Writing to an appengine blob asynchronously and finalizing it when all tasks complete

Question

I have a difficult problem.

I am iterating through a set of URLs parameterized by date and fetching them. For example, here is an example of one:

somewebserv

Answer 1

Here is an example using Java Pipeline

package com.example;

import com.google.appengine.tools.pipeline.FutureValue;
import com.google.appengine.tools.pipeline.Job1;
import com.google.appengine.tools.pipeline.Job2;
import com.google.appengine.tools.pipeline.Value;

public class PipelineRecursionDemo {

  /**
   * A Job to count the number of letters in a word
   * using recursion
   */
  public static class LetterCountJob extends Job1 {

    public Value run(String word) {
      int length = word.length();
      if (length < 2) {
        return immediate(word.length());
      } else {
        int mid = length / 2;
        FutureValue first = futureCall(new LetterCountJob(),
            immediate(word.substring(0, mid)));
        FutureValue second = futureCall(new LetterCountJob(),
            immediate(word.substring(mid, length)));
        return futureCall(new SumJob(), first, second);
      }
    }
  }

  /**
   * An immediate Job to add two integers
   */
  public static class SumJob extends Job2 {

    public Value run(Integer x, Integer y) {
      return immediate(x + y);
    }
  }
}