Backup has cannot add signal handlers, pcntl_async_signals function error

Hi @redsoftdev,

It sounds like the pcntl_async_signals method is not enabled in the version of PHP currently running on your web server and enabling it should get rid of the error message. You might need to reach out to your hosting provider to see if that is something that they can handle for you.

Hopefully making that configuration change gets the backup schedule working again and let us know if there is anything else that we can do to help!

I got some insight from the developers on this and it sounds like the missed scheduled backups might be related to something else.

Is this the first time you’ve tried to create scheduled backups or were they working previously? If they were working before, were there any recent configuration changes made to your website like installing new plugins or a change in hosting providers?

Are you using Cron or WP Cron to handle the scheduling of your backups? Is there any change when switching from one scheduler to another in the Backup Schedule settings?

Thanks for getting back to me with an update.

This is the first time that I am trying to create scheduled backups.

I was using Cron as that was set by default, I have changed it to WP Cron for one site and scheduled a backup which started to run but the error message “Cannot add signal handlers, pcntl_async_signals function does not exist” started to be displayed in the logs.

Hi @redsoftdev!

Did your manual backup generate successfully or were there issues with that completing as expected? If manual backups aren’t working either then there might not be anything wrong with the scheduler itself and the problem could be coming from elsewhere.

Which Compressor are you currently using to generate backups? You can find which Compressor you are using under the Backup Process settings. Try switching the Compressor to System Zip if you are not already using it to see if maybe that will get backups working.

Also, does your website pass the functionality tests in the Preflight Check tool?

I have tried to back up a site manually a couple of times using ZipArchive and I get this error message

[2022-04-07 13:14:53 UTC] Backup process running: Yes (pgid = 47190)
[2022-04-07 13:16:38 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-07 13:16:38 UTC] Backup process running: Yes (pgid = 47190)
[2022-04-07 13:16:48 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-07 13:16:48 UTC] Backup process running: No
[2022-04-07 13:16:53 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.

