# README
UberChallenge
My email sender for the UBER challenge. https://github.com/uber/coding-challenge-tools/blob/master/coding_challenge.md
TL;DR
Just go and try it! www.uberchallenge.email The API: https://api.uberchallenge.email/email (I would describe it later)
##Problem description: This service allows you to send emails using different email providers. For now it supports Mailgun and Sendgrid.
The best and the only feature of this service is that it falls back to the secondary provider if first is down.
- Mailgun has 99.99% SLA.
- Sendgrid does not have an SLA.
Scope
The solution focuses on the back-end, but also has a front-end part which allows to play with the service and send some emails.
Architecture
Back-end and front-end are completely separated. They have nothing in common.
I just placed them into a single repo so it would be easier for you to review.
Back-end
Back-end is a Go app. I have absolutely no experience with Go and started learning it after I decided to write this project.
Why Go?
- Go is designed to be fast, safe and reliable.
- It's statically typed.
- It is also designed for web.
- This service is IO-heavy. It spends most of the time communicating with the providers.
- Go runs every request in it's own goroutine, so if one request get's stuck or slow or fails it would not affect other users.
The whole back-end contains of a single endpoint which allows you to (surprise!) send emails. It you want to test it you can execute this command from console:
curl -X POST -H "Content-Type: application/json" \
-d='{"to":"[email protected]", \
"subject": "Lorem", \
"body": "ipsum"}' \
https://api.uberchallenge.email/email -i
I wanted to keep it as simple as possible, that's why I'm not using any frameworks.
You don't need them for such a simple app.
It also has preferred_provider parameter which is not required.
You can set it to sendgrid if you're brave. By default we start sending with mailgun.
####Back-end is deployed on Heroku and this gives me a couple of benefits
- Monitoring & metrics
- Logging
- Continuous deployment (github integration and easy rollbacks)
- Scalability (the servers are completely stateless, so I can just add more instances with a single command)
If this night this service would become EXTREMELY popular I CAN (but wouldn't because of the costs) handle the load. I would receive an email from mailgun, that I would reach the quota soon. The only two actions that I need to do is to change the mailgun plan and scale the number of heroku instances.
If I would have more time and motivation I would use some of the auto-scaling solutions, but it seemed to be an overkill.
Security
The service checks the correctness of the client input and uses https.
I do not store any tokens/API keys in the repo.
In order to run the service you need to set those environment variables:
SENDGRID_API_KEY
MAILGUN_DOMAIN
MAILGUN_API_KEY
MAILGUN_API_KEY
PORT (heroku sets it)
And execute:
go run web.go
If you're planning to use only one provider you don't need to set the variables for the other one.
Font-end
Front-end is in docs directory. It's just a couple of static files, so you can run it on your local machine. I'm serving them using github pages connected to a custom domain. GitHub Pages sites have a bandwidth limit of 100GB or 100,000 requests per month. If my front-end would become EXTREMELY popular at night I would receive a polite email from GitHub (they guarantee it) and would setup a CDN in front of GH pages. GH pages is already a CDN, so it also allows we to serve my page faster to the users in different locations.
Security
I do not have any confidential or sensitive information on those pages, that's why I don't use https for Front-end. (Also because GH Pages does not support https for custom domains yet) If it would be critical I can setup a CDN in front of it/instead of it and have https.
Speed
I did not use any heavy css frameworks like bootstrap. I used milligram which is only 2kB gzipped.
Other projects I'm proud about
- Interpreter of my own functional language written in Haskell
- Algorithmic trading bot for Jane Street hackathon
- Awesome work on Profilers and JS packaging that I've done at Quora, but cannot describe here because of an NDA.