CloudCamp Barcelona 2009

Marc Sturlese — Wed, 17 Jun 2009 23:43:49 +0000

Last Monday took place in Barcelona the first CloudCamp ever done in the city. Altough I was expecting more technical stuff it was good to be there and listen to what people have to say.
The first part of the event consisted of some quick explanations from different companies related with cloud computing. Basically, were explaining the cloud choises and advantages they were offering. The one I enjoyed the most was the Abiquo’s presentation of their new software, Abicloud. Through a really nice GUI developed with Flex, Abicloud, among other stuff, allows you to set up virtual machines configuring automatically an apache server, mysql database… with just a few drag & drop actions. You can use you own machines, servers from an ISP or even combine both. Elastically, you can increase or decrease the number of virtual machines. This can be very convenient for sites with hight traffic peaks or testing environements.
I am not going to talk more about it as with a five minutes presentation just could get the main idea. Can’t wait to have some free time to start playing with it. Just will add that Abicloud is completely open source.

After the quick talks, the following topics were discussed:

What guarantees do I have with Cloud Computing?
What legal issues are there with your data?
Are standards important? If so, wich ones?
What is the benefit for a company with only a few dozens of servers?
Best platfrom to starting a cloud hosting company?
Is cloud computing green? If so, what?

In the end people were divided in groups depending on in wich topic wanted to go deeper. I attended to “How to develope applications that are going to run in the cloud”. There I could have an interesting quick chat about application scalability and how to dump mysql databases to HDFS using the Cloudera’s tool Sqoop.

MySQL streaming setting fetchSize to Integer.MIN_VALUE

Marc Sturlese — Sat, 17 Jan 2009 19:53:04 +0000

Have you ever experienced a java.lang.OutOfMemoryError: Java heap space
due to too big selects?
We can avoid that thanks to the fetchSize parameter initialized at statement creation time. FetchSize decides how many rows of the select MySQL must store in the buffer before dealing with the data. Setting that parameter to it’s minimum value we will be able to do streaming with all rows.
The minimum value is still pretty odd for me as I thought it would be 1 (thinking 1 was the minum numer of rows to be stored in the buffer) but it is -2^31, the minimum value java can store in an Integer!

Another solution would be to paginate the select setting a limit value. The problem with this is that the more selects we do, the slower MySQL will deal with rows. Doing streamaing with the fetchSize parameter we just need one select and the “rows deal with speed” does not decrease. MySQL will deal with the rows buffering by itself.

The statement creation should look like this:

try {
Connection c = getConnection();
stmt = c.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
stmt.setFetchSize(Integer.MIN_VALUE);
…

Marc Sturlese » MySQL

CloudCamp Barcelona 2009

MySQL streaming setting fetchSize to Integer.MIN_VALUE