutLogEvents

Environment variables

All configuration is handled through Environment variables on the AWS Management Console. If not provided default values will be used.

Variable	Description	Type	Default Value
filename_filter	Filename filter used by node.js for fine-grained filter	RegEx	.htm, .html
page_size	The size of PDF pages	String	'letter'
header_left	Text to display left-aligned in the Header	String1	Empty string
header_center	Text to display center-aligned in the Header	String1	Empty string
header_right	Text to display right-aligned in the Header	String1	Empty string
footer_left	Text to display left-aligned in the Footer	String1	Empty string
footer_center	Text to display center-aligned in the Footer	String1	Empty string
footer_right	Text to display right-aligned in the Footer	String1	Empty string
page_zoom	Page scaling	Number	1.00
disable_javascript	Show JavaScript run on the webpage	Boolean2	false
print_media_type	Use the "print" media type when generating the PDF	Boolean2	false
enable_forms	Convert HTML form elements to PDF form elements	Boolean2	false
disable_external_links	Do not load resources from remote webpages	Boolean2	false
no_background	Do not print background	Boolean2	false
no_images	Do not load or print images	Boolean2	false
grayscale	Generate the PDF in grayscale	Boolean2	false

¹ See wkhtmltopdf documentation > "Footers and Headers"

² Valid boolean values: "true" or "false"

Create the AWS Lambda function

1. Log into your AWS account
2. Under Lambda, click Create a Lambda function button
3. Select s3-get-object as the blueprint and click the Next button
4. Configure Trigger
5. Bucket - Select the S3-website bucket.
6. Event type = Object Created (All)
7. Prefix - Set based on your needs
8. Suffix - Set based on your needs (Recommend: ".html")
9. Check Enable trigger
10. Click Next button
11. Configure function
12. Name - Enter name of your function (e.g. "s3html-to-pdf"),
13. Runtime = Node.js 4.3
14. Code entry type = Upload a .ZIP file
15. Click Upload button to upload this project as zip archive.
16. Set desired Environment variables to configure the function
17. Role = Create new role from template(s)
18. Role name - Enter name for the new role (e.g. "s3html-to-pdf-lambda-role")
19. Policy templates - Remove the default S3 object read-only permission. Leave this field empty.
20. Timeout (under Advanced settings) - Set to 10 seconds or more
21. Click Next button
22. Review your configuration and click Create function button

Configure additional permissions to the lamda role

1. Log into your AWS account
2. Under IAM, click Policies in the left navigation pane
3. Click Create Policy button
4. Select Create Your Own Policy
5. Policy Name - Enter the name of the policy (e.g. "s3-pdfUpload-policy")
6. Policy Document - Use the policy document below
7. Click Create Policy button
8. Click Roles in the left navigation pane
9. Choose the Lambda Role we created earlier (e.g. "s3html-to-pdf-lambda-role")
10. Click Attach Policy button on the Permissions tab
11. Select the policy we just created (e.g. "s3-pdfUpload-policy")
12. Click Attach Policy button

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:PutObjectTagging"
            ],
            "Resource": [
                "arn:aws:s3:::*/*.pdf"
            ]
        }
    ]
}

Testing function

For the test we will be using the S3 Put sample event, changing only the parameters that are used by the function

1. Click Actions button, then click Configure test event
2. Select S3 Put
3. In the JSON, update the following parameters
4. Records[0].s3.bucket.bucketname - Enter your bucket's name
5. Records[0].s3.object.key - Enter an existing html webpage from your bucket
6. Click Save and test button. If your function is working correctly, you should receive following output:

Common Errors

"/var/task/wkhtmltopdf: Permission denied"

The wkhtmltopdf command does not have execute permissions.

Repackage zip to include POSIX execute permission (e.g. 755) on this file

"network error: ContentOperationNotPermittedError"

Resource returned HTTP 403 - Forbidden error.

Ensure public read access on either bucket policy or ACLs.