在PHP中缓存以加快速度

Question

I am running application (build on PHP & MySql) on VPS. I have article table which have millions of records in it. Whenever user login i am displaying last 50 records for each section.

So every-time use login or refresh page it is executing sql query to get those records. now there are lots of users on website due to that my page speed has dropped significantly.

I done some research on caching and found that i can read mysql data based on section, no. articles eg (section - 1 and no. of articles - 50). store it in disk file cache/md5(section no.).

then in future when i get request for that section just get the data from cache/md5(section no).

Above solution looks great. But before i go ahead i really would like to clarify few below doubts from experts .

• Will it really speed up my application (i know disk io faster than mysql query but dont know how much..)
• i am currently using pagination on my page like display first 5 articles and when user click on "display more" then display next 5 articles etc... this can be easily don in mysql query. I have no idea how i should do it in if i store all records(50) in cache file. If someone could share some info that would be great.
• any alternative solution if you believe above will not work.
• Any opensource application if you know. (PHP)

Thank you in advance

Regards, Raj

Answer 1

I ran into the same issue where every page load results in 2+ queries being run. Thankfully they're very similar queries being run over and over so caching (like your situation) is very helpful.

You have a couple options:

1. offload the database to a separate VPS on the same network to scale it up and down as needed

2. cache the data from each query and try to retrieve from the cache before hitting the database

In the end we chose both, installing Memecached and its php extension for query caching purposes. Memecached is a key-value store (much like PHP's associative array) with a set expiration time measured in seconds for each value stored. Since it stores everything in RAM, the tradeoff for volatile cache data is extremely fast read/write times, much better than the filesystem.

Our implementation was basically to run every query through a filter; if it's a select statement, cache it by setting the memecached key to "namespace_[md5 of query]" and the value to a serialized version of an array with all resulting rows. Caching for 120 seconds (3 minutes) should be more than enough to help with the server load.

Answer 2

If Memecached isn't a viable solution, store all 50 articles for each section as an RSS feed. You can pull all articles at once, grabbing the content of each article with SimpleXML and wrapping it in your site's article template HTML, as per the site design. Once the data is there, use CSS styling to only display X articles, using JavaScript for pagination.

Since two processes modifying the same file at the same time would be a bad idea, have adding a new story to a section trigger an event, which would add the story to a message queue. That message queue would be processed by a worker which does two consecutive things, also using SimpleXML:

1. Remove the oldest story at the end of the XML file

2. Add a newer story given from the message queue to the top of the XML file

If you'd like, RSS feeds according to section can be a publicly facing feature.