Send notification when CSS/xPath filter is missing after more than 6 (configurable) attempts (#771)

changedetectionio/forms.py

@@ -349,6 +349,8 @@ class watchForm(commonSettingsForm):
     save_button = SubmitField('Save', render_kw={"class": "pure-button pure-button-primary"})
     save_and_preview_button = SubmitField('Save & Preview', render_kw={"class": "pure-button pure-button-primary"})
     proxy = RadioField('Proxy')
+    filter_failure_notification_send = BooleanField(
+        'Send a notification when the filter can no longer be found on the page', default=False)
 
     def validate(self, **kwargs):
         if not super().validate():
@@ -387,6 +389,11 @@ class globalSettingsApplicationForm(commonSettingsForm):
     api_access_token_enabled = BooleanField('API access token security check enabled', default=True, validators=[validators.Optional()])
     password = SaltyPasswordField()
 
+    filter_failure_notification_threshold_attempts = IntegerField('Number of times the filter can be missing before sending a notification',
+                                                                  render_kw={"style": "width: 5em;"},
+                                                                  validators=[validators.NumberRange(min=0,
+                                                                                                     message="Should contain zero or more attempts")])
+
 
 class globalSettingsForm(Form):
     # Define these as FormFields/"sub forms", this way it matches the JSON storage

changedetectionio/html_tools.py

@@ -1,5 +1,4 @@
 import json
-import re
 from typing import List
 
 from bs4 import BeautifulSoup
@@ -8,16 +7,23 @@ import re
 from inscriptis import get_text
 from inscriptis.model.config import ParserConfig
 
+class FilterNotFoundInResponse(ValueError):
+    def __init__(self, msg):
+        ValueError.__init__(self, msg)
 
 class JSONNotFound(ValueError):
     def __init__(self, msg):
         ValueError.__init__(self, msg)
 
+
 # Given a CSS Rule, and a blob of HTML, return the blob of HTML that matches
 def css_filter(css_filter, html_content):
     soup = BeautifulSoup(html_content, "html.parser")
     html_block = ""
-    for item in soup.select(css_filter, separator=""):
+    r = soup.select(css_filter, separator="")
+    if len(r) == 0:
+        raise FilterNotFoundInResponse(css_filter)
+    for item in r:
         html_block += str(item)
 
     return html_block + "\n"
@@ -42,7 +48,11 @@ def xpath_filter(xpath_filter, html_content):
     tree = html.fromstring(bytes(html_content, encoding='utf-8'))
     html_block = ""
 
-    for item in tree.xpath(xpath_filter.strip(), namespaces={'re':'http://exslt.org/regular-expressions'}):
+    r = tree.xpath(xpath_filter.strip(), namespaces={'re': 'http://exslt.org/regular-expressions'})
+    if len(r) == 0:
+        raise FilterNotFoundInResponse(css_filter)
+
+    for item in r:
         html_block += etree.tostring(item, pretty_print=True).decode('utf-8') + "<br/>"
 
     return html_block

changedetectionio/model/App.py

@@ -5,6 +5,8 @@ from changedetectionio.notification import (
     default_notification_title,
 )
 
+_FILTER_FAILURE_THRESHOLD_ATTEMPTS_DEFAULT = 6
+
 class model(dict):
     base_config = {
             'note': "Hello! If you change this file manually, please be sure to restart your changedetection.io instance!",
@@ -30,6 +32,7 @@ class model(dict):
                     'extract_title_as_title': False,
                     'empty_pages_are_a_change': False,
                     'fetch_backend': getenv("DEFAULT_FETCH_BACKEND", "html_requests"),
+                    'filter_failure_notification_threshold_attempts': _FILTER_FAILURE_THRESHOLD_ATTEMPTS_DEFAULT,
                     'global_ignore_text': [], # List of text to ignore when calculating the comparison checksum
                     'global_subtractive_selectors': [],
                     'ignore_whitespace': True,

changedetectionio/model/Watch.py

@@ -41,6 +41,8 @@ class model(dict):
             'trigger_text': [],  # List of text or regex to wait for until a change is detected
             'text_should_not_be_present': [], # Text that should not present
             'fetch_backend': None,
+            'filter_failure_notification_send': True,
+            'consecutive_filter_failures': 0, # Every time the CSS/xPath filter cannot be located, reset when all is fine.
             'extract_title_as_title': False,
             'check_unique_lines': False, # On change-detected, compare against all history if its something new
             'proxy': None, # Preferred proxy connection

changedetectionio/notification.py

@@ -34,7 +34,6 @@ def process_notification(n_object, datastore):
         valid_notification_formats[default_notification_format],
     )
 
