Solved

MYSQL/PHP -- Server and Nodes grabbing duplicates rarely.

Posted on 2013-05-27
1
468 Views
Last Modified: 2013-05-28
Hello there!

I have a server that holds all the data, and two nodes. The nodes have a similar table to the server that grab data from it and mark that it grabbed the data, so you do a simple

"select * from table where status='new'". from the node to the servers MYSQL. So all the nodes call this and grab new data. This is done using PHP.

from the node to the server (So we are doing remote MYSQL grabbing here of records.)


Then once it grabs it, i t changes the status to 'complete' on the main server. This was meant to prevent another node from grabbing the same data however because of latency sometimes the nodes grab the same record and process it. Both marking it as complete. It is not common but it does happen. So it is checking at about the same time, processing it because the record hasn't been marked 'complete' by the node until it's actually grabbed it.



So picture two node servers grabbing from the main server, at the same time, running the select * where status=new query, and processing/marking the record as status=complete, at similar times, enough that the latency is doing that.



How can I ensure that the nodes aren't grabbing the same records? Does anyone have any idea? I want to be able to use for example 10 node servers, not just 2 if needed without issues. At this time I think it could cause alot of duplicate grabbing and issues through MYSQL.


I understand that the nodes grabbing the data could be a problem. it would prevent it if the main server had a script and handled it, but the nodes are meant to be pluggable without any interaction or changes on the main server side (telling it that theres a new node etc isn't needed.) Few other things, but yeah, script is on the node sides ;)


Thanks guys, any advice is helpful. Even if it reduces it a large amount.
0
Comment
Question by:Valleriani
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
1 Comment
 
LVL 110

Accepted Solution

by:
Ray Paseur earned 500 total points
ID: 39199843
Maybe learm about LOCK TABLES (?)

If you're thinking of using a SELECT * statement, you might want to get a DBA involved early to help you understand why you do not want to use SELECT * and to help you organize the data and queries at the outset.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

3 proven steps to speed up Magento powered sites. The article focus is on optimizing time to first byte (TTFB), full page caching and configuring server for optimal performance.
Microsoft Access is a place to store data within tables and represent this stored data using multiple database objects such as in form of macros, forms, reports, etc. After a MS Access database is created there is need to improve the performance and…
The viewer will learn how to dynamically set the form action using jQuery.
The viewer will learn how to create and use a small PHP class to apply a watermark to an image. This video shows the viewer the setup for the PHP watermark as well as important coding language. Continue to Part 2 to learn the core code used in creat…

729 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question