Landing page project for my personal web site

Courtesy of Gliffy.

Work in progress:
...here

Image:


Editable chart:

Alexa Site Compare widget

...cannot be pasted here apparently. So it can be found here.

Google Map Search

Here...

Monocle's RSS feed

Twitter's db maint

...is down for database maintenance. DBCC I guess? A bit funny to see yet another reason why the service is down. I can think of several ways to monetize it, but certainly not with the amount of downtime they are having.

Widgets ecosystem

Allright, widgets are the new rage. Here are your options:

• Mac Dashboard Widgets: the OG of widgets; Google has a few too
• ...copied by MS in Vista: Windows Sidebar Gadgets
• Google Gadgets: desktop or web
• Yahoo Widgets: desktop, within the yahoo RT
• Opera has its own which work on the desktop, mobile phone, or Tv (have to see this one!)

Then there are the 'social sites' plug-in widgets (eg for Facebook: Washington Post's collection of widgets). Also, offerings such as this one that provide the backdrop for widgets to work. Or, for a really useful collection of widgets, look here.

Finally, there are aggregator sites such as these: WidgetBox and SexyWidget.

A cool company that authors widgets.

Blogger API

Using the Blogger API: of course, from JavaScript you are restricted by the same domain origin security requirement. Google has a nice API that allows JS to work... still trying to figure out a way to use this feature. The irony is that the demo I link to reads this very postings.

More programmable web

Lately the 'programmable web' has become more and more of a reality. Amazon, Google, and Adobe among others have made big contributions. Here are some:

• Amazon S3
• REST/SOAP based storage
  
• Amazon SQS
• SOAP based queuing
  
• Amazon SimpleDB (still in beta)
• similar to GoogleBase?
• attribute-based semistructured repository
  
• Amazon EC2
• on demand virtual servers accessible via web services
  
• GoogleBase
• shared repository that can be queried using a SQL-type of language
  
• GoogleGears Database
• browser extension allowing the use of a local SQLite database (SQLite is just taking off: Adobe AIR also uses it)
  
• GoogleGears WorkerThread
• browser extension allowing multithreading
• the threads are created locally; they are real OS threads spawned within the browser process
• the threads communicate via text messages
  

On one hand, Adobe and Google bring web functionality to the desktop (stepping out of the browser sandbox: the AIR environment; GoogleGears); on the other hand, Amazon and Yahoo offer services that extend typical desktop or client/server functionality to the web.

I do not think the day is too far away when you will be able to compile a program online (if Office is going the software as service way, why not Visual Studio?) and deploy it to a virtual environment on the cloud, and run it there. Possibly, the only thing that is missing is a set of libraries to abstract the communication protocols (SOAP, XML-RPC, ATOM, etc... still too many).

Google Gears demo

Had some fun with Google Gears. To run this you need Google Gears installed, and it will not work with Safari.

Google Gears demo

Ruby and SQLite3 in Windows

If you need to run Ruby with SQLite in Windows, since you cannot set up the environment in the script like you can in Unix (#!), make sure you have the sqlite3.rb and sqlite3.dll in the same directory where the Ruby script is. Figuring this out caused me much grief.

Postgres and Ruby




On Mac OS X the Postgres binaries are saved in /usr/local/bin. Here is a handy Postgres launcher that can be saved in the user’s directory (as postgres_start.sh for example):

su -l postgres -c "/usr/local/bin/pg_ctl start -D /Users/postgres/datadir"

Where datadir is the directory (owned by the postgres user) where Postgres has the data files.

To create a custom tablespace in Postgres, make an empty directory first and use that as the location for the tablespace in pgAdmin3.

Sample Ruby code to access Postgres; notice that the first line is needed to set up the environment; without it the require fails.

#! /usr/bin/env ruby
#
# original file src/test/examples/testlibpq.c
# Modified by Razvan
# Calls PL/SQL function in Postgres

require 'postgres'

def main
norecs = 0
pghost = "localhost"
pgport = 5432
pgoptions = nil
pgtty = nil
dbname = "razvan"

begin
conn = PGconn.connect(pghost,pgport,pgoptions,pgtty,dbname)

res = conn.exec("BEGIN")
res.clear
res = conn.exec("SELECT * FROM insertrt('another row')")

if (res.status != PGresult::TUPLES_OK)
raise PGerror,"RB-Error executing command.\n"
end

printf("\nRB-Results\n")
res.result.each do |tupl|
tupl.each do |fld|
printf("RB-%-15s",fld)
norecs = norecs + 1
end
end

res = conn.exec("END")
printf("\nRB-Records: %i\n", norecs)
res.clear
conn.close

rescue PGError
if (conn.status == PGconn::CONNECTION_BAD)
printf(STDERR, "RB-Connection lost.")
else
printf(STDERR, "RB-Error:" )
printf(STDERR, conn.error)
end
exit(1)
end #rescue
end #end def main

main #invoke code

This calls the following Postgres plpgsql function:

CREATE OR REPLACE FUNCTION insertrt(data character varying)
RETURNS bigint AS
$BODY$
DECLARE
id bigint;
BEGIN
id := 0;
IF EXISTS(SELECT * FROM "RTable") THEN
SELECT MAX("Id") INTO id FROM "RTable";
END IF;
id := id + 1;
INSERT INTO "RTable" ("Data", "Id")
VALUES(data, id);
RAISE NOTICE 'New id is %', id;
RETURN id;
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION insertrt(character varying) OWNER TO postgres;
GRANT EXECUTE ON FUNCTION insertrt(character varying) TO postgres;


To execute this function do a SELECT * FROM insertrt( ‘parameter’ ). Interesting in the function, SELECT INTO variable. Also notice “ ‘s used to enclose field names and table names. The output of RAISE NOTICE is displayed by the Ruby console.

