Finally, here we are on the third part of the streaming system history. I'm sorry it took so long, but I had many, many things to do for work and I was very busy with real life stuff.
In this part I'm going to introduce systems from 2011. If you find any mistake or anything incomplete feel free to let me know by commenting the post! Not all the 2011 systems are shown in this post, I will complete it with the final, fourth part.
In this part I'm going to quickly talk about Storm (2011) and WebRTC (2011).
Storm is a distributed computational...
Saturday, December 28, 2013
Monday, November 25, 2013
Here I am again with some history on streaming systems! Today I would like to dive into systems born from 2005 to 2010. If you find any mistake please comment the post and let me know!
In this post I'm going to talk about the second generation of streaming systems: Borealis (2005), SPC (2006), DryadLINQ (2008) and S4 (2010).
Borealis is a distributed stream processing engine which inherits much from Aurora and Medusa. Aurora is a framework for monitoring application born around 2002. At the high level, the system model is made...
Friday, November 15, 2013
Lately I've been very busy studying streaming systems in general. I've took a look at the last decade streaming systems and what literature proposed. I want to share a little bit my findings summing up things here a little bit. I'm going to divide this series of posts in three, one for each generation of streaming systems. All the data should be more or less correct, but feel free to comment below and ask question of correct mistakes if there are! I would like to be the more precise as possible.
The first generation of streams proposes, among...
Thursday, November 7, 2013
Hi all, I'm sorry I couldn't post much later. I've been in vacation for a while, and then suddenly a big chunk of work arrived, and I had practically 0 time to write here. I'm not even programming anymore, just paper writing and teaching assisting. Hopefully I'll be back on track after the 15th, the last deadline for the last paper I wrote.
Until next time, see ...
Tuesday, August 13, 2013
Quick post (personal reminder above all) about how to install a specific version of Node.js. I'm working on Ubuntu 12.04. The idea is to clone the whole repository and then checkout only the interested version. Then install it. Here are the commands.
git clone https://github.com/joyent/node.git
cd node
git checkout "v0.8.18"
export JOBS=2
./configure
make
make install
And you are good to go!...
Monday, August 12, 2013
Hi all, I've been very busy lately, and then I went for a holiday, so I didn't update the blog. Sorry!
I recently came back from the seaside and started to work on a bug I had since forever. I thought it was a deeply rooted bug that was spread in different methods. It turns out it was not like that. And that's what I discovered:
First of all, I had this array that kept count of how many distributed processes answered a pull request. Each process has an ID, and it corresponded with the index of the array. The array first is filled with false values....
Monday, July 1, 2013
Hi all. Today I decided to add a small functionality to my project: when I start my framework, I run stuff one after the other with a list of commands; I decided to add a functionality that reads a particular file (which I want to be a .k file) and extract the commands from that list.
To do so I need some things:
Read a file
Make sure it's a .k file
Split it line by line
Execute each line
Reading a file in node.js is very simple. We just need to import the fs module and call the function readFile:
fs.readFile(cmd[1], 'utf8', function(err,...
Thursday, June 27, 2013
Hi all. I've been quite busy lately. I travelled more than I expected and I didn't work much on JavaScript and my project. What I did was mostly bug fixing on not-so-interesting stuff, which did not lead me to interesting discoveries about the language in general.
What I wanted to post today is about OUYA, this new gaming platform. It's a small console with an Android engine inside. You plug it to your TV through an HDMI cable and can start browsing...
Tuesday, May 28, 2013
I'm sorry for the long lack of updates. Recently I've been very busy. I travelled a lot and I had a lot of work to do, so not really much time to work on my project and discover new interesting things.
Today I want to post something that bothered me for a while. I was calling an asynchronous function, m_cli.get(), inside a for loop and wanted to keep the index variable as it was going to be used in the callback.
The first approach was the following, and of course was not working:
for(var i = 0; i < list.length; i++){
mc_cli.get(list[i],...
Friday, April 19, 2013
First of all, I'm sorry for the lack of updates. I've been very busy with teaching and grading. Plus, my research is not leading me to discover new libraries or programming models, so I have nothing to write here.
Lately, I've been working with deploying my Raspberry Pi integrated with some sensors. I wanted to a robust deployment, but how to do that? Should I bring my monitor wherever I want to deploy the Pi to set it up?
Luckily there is a very easy way to do that. In this way, whatever happens (like power supply unplugged), whenever the Pi is...
