Hi,
I'm building a high traffic intensive application that involves the browser
making an AJAX request to the server every second and is expecting the
server to return JSON. At any given second the server responds with the
same JSON back to each browser (regardless of which user logged in).
Because the response is the same for each browser request I decided to
remove the DB overhead by caching that response using Redis.
The view responsible for returning the JSON has code similar to this:
products_json = []
if cache.get(CACHE_LATEST_PRODUCTS_KEY) == None:
//Query the DB as necessary and construct the JSON response
...
//Populate the cache
cache.set(CACHE_LATEST_PRODUCTS_KEY, products_json)
else:
products_json = cache.get(CACHE_LATEST_PRODUCTS_KEY)
In settings.py TIMEOUT is set to 1.
I have 2 questions:
1) In a clustered environment where there are several django servers
running, each of those servers initially will end up querying the DB to
construct the JSON, this can also happen at any time in the future if the
entry expires in the cache while multiple requests are being processed by
the django servers. How can I synchronize the cache look ups so that only
one of the Redis SET's takes place. Should I take out the code that queries
the db and sets the cache entry from the view and move that logic to some
sort of periodic task?
2) Is it possible to cache for less than a second? I've tried setting
TIMEOUT to 0.7 but I didn't see the results I was expecting..
Many Thanks,
Moe
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