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 cloudexchange.org 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 cloudexchange.org.

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.

Decision Model Java Implementation

I made some little changes to the java port of the 'Decision Model ...' paper software. And added Javadoc comments to this source code, which can be checked out from the SVN repository. This software needs a lot of memory because it first of all reads a couple of 100000 records to memory from the input CSV file then uses it to do a lot of simulations ... and finally writes all the results from memory back to file. (Actually this process starts all over for every task length). I think to boost the performance it would not be a bad idea to only take the history spot prices of one instance type as input and do the simulation only for one category/instance type at a time. This would almost make all arrays used in the program a dimension smaller. And it's not that hard to then write something around it that runs the program a couple of times with different input for the different instance types. Also the program still takes its own input file, but this can easily be changed by implementing a data input reader that takes the cloudexchange CSV files as input. A backup of the source code of this program can be downloaded here.

Port Spotmodel to Java

This weekend I was feeling a bit sick, so I couldn't do that much. But I was in a programming mode and decided to port the Spotmodel software that accompanied the 'Decision Model for Cloud Computing under SLA constraints' paper from C to Java. The original source code can be found here and the newly created Java project here. The code is also available though SVN, for which I'll mail you the credentials. Note that the code should still undergo some design changes (for the moment it needs a lot of memory for example) and javadoc comments should be added.