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https://github.com/wooyek/short-url

Experiment web service that shortens URLs
https://github.com/wooyek/short-url

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Experiment web service that shortens URLs

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# Short-URL



This is a job application coding challenge project.



Create a web service that shortens URLs for 1000s of concurrent users. Users

should be able to submit a long URL, then receive a unique shortened URL that

redirects to the long URL. 



## Demo



This application will be available for a short time under http://shorts.gq 



For eg. this http://shorts.gq/0 should redirect you to my GitHub profile.



## Performance and scalability considerations



We need to generate unique values and make them short. Generating random UUIDs 

would be against "make them short" requirement. So in order to generate short

values we need a shared counter like value that will be assigned used as key 

for url mapping.



I chose redis for atomic [INCR](https://redis.io/commands/incr/) command and

[persistent storage](https://redis.io/docs/manual/persistence/). 

It would be a bottleneck, but it [should do fine](https://redis.io/docs/reference/optimization/benchmarks/)

until we'll need to service more than 50K mapping requests per second. 



Deployment on k8s cluster with autoscaling would take care of rest of 

scalability issues.



## Metrics and monitoring 



I focused on the getting the app running on live k8s cluster and did not 

implement metrics. But ATM I think we could get away with the ones available

out of the box with [Prometheus k8s support](https://kubernetes.io/docs/concepts/cluster-administration/system-metrics/): 



- Metrics for ingress/load balancer to monitor HTTP traffic

  - the usual stuff related to usage, latencies and errors

- [Redis metrics](https://docs.redis.com/latest/rs/monitoring-metrics/prometheus-metrics-definitions/)

  - Storage capacity and latencies 

  - The "counter" value with limit as 64 bit signed integer, we should be pretty

    safe, but let's monitor how quicly we're depleting the rest of the results.

 

## Future 



- Re-use mappings for previously seen destination  

- Multiple redis instances and dispatching with consistent hashing

- Expiration on time on url mappings.

- Rolling forward with new redis instances for new mappings and decommissioning

  instances that expired all the previous values.



## User interface



I was asked to not waste time on UI, so I decided to stick with whatever 

is available out of the box. 



## Testing



The project was tested locally on [minikube](https://minikube.sigs.k8s.io/docs/start/) 

with ingress and repository addons enabled. Please see [Makefile](Makefile)

commands with minikube-prefix.



To create deployment on minikue please override `REGISTRY` env variable with 

whatever minikube will show as prefix for `shorts` image uploaded to the local 

minikube images store:



```bash

env REGISTRY=docker.io/library make minikube-create-deployment

```



Please beware that minikube deployment uses `imagePullPolicy: Never` for 

prohibit image downloads from non-existent external source.



A [docker-compose](docker-compose.yaml) is provided for simplified environment

setup and to provide redis for integration tests.



# Other job application code challenges



Please take a look at other code challenge projects I have prepared in the past.



- https://github.com/wooyek/star-wars-explorer

- https://github.com/wooyek/secure-share

- https://github.com/wooyek/secure_share_kiss



And other notable projects — please beware that they are legacy at this point



- https://github.com/wooyek/fakturownia-python

- https://github.com/wooyek/django-error-views

- https://github.com/wooyek/django-email-queue

- https://github.com/wooyek/django-multiinfo

- https://github.com/wooyek/django-opt-out

- https://github.com/wooyek/django-settings-strategy

- https://github.com/wooyek/django-model-cleanup