Process for updating a live website_问答_开发者

What is the best process for updating a live website?

I see that a lot of websites (e.g. StackOverflow) have warnings that there will be downtime for maintenance in advance. How is that usually coded in? Do they have a config value which determines whether to display such a message in the website header?

Also, what do you do if your localhost differs from the production server, and you need to make sure that everything works the same after you transfer? In my case, I set up development.mydomain.com (.htaccess authentication required), which has its own database and is basically my final staging area before uploading everything to the live production site. Is this a good approach to staging?

Lastly, is a simple SFTP upload the way to go? I've read a bit about some more complex methods like using server-side hooks in Git.. Not sure how this works exactly 开发者_JAVA技巧or whether it's the approach I should be taking.

Thanks very much for the enlightenment..

babonk

This is (approximately) how it's done on Google App Engine:

Each time you deploy an application, it is associated with a subdomain according to it's version:

version-1-0.example.com

version-1-1.example.com

while example.com is associated with one of the versions.

When you have new version of server-side software, you deploy it to version-2-0.example.com, and when you are sure to put it live, you associate example.com with it.

I don't know the details, because Google App Engine does that for me, I just set the current version.

Also, when SO or other big site has downtime, that is more probable to be a hardware issue, rather than software.

That will really depend on your website and the platform/technology for your website. For simple website, you just update the files with FTP or if the server is locally accessible, you just copy your new files over. If you website is hosted by some cloud service, then you have to follow whatever steps they offer to you to do it because a cloud based hosting service usually won’t let you to access the files directly. For complicated website that has a backend DB, it is not uncommon that whenever you update code, you have to update your database as well. In order to make sure both are updated at the same time, you will have to take you website down. To minimize the downtime, you will probably want to have a well tested update script to do the actual work. That way you can take down the site, run the script and fire it up again.

With PHP (and Apache, I assume), it's a lot easier than some other setups (having to restart processes, for example). Ideally, you'd have a system that knows to transfer just the files that have changed (i.e. rsync).

I use Springloops (http://www.springloops.com/v2/) to host my git repository and automatically deploy over [S/]FTP. Unless you have thousands of files, the deploy feels almost instantaneous.

If you really wanted to, you could have an .htaccess file (or equivalent) to redirect to a "under maintenance" page for the duration of the deploy. Unless you're averaging at least a few requests per second (or it's otherwise mission critical), you may not even need this step (don't prematurely optimize!).

If it were me, I'd have a an .htacess file that holds redirection instructions, and set it to only redirect during your maintenance hours. When you don't have an upcoming deploy, rename the file to ".htaccess.bak" or something. Then, in your PHP script:

<?php if (file_exists('/path/to/.htaccess')) : ?>
<h1 class="maintenance">Our site will be down for maintenance...</h1>
<?php endif; ?>

Then, to get REALLY fancy, setup a Springloops pre-deploy hook to make sure your maintenance redirect is setup, and a post-deploy hook to change it back on success.

Just some thoughts.

-Landon