计算90,000+文件的MD5并存储到数据库

Question

I am working on a script that downloads all of my images, calculates the MD5 hash, and then stores that hash in a new column in the database. I have a script that selects the images from the database and saves them locally. The image's unique id becomes the filename.

My problem is that, while cURLQueue works great for quickly downloading many files, calculating the MD5 hash of each file in a callback slows the downloading down. That was my first attempt. For my next attempt, I would like to separate the downloading and hashing parts of my code. What is the best way to do this? I would prefer to use PHP, as that is what I am most familiar with and what our servers run, but PHP's thread support is lacking to say the least.

Thoughts are to have a parent process that establishes a SQLite connection, then spawn many children that choose an image, calculate the hash of it, store it in the database, and then delete the image. Am I going down the right path?

Answer 1

There are a number of ways to approach this, but which you choose really depends on the particulars of your project.

A simple way would be to download the images with one PHP, then place them on the file system and add an entry to the queue database. Then a second PHP program would read the queue, and process those waiting.

For the second PHP program, you could setup a cron job to just check regularly and process all that are waiting. A second way would be to spawn the PHP program in the background every time a download finishes. The second method is more optimal, but a little more involved. Check out the post below for info on how to run a PHP script in the background.

Is there a way to use shell_exec without waiting for the command to complete?