Admin tools: Link crawler robot
Link crawler robot 2018070200
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What is this?
This is a link checking robot, that crawls your Moodle site following links and reporting on links that are either broken or that link to very large files.
How does it work?
It is an admin tool plugin with a Moodle cron task. It logs into your Moodle via curl effectively from outside Moodle. The cronjob scrapes each page, parses it and follows links. By using this architecture it will only find broken links that actually matter to students.
Since the plugin cronjob comes in from outside it needs to authenticate in Moodle.
The plugin has a dependency on the moodle-auth_basic. To install the dependency plugin as a git submodule:
git submodule add https://github.com/catalyst/moodle-auth_basic auth/basic
Installing plugin source code
Install plugin moodle-tool_crawler as a git submodule:
git submodule add https://github.com/central-queensland-uni/moodle-tool_crawler.git admin/tool/crawler
When installing the plugins please keep in mind the official Moodle recommendations: installing Moodle plugins
Login to Moodle after you have downloaded the plugin code with git. You will be forwarded to URL http://your_moodle_website.com/admin/index.php with Plugins check. There you should see plugins "Basic authentication" and "Link checker robot".
Click button "Upgrade Moodle database now" which should initiate plugins installation.
Now you should see page "Upgrading to new version" with plugins installation statuses and button "Continue".
**Note! Plugin auth_basic is disabled by default after installation. You will need to enable it manually from
Home ► Site administration ► Plugins ► Authentication ► Manage authentication**
After clicking "Continue" you will get to the page "New settings - Link checker robot". While you may leave other settings default, you might want to setup a custom bot username and make sure to change bot password.
It is recommended that bot user should be kept with readonly access to all the site pages you wish to crawl. You can give the robot similar read capabilities that real students have. Never give your bot user write capabilities.
It can also be a good idea to give your robot some extra permissions, like visibility of hidden courses or activites so it can crawl content which is being developed and will be later delivered to students. If you are worried about load and total crawl time then you can filter out whole courses, eg last years archives courses, see below for more details.
After verifying all settings click "Save changes".
Enable auth_basic plugin (if you haven't done that earlier) from
Home ► Site administration ► Plugins ► Authentication ► Manage authentication
Now navigate to URL http://your_moodle_website.com/admin/tool/crawler/index.php". It will show some stats about the Link checker Robot.
Click "Auto create" button against "Bot user". This actually creates the user with the username and password you have configured previously on page "New settings - Link checker robot".
Once bot user is created "Bot user" line in status report should be showing "Good".
Disabling crawling of specific course categories
This is achieved by configuring proper security roles in Moodle and assigning these roles to the robot user on desired categories.
Import role "Robot" from admin/tool/crawler/roles/robot.xml on
Site administration ► Users ► Permissions ► Define roles ► Add a new role
Add this role to the "Link checker robot" user on
Site administration ► Users ► Permissions ► Assign system roles.
Import role "Robot nofollow" from file admin/tool/crawler/roles/robotnofollow.xml on
Site administration ► Users ► Permissions ► Define roles ► Add a new role.
To disable crawling of, say "Category ABC", go to
Site administration ► Courses ► Manage courses and categories ► Category ABC
then click on "Assign roles" in the left navigation menu. Click on role "Robot nofollow", click on user "Link checker Robot" under "Potential users" and add him to "Existing users".
The above configuration applies role "Robot" on the whole Moodle site and lets crawler to access general content. And "Role nofollow" prohibits crawler from accessing the specific category.
In the same way it is possible to restrict crawler from accessing other Moodle contexts such as courses, activities and blocks.
The same effect could be achieved even without role "Robot nofollow" by assigning role "Robot" on the contexts you want to be crawled. But using the combination of two roles gives more flexibility.
Test basic authentication with curl
Example in bash:
curl -c /tmp/cookies -v -L --user moodlebot:moodlebot http://your_moodle_website.com/course/view.php?id=3
This command should log you in with specified credentials via Basic HTTP Auth. It will dump headers, requests and responses and among the output you should be able to see the line "You are logged in as ".
Once Basic HTTP auth works test running the robot task from the CLI:
php admin/tool/task/cli/schedule_task.php --execute='\tool_crawler\task\crawl_task' Scheduled task: Link checker robot ... used 2997 dbqueries ... used 59.828736066818 seconds Task completed.
If this worked then it's a matter of sitting back and waiting for the robot to do it's thing. It works incrementally spreading the load over many cron cycles, you can watch it's progress in
4 new admin reports are available for showing the current crawl status, broken links and URLs and slow links. They are available under:
Administration > Reports > Link checker
Issues and Feedback
Please raise any issues in GitHub:
If you need anything urgently and would like to sponsor it's implementation please email me: Brendan Heywood.
- Version build number
- Version release name
- Stable version
- MD5 Sum
- Supported software
- Moodle 2.7, Moodle 3.1, Moodle 3.2, Moodle 3.3, Moodle 3.4, Moodle 3.5
- This is the latest release for Moodle 2.7
- This is the latest release for Moodle 3.1
- This is the latest release for Moodle 3.2
- This is the latest release for Moodle 3.3
- This is the latest release for Moodle 3.4
- This is the latest release for Moodle 3.5
Version control information
- Version control system (VCS)
- VCS repository URL
- VCS tag
Default installation instructions for plugins of the type Admin tools
- Make sure you have all the required versions.
- Download and unpack the module.
- Place the folder (eg "mytool") in the "admin/tool" subdirectory.
- Visit http://yoursite.com/admin to finish the installation