-
     # Insert variables into the notification content
     notification_parameters = create_notification_parameters(n_object, datastore)
 

changedetectionio/templates/edit.html

@@ -62,6 +62,12 @@
                     <div class="pure-control-group">
                         {{ render_checkbox_field(form.extract_title_as_title) }}
                     </div>
+                    <div class="pure-control-group">
+                        {{ render_checkbox_field(form.filter_failure_notification_send) }}
+                        <span class="pure-form-message-inline">
+                         Sends a notification when the filter can no longer be seen on the page, good for knowing when the page changed and your filter will not work anymore.
+                        </span>
+                    </div>
                 </fieldset>
             </div>
 

changedetectionio/templates/settings.html

@@ -36,7 +36,13 @@
                         {{ render_field(form.requests.form.jitter_seconds, class="jitter_seconds") }}
                         <span class="pure-form-message-inline">Example - 3 seconds random jitter could trigger up to 3 seconds earlier or up to 3 seconds later</span>
                     </div>
-
+                    <div class="pure-control-group">
+                        {{ render_field(form.application.form.filter_failure_notification_threshold_attempts, class="filter_failure_notification_threshold_attempts") }}
+                        <span class="pure-form-message-inline">After this many consecutive times that the CSS/xPath filter is missing, send a notification
+                            <br/>
+                        Set to <strong>0</strong> to disable
+                        </span>
+                    </div>
                     <div class="pure-control-group">
                         {% if not hide_remove_pass %}
                             {% if current_user.is_authenticated %}

changedetectionio/tests/test_filter_failure_notification.py

@@ -0,0 +1,123 @@
+import os
+import time
+import re
+from flask import url_for
+from .util import set_original_response, live_server_setup
+from changedetectionio.model import App
+
+
+def set_response_with_filter():
+    test_return_data = """<html>
+       <body>
+     Some initial text</br>
+     <p>Which is across multiple lines</p>
+     </br>
+     So let's see what happens.  </br>
+     <div id="nope-doesnt-exist">Some text thats the same</div>     
+     </body>
+     </html>
+    """
+
+    with open("test-datastore/endpoint-content.txt", "w") as f:
+        f.write(test_return_data)
+    return None
+
+
+# Hard to just add more live server URLs when one test is already running (I think)
+# So we add our test here (was in a different file)
+def test_check_notification(client, live_server):
+    live_server_setup(live_server)
+    set_original_response()
+
+    # Give the endpoint time to spin up
+    time.sleep(1)
+
+    # Add our URL to the import page
+    test_url = url_for('test_endpoint', _external=True)
+    res = client.post(
+        url_for("form_watch_add"),
+        data={"url": test_url, "tag": ''},
+        follow_redirects=True
+    )
+    assert b"Watch added" in res.data
+
+    # Give the thread time to pick up the first version
+    time.sleep(3)
+
+    # Goto the edit page, add our ignore text
+    # Add our URL to the import page
+    url = url_for('test_notification_endpoint', _external=True)
+    notification_url = url.replace('http', 'json')
+
+    print(">>>> Notification URL: " + notification_url)
+
+    # Just a regular notification setting, this will be used by the special 'filter not found' notification
+    notification_form_data = {"notification_urls": notification_url,
+                              "notification_title": "New ChangeDetection.io Notification - {watch_url}",
+                              "notification_body": "BASE URL: {base_url}\n"
+                                                   "Watch URL: {watch_url}\n"
+                                                   "Watch UUID: {watch_uuid}\n"
+                                                   "Watch title: {watch_title}\n"
+                                                   "Watch tag: {watch_tag}\n"
+                                                   "Preview: {preview_url}\n"
+                                                   "Diff URL: {diff_url}\n"
+                                                   "Snapshot: {current_snapshot}\n"
+                                                   "Diff: {diff}\n"
+                                                   "Diff Full: {diff_full}\n"
+                                                   ":-)",
+                              "notification_format": "Text"}
+
+    notification_form_data.update({
+        "url": test_url,
+        "tag": "my tag",
+        "title": "my title",
+        "headers": "",
+        "css_filter": '#nope-doesnt-exist',
+        "fetch_backend": "html_requests"})
+
+    res = client.post(
+        url_for("edit_page", uuid="first"),
+        data=notification_form_data,
+        follow_redirects=True
+    )
+    assert b"Updated watch." in res.data
+    time.sleep(3)
+
+    # Now the notification should not exist, because we didnt reach the threshold
+    assert not os.path.isfile("test-datastore/notification.txt")
+
+    for i in range(0, App._FILTER_FAILURE_THRESHOLD_ATTEMPTS_DEFAULT):
+        res = client.get(url_for("form_watch_checknow"), follow_redirects=True)
+        time.sleep(3)
+
+    # We should see something in the frontend
+    assert b'Did the page change its layout' in res.data
+
+    # Now it should exist and contain our "filter not found" alert
+    assert os.path.isfile("test-datastore/notification.txt")
+    notification = False
+    with open("test-datastore/notification.txt", 'r') as f:
+        notification = f.read()
+    assert 'CSS/xPath filter was not present in the page' in notification
+    assert '#nope-doesnt-exist' in notification
+
+    # Remove it and prove that it doesnt trigger when not expected
+    os.unlink("test-datastore/notification.txt")
+    set_response_with_filter()
+
+    for i in range(0, App._FILTER_FAILURE_THRESHOLD_ATTEMPTS_DEFAULT):
+        client.get(url_for("form_watch_checknow"), follow_redirects=True)
+        time.sleep(3)
+
+    # It should have sent a notification, but..
+    assert os.path.isfile("test-datastore/notification.txt")
+    # but it should not contain the info about the failed filter
+    with open("test-datastore/notification.txt", 'r') as f:
+        notification = f.read()
+    assert not 'CSS/xPath filter was not present in the page' in notification
+
+    # cleanup for the next
+    client.get(
+        url_for("form_delete", uuid="all"),
+        follow_redirects=True
+    )

