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POHow to use Google App Engine's (Java) Task Queues to Persist a lot of data / rows in one Entity
 

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  1. POHow to use Google App Engine's (Java) Task Queues to Persist a lot of data / rows in one Entity
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    <p>I'm trying to persist roughly 28,000 "rows" in a single entity e.g. EMPLOYEE</p> <p>Basically, my goal is to avoid being terminated / timing out by using PUTs that exceed 30 seconds - which is what might happen if I just do 28,000 PUTs by invoking a doPost() request sent to a servlet. </p> <p>So I'm thinking of using tasks described in the Google App Engine documentation.</p> <p>Essentially, I would like to upload a csv file in the war directory with 28,000 "employees". Then create a task that will async PUT these 28,000 employee rows to the EMPLOYEE entity.</p> <ul> <li><p>Q1: Is this a viable solution or is there a better way? Again, the goal is to performthe PUTs to avoid being terminated due to the 30 second limit.</p></li> <li><p>Q2: Also what queue.xml configurations should I use to ensure I can perform these PUTs as fast as possible?</p></li> <li><p>Q3: Now, I've tried it, similar to blog entry: <a href="http://gaejexperiments.wordpress.com/2009/11/24/episode-10-using-the-task-queue-service/" rel="nofollow">http://gaejexperiments.wordpress.com/2009/11/24/episode-10-using-the-task-queue-service/</a> but I'm getting the following error after 23 or so seconds:</p> <pre><code>SEVERE: Job default.task1 threw an unhandled Exception: com.google.apphosting.api.ApiProxy$ApplicationException: ApplicationError: 5: http method POST against URL http://127.0.0.1:8888/dotaskservlet timed out. at com.google.appengine.api.urlfetch.dev.LocalURLFetchService.fetch(LocalURLFetchService.java:236) at com.google.appengine.api.taskqueue.dev.LocalTaskQueue$UrlFetchServiceLocalTaskQueueCallback.execute(LocalTaskQueue.java:471) at com.google.appengine.api.taskqueue.dev.UrlFetchJob.execute(UrlFetchJob.java:77) at org.quartz.core.JobRunShell.run(JobRunShell.java:203) at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520) 16/02/2011 12:12:55 PM org.quartz.core.ErrorLogger schedulerError SEVERE: Job (default.task1 threw an exception. org.quartz.SchedulerException: Job threw an unhandled exception. [See nested exception: com.google.apphosting.api.ApiProxy$ApplicationException: ApplicationError: 5: http method POST against URL http://127.0.0.1:8888/dotaskservlet timed out.] at org.quartz.core.JobRunShell.run(JobRunShell.java:214) at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520) * Nested Exception (Underlying Cause) --------------- com.google.apphosting.api.ApiProxy$ApplicationException: ApplicationError: 5: http method POST against URL http://127.0.0.1:8888/dotaskservlet timed out. at com.google.appengine.api.urlfetch.dev.LocalURLFetchService.fetch(LocalURLFetchService.java:236) at com.google.appengine.api.taskqueue.dev.LocalTaskQueue$UrlFetchServiceLocalTaskQueueCallback.execute(LocalTaskQueue.java:471) at com.google.appengine.api.taskqueue.dev.UrlFetchJob.execute(UrlFetchJob.java:77) at org.quartz.core.JobRunShell.run(JobRunShell.java:203) at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520) </code></pre></li> <li><p>Q4: I've also checked the Datastore Viewer at <a href="http://localhost:8888/_ah/admin" rel="nofollow">http://localhost:8888/_ah/admin</a> and it seems to have only created 1000 results in that entity. Is 1000 the limit?</p></li> <li><p>Q5: How do I get rid of that above error?</p></li> <li><p>Q6: Can any confirm that the maximum allowed time is 10minutes for a task? or is it still 30seconds? I did come accross this: <a href="http://code.google.com/appengine/docs/java/taskqueue/overview.html#Task_Execution" rel="nofollow">http://code.google.com/appengine/docs/java/taskqueue/overview.html#Task_Execution</a></p></li> </ul>
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    1. COBtw, I think your misinterpreting the concept of an Entity. Each 'entity' is an instance of a 'kind' (as object is to class in Java, as row is to table in a database). I assume you mean you want to create 28 000 entities of the kind EMPLOYEE? See for example http://code.google.com/appengine/docs/java/datastore/entities.html#Kinds_IDs_and_Names
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    2. COYes, your assumptions are correct. Sorry for the badly used/ mix terms.
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