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  • Managing scalability and availability with two servers running Apache Httpd, Apache Mina and MySQL

    - by celalo
    Hello, I am not a developer and I don't much experience with scalable server architectures. But I am in need of a highly available and scalable system for one of my projects. There is going to be two servers I am going to use for the time being. Both with 4 core CPUs and 8 GB RAM with RAID structures running CentOS 5.4. I will also have feature called "Failover IP" which enables to direct an IP address to another server within short time. The applications which will be run on the servers: There is going to be a Java application based on Apache Mina server for handling TCP requests from some hundreds of network devices where the devices are going to send request as much as one request per minute. Handling those requests, includes parsing the requests and inserting a few rows to the Database. Parsing requests before inserting data to the DB does take neglectable time. There is going to be MySQL server, as I stated above. Also there is going to be a PHP web application running on Apache Httpd Server which uses the same DB with the Java application. What I wish to have is to make use of those two servers at the most. I was imagining to have the servers identical, sharing the work load. MySQL could be a cluster maybe? And if some application fails or the whole machine goes down, the other will continue serving the requests seamlessly. Reminding that a "Failover IP" feature will be available for me to take advantage of. Also, It should be kept in mind that number of servers could increase in time, to meet the demand. What can you suggest? Which kind of tools I can make use of? Which kind of monitoring software (paid/unpaid) I have? Thanks in advance.

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  • How to know about MySQL 'refused connections'

    - by celalo
    Hello, I am using MONyog to montitor my two mysql servers. I get alert emails from MONyog when something goes wrong. There is an error I could not find out why. It says: Connection History: Percentage of refused connections) - 66.67% the percentage is not important, this is just about having refused connections. I get this email every half an hour. So this is like a constant situation. This must be my mistake, because I just set up those servers and there is no chance somebody else could be interfering the servers. MONyog advices me: Try to isolate users/applications that are using an incorrect password or trying to connect from unauthorized hosts. A client will be disallowed to connect if it takes more than connect_timeout seconds to connect. Set the value of log_warnings system variable to 2. This will force the MySQL server to log further information about the error. I added log_warnings=2 to my.cnf and I enabled logging like this: [mysqld_safe] . . log_warnings=2 log-error = /var/log/mysql/error.log . . . . [mysqld_safe] . log-error=/var/log/mysqld.log . . I cannot see any warnings at /var/log/mysql/error.log I can see some warnings at /var/log/mysqld.log but they are about something else. In sum, my question is how can I detect refused connections? Please let me know if any more info is required. Thanks in advance.

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  • Filtering MySQL query result according to a interval of timestamp

    - by celalo
    Let's say I have a very large MySQL table with a timestamp field. So I want to filter out some of the results not to have too many rows because I am going to print them. Let's say the timestamps are increasing as the number of rows increase and they are like every one minute on average. (Does not necessarily to be exactly once every minute, ex: 2010-06-07 03:55:14, 2010-06-07 03:56:23, 2010-06-07 03:57:01, 2010-06-07 03:57:51, 2010-06-07 03:59:21 ...) As I mentioned earlier I want to filter out some of the records, I do not have specific rule to do that, but I was thinking to filter out the rows according to the timestamp interval. After I achieve filtering I want to have a result set which has a certain amount of minutes between timestamps on average (ex: 2010-06-07 03:20:14, 2010-06-07 03:29:23, 2010-06-07 03:38:01, 2010-06-07 03:49:51, 2010-06-07 03:59:21 ...) Last but not least, the operation should not take incredible amount of time, I need this functionality to be almost fast as a normal select operation. Do you have any suggestions?

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  • how to enable layout in XmlHttpReeuqest in symfony

    - by celalo
    Symfony detects if it receives a XmlHttpRequest and automatically turns off your debug bar and layout. However I'd like to have the response decorated with a specified layout. Also I don't want to add custom line of code in the [FONT=Courier]action[/FONT] to enable the layout, I wish I can just make a configuration through yml files. Thanks in advance.

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  • Getting percentage of "Count(*)" to the number of all items in "GROUP BY"

    - by celalo
    Let's say I need to have the ratio of "number of items available from certain category" to "the the number of all items". Please consider a MySQL table like this: /* mysql> select * from Item; +----+------------+----------+ | ID | Department | Category | +----+------------+----------+ | 1 | Popular | Rock | | 2 | Classical | Opera | | 3 | Popular | Jazz | | 4 | Classical | Dance | | 5 | Classical | General | | 6 | Classical | Vocal | | 7 | Popular | Blues | | 8 | Popular | Jazz | | 9 | Popular | Country | | 10 | Popular | New Age | | 11 | Popular | New Age | | 12 | Classical | General | | 13 | Classical | Dance | | 14 | Classical | Opera | | 15 | Popular | Blues | | 16 | Popular | Blues | +----+------------+----------+ 16 rows in set (0.03 sec) mysql> SELECT Category, COUNT(*) AS Total -> FROM Item -> WHERE Department='Popular' -> GROUP BY Category; +----------+-------+ | Category | Total | +----------+-------+ | Blues | 3 | | Country | 1 | | Jazz | 2 | | New Age | 2 | | Rock | 1 | +----------+-------+ 5 rows in set (0.02 sec) */ What I need is basically a result set resembles this one: /* +----------+-------+-----------------------------+ | Category | Total | percentage to the all items | (Note that number of all available items is "9") +----------+-------+-----------------------------+ | Blues | 3 | 33 | (3/9)*100 | Country | 1 | 11 | (1/9)*100 | Jazz | 2 | 22 | (2/9)*100 | New Age | 2 | 22 | (2/9)*100 | Rock | 1 | 11 | (1/9)*100 +----------+-------+-----------------------------+ 5 rows in set (0.02 sec) */ How can I achieve such a result set in a single query? Thanks in advance.

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  • strange messages in log file @^@^@^@^@^@^@^@^@^@^@^@^@^@^@^....

    - by celalo
    Hello, I have a application server for network operations written with JAVA based on Apache Mina. Recently I encounter a strange behavior in my log files. I noticed that the log file is full of @^@^@^@^@^@^@^@^@^@^@^@^.... characters. I mean those unexpected characters are vast amount of as such the log file gets hundreds of GB in a couple of hours! I have no clue about this problem and it is almost impossible to google it. What could be the reason? Are those set of characters any familiar to anybody? I can give more details about the application if needed. Thanks in advance.

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