Email Summary sending several mails

Thanks, that’s what I was looking for, to narrow it down — if we could rule out the cron jobs getting duplicated in advance, then it’s definitely the processing/sending portion that causes the problem.

I’ve tried to trigger this myself again, by repeatedly adjusting a test server’s clock just before the time the report would be sent, using some different timezone settings and other options, and still can’t reproduce it.

For the other two sites that are on the same server — do they load much faster when you visit them with an empty cache? When I visit the one site I know of, it takes over 10 seconds to load on the first visit — sometimes delays like that can lead to 3 or 4 visits being processed at the same time, and/or finishing out of order. If I could confirm that, we may be able to fix the issue.

If you don’t mind sharing a copy of the site’s access log that covers the 14th, I may be able to see if a number of visits coming in closely together could be causing the issue. My email is: mattr (at) wordfence.com

I’ve just sent you an email with my log data.

Thanks, I got the log. Are you using the W3 Total Cache plugin, and if so, do you have database caching enabled?

In the log, I didn’t see multiple hits really close together that might have caused the other problem I was thinking of.

The database cache might be causing wp-cron to act as if it hasn’t run yet, causing each scheduled job to run more than once. If you disable only the “database cache” and the “object cache”, that may help.

Yes, I’m using W3 Total Cache only for this site and with database and object cache enabled.

You want me to disable database cache only to test this, right? Since, it will impact my site performance.

Mails are scheduled to next Monday, so I will try this then.

I would normally leave database caching off, because it can cause issues with too many plugins. For example, I had a membership plugin with problems from this — it would check if a user exists (which would be cached), then it would create a user, and try to read the ID from that new user — but the database cache “remembered” that the user didn’t exist a few milliseconds earlier, so the plugin couldn’t read the ID of the new user it just created.

Database caching and object caching usually have a relatively small effect on performance overall, especially if you already have page caching enabled. The database cache won’t actually make any difference for any visitor who sees a cached page (the cached pages are served directly from the disk, so there are no database queries). If the site isn’t getting constant traffic, the database cache often expires before the next visitor arrives, too.

You could try running tests using sites like webpagetest.org (or chrome or firefox’s developer tools) to compare performance with and without the database cache enabled — I don’t think there will be a significant difference. You would probably need multiple tests to see it with the cache plugin fully working.

Thanks for taking the time to reply me and, above all, for sharing your knowledge!

I’m also having issues with WPML plugin and database or object caching. So, tomorrow I will make some tests but I think that I’m going to disable at least database caching.

Thanks for taking the time going back and forth with testing the various possibilities, too!

In addition to (hopefully) making it work for you, it helps us find bugs or conflicts with other plugins when we get clear responses and details like you’ve provided.

Often, other people ask a question, we answer it, and never hear from them again, whether it worked or not!

Finally, W3 Total Cache is to blame!

Today I received only one summary mail with database and object caching disabled.

Great, thanks for following up! There might be some sites where the W3TC database cache works fine, but it might need very specific settings to avoid any plugin conflicts, or possibly even WP core issues.