Tornado “error: [Errno 24] Too many open files” error

Question

I\'ve worked with Tornado quite a bit, but this is the first time I\'ve run into this sort of error. I\'ve been working on a very basic URL shortener. URLs are put into the

Answer 1

Very simple, the RequestHandler object is instantiated for every request. Which means that the cached object that you're saving is on the RequestHandler (e.g. expand) object.

If you were to add a simple "print 'CREATED!'" to the dbmongo(...) function you would see that it's created on every GET request.

What you need to do is attach the handler to the class object, or a "global" as needed, though the best case is to put it on the Tornado Application object.

Simple:

class setup(tornado.web.RequestHandler):
    @classmethod
    def dbmongo(cls):
        if not hasattr(cls, '_dbmongo'):
            cls._dbmongo = apymongo.Connection("127.0.0.1", 27017)
        return cls._dbmongo

Second approach is just to make it a global in your file:

dbmongo_connection = None
def dbmongo():
    if not dbmongo_connection:
        dbmongo_connection = apymongo.Connection("127.0.0.1", 27017)
    return dbmongo_connection

Both of these have the same problem which is that if you have lots of classes that want to use the DB connection, it's harder to share it. Since the DB is a shared entity you probably want one for your whole application.

class MongoMixin(object):
    def mongodb(self):
        if not hasattr(self.application, 'mongodb'):
            self.application.mongodb = apymongo.Connection(self.application.settings.get("mongohost", "127.0.0.1"), 27017)
        return self.application.mongodb

class expand(tornado.web.RequestHandler, MongoMixin):
    def get(self):
       db = self.mongodb()