Improving Django PDF Processing Architecture

Based on your current setup, I can suggest several improvements to your architecture, particularly around task scheduling and validation.

Current Architecture Issues

1. Using save() methods to trigger tasks can lead to unexpected behavior, especially during bulk operations or when models are saved programmatically
2. PDF validation in the request cycle is causing user-facing delays
3. Potential race conditions when multiple tasks update the same model instances

Recommended Architecture Changes

1. Move Task Scheduling Out of Model Methods

Instead of triggering tasks in save() methods, consider using signals or explicit task scheduling in your views:

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# Using signals
from django.db.models.signals import post_save
from django.dispatch import receiver

@receiver(post_save, sender=Reportfile)
def handle_reportfile_save(sender, instance, created, **kwargs):
    if not instance.processed:
        dissect_pdf.delay(instance.id)

@receiver(post_save, sender=Sendtask)
def handle_sendtask_save(sender, instance, created, **kwargs):
    if instance.status == 'pending':
        send_report_part.delay(instance.id)

2. Separate Validation from Request Cycle

Move the PDF validation to an asynchronous task:

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# In your view
def post(self, request, *args, **kwargs):
    form = self.get_form()
    if form.is_valid():
        # Do minimal validation (file type, size)
        reportfile = form.save(commit=False)
        reportfile.processed = False
        reportfile.save()
        
        # Queue validation task
        validate_pdf.delay(reportfile.id)
        
        return redirect('success_page')
    return self.form_invalid(form)

3. Implement a State Machine Pattern

Track the status of your files more explicitly:

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class Reportfile(models.Model):
    STATUS_CHOICES = (
        ('uploaded', 'Uploaded'),
        ('validating', 'Validating'),
        ('invalid', 'Invalid'),
        ('processing', 'Processing'),
        ('processed', 'Processed'),
        ('sending', 'Sending'),
        ('completed', 'Completed'),
        ('failed', 'Failed'),
    )
    status = models.CharField(max_length=20, choices=STATUS_CHOICES, default='uploaded')
    # other fields...

4. Use Task Chains for Dependencies

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from celery import chain

# In your view or signal handler
def handle_new_report(reportfile_id):
    # Create a chain of tasks
    chain(
        validate_pdf.s(reportfile_id),
        dissect_pdf.s(),
        create_send_tasks.s()
    ).apply_async()

5. Implement Progress Feedback

Consider using WebSockets (Django Channels) to provide real-time feedback to users about the processing status.

Additional Recommendations

1. Add proper error handling and retries in your tasks
2. Consider using a dedicated file storage service for large files
3. Implement rate limiting for uploads
4. Add a task monitoring dashboard (Flower for Celery)
5. Consider using a more robust task queue like Celery instead of django-tasks for complex workflows

These changes should help make your application more robust, maintainable, and provide a better user experience by moving heavy processing out of the request cycle.