Question

I have a NewRequest event handler (subscriber) in Pyramid which looks like this:

@subscriber(NewRequest)
def new_request_subscriber(event):
    request = event.request
    print('Opening DB conn')
    // Open the DB
    request.db = my_connect_to_db()
    request.add_finished_callback(close_db_connection)

However, I have observed that a connection to the DB is opened even if the request goes to a static asset, which is obviously unnecessary. Is there a way, from the NewRequest handler, to check if the request is bound for a static asset? I have tried comparing the view_name to my static view’s name, but apparently the view_name attribute is not available at this early stage of processing the request.

If anyone has any interesting ideas about this, please let me know!

Answer 1

The brute force way is to compare the request.path variable to your static view’s root, a la request.path.startswith('/static/').

The method I like the best and use in my own apps is to add a property to the request object called db that is lazily evaluated upon access. So while you may add it to the request, it doesn’t do anything until it is accessed.

import types

def get_db_connection(request):
    if not hasattr(request, '_db'):
        request._db = my_connect_to_db()
        request.add_finished_callback(close_db_connection)
    return request._db

def new_request_subscriber(event):
    request = event.request
    request.db = types.MethodType(get_db_connection, request)

Later in your code you can access request.db() to get the connection. Unfortunately it’s not possible to add a property to an object at runtime (afaik), so you can’t set it up so that request.db gives you what you want. You can get this behavior without using a subscriber by the cookbook entry where you subclass Request and add your own lazy property via Pyramid’s @reify decorator.