Unable to store and retrieve data from Appengine Servlet Context

[Sateesh]

Hi

Is there a way that i can use Servlet Context on Appengine.
Here is our scenario

We have GWT application
Client call a server method to get the xml data (which is around 5 mb)
Server method will prepare a map with a unique key and value as in
progress
Server will send request to another server (SERVER2) with key as
parameter
SERVER2 sends SUCCESS message after spanning a thread to fetch xml
from data store.
Client will use polling mechanism to see the status for this request
in Servelet context stored map
SEVER2 later post back the data to a servlet which will update the
value of a map in ServletContext
Client will pickup this and use in rendering

It seems that i am unable to store data in to Servlet Context in
Appengine.
In my case mem cache is not the right choice as my data is huge.
Please suggest how to over come this situation

Thanks
Sateesh

[Ikai Lan (Google)]

I don't believe you can do this. The reason is that Servlet Context exists a 1:1 mapping per servlet container, and you may have multiple, load balanced JVMs up. You'll want to revisit Memcache, which is the closest thing to shared memory that you have available to you.

Ikai Lan 
Developer Programs Engineer, Google App Engine

Blog: http://googleappengine.blogspot.com 

Twitter: http://twitter.com/app_engine

Reddit: http://www.reddit.com/r/appengine

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[Neill]

You need to enable sessions in the appengine-web.xml,

<!-- HTTP Sessions are disabled by default. To enable HTTP sessions specify: -->

<sessions-enabled>true</sessions-enabled>

<!-- It's possible to reduce request latency by configuring your application 

to asynchronously write HTTP session data to the datastore: -->

<async-session-persistence enabled="true" />

<!-- With this feature enabled, there is a very small chance your app will 

see stale session data. For details, see http://code.google.com/appengine/docs/java/config/appconfig.html#Enabling_Sessions -->