I'm trying to deploy my first django site through mod_wsgi (on a VPS that also serves PHP pages). Once the first django page is loaded the site runs pretty quick, but loading up that first page is excruciating - at least 15 seconds, sometimes 30 seconds+.
During the first page loadup memory (384MB) is maxed out & other tasks also slow to a crawl. I'm pretty new to django so not quite sure how to solve this. Unfortunately running django through it's own server (as opposed to one that also serves PHP) isn't really feasible.
Any suggestions appreciated.
As answered on #django, likely because embedded mode being used and not daemon mode. Dangers of this described at:
http://blog.dscpl.com.au/2009/03/load-spikes-and-excessive-memory-usage.html
Related
I have to ask a more or less non-typical SO question and hope you don't mind. Right now I am developing my very first web application. I did set up an AJAX function that requests some data from a third party API and populates my html containers with the returned data.
Right now I query one single object and populate 3 html containers with around 15 lines of Javascript code. When i activate the process/function by clicking a button on my frontend, it needs around 6-7 seconds until the html content is updated.
Is this a reasonable time? The user experience honestly will be more than bad considering that I will have to query and manipulate far more data (I build a one-site dashboard related to soccer data).
There might be very controversal answers to that question, but what would be a fair enough time for the process to run using standard infrastructure? 1-2 seconds? (I will deploy the app on heroku or digitalocean and will implement a proper caching environment to handle "regular visitors").
Right now
I use a virtualenv and django server for the development
and a demo server from the third party API which might be slowed down for whatever reason (how to check this?)
which might effect the current time needed (there will be many more variables obv.).
Looking forward to your answers.
I personally think (probably a lot people might too) 6-7 secs is a significant delay for rendering a small page. The cause of this issue might not came from django directly. Check for the following:
I use a virtualenv and django server for the development
you may be running django devserver, production server might make things bit faster (use django-debug-toolbar to find what causing the delay)
Do db index in your model.
a demo server from the third party API which might be slowed down for whatever reason
use chrome developer tools 'network' tab to watch how long that third party call takes. it might not visible there if you call api in your view.py. in that case, add some timing code there to calculate how long it takes to return.
I have a django web app that uses postgres db.It allows users to login and make some posts which get saved to db and later on the user can list how many posts he made on a particular day etc and list the posts belonging to a particular category etc.While this worked without any delay in my machine,it is taking a lot of time to load each page when hosted on a free host.
How do you find out why this is happening?which part of the app should I look first?Is there any meaning in using a profiler since this app used to run with no delays in my local machine?
I would like to find out how to approach this problem in general.I was able to access other apps hosted on the same free host without much delays ..so this may be a problem specific to my app
I would like some advice regarding this..If anyone can help..
thank you
p.s:(I intentionally left out the host's name because ,since that was a free service ,there was no point in complaining and also other apps on the same host works well)
The here is the free host bit, when on a free host you could be sharing a box with hundreds of other sites (that can equate to a very small amount of ram or CPU). Pay a little money, ($30 dollars / £22 a year) and get your self a better host.
You will find the performance and reliability so much better.
Failing that I would firstly find out what the latency between you and the server is, on a local machine there is no / little network traffic so your pages will appear to load a lot faster.
Next i would look at the actual download speeds you are getting. It could be that your site is limited to 20-30k, which means even a small site will take over a second to load.
Are you hosting many images? If this is the case are you serving them through django or is the webserver doing this. If it is django then make the webserver take this load.
Finally check the processing speed of the pages. Analise the queries which are being run and find out what is taking the time. Make sure that postgres is correctly configured and has enough resources. You can analyses the query speed using the django debug toolbar.
I have a site where it takes a few seconds to generate a page, due to having a crappy server. People visiting it will spam the refresh button. The problem is that the threads that are already loading the page don't stop, so you end up having 2-3 things generating the same page, all but one being discarded. Is there any way to check whether a page load is no longer necessary so I can abort?
Not that i'm aware of even if you could detect from the users browser I don't think apache can be notified and even if it could interrupting a running django thread isn't that easy a solution. Have you looked into caching your pages? Should give you the most performance improvement ESP. If generating pages is your bottleneck.
This is a nagging issue that I've had with Django.
Compared to a typical PHP site, it takes forever to refresh and see any changes I've made. During development I have Apache set to MaxRequestsPerChild 1 - this is fairly slow but is necessary because you end up viewing 'stale' code without it. Running the development server is far worse as it restarts and churns away after a one-liner change.
With PHP, changes are instantaneous.
Is there any way to accelerate this on the Django side?
For development, it's rarely useful to be running Django behind a "real" web server like Apache. I understand the frustration with the auto-reloading dev server, but you can always give the --noreload option if you want to control the restarting yourself. I leave it on because I forget to restart, and the time that it saves me is usually worth a couple frustrating moments while editing.
However, I've never found the development server being the hinderance. Use SQLite while developing. Setting up a "real" database is usually not necessary when coding and testing. And templates will always refresh instantaneously.
I am using a django with apache mod_wsgi, my site has dynamic data on every page and all of the media (css, images, js) is stored on amazon S3 buckets liked via "http://bucket.domain.com/images/*.jpg" inside the markup . . . . my question is, can varnish still help me speed up my web server?
I am trying to knock down all the stumbling blocks here. Is there something else I should be looking at? I have made a query profiler for my code at each page renders at about 0.120 CPU seconds which seems quick enough, but when I use ab -c 5 -n 100 http://mysite.com/ the results are only Requests per second: 12.70 [#/sec] (mean) . . .
I realize that there are lots of variables at play, but I am looking for some guidance on things I can do and thought Varnish might be the answer.
UPDATE
here is a screenshot of my profiler
The only way you can improve your performance is if you measure what is slowing you down. Though it's not the best profiler in the world, Django has good integration with the hotshot profiler (described here) and you can figure out what is taking those 0.120 cpu seconds.
Are you using 2 cpus? If that's the case than perhaps the limitation is in the db when you use ab? I only say that because 0.120 * 12.70 is 1.5 which means that there's .5 seconds waiting for something. This could also be IO or something.
Adding another layer for no reason such as varnish is generally not a good idea. The only case where something like varnish would help is if you have slow clients with poor connections hold onto threads, but the ab test is not hitting this condition and frankly it's not a large enough issue to warrant the extra layer.
Now, the next topic is caching, which varnish can help with. Are your pages customized for each user, or can it be static for long periods of time? Often times pages are static except for a simple login status screen -- in this case consider off loading that login status to javascript with cookies. If you are able to cache entire pages then they would be extremely fast in ab. However, the next problem is that ab is not really a good benchmark of your site, since users aren't going to just sit at one page and hit f5 repeatedly.
A few things to think about before you go installing varnish:
First off, have you enabled the page caching middleware within Django?
Are etags set up and working properly?
Is your database server performing optimally?
Have you considered setting up caching using memcached within your code for common results? (particularly front pages and static pages displayed to non-logged-in users)
Except for query heavy dynamic pages that absolutely must display substantially different data for each user, .12 seconds seems like a long time to serve a page. Look at how you can work caching into your app to improve that performance. If you have a page that is largely static other than a username or something similar, cache the computed part of the page.
When Django's caching is working properly, ab on public pages should be lightning fast. If you aren't using any of the other features of Apache, consider using something lighter and faster like lighttpd or nginx.
Eric Florenzano has put together a pretty useful project called django-newcache that implements some advanced caching behavior. If you're running into the limitations of the built-in caching, consider it. http://github.com/ericflo/django-newcache