We have a couple of site setting, `slow_down_crawler_user_agents` and `slow_down_crawler_rate`, that are meant to allow site owners to signal to specific crawlers that they're crawling the site too aggressively and that they should slow down.
When a crawler is added to the `slow_down_crawler_user_agents` setting, Discourse currently adds a `Crawl-delay` directive for that crawler in `/robots.txt`. Unfortunately, many crawlers don't support the `Crawl-delay` directive in `/robots.txt` which leaves the site owners no options if a crawler is crawling the site too aggressively.
This PR replaces the `Crawl-delay` directive with proper rate limiting for crawlers added to the `slow_down_crawler_user_agents` list. On every request made by a non-logged in user, Discourse will check the User Agent string and if it contains one of the values of the `slow_down_crawler_user_agents` list, Discourse will only allow 1 request every N seconds for that User Agent (N is the value of the `slow_down_crawler_rate` setting) and the rest of requests made within the same interval will get a 429 response.
The `slow_down_crawler_user_agents` setting becomes quite dangerous with this PR since it could rate limit lots if not all of anonymous traffic if the setting is not used appropriately. So to protect against this scenario, we've added a couple of new validations to the setting when it's changed:
1) each value added to setting must 3 characters or longer
2) each value cannot be a substring of tokens found in popular browser User Agent. The current list of prohibited values is: apple, windows, linux, ubuntu, gecko, firefox, chrome, safari, applewebkit, webkit, mozilla, macintosh, khtml, intel, osx, os x, iphone, ipad and mac.
Googlebot handles no-index headers very elegantly. It advises to leave as many routes as possible open and uses headers for high fidelity rules regarding indexes.
Discourse adds special `x-robot-tags` noindex headers to users, badges, groups, search and tag routes.
Following up on b52143feff we now have it so Googlebot gets special handling.
Rest of the crawlers get a far more aggressive disallow list to protect against excessive crawling.
Google insists on indexing pages so it can figure out if they
can be removed from the index.
see: https://support.google.com/webmasters/answer/6332384?hl=en
This change ensures the we have special behavior for Googlebot
where we allow indexing, but block the actual indexing via
X-Robots-Tag
Previously people were not consistent about mocking which left internals in
a fragile state when running subfolder specs.
This introduces a simple helper `set_subfolder` which you can use to set
the subfolder for the spec. It takes care of proper configuration of subfolder
and teardown.
```
# usage
set_subfolder "/my_amazing_subfolder"
```
You should no longer stub base_uri or global_settings
* FEATURE: Allow customization of robots.txt
This allows admins to customize/override the content of the robots.txt
file at /admin/customize/robots. That page is not linked to anywhere in
the UI -- admins have to manually type the URL to access that page.
* use Ember.computed.not
* Jeff feedback
* Feedback
* Remove unused import
This change both speeds up specs (less strings to allocate) and helps catch
cases where methods in Discourse are mutating inputs.
Overall we will be migrating everything to use #frozen_string_literal: true
it will take a while, but this is the first and safest move in this direction
Also moved to default crawl delay bing so no more than a req every 5 seconds is allowed
New site settings:
"slow_down_crawler_user_agents" - list of crawlers that will be slowed down
"slow_down_crawler_rate" - how many seconds to wait between requests
Not enforced server side yet
