Basic support for broadcast messages

README.md

@@ -53,3 +53,25 @@ docker compose exec app python scripts/talk_to_process_manager.py
 ```
 
 Take the servers down with `docker compose down`
+
+### Working with Kafka
+
+Due to the complexities of containerising Kafka it is not possible to use the standard
+Docker Compose setup. Instead when working with functionality that requires Kafka it is
+necessary to run the individual components manually.
+
+1. Start Kafka - See [Running drunc with pocket kafka].
+
+1. Start the drunc shell:
+   `poetry run drunc-unified-shell --log-level debug ./data/process-manager-pocket-kafka.json`
+
+1. Start the application server:
+   `poetry run python manage.py runserver`
+
+1. Start the Kafka consumer:
+   `poetry run python scripts/kafka_consumer.py`
+
+From here you should be able to see broadcast messages displayed at the top of the index
+page on every refresh.
+
+[Running drunc with pocket kafka]: https://github.com/DUNE-DAQ/drunc/wiki/Running-drunc-with-pocket-kafka

data/README.md

@@ -0,0 +1,5 @@
+# Data files
+
+## process-manager-pocket-kafka.json
+
+Process manager configuration file for use in local development with Kafka.

data/process-manager-pocket-kafka.json

@@ -0,0 +1,13 @@
+{
+    "type": "ssh",
+    "name": "SSHProcessManager",
+    "command_address": "0.0.0.0:10054",
+    "authoriser": {
+        "type": "dummy"
+    },
+    "broadcaster": {
+        "type": "kafka",
+        "kafka_address": "127.0.0.1:30092",
+        "publish_timeout": 2
+    }
+}

docker-compose.yml

@@ -12,6 +12,8 @@ services:
     volumes:
       - .:/usr/src/app
       - db:/usr/src/app/db
+    environment:
+      - PROCESS_MANAGER_URL=drunc:10054
   drunc:
     build: ./drunc_docker_service/
     command:

dune_processes/settings/settings.py

@@ -9,6 +9,7 @@
 https://docs.djangoproject.com/en/5.1/ref/settings/
 """
 
+import os
 from pathlib import Path
 
 # Build paths inside the project like this: BASE_DIR / 'subdir'.
@@ -133,3 +134,5 @@
 
 INSTALLED_APPS += ["django_bootstrap5"]
 DJANGO_TABLES2_TEMPLATE = "django_tables2/bootstrap5.html"
+
+PROCESS_MANAGER_URL = os.getenv("PROCESS_MANAGER_URL", "localhost:10054")

main/templates/main/index.html

@@ -4,9 +4,21 @@
 {% block title %}Home{% endblock title %}
 
 {% block content %}
+
 <div class="col">
+  {% if messages %}
+  <h2>Messages</h2>
+  <div style="white-space: pre-wrap;">
+    {% for message in messages %}
+    {{ message }}
+    {% endfor %}
+  </div>
+  <hr class="solid">
+  {% endif %}
+
   <a href="{% url 'main:boot_process' %}" class="btn btn-primary">Boot</a>
   {% render_table table %}
 </div>
 
+
 {% endblock content %}

main/urls.py

@@ -12,4 +12,5 @@
     path("flush/<uuid:uuid>", views.flush_process, name="flush"),
     path("logs/<uuid:uuid>", views.logs, name="logs"),
     path("boot_process/", views.BootProcessView.as_view(), name="boot_process"),
+    path("message/", views.deposit_message, name="message"),
 ]

main/views.py

@@ -3,11 +3,15 @@
 import asyncio
 import uuid
 from enum import Enum
+from http import HTTPStatus
 
 import django_tables2
+from django.conf import settings
 from django.http import HttpRequest, HttpResponse, HttpResponseRedirect
 from django.shortcuts import render
 from django.urls import reverse, reverse_lazy
+from django.views.decorators.csrf import csrf_exempt
+from django.views.decorators.http import require_POST
 from django.views.generic.edit import FormView
 from drunc.process_manager.process_manager_driver import ProcessManagerDriver
 from drunc.utils.shell_utils import DecodedResponse, create_dummy_token_from_uname
@@ -22,11 +26,18 @@
 from .forms import BootProcessForm
 from .tables import ProcessTable
 
+# extreme hackiness suitable only for demonstration purposes
+# TODO: replace this with per-user session storage - once we've added auth
+MESSAGES: list[str] = []
+"""Broadcast messages to display to the user."""
+
 
 def get_process_manager_driver() -> ProcessManagerDriver:
     """Get a ProcessManagerDriver instance."""
     token = create_dummy_token_from_uname()
-    return ProcessManagerDriver("drunc:10054", token=token, aio_channel=True)
+    return ProcessManagerDriver(
+        settings.PROCESS_MANAGER_URL, token=token, aio_channel=True
+    )
 
 
 async def get_session_info() -> ProcessInstanceList:
@@ -63,8 +74,10 @@ def index(request: HttpRequest) -> HttpResponse:
     table_configurator = django_tables2.RequestConfig(request)
     table_configurator.configure(table)
 
-    context = {"table": table}
+    global MESSAGES
+    MESSAGES, messages = [], MESSAGES
 
+    context = {"table": table, "messages": messages}
     return render(request=request, context=context, template_name="main/index.html")
 
 
@@ -199,3 +212,18 @@ def form_valid(self, form: BootProcessForm) -> HttpResponse:
         """
         asyncio.run(_boot_process("root", form.cleaned_data))
         return super().form_valid(form)
+
+
+@require_POST
+@csrf_exempt
+def deposit_message(request: HttpRequest) -> HttpResponse:
+    """Upload point for broadcast messages for display to end user.
+
+    Args:
+      request: the triggering request.
+
+    Returns:
+      A NO_CONTENT response.
+    """
+    MESSAGES.append(request.POST["message"])
+    return HttpResponse(status=HTTPStatus.NO_CONTENT)

pyproject.toml

@@ -45,7 +45,7 @@ module = "tests.*"
 disallow_untyped_defs = false
 
 [[tool.mypy.overrides]]
-module = ["druncschema.*", "drunc.*", "django_tables2.*"]
+module = ["druncschema.*", "drunc.*", "django_tables2.*", "kafka.*"]
 ignore_missing_imports = true
 
 [tool.django-stubs]

scripts/kafka_consumer.py

@@ -0,0 +1,33 @@
+"""Example client that consumes messages from Kafka and sends them to the web app."""
+
+import os
+from urllib.parse import urlencode
+from urllib.request import Request, urlopen
+
+from druncschema.broadcast_pb2 import BroadcastMessage
+from kafka import KafkaConsumer
+
+KAFKA_URL = os.getenv("KAFKA_URL", "127.0.0.1:30092")
+SERVER_URL = os.getenv("SERVER_URL", "http://localhost:8000")
+
+
+def main() -> None:
+    """Listen for Kafka messages and process them indefinitely."""
+    consumer = KafkaConsumer(bootstrap_servers=[KAFKA_URL])
+    consumer.subscribe(pattern="control.*.process_manager")
+
+    print("Listening for messages from Kafka.")
+    while True:
+        for messages in consumer.poll(timeout_ms=500).values():
+            for message in messages:
+                print(f"Message received: {message}")
+                bm = BroadcastMessage()
+                bm.ParseFromString(message.value)
+
+                data = urlencode(dict(message=bm.data.value))
+                request = Request(f"{SERVER_URL}/message/", data=data.encode())
+                urlopen(request)
+
+
+if __name__ == "__main__":
+    main()