Google App Engine application is temporarily over its serving quota

After developing a google app engine application for two months and investing a lot of time in it, and now serving more than 500,000 page views per month I got the following error appear on my website:

"Over Quota

This Google App Engine application is temporarily over its serving quota. Please try again later."


It seems that i had a small mistake which caused runtime exceptions in some of the requests, This small mistake cause my web site to shutdown for several hours!!!!

I really don't understand Google making this error apeear, I understand that they want to secure their servers but why to shutdown an application for several hours, once the error was fixed the server should be activate again.

Now that the server is done, and many users see the error they won't use the application again!

For this reason I really don't recomment you use Google App Engine.

Google App Engine

One month after I started writing my first Google App Application I had reached more then 1000 Page View per one day!!!



One of the great advanatges of GAE over creating my own Web Server is that robutness of Google servers, My application is up 100% of the time, And after writing the application in correct way without consuming too much CPU per request and handling exceptions the application can be used anytime by the users.



The question is what would happen when GAE would support also Java, I realy don't know how I would be able to convert my application from Python to Java

Google App Engine Tips

1. Often your application would work just fine locally but after deploying it the application won't work, a reason for that is that when running locally there is no CPU limit but on Google servers there is a CPU limit, My advice is to deploy your application at night this would enable you to test your application live without interfering the users
2. Check your Logs frequently to see if your application throws exceptions to the user, You should strive to a point that no error logs would be displayed at all.
3. To delete old entities you can access from "Application Overview" then choose "Data Viewer" and then select the entity click on the top check-box and then click the delete button, once there are no rows the entity would be removed.
4. Don't upload an application if you havn't fully tested it before locally.

More tips would be posted in the next posts

My First Google App Engine Application

Ok, I finally succeed writing the Beta version of my Google App Engine application, This application translate from Hebrew Language to 15 other Langauges - Engish, Russian, Japanesse, Chinesse, Korean. The application use the datastore to hold the dictionary and also it auto-correct words which are misspelled, You can check the application at this url -

http://tirgumchik.appspot.com

Deploying such application myself which would be both robutness and scalable can cost a lost of money, If buying servers and paying for high bandwith internet connection and maintaining the DB and using Load Balancer and so on, I think that it's worth it.

Google App Engine in Java Language

As A Java Developer it is very hard to use Google App Engine.
As for now Google App Engine supports only Python Programming language, Trying learning and writing Python languages can be very frustrating when you are used to the good pleasing Eclipse IDE.

Then I found this nice project:

http://code.google.com/p/java2python/

You can write you Google App Engine Application in Java Language and then just convert it to Python and upload it to Google Servers!!!

Enjoy

Google App Engine Limits

Google App Engine has many unknown limits and resterictions, here are few of them:

• Data store is limit to 500mb
• 5,000,000 monthly page views
• 3 applications per user
• Application response time to user must be short something like 3 seconds
• Bulk upload failed to load long strings, I didn't succed upload strings which are more then 40 letters long
• Unicode charcters can't store in datastore
• Bulk upload cookie expiration is 15 minutes long, If your upload takes more time then you would need to run bulk upload several times again and again
• Number of users which can user Goolge App Engine is limit for now
• It is not possible to rewrite datastore date only to add more rows using bulk upload
• Google App Engine is limit for now only to Python programming language

Nevertheless Google App Engine works and it has many advantages which are not exists elsewhere, It is ideal for developers which don't have the resource to maintain a complex website for their applications.

Google App Engine Work !!!

After hard work and many workarounds I managed to run my first Google App Engine application !!!

And it works great, The performances are amazing, I have more than 10,000 rows in my tables and selecting the rows takes few milliseconds.

I manage to find workaround for the unicode problem by not writing unicodes in the Goole App Engine datastore, I also managed to find workaround for the bulk upload problem by loading the entities one by one and not 10 entities at a time.

So regarding my last post which suggest not to use Google App Engine, I change my mind, You can use it but you would need to work very hard to make it work.

Google App Engine and GWT

First there was GWT - Google Web Toolkit a very nice framework to develop Ajax applications in Java language which then translate to JavaScript, It worked with Tomcat Web Server. Then Google decide to release Google App Engine a service which provide the ability to develop applications in Python language and deploy them on their servers for free and provide datastore which is like DB to store data.

It seems like their is no syncrhonization at all with the two groups GWT and Google App Engine, once Google goes for Java and then for Python, Is there any direction to which Google wants to go to?

In their website they claim that they choosed Pyhton because it is secure language, There is no more secure lagnuage than Java, How would GWT developers would deploy their applications on Google App Engine, would they need now to convert their code to Python? I really confused

Why not using Google App Engine

After worked several days with Google App Engine, I was realy dissapointed, It seems that since it has just released and it is in "Preview Release" it contains some bugs and since Google choose Python as the programming language it make it hard to develop for programmers which don't know well Python, Here are the problems that I come with

• Python is VERY hard language to develop applications which required Unicode, Maybe for english applications its not so bad language but when you try writing something which is not english you need to find yourself using decode, encode, unicode and other awful methos.
• It seems that urlfetch method which retrieve data from other urls doesn't support unicode
• I tried to upload my datastore to the application server, when I do it locally it works, however when I try to upload the datastore remotly on Google Servers it fails.
• Datastore also doesn't support unicode characters, everything has to be in english
• Sometimes after uploading the application to the Google Servers it says error 500, However the application works just find locally
• Python language is the only programming language I know which requires not using Tabs inside the source code and it doesn't use { and } characters to define block but rather it looks on where the line begins. There are much more advance programming languages like Java which could fit more to be used with Google App Engine

In summary I think that I would wait some time before Google App Engine would have more stable versions.

Working with Google App Engine

I just got today invitation to try Google App Engine,
It seems that I'm one of the lucky 10,000 people that got invitation to try it.

Well first I had to admit that I don't know shit about Phyton, Google App Engine is based about Phyton language, However it seems that it is not hard to learn this langauge once you know Php, Java or other programming language.

The big advantage of Google App Engine, is that you don't have to take care about all installing and deploying applications, taking care for performance or load balancing, you get all this things for Free!!!

It seems that it is pretty easy to develop applications using Google App Engine, you just need to install phyton, and Google App Engine SDK, and thats all.

Then you are your phyton application file, and you can test it localy by running GAE (Goolge App Engine) locally.

Once you finished writing you application you just upload it to the Google Server.

The biggest advanatge of GAE in my opinion it is ability to store data and retrive data from the database using GQL Google Query Language which is just like SQL but a bit different, This allow the application writing highly scalabe SQL selects.

Once I would finish writing my application I would publish it here.
Please comment if you have any questions.