feat: Add event listener for course publish

Creates the edx-platform plugin plumbing, adds some new requirements, maps the appropriate Django Signal to push course structure to ClickHouse.

event_sink_clickhouse/apps.py

@@ -3,6 +3,7 @@
 """
 
 from django.apps import AppConfig
+from edx_django_utils.plugins import PluginSettings, PluginSignals
 
 
 class EventSinkClickhouseConfig(AppConfig):
@@ -11,3 +12,41 @@ class EventSinkClickhouseConfig(AppConfig):
     """
 
     name = 'event_sink_clickhouse'
+    verbose_name = "Event Sink ClickHouse"
+
+    plugin_app = {
+        PluginSettings.CONFIG: {
+            'lms.djangoapp': {
+                'production': {PluginSettings.RELATIVE_PATH: 'settings.production'},
+                'common': {PluginSettings.RELATIVE_PATH: 'settings.common'},
+                'devstack': {PluginSettings.RELATIVE_PATH: 'settings.devstack'},
+            },
+            'cms.djangoapp': {
+                'production': {PluginSettings.RELATIVE_PATH: 'settings.production'},
+                'common': {PluginSettings.RELATIVE_PATH: 'settings.common'},
+                'devstack': {PluginSettings.RELATIVE_PATH: 'settings.devstack'},
+            }
+        },
+        # Configuration setting for Plugin Signals for this app.
+        PluginSignals.CONFIG: {
+            # Configure the Plugin Signals for each Project Type, as needed.
+            'cms.djangoapp': {
+                # List of all plugin Signal receivers for this app and project type.
+                PluginSignals.RECEIVERS: [{
+                    # The name of the app's signal receiver function.
+                    PluginSignals.RECEIVER_FUNC_NAME: 'listen_for_course_publish',
+
+                    # The full path to the module where the signal is defined.
+                    PluginSignals.SIGNAL_PATH: 'xmodule.modulestore.django.SignalHandler.course_published',
+                }],
+            }
+        },
+    }
+
+    def ready(self):
+        """
+        Import our Celery tasks for initialization
+        """
+        super().ready()
+
+        from . import tasks

event_sink_clickhouse/destination.py

@@ -0,0 +1,190 @@
+import csv
+import io
+
+from django.conf import settings
+from django.utils import timezone
+
+import requests
+
+
+class ClickHouseDestination:
+    connection_overrides = None
+    log = None
+
+    def __init__(self, connection_overrides, log):
+
+        self.ch_url = settings.EVENT_SINK_CLICKHOUSE_BACKEND_CONFIG["url"]
+        self.ch_auth = (settings.EVENT_SINK_CLICKHOUSE_BACKEND_CONFIG["user"],
+                        settings.EVENT_SINK_CLICKHOUSE_BACKEND_CONFIG["password"])
+
+        self.connection_overrides = connection_overrides
+        self.log = log
+
+    @staticmethod
+    def strip_branch_and_version(location):
+        """
+        Removes the branch and version information from a location.
+        Args:
+            location: an xblock's location.
+        Returns: that xblock's location without branch and version information.
+        """
+        return location.for_branch(None)
+
+    @staticmethod
+    def get_course_last_published(course_key):
+        """
+        Approximately when was a course last published?
+
+        We use the 'modified' column in the CourseOverview table as a quick and easy
+        (although perhaps inexact) way of determining when a course was last
+        published. This works because CourseOverview rows are re-written upon
+        course publish.
+
+        Args:
+            course_key: a CourseKey
+
+        Returns: The datetime the course was last published at, stringified.
+            Uses Python's default str(...) implementation for datetimes, which
+            is sortable and similar to ISO 8601:
+            https://docs.python.org/3/library/datetime.html#datetime.date.__str__
+        """
+        # Import is placed here to avoid model import at project startup.
+        from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
+
+        approx_last_published = CourseOverview.get_from_id(course_key).modified
+        return str(approx_last_published)
+
+    @staticmethod
+    def serialize_item(item, index):
+        """
+        Args:
+            item: an XBlock
+            index: a number indicating where the item falls in the course hierarchy
+
+        Returns:
+            fields: a *limited* dictionary of an XBlock's field names and values
+            block_type: the name of the XBlock's type (i.e. 'course'
+            or 'problem')
+        """
+        from xmodule.modulestore.store_utilities import DETACHED_XBLOCK_TYPES
+
+        course_key = item.scope_ids.usage_id.course_key
+        block_type = item.scope_ids.block_type
+
+        rtn_fields = {
+            'org': course_key.org,
+            'course_key': str(course_key),
+            'course': course_key.course,
+            'run': course_key.run,
+            'location': str(item.location),
+            'display_name': item.display_name_with_default.replace("'", "\'"),
+            'block_type': block_type,
+            'detached': 1 if block_type in DETACHED_XBLOCK_TYPES else 0,
+            'edited_on': str(getattr(item, 'edited_on', '')),
+            'time_last_dumped':  str(timezone.now()),
+            'order': index,
+        }
+
+        return rtn_fields, block_type
+
+    def serialize_course(self, course_id):
+        """
+        Serializes a course into a CSV of nodes and relationships.
+
+        Args:
+            course_id: CourseKey of the course we want to serialize
+
+        Returns:
+            nodes: a csv of nodes for the course
+            relationships: a csv of relationships between nodes
+        """
+        # Import is placed here to avoid model import at project startup.
+        from xmodule.modulestore.django import modulestore
+
+        # create a location to node mapping we'll need later for
+        # writing relationships
+        location_to_node = {}
+        items = modulestore().get_items(course_id)
+
+        # create nodes
+        i = 0
+        for item in items:
+            i += 1
+            fields, block_type = self.serialize_item(item, i)
+            location_to_node[self.strip_branch_and_version(item.location)] = fields
+
+        # create relationships
+        relationships = []
+        for item in items:
+            for index, child in enumerate(item.get_children()):
+                parent_node = location_to_node.get(self.strip_branch_and_version(item.location))
+                child_node = location_to_node.get(self.strip_branch_and_version(child.location))
+
+                if parent_node is not None and child_node is not None:
+                    relationship = {
+                        'course_key': str(course_id),
+                        'parent_location': str(parent_node["location"]),
+                        'child_location': str(child_node["location"]),
+                        'order': index
+                    }
+                    relationships.append(relationship)
+
+        nodes = list(location_to_node.values())
+        return nodes, relationships
+
+    def dump(self, course_key):
+        nodes, relationships = self.serialize_course(course_key)
+        self.log.info(
+            "Now dumping %s to ClickHouse: %d nodes and %d relationships",
+            course_key,
+            len(nodes),
+            len(relationships),
+        )
+
+        course_string = str(course_key)
+
+        try:
+            # Params that begin with "param_" will be used in the query replacement
+            # all others are ClickHouse settings.
+            params = {
+                # Fail early on bulk inserts
+                "input_format_allow_errors_num": 1,
+                "input_format_allow_errors_ratio": 0.1,
+            }
+
+            # "query" is a special param for the query, it's the best way to get the FORMAT CSV in there.
+            params["query"] = "INSERT INTO coursegraph.coursegraph_nodes FORMAT CSV"
+
+            output = io.StringIO()
+            writer = csv.writer(output, quoting=csv.QUOTE_NONNUMERIC)
+
+            for node in nodes:
+                writer.writerow(node.values())
+
+            response = requests.post(self.ch_url, data=output.getvalue(), params=params, auth=self.ch_auth)
+            self.log.info(response.headers)
+            self.log.info(response)
+            self.log.info(response.text)
+            response.raise_for_status()
+
+            # Just overwriting the previous query
+            params["query"] = "INSERT INTO coursegraph.coursegraph_relationships FORMAT CSV"
+            output = io.StringIO()
+            writer = csv.writer(output, quoting=csv.QUOTE_NONNUMERIC)
+
+            for relationship in relationships:
+                writer.writerow(relationship.values())
+
+            response = requests.post(self.ch_url, data=output.getvalue(), params=params, auth=self.ch_auth)
+            self.log.info(response.headers)
+            self.log.info(response)
+            self.log.info(response.text)
+            response.raise_for_status()
+
+            self.log.info("Completed dumping %s to ClickHouse", course_key)
+
+        except Exception:  # pylint: disable=broad-except
+            self.log.exception(
+                "Error trying to dump course %s to ClickHouse!",
+                course_string
+            )

