I use GWT with Appengine. We use No 3 mentioned by Klaus in our project
extensively. I can poll the task completion with GWT timer.
Here are the steps approximately:
Create the following Objectify class
class MyTask {
@Id long id;
int status;
}
- GWT client uses rpc to initiate the task for your business logic
- On the server, do a new MyTask with status = 0;
- Pass the MyTask also into the Deferred task.
- Return MyTask key back to the client
- In the Deferred task,
- do the business logic. After your logic is complete, store the
results in the memcache with the MyTask key as the value.
- update the MyTask status value to 1 and do put().
- Client keeps polling using RPC for the value of MyTask key.
- Client checks the value of the MyTask status. If its value is 1, then
- do RPC, to get the results from the memcache.
-Aswath
www.accounting-guru.net.
On Mon, Dec 16, 2013 at 10:01 PM, Anil S <sadinenia...@gmail.com> wrote:
> Thank you very much for all your responses.
>
>
> On Sunday, December 15, 2013 3:52:22 PM UTC-5, Klaus Post wrote:
>>
>> Hi!
>>
>> You should probably take a general look at what you are dealing with, and
>> consider some which common options are available.
>>
>> Some of these could apply to your project:
>>
>> 1) Segment data into smaller chunks, and deliver partial data if possible.
>> 2) Have precomputed a summary, if you are summing up large amount of
>> items, that are updated on write, or as a cron job every 5 minutes if
>> changes are flowing in all the time.
>> 3) Start a background task doing the report, send an update to the client
>> when the result is ready, so the user can be notified.
>> 4) If your app is calculation heavy - and not database (datastore) heavy,
>> consider using the Compute Engine.
>> 5) I haven't tried it myself, but mapreduce could help you summarising
>> big amounts of data. Just google "app engine mapreduce".
>>
>> Either way your design should have a maximum execution time of only a
>> fraction of the timeout limit - 10 seconds is an acceptable *worst case*
>> target. My rule of thumbs is - if you cannot promise that, you should
>> redesign what you are doing.
>>
>> I hope this helps a bit.
>>
>> Regards,
>>
>> Klaus
>> On Sunday, December 15, 2013 12:01:19 PM UTC+1, Anil S wrote:
>>>
>>>
>>> HI,
>>>
>>> I have been using Google app engine for a while and faced some timeout
>>> issues while handling large data sets. MY application developed on Java
>>> Platform.
>>>
>>> Problem:
>>> When customer selects a date duration from UI, request goes to app
>>> engine to fetch the data from data store and run through custom logic on
>>> results and sends summarized view of data back to display in chats. Due to
>>> large volume of data, I am getting DeadlineExceededException.
>>>
>>> I can't really use task queues as I need to show the data on view for
>>> user request.
>>>
>>> Can anyone suggest how to resolve this issue?
>>>
>>> Note: I am using Objectfy 4
>>>
>>> Thanks in advance,
>>> Anil.
>>>
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