Monday, November 22, 2010

Decision Model Java (Memory Fix + Link EC2 API)

I handled two problems that still existed with the Java port of the spot model software attached to the "Decision Model for Cloud Computing under SLA Constraints" paper.
  • The first problem I attacked is the fact that the software needed a lot of memory. This was the case because it first of all read a couple of 100000 records to memory from the input CSV file to then use this data to do a lot of simulations ... and to finally write all the results from memory back to file. I fixed this issue by adjusting the source code such that only the history spot prices of one instance type is read at once. Since there are no correlations between the data records of different instance types, it is possible to do the simulation (for the different task lengths and different checkpointing schemes) for every instance type/category separately.

  • A second thing that I changed is the input file for this application, previously it took one data.csv file as input containing the spot price history data for every instance type (different columns). This file did not contain any date information, every record contained the price for a minute of time. Now the application takes the CSV files from as input, which means there is a separate file for every region-os-instance combination that has two columns: the first one contains the date, the second one the corresponding spot price for that instance at that time. Also, to use up-to-date spot price history information and to ensure that all my applications would remain usable would cloudexchange ever cease operations, I made a link with the EC2 API. So, in a separate project (called AmazonSDK) I created an application that connects with the different Amazon EC2 endpoints and requests the spot price history of the corresponding region. This data is then processed by my application and the output files are organised and formatted the same way as the ones that can be found on
Both projects can be checked out from the SVN repository, but backups can be found here:
  • The Decision Model project here.
  • The AmazonSDK project here.

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