Question:
Say you are creating a facebook style app for the app engine. How would you handle user profile pics?
As far as I know, you would have to either store the images in the datastore or blobstore. Which means every fetch to a picture would require going through a dynamic handler and using up at least 20ms cputime.
Is there an efficient way to do this? Or is this just something the app engine can't currently handle?
Solution:1
You don't have this issue anymore, since get_serving_url() doesn't use any of your CPU quota (only outgoing bandwidth and storage). Plus it gives you scaling and cropping for free.
Solution:2
Let's compare a few different options:
- $0.10 per CPU hour
- $0.12 per gigabyte outgoing bandwidth
Google Storage for Developers:
- $0.01 per 10,000 GET requests
- $0.15 per gigabyte downloaded for Americas and EMEA
- $0.01 per 10,000 GET requests
- $0.15 per gigabyte up to 10 TB / month data transfer out
Say you're serving 10 million images at 50KB each.
On App Engine, with a dynamic handler using 20ms per request, this is going to cost you $57.22 in outgoing bandwidth plus $5.55 in CPU time. On Google Storage or S3, you'll pay $71.52 for the outgoing bandwidth plus $10 for the GETs.
So basically if your handler uses less than 36ms CPU time, it's cheaper on App Engine than on services designed for this exact purpose. Somebody double-check my math, please. =)
Solution:3
And cache the most recently used images in the memcache. That's pretty much all the platform affords.
GAE is a good tool for the class of applications it was built for. Making a Flickr clone is outside its design intentions.
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