web-crawler

Write a web crawler that can be given a URL and show all the URLs that URL links to within the domain. It will then find all the URLs that those URLs link to, and carry on until it has built the graph of the website with the links between pages. Display this graph to the user.

E.g. if www.example.com linked to two pages: www.example.com/foo & www.example.com/bar. And www.example.com/foo linked to www.example.com/bar you might see an output like:

www.example.com links to:
  www.example.com/foo
  www.example.com/bar
www.example.com/foo links to:
  www.example.com/bar

Found 3 links to 2 unique URLs.

anything linked outside of the www.example.com domain wouldn't be visited or included in this output.

The will be a number of design decisions to make which might effect what's included in your graph of links between URLs. Stating how many links you find will help comparison of completeness and performance of different solutions you might try.

Adding a Solution

Submit a PR to add a binary under src/bin/.

Things to Consider

• speed - how to make it as fast as possible?
• correctness/completeness
  • does it collect all the links it can?
  • does it handle relative links?
  • what to do when links are broken?
  • do you include links to sub-domains?
  • what to do about fragments & queries?
  • etc...
• input URL - does this have to be the base URL?
• output - how to display the results? terminal? serve to HTML to view in browser?
• progress - how to show the user it is working?

If you want to focus on speed and the design of how to achieve it: some basic, by no means correct or complete, implementations of some of "the other bits" are included in src/lib.rs. You can use these and or improve them.

Testing Performance

The solution should ultimately work on any website, and it's worth testing against a range of websites. It would be interesting to see how the performance is impacted between smaller and bigger sites. Starting with smaller websites that do a decent amount of linking internally is probably best.

To test:

cargo build --release
time cargo run --release --bin <your solution binary> -- <url>

Some <url> suggestions:

https://python-poetry.org
https://serde.rs
https://www.beyondmeat.com