Optimizing mysql database - List of tasks eats up my server

I run a service that takes user request and adds it to a table named 'queue' that has 3 fields: userid, queuenumber, and processed.

I store there tasks that need to be processed ( I can process less tasks than I get requests )

Unfortunately, I don't really know much about mysql optimization and my processing script ( that I run 50 versions in parallel ) uses queries like those:

SELECT * FROM `queue` WHERE `processed` = 0 ORDER BY `queue`.`queuenumber`

When any instance of the code takes a row to process, it marks it processed = 1 so it won't be taken up by the other instances.

So when I run 50 instances of this code, it becomes heavy on the MySQL database ( and I have only 4GB of ram )

Because of that, I get stats like those:


Received 15.8 MiB
Sent    42.9 GiB    

ΓΈ per hour

Received: 3 MiB
Sent: 8.1 GiB

Some stats from phpmyadmin:

How do I optimize this? To be able to run this code in parallel but not list the whole tables?

// EDIT:

The results of create table are:

CREATE TABLE queue ( userid int(11) NOT NULL, queuenumber int(11) NOT NULL AUTO_INCREMENT, processed tinyint(1) NOT NULL, PRIMARY KEY (queuenumber), UNIQUE KEY queuenumber (queuenumber), UNIQUE KEY userid (userid) ) ENGINE=InnoDB AUTO_INCREMENT=121617 DEFAULT CHARSET=latin1


Implementing queues with an RDBMS is an anti-pattern: http://blog.engineyard.com/2011/5-subtle-ways-youre-using-mysql-as-a-queue-and-why-itll-bite-you

However if you insist there are ways to do it consistently without race conditions.

First implement a notification (outside of MySQL) when a new row is enqueued so you don't have to poll for new data in a fast loop - maybe this is why your traffic is so high. I have seen UDP multicast used for this, or UNIX signals.

Now check table is using InnoDB


If you need to change it to InnoDB


If you have multiple consumers processing jobs ensure your locking is race free; every time a consumer encounter a new job the first thing it should try to do is to update it with it's unique process-id. each consumer should perform an update on the table to assign the row/job to a consumer by ID

You will need to have a process column on your table

ALTER TABLE `queue` ADD `process` int unsigned default NULL;

Add an index to help you select the rows efficiently

ALTER TABLE `queue` ADD KEY (`processed`,`process`);

Now your consumers can run the following in their code

UPDATE `queue` SET process = ? WHERE process IS NULL AND processed = 0 LIMIT 1;

You can set ? to be the pid or thread-id of the consumer. You can tell if the update found a row by either checking the affected rows in the response of the query (fastest) or try to get the row details anyway - maybe you will return 0 rows which means the update did nothing - a different consumer got the job.

SELECT * FROM `queue` WHERE process = ? AND processed = 0;

When your consumer is finished with the row/job it can just set processed to 0 on that row (maybe you should consider an auto-inc primary key on the table you you can accurately address a single row)

ALTER TABLE `queue` ADD `id` bigint unsigned NOT NULL auto_increment FIRST, ADD primary key (`id`);

If your consumers crash for whatever reason you can tell what was going on by looking at the row - if processed = 0 but process has been set then something crashed while processing that row.

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