If you were careful reading Google App Engine documentation, you could have read this: “If you access your site while signed in using an administrator account, App Engine includes per-request statistics in the response headers. The header X-AppEngine-Estimated-CPM-US-Dollars represents an estimate of what 1,000 requests similar to this request would cost in US dollars.”
Well, although I’ve been using GAE periodically for the last several months, I became aware of the above just last week. I guess during the first several weeks a developer need to adapt and put his way of thinking in line with App Engine. However, when the things settle and one is more comfortable with the environment, a different kind of questions start to pop up… How can you put a price tag on your SaaS offering without knowing how much would it cost you in the first place? How do you know where to draw a line with your “free use plan” and which conversion rate do you need for a sustainable growth?
Obviously, the estimated cost information is simply too useful to be ignored. Unfortunately, I could not find a ready to use solution so I used my modest knowledge of programming a Firefox extension and made an add-on that for an App Engine site shows the total estimated cost in the Firefox status bar:
Feel free to download GAE Cost add-on for Firefox and use it with your GAE applications. Please notice that:
- you have to be signed in using an administrator account (via Google), and
- stated cost are for 1000 similar requests.
You can reset the cost counters using options in the context menu of the label.
To find out a cost of a particular request, open Firefox Error Console. There you can find not only cost information but also resource usage details (server-side time, app server CPU time, and API CPU time) for each request.
If you find some requests more “expensive” than expected, you can use an excellent Appstats profiling tool available with the latest GAE SDK to find out what’s going on.
Hope you’ll find this useful.
{ 6 comments… read them below or add one }
Nice works.
I tried it and the cost showing is total amount. It is better should you add some reports showing cost for each request. It will help developers identify which is the most expensive one.
I though about it but I’ve found a total quite useful for checking a cost of a use case for example. Beside, this way was simple to implement.
Showing just a single request would require a totally different UI approach. Each page loads some assets and can trigger additional Ajax requests so an add-on cannot decide to show just a single request estimate.
Price for a single request can be easily investigated using Firebug’s Net panel.
Neat and simple tool – thank you for putting this together!
The fact that it doesn’t reset between requests makes a lot of sense. But if you wanted to, maybe when you hover over the label it could also include what the previous request’s info was from the all headers (e.g., resource usage too). It might also be nice if the popup included total resource usage from all the headers combined.
It totally slipped my mind but per request cost and resource usage is already available in Firefox Error Console (I updated the post with this). Yes, I planned to add resource usage totals to the tooltip text; expect an update later today or over weekend.
The add-on has been updated (v1.1) to show the total App Engine resource usage in the tooltip.
Perfect — I can’t think of anything else I want it to do now
. Thanks radomir!