G1 Android Phone
I just received my G1 phone in the mail as it is spectacular. The touch screen works very well and the built-in GPS, wi-fi, and 3G network/ functionalities will allow developers build some very exciting new applications for these phones. It also has a compass that is demonstrated using the Street View of Google Maps. When viewing Street View, if you start spinning in one spot the image will rotate according to the direction the back of the phone is facing. It probably has a built-in level also that allows the Street View to pan up to the sky or down to the ground when the phone is moved in those directions.
The Android Market is where users can download application that runs on the phone built by developers (Google and other developers). It currently has about 50 applications from their Android Developer Challenge. On October 27, 2008, they will open up the Android Market to all developers to submit their applications. Currently, all applications in the market must be free of charge, but in the first quarter 2009 they will allow applications that charge a fee. It is interesting that Google has made the Android Market totally open and policed/ ranked by users. They will not require approval for any application and anyone can put applications on the market. That is very different form Apple's iPhone App Store where they are gatekeepers to every application sold to iPhone users by using a review process. We will see how this pans out, but so far it seems promising.
Well, I'm going to start building Android Apps so that's it for now.
Mysql on 32bit processor vs 64bit processor
Here is the continuation of the experiment done previously on Mysql on Windows vs Linux. After doing more analysis and observation, it appeared that the difference in speed for the benchmark tests were not related to Windows and Linux but were related to the processor. The previous test just happened to have AMD 64s on the Linux machines and Intel Xeon 32bits on Windows. We hypothesized that the increased throughput of the 64bit processors resulted in about half the time required to return the same query run on a 32bit machine.
So we decided to test the same query again on a Windows machine with an AMD 64 X2. This time the result for the query took 7.35 second, almost the same as the other AMD 64s running Linux.
One more test to run the query on a Windows Intel 64bit chip machine would better solidify our hypothesis.
Mysql server has gone away
I have a spider crawling the web written in PHP running constantly to insert and update data in a Mysql database. Today, it kept stopping on a records with the error message, "Mysql server has gone away". It certainly did not time out as just starting the process again would result in this message immediately. The script did not close out the connection to the DB as it had worked just fine for over a year.
Finally, I found that the problem was max_allowed_packet setting in my.cnf was too small. It was set to 2MB and when Mysql receives a query larger than that, it assumes that something must have gone wrong and closes the connection. I increased that parameter to 4MB and everything is working fine now.
Mysql on Windows vs Linux
I was working on optimizing a Mysql database today and accidentally stumbled upon a benchmarking exercise. The original Mysql database is hosted on a Windows Server 2003. I develop on a Mysql database server running on Ubuntu Linux. The Linux server ran the same query twice as fast as the Windows server without using caching or anything. I know that Linux does I/O caching on its own as well so I even tried running the query after a fresh reboot to rule out that factor. Then I got help from a colleague and started tweaking with the my.cnf/my.ini to make sure they were the same and each time, the results came back about the same. Mysql on Windows was consistently slower than Mysql on Linux.
Then we decided to load the database onto other servers for more data points on this Mysql performance test. We ran the same query returning 429 rows of data with 13 table joins and a couple of sub-queries. All queries were run on the command line client on the servers themselves to avoid network lag. All servers are running Mysql 5.0.x.
Results
1. Ubuntu Linux: 0.70 seconds
2. CentOS: 0.78 seconds
3. Windows 2003 Server: 1.40 seconds
4. Windows 2003 Server: 1.42 seconds
Server hardware
1. Ubuntu Linux
AMD ATHLON 64 X2 4200+
2GB DDR400
200GB 7200RPM SATA/150
2. CentOS
Dual Opteron 240
2GB DDR ECC
120GB 7200RPM SATA/300
3. Windows 2003 Server
Dual Xeon
2GB DDR ECC
7200RPM PATA
4. Windows 2003 Server
2 Dual Xeon (4 CPUs)
8GB DDR ECC
3 73GB 10,000RPM SCSI in RAID 5
A followup to the benchmark that clarifies the cause of the differences
Mysql SQL_NO_CACHE Benchmark Problem
I have been trying to benchmark the sql calls to mysql from an application without success. Even when I set the SELECT statement to SQL_NO_CACHE, the results seemed to be still cached. Apparently, Linux does its own caching of disk reads also. That was giving me incorrect benchmark results if I hit the same data twice.
For those using Linux kernel 2.6.16 or higher, you can clear Linux cache with the following command.
echo 3 > /proc/sys/vm/drop_caches
Unfortunately for me, I am stuck on 2.5.xx and will have to figure out another method.
Open Source Is Much More Serious These Days
If you still think open source applications are just the wild west without any sort of structured support, think again. The Drupal Conference happening in Boston is an example of how organized open source has become. No longer are conventions just for Microsoft, IBM, Oracle, etc.
zen cart Warning: session_start() No such file or directory (2) in /dir/public_html/includes/functions/sessions.php on line 102
The error comes up when trying to use file based session storage instead of database. Apparently, the configuration for what directory to store the session is not in the configuration files but in the database table "configuration".
If you upgrade your php to version 5.2.1, the database session storage breaks. Therefore, I had to switch to file system based storage. But the catch was that I no longer could log into admin as the session could not start. The configuration.php files did not have this constant.
The way to fix this is to log into your database and update the session directory record.
"UPDATE configuration SET configuration_value='/your/new/direcotory/' WHERE configuration_title='session directory';"
System Specs:
php.5.2.1
zencart 1.3.5
apache 1.3.37
MySQL 5.0.45
Apache SSL IfDefine – Error
Just encountered a problem that was painful to deal with while configuring SSL on apache for linux. The httpd.conf had a tag,
$ service httpd -D SSL -k start
Also, I found that restart does not always take new changes to my conf files.
$ service httpd -D SSL -k restart
Instead, use the stop then the start command to be sure.
$service httpd -D SSL -k stop
$service httpd -D SSL -k start
That was a source of much pain while working on this particular server.
Zencart and Ultimate URL – 1054 Unknown column ‘c.parent_id’ in ‘on clause’
Configuration:
Linux
Apache 1.3
Mysql 5
PHP 5
Zencart 1.3.5
Chemo Ultimate URL for Zencart 1.3.5
Problem:
After installation, the error message
1054 Unknown column 'c.parent_id' in 'on clause'
shows up on any page in the catalog.
Fix:
Make the following change to /include/classes/seo.url.php
Original:
SELECT c.categories_id as id, c.parent_id, cd.categories_name as cName, cd2.categories_name as pName
FROM ".TABLE_CATEGORIES." c,
".TABLE_CATEGORIES_DESCRIPTION." cd
LEFT JOIN ".TABLE_CATEGORIES_DESCRIPTION." cd2
ON c.parent_id=cd2.categories_id AND cd2.language_id='".(int)$this->languages_id."'
WHERE c.categories_id=cd.categories_id
AND cd.language_id='".(int)$this->languages_id."'";
Change:
"SELECT c.categories_id as id, c.parent_id, cd.categories_name as cName, cd2.categories_name as pName
FROM
".TABLE_CATEGORIES_DESCRIPTION." cd,
".TABLE_CATEGORIES." c
LEFT JOIN ".TABLE_CATEGORIES_DESCRIPTION." cd2
ON c.parent_id=cd2.categories_id AND cd2.language_id='".(int)$this->languages_id."'
WHERE c.categories_id=cd.categories_id
AND cd.language_id='".(int)$this->languages_id."'";