Donncha Ó CaoimhJust testing the load on my server. May delete later.
Also, enjoy the video of Gaybo on the Late Late Show in the early 80s.
https://odd.blog/2022/12/21/computers-are-the-big-thing-this-year/
261 embed requests since this was posted a few minutes ago.
359 requests for the post itself.
1 minute load average topped out at 1.34 for 5 seconds before going back to 0.34.
I had garbage collection TTL set to 60 seconds and I think it expired in the middle of that rush of requests for the page.
I had tail -f on my log in a screen session, which adds a bit to the load too.
My blog was still very responsive the whole time.
Now to test it again with a longer TTL. Not sure if Mastodon instances cache the preview.
https://odd.blog/2022/12/21/computers-are-the-big-thing-this-year/
Tom Walker@donncha This is what I've been saying to people when they mention this embed-previews rush problem – it won't take down your blog if you have some caching set up. As you would know of course!
@tomw the only thing I will say, is the very initial rush might cause problems if they don't have the spare capacity to meet it.
That's why I have the "5 min spare servers". I'm going to change that to 1, restart Apache and test it again with this URL:
@tomw With start and min spare servers set to 1 it took much longer to service every request and Load went up to 1.24.
It definitely pays to have the capacity there in the first place, even if the web server is just idling.
Also, if it's a new post, there might not be a cache file there when the first few requests come in for it. This is a long standing problem though. Popular sites with RSS feeds have (or had) the same issue when feed readers were popular. Need to pre-load new posts...
@donncha Yes that makes sense. It would maybe be worth doing some kind of guide for people – the discussions I've seen tend to jump straight to talking about Cloudflare, CDNs etc when this can be solved at the WP level with cache (and yeah maybe some web server config as needed).
@tomw Good idea. Even "simple caching" with WP Super Cache works wonders.
I'll test with caching turned off and monitor the load. :)
Here's another old blog post. Not cached at all.
@tomw Interesting. Load average only spiked to 1.12 with no caching! Not bad!
267 requests for the embed of that page.
290 requests for the page itself.
No extra caching like memcached or anything.
This is with Apache reset to 5 start servers, min spare servers set to 10 again.
@donncha Great! I think the bit people don't get is that you just need to avoid hitting the database with every page load, at a minimum, and you'll get through it. That's what's been taking people's sites down.