Sending a Slack DM to the "Users to Notify" When a Comment Is Added in Backlog

I built an AWS Serverless Application Model project with Golang that sends a Slack DM to the “users to notify” when a comment is added in Backlog. ♪

For how to use it, please take a look at the Git project!

kenzo0107/backlog-to-slack-dm

If anything is unclear, feel free to reach out. ♪

Points Considered During Development

Are there any SDKs related to the Backlog API out there?

griffin-stewie/go-backlog seemed to have everything in place, so I gave it a try.

The parts I wanted to use are the following:

• The type Activity struct that receives event information when a comment is added
• Executing the API that retrieves the email address from the ID of the user to be notified, obtained from the above

However, in this library, the Notifications field in Activity, which contains the information I wanted to notify on, was commented out, so I couldn’t use it as is.

Since I was pressed for time, I forked it and handled it in kenzo0107/go-backlog.

Simply uncommenting it wasn’t enough to make it work — it raised an error during json.Unmarshal, so I had to handle some other parameters as well.

How should access control from Backlog be handled?

There was a mention of Basic authentication for access control from Backlog, so I went with Basic authentication.

If you want a method that isn’t affected by IP address changes, you can add Basic authentication to the Webhook URL to achieve authentication that doesn’t depend on the IP address.

Please tell me the IP address of the Webhook sending server

The IP range may change without notice, and it might be hard for anyone other than the creator to notice. For that reason, I embedded the Basic authentication credentials into the URL set in the Backlog Webhook, like https://<user>:<password>@.......

I had this authenticated with API Gateway + a Lambda Authorizer (Request Type).

What about the IPs to allow when executing the Backlog API?

By placing the Lambda that executes the Backlog API in a Private Subnet routed through a NAT Gateway, I fixed the egress IP, and set that IP as an allowed IP on the Backlog side.

Caveats

Backlog Webhooks must be configured per project

It wasn’t possible to configure all projects at once. (As of 2020-02-27)

I handled this by notifying each project administrator of the credentials as confidential information.

Summary

There are still some areas where I haven’t fully written tests, but I’ve confirmed that it works without issues.

I hope this is helpful in some way to those who use Backlog.

That’s all.