changedetectionio/update_worker.py

@@ -3,6 +3,8 @@ import queue
 import time
 
 from changedetectionio import content_fetcher
+from changedetectionio.html_tools import FilterNotFoundInResponse
+
 # A single update worker
 #
 # Requests for checking on a single site(watch) from a queue of watches
@@ -19,6 +21,32 @@ class update_worker(threading.Thread):
         self.datastore = datastore
         super().__init__(*args, **kwargs)
 
+    def send_filter_failure_notification(self, uuid):
+
+        threshold = self.datastore.data['settings']['application'].get('filter_failure_notification_threshold_attempts')
+        watch = self.datastore.data['watching'].get(uuid, False)
+
+        n_object = {'notification_title': 'Changedetection.io - Alert - CSS/xPath filter was not present in the page',
+                    'notification_body': "Your configured CSS/xPath filter of '{}' for {{watch_url}} did not appear on the page after {} attempts, did the page change layout?\n\nLink: {{base_url}}/edit/{{watch_uuid}}\n\nThanks - Your omniscient changedetection.io installation :)\n".format(
+                        watch['css_filter'],
+                        threshold),
+                    'notification_format': 'text'}
+
+        if len(watch['notification_urls']):
+            n_object['notification_urls'] = watch['notification_urls']
+
+        elif len(self.datastore.data['settings']['application']['notification_urls']):
+            n_object['notification_urls'] = self.datastore.data['settings']['application']['notification_urls']
+
+        # Only prepare to notify if the rules above matched
+        if 'notification_urls' in n_object:
+            n_object.update({
+                'watch_url': watch['url'],
+                'uuid': uuid
+            })
+            self.notification_q.put(n_object)
+            print("Sent filter not found notification for {}".format(uuid))
+
     def run(self):
         from changedetectionio import fetch_site_status
 
@@ -55,11 +83,23 @@ class update_worker(threading.Thread):
                     except content_fetcher.ReplyWithContentButNoText as e:
                         # Totally fine, it's by choice - just continue on, nothing more to care about
                         # Page had elements/content but no renderable text
-                        if self.datastore.data['watching'].get(uuid, False) and self.datastore.data['watching'][uuid].get('css_filter'):
-                            self.datastore.update_watch(uuid=uuid, update_obj={'last_error': "Got HTML content but no text found (CSS / xPath Filter not found in page?)"})
-                        else:
                         self.datastore.update_watch(uuid=uuid, update_obj={'last_error': "Got HTML content but no text found."})
-                        pass
+                    except FilterNotFoundInResponse as e:
+                        err_text = "Filter '{}' not found - Did the page change its layout?".format(str(e))
+                        c = 0
+                        if self.datastore.data['watching'].get(uuid, False):
+                            c = self.datastore.data['watching'][uuid].get('consecutive_filter_failures', 5)
+                        c += 1
+
+                        # Send notification if we reached the threshold?
+                        threshold = self.datastore.data['settings']['application'].get('filter_failure_notification_threshold_attempts', 0)
+                        print("Filter for {} not found, consecutive_filter_failures: {}".format(uuid, c))
+                        if threshold >0 and c >= threshold:
+                            self.send_filter_failure_notification(uuid)
+                            c = 0
+
+                        self.datastore.update_watch(uuid=uuid, update_obj={'last_error': err_text,
+                                                                           'consecutive_filter_failures': c})
                     except content_fetcher.EmptyReply as e:
                         # Some kind of custom to-str handler in the exception handler that does this?
                         err_text = "EmptyReply - try increasing 'Wait seconds before extracting text', Status Code {}".format(e.status_code)
@@ -89,6 +129,7 @@ class update_worker(threading.Thread):
                                 fname = watch.save_history_text(contents=contents, timestamp=str(round(time.time())))
 
                             # Generally update anything interesting returned
+                            update_obj['consecutive_filter_failures'] = 0
                             self.datastore.update_watch(uuid=uuid, update_obj=update_obj)
 
                             # A change was detected