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https://github.com/destrangis/urlmonitor

Check urls and run actions if changed
https://github.com/destrangis/urlmonitor

monitoring monitoring-application python web yaml

Last synced: 6 days ago
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Check urls and run actions if changed

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README 

        
## UrlMonitor



This program is intended to be run periodically from cron or a systemd ``.timer`` service on GNU/Linux, a Periodic Task on Windows, or whatever you are using.



When run, the program will check the URLs from its list, and, if they have changed since the last time they were checked, will run a series of actions as a result.



The list of URLs and actions to be run if changed are specified in a YAML file (by default called ``urllist.yml``). This file consist on a LIST of OBJECTS, each containing the fields name with a descriptive string, url with the url to be checked, and actions, which is a LIST of OBJECTS, where the key is the action name and the value are the arguments, which can be a STRING or a LIST of strings.



An example of urllist.yml file:



```yaml

---

- name: Check for new versions of my favourite software

  url: https://www.coolproject.org/download/files

  actions:

    - email_notify:

        - [email protected]

        - [email protected]



- name: Get latest version of the software

  url: https://www.coolproject.org/latest

  actions:

    - re_match:

        - '[Ss]ource [Tt]arball.*The file'

      - run_script: wget {re_match[1]}

```

This action sets the following variables:



Variable    | Value

------------|-----------------------------------

return_code | The exit code of the program

error       | The error encountered, if any

stdout      | Whatever the program has written to its standard output

stderr      | Whatever the program has written to its error output



### Writing Custom Actions

You can write a custom action easily. You just need to write a Python module that exports a callable called ``action_object`` with the following signature:



```python

def action_object(name, arglst, url, content, variables, log):

    pass

```



Where the arguments are:



Argument  | Description

----------|--------

name      | The action name

arglst    | The list of arguments.

url       | The url that changed

content   | The content (possibly HTML) of the url

variables | A mapping containing the variables and their values

log       | A logging object



If the arguments in ``arglst`` will be expanded by the calling routine and should contain the final value.



If your action requires configuration parameters, you can create a class that has a ``__call__`` method and instantiate into ``action_object``. At configuration time, the program will call the ``initialise`` method with a dictionary containing the configuration parameters as argument.



In order to simplify the process, the module ``actionbase`` provides the class ``Action`` from which your action can inherit. This already provides an ``initialise`` method which will install the configuration parameters, which you can access as instance attributes of ``action_object``. In addition, you should provide a list of expected parameters and a default value for those that can have one in the class variables ``check_cfg_vars`` and ``default_vars``. An exception is raised if a parameter that has been specified in ``check_cfg_vars`` is not found and there is no default value.



As an example, you can check the code for the ``email_notify`` action.



```python

from urlmonitor.actionbase import Action



class _EmailAction(Action):



    check_cfg_vars = [ "smtp_server", "from_address", "smtp_encryption",

            "smtp_user", "smtp_password", "smtp_port"]

    default_vars = {

        "from_address": "urlmonitor@{}".format(_NODE),

        "smtp_encryption": None,

        "smtp_user": None,

        "smtp_password": "",

        "smtp_port": 0,

        }



    ...



    def __call__(self, name, arglst, url, content, variables, log):

        ...

        

action_object = _EmailAction()

```



### License



This software is released under the **MIT License**