Thursday, April 4, 2013
First of all, I'm sorry for the lack of updates. Lately I've been writing papers and not really coding. Moreover in the last few days I was on vacation, so no computer either.
Anyways. In my project I'm using ZeroMQ which is a very good socket library. I use that to make my workers communicate with each other.
Lately my main concern was message loss. Since I increase and decrease the number of workers, it may happen that some worker gets shut down when it is receiving, processing or sending a message.
The very first approach I had to...
Tuesday, March 26, 2013
While writing the last paper I'm working on, I realised I also needed to cite some web reference. As I'm used to input BibTeX entries that are papers or books, I didn't really know how to cite websites.
Apparently this is not supported by BibTeX, which is strange since the web is growing more and more important nowadays, so I found out another way to cite the online resources. This is not really the correct way to do it, as it hasn't been figured out yet, and some trick were using the @MISC type. I will use the @ONLINE type:
@ONLINE{Caio:2013:Online,
author...
Friday, March 22, 2013
Lately I've been experimenting quite a lot with Raspberry Pi, but I was curious about what can Node do on Arduino. So I got an Arduino and searched for some useful library to run Node on it. I immediately found out what I was looking for : Noduino.
The framework is really easy to run: just download the branch, then upload on your Arduino the du.ino file and you are good to go. I tried a very simple example given in the repo: test.walkLED.js and...
Monday, March 18, 2013
When I first ordered my RaspberryPis, I didn't realize I would need some kind of male-to-female cables to connect the breadboard to the I/O pins on the Pis, which are male. I decided to spend I little bit more and buy the Cobbler Breakout Kits. These kits are very easy to solder and give some help in building circuits: on the board there are all the names of the pins which corresponds to the pins on the Pi. Here is one already soldered (don't mind...
Monday, March 11, 2013
Hi there. This post is not going to be on JavaScript but it will be a bit more centered on the Raspberry Pi and what I did today. As pointed out in an old blog post, I'm working on a software that creates streams of data and pass them through a topology. As data sink, I though it would be very nice to have a Raspberry Pi which gathers data from the environment, for example.
Today I started to implement something on the RPi. Nothing serious, but I...
Tuesday, March 5, 2013
Sometimes we need to play with timed events. JavaScript comes to the rescue giving access to setTimeout and setInterval. The first one fires only once after a certain amount of time passes, while the second one fires every time a given interval passes. For example if we give 1000 as one of the input variables to setInterval, it will fire every second.
One problem that may arise using these functions is when we want to call a function defined somewhere else and pass a parameter to it. If we try to do the following:
var myFun = function(param)...
Monday, March 4, 2013
While taking some measure on one of my softwares, I noticed instead of going through the ftp every time to get the results, I could just open some text editor. For this things I installed gedit on the Ubuntu remote machine I'm working on. I tried the following command
gedit filename.txt
Cannot open display:
Run 'gedit --help' to see a full list of available command line options.
As you can see it produced that error. The problem I had (and apparently is quite common), it's the fact that when I logged on my remote machine through ssh...
Saturday, March 2, 2013
Recently I've been testing the application I'm working on. Since it is already complicated by itself I don't want to add a database support to it. Instead, I thought about writing data on a file. In the context of my software, I'm sending messages to different processes on remote machines and I want to be sure I'm not loosing any of those messages. To check this, when I receive a message I store its ID (every message has one) in a file, appending it to the end. Then by using the sort bash command I sort them and see which messages I lost (or...
Thursday, February 21, 2013
Lately I've been working on an extension for Google Chrome to read the last entry of the famous xkcd comic. At a certain point I stopped because I didn't understand how to dynamically resize the popup window of the Chrome extension. This required quite some research to understand what was going wrong, here is how I created the extension, which problem I had and how I solved it.
How I did it
The extension is very easy, it executes a GET request to the xkcd website, gets the content of the index page and returns it. What I used to...
Friday, February 15, 2013
I was printing some results for a chart while, after 10 minutes of executing the test, I realised I forgot to put the \n command after the number I wanted to print. I know the numbers I was printing were smaller than 10, so I came up with a useful command to append a new line after each character in a file:
sed 's/\(.\)/\1\n/g' -i filename
And that's it. As easy as that. I'm sorry for the lack of updates but lately I've been very bu...