event_sink_clickhouse/settings/common.py

@@ -0,0 +1,16 @@
+"""
+Default settings for the openedx_event_sink_clickhouse app.
+"""
+
+
+def plugin_settings(settings):
+    """
+    Adds default settings
+    """
+    settings.EVENT_SINK_CLICKHOUSE_BACKEND_CONFIG = {
+        # URL to a running ClickHouse server's HTTP interface. ex: https://foo.openedx.org:8443/ or
+        # http://foo.openedx.org:8123/
+        "url": "http://clickhouse:8123",
+        "username": "ch_admin",
+        "password": "dazimUehjqKjWdpDNhRrGOfp"
+    }

event_sink_clickhouse/signals/handlers.py

@@ -0,0 +1,16 @@
+"""
+Signal handler functions, mapped to specific signals in apps.py.
+"""
+
+
+def receive_course_publish(sender, course_key, **kwargs):  # pylint: disable=unused-argument
+    """
+    Receives publishing signal and performs publishing related workflows, such as
+    registering proctored exams, building up credit requirements, and performing
+    search indexing
+    """
+    # import here, because signal is registered at startup, but items in tasks are not yet able to be loaded
+    from ..tasks import dump_course_to_clickhouse
+
+    course_key_str = str(course_key)
+    dump_course_to_clickhouse.delay(course_key_str)

event_sink_clickhouse/tasks.py

@@ -0,0 +1,31 @@
+"""
+This file contains a management command for exporting course modulestore data to ClickHouse
+"""
+
+import logging
+
+from celery import shared_task
+from edx_django_utils.cache import RequestCache
+from edx_django_utils.monitoring import set_code_owner_attribute
+from opaque_keys.edx.keys import CourseKey
+
+from .destination import ClickHouseDestination
+
+log = logging.getLogger(__name__)
+celery_log = logging.getLogger('edx.celery.task')
+
+
+@shared_task
+@set_code_owner_attribute
+def dump_course_to_clickhouse(course_key_string, connection_overrides=None):
+    """
+    Serializes a course and writes it to neo4j.
+
+    Arguments:
+        course_key_string: course key for the course to be exported
+        connection_overrides (dict):  overrides to ClickHouse connection
+            parameters specified in `settings.COURSEGRAPH_CONNECTION`.
+    """
+    course_key = CourseKey.from_string(course_key_string)
+    destination = ClickHouseDestination(connection_overrides=connection_overrides, log=celery_log)
+    destination.dump(course_key)

requirements/base.in

@@ -1,5 +1,8 @@
 # Core requirements for using this application
 -c constraints.txt
 
+celery             # Asynchronous task execution library
 Django             # Web application framework
-
+requests           # HTTP request library
+edx-django-utils   # Django utilities, we use caching and monitoring
+edx-opaque-keys    # Parsing library for course and usage keys