Since gems does not work with OS X Tiger’s Ruby, the Postgres adapter has to be built manually.

Back again

It has been some time since I managed to post any entries. Currently I am busy learning Ruby; not yet sure how it related to distributed systems, but since forever I have been looking for a language that would not be too syntactically twisted yet powerful enough - this little scripting language might just be it. So watch out for some projects coming soon.

At the same time, I have been playing with OS X's Automator. While the choice of actions is limited (really, who would need to script iCal or GarageBand actions?), the possibilities offered by a all-pervasive workflow engine seem intriguing. I'm not crazy about Applescript, but then there is a library that enables Ruby to perform Applescript actions :D

Roger Wolter lecture notes

A few ideas from an article by Microsoft's Roger Wolter on the MS infrastructure support for reliability in connected systems 9 (in MS Architecture Journal, vol 8):

- SOA = connected systems
- services communicate through well defined message formats => reliability = reliability of the communication infrastructure
- message handling between services more complex than client/server because server must make client decisions
- message infrastructures in the MS world: MSMQ, SQLS Broker, BizTalk (also offers data transformation)
- problems:
1. execution reliability (handling volume): different technologies deal with this differently, e.g. stored procedure 'activation' in Service Broker
2. lost message (communication reliability)
3. data reliability

Quartz Composer

For the last few days I have been experimenting with Apple's Quartz Composer. While this is primarily a motion-design tool (and a very powerful one indeed), it is also an example of a very effective graphical programming environment. Prior to this, I had seen such tools in the Windows environment and was less than impressed, but QC is really amazingly powerful; you can parse structures, use variables, loops, and everything somehow fits together very well. I see uses for this metaphor in the BPEL world, at the very least, but the whole world of distributed computing seems a good fit for it.

By the way, this is the 'code' behind one of the rather phenomenal demos that can be found here.

Web OS part II

To further illustrate the merging of Web, Database, and fileshare services, I'm currently involved in a Sharepoint installation process where data from users' file shares will be moved to the Sharepoint collaborative environment, with a SQL Server database as physical storage. Thus, the Internet replaces the file storage functionality, by delegating the actual storage to the SQL engine.

MacOS run loops and console mode

Run loops do NOT run automatically in console mode, not even on the main thread. It kind of makes sense, run loops are one of the mechanisms that support GUI events. So you have to create a run loop manually when running in console mode; it can use multiple timers, and it will pre-empt the main thread, whose execution will only resume after the run loop's timers finish running.

Adventures in multithreading

An insidious race condition arises in the following situation (which I encountered in Objective-C, but any language that passes by reference will allow for the same):

I have a consumer function which writes a message to a file or database and which can be called by multiple threads - so it is LOCKed. This function is called by threads generated by a loop, where the thread instantiation function takes as parameter a string which is modified by each loop iteration. E.g., in pseudo-C:

string msg;
for( i = 0; i < 10; i++ ){
fsprintf( msg, "parameter: %i", i );
launchThread( msg );
}

void launchThread( string parm ){
plock lock;
fprintf( fHandle, parm );
plock unlock;
}

Of course since the fprintf needs to be atomic (in order not to generate a bus error), it is the one that has to be locked. However, msg is a shared resource as well. If you run this code as it is you will get an output similar to the following:

parameter20
parameter20
parameter30

Instead of the expected:

parameter1
parameter2
parameter3

That is because msg is modified by the loop and by the time thread #x has picked it up, who knows what value it has - certainly not one in sync with #x.

The solution is to provide as parameter to the thread a full immutable copy of msg and not a reference to msg.

Again, GoogleMaps

..it seems it's an issue of latency. From a really fast connection it was able to recognize both Tokyo and Hong Kong. London is still un-geocodable though I am afraid.

Objective-C

I have recently started looking into Objective-C. In my experience, one of the biggest hurdles when learning C++ is understanding who does what; textbooks focus on OO and spend a lot of time on discussing buiding classes and coming up with silly examples, and little is said about how does this translate into executable code. With C you still have a pretty good idea how the code becomes machine code. With C++ the connection is broken; a class does not map to registries and you are left with a major gap in the continuum. The same problem (even to a larger extent) occurs with SQL or VM-type languages such as C#, Java, or Actionscript.

The ObjC instructions from Apple are the only ones I have seen so far that do a good job at explaining the runtime, and how OO constructs become procedural code. I am very impressed.

I have a first attempt at writing Mac OS X code here, a Cocoa front end to Unix queues. IPCS seems to not work with queues on Mac, but other than that the system calls seem to work quite well.

GoogleMaps v2

I finally rewrote the Maps application in a more objectified JavaScript. The source code is here and you can see it in action here. It seems that the Google Geocoder also does not recognize London, besides Hong Kong (actually, HK is sometimes recognized! what gives?) and Tokyo.

Flickr (FlickrMaps) uses it in a similar fashion.

Here is the UML Sequence Diagram of the interactions caused by this application: