Update 'README.md'

README.md

@@ -1,11 +1,91 @@
-This link checker / sitemap generator is built using spatie/crawler which uses guzzle to do the crawling.
+This is very similar to spatie/http-status-check but due to the way guzzle handles redirects I wasn't happy with the results; known 404's, and even whole areas of the site were missing from crawl results. By following this https://github.com/guzzle/guzzle/blob/master/docs/faq.rst#how-can-i-track-redirected-requests I was able to get a crawl result with the complete list of responses as I was expecting.
 
-This is very similar to spatie/http-status-check but due to the way guzzle handles redirects I wasn't happy with the results; known 404's, and even whole chunks of known URLs were missing from crawl results. By following this https://github.com/guzzle/guzzle/blob/master/docs/faq.rst#how-can-i-track-redirected-requests I was able to get a crawl result with the complete list of responses as I was expecting.
+Additionally I wanted to have a list of **all** the pages a 404 or specific link was found on. This was not possible as only the first FoundOn URL is reported. I created a patch to add a new function to the observer to make this possible. https://patch-diff.githubusercontent.com/raw/spatie/crawler/pull/280 without this the `CrawlerTest::testInterlinked` test will fail.
 
-The node.js test server is copied directly from spatie/http-status-check but refactored to offer a more diverse range of tests cases that cover the redirect issues noted above.
+There is also another patch applied to guzzle to prevent the crawl failing with `EXCEPTION: Status code must be an integer value between 1xx and 5xx` without this patch `CrawlerTest::testInvalidStatusCode` will fail.
+
+The node.js test server is copied directly from spatie/http-status-check but refactored to offer a more diverse range of tests cases that cover the redirect issues and new functionality described above.
 
 The examples below are run against the test server in this project.
 
+---
+
+By default `spatie/http-status-check` has `guzzle` set to not follow redirects. This results in the potential for parts of the site to be uncrawlable if they are behind a 301 or 302 redirect, and not linked internally anywhere else with a non-redirecting link.
+
+Some webservers include a `<a href="destination">` link on the 301/302 body and this will mitigate the problem (spaite follows and indexes), however if the webserver does not do this, then the link won't be followed to its true destination, and the destination won't be indexed.
+
+This is most obvious with a redirect to a not found page: You'd expect to see a 404 here:
+
+```
+./http-status-check scan http://localhost:8080/redirectToNotFound
+
+Start scanning http://localhost:8080/redirectToNotFound
+
+[2020-02-22 12:07:22] 302 Found - http://localhost:8080/redirectToNotFound
+
+Crawling summary
+----------------
+Crawled 1 url(s) with statuscode 302
+```
+
+Or a redirect to a page with links: You'd expect to see the rest of the site here:
+```
+$ ./http-status-check scan http://localhost:8080/redirectToFound
+
+Start scanning http://localhost:8080/redirectToFound
+
+[2020-02-22 12:08:34] 302 Found - http://localhost:8080/redirectToFound
+
+Crawling summary
+----------------
+Crawled 1 url(s) with statuscode 302
+```
+
+If I enable `RequestOptions::ALLOW_REDIRECTS` as suggested here https://github.com/spatie/crawler/issues/263 I get:
+
+```
+$ ./http-status-check scan http://localhost:8080/redirectToNotFound
+
+Start scanning http://localhost:8080/redirectToNotFound
+
+[2020-02-22 12:13:53] 404: Not Found - http://localhost:8080/redirectToNotFound
+
+Crawling summary
+----------------
+Crawled 1 url(s) with statuscode 404
+```
+
+and
+
+```
+$ ./http-status-check scan http://localhost:8080/redirectToFound
+
+Start scanning http://localhost:8080/redirectToFound
+
+[2020-02-23 18:10:19] 200 OK - http://localhost:8080/redirectToFound
+
+Crawling summary
+----------------
+Crawled 1 url(s) with statuscode 200
+```
+
+This looks better, we can see the 404 and the 200 now, however on closer inspection you'll notice there are no 301 or 302's being shown. And the redirectToFound is actually showing as a 200 where the real response was 301, the 200 should be associated with the /found URL that is still missing from the results. For generating a sitemap of valid paged we'd need the destination URL, not the redirect URL.
+
+Enter my sitemap crawler:
+
+```
+$ bob@chodbox:~/Projects/sitemap$ bin/crawler crawl http://localhost:8080/redirectToNotFound
+
+302 http://localhost:8080/redirectToNotFound
+404 http://localhost:8080/notFound
+
+$ bin/crawler crawl http://localhost:8080/redirectToFound
+
+302 http://localhost:8080/redirectToFound
+200 http://localhost:8080/found
+```
+
+
 ## EXCEPTION: Status code must be an integer value between 1xx and 5xx
 I ran across this exception https://github.com/spatie/crawler/issues/271
 and the patch for GuzzleHttp/Guzzle fixed it https://github.com/guzzle/guzzle/pull/2591