Wednesday, February 13, 2013
Today I was working while I was asked how to remove an event listener from an element which had an
click event. At first I didn't really remember how to do it, so I Googled a bit and I found this way:
document.getElementById("your_element_id").addEventListener('click', function(){
//do something
this.removeEventListener('click',arguments.callee,false);
}, false);
As you can see, all the work is done by addEventListener and removeEventListener functions. The first one takes as parameter the event (click in...
Tuesday, February 12, 2013
I think everybody is familiar with the setInterval and the setTimeout functions. They create a timed event which will occur after a given timeout. setInterval creates an interval: after the given time it will repeat the same action over and over, while the setTimeout function will only execute the action once. Let's see a small example on how they work:
var timed_function = function(){
console.log("hello!");
}
var timeout = setInterval(timed_function, 1000);
The shown example will execute every second (1000 milliseconds)...
Friday, February 8, 2013
In this final part I will show how I installed Node.JS on the Raspberry Pi on the Raspbian Wheezy OS.
First of all, open a terminal and execute the following commands:
cd /usr/src
sudo wget http://nodejs.org/dist/v0.8.16/node-v0.8.16.tar.gz
This will change the directory to /usr/src/ and download Node.JS version 0.8.16. I know this is not the last version, but I needed that because my project runs on it and it's not yet time to upgrade to the latest version (even though I'm pretty sure everything is going to be all right).
After the download...
Wednesday, February 6, 2013
So after you plug everything (the power supply last), on the screen you should see Raspbian Wheezy booting. Lots of logs in the console and finally what looks like a BIOS screen:
If you don't then you will have the problem I had. In the past hours I struggled a lot because I couldn't see anything on the screen. I tried reinstalling the OS image on the SD (in at least three different ways) and plugging different devices but nothing happened. In...
Tuesday, February 5, 2013
During these days I borrowed a Raspberry Pi. I would like to try to set up a Node.js server on it. I decided to write this post to show how I did the whole thing. Just to make things clear, I'm running on OSX.
So first of all once you have your Raspberry Pi, you should mount the OS image on the SD card. Some RPi comes with an SD card with everything setup. If that's the case, you are lucky and can skip this post. Otherwise, just connect the SD card...
Monday, February 4, 2013
Some time ago I needed to measure the performance of the cores I was using on a machine while a Node.js server was running. I came up with different ideas, including writing a bash script that would measure it the hardcore way. I then realised I could use the os module that comes with Node and use the data it returns to measure it myself.
First of all, take a look at the specification of the method os.cpus() here. It shows how to call it and what is the return value. To measure the performance of the system, it is sufficient to take...
Sunday, February 3, 2013
Some time ago I was talking with a second-year student after a C exam. He was pretty satisfied about the job done, but asked me a question about the ~ operator. At first I didn't quite remember, so I told him that was probably the bitwise not. Later I discovered I was right, so I took the opportunity to refresh my knowledge of the bitwise operations in JavaScript. The purpose of this article is to show which bitwise operations JavaScript offers.
First of all, we can only apply bitwise operations on numeric operands that have integer values. These...
Saturday, February 2, 2013
Sometimes, even if it is considered bad habit, we need to check the class of an object in JavaScript. Classes may be defined by the programmer, but I will cover this topic later, for now let's just focus on classes defined by the interpreter. There are many, for example:
Object
String
Number
Date
Function
...
To check if an object is an instance of a specific class, JavaScript offers the instanceof method, which may be used in the following way:
var mynmbr = new Number(1);
var mystrng = new String("disasterjs!");
var myfunc = function(){
...
Friday, February 1, 2013
Some time ago I had a problem with arrays and assignments. I was working with a distributed system in JavaScript; the root process sent some "work" to do to some subprocesses (workers) and those returned an array as result, which was modified inside the callback of the dispatching function.
The issue was that when I modified the array, I then assigned it to a variable and passed it to a function. The problem was that while I was working in the callback with this array, it got modified somehow. I later understood that the problem was due to the...
One of the first issues I had with this blog was how to syntax-highlight code snippets. All I could find on the internet was garbage and old tutorials with the previous Blogger interface. Then I finally found this blog that proposed a working solution. Actually, it's the only solution that worked, so I'm suggesting it here, but I'm not entirely satisfied with the CSS that comes with it, so I might slightly modify it sooner or later.
If somebody knows a better solution, let me know in the comments, I'll be glad to take a look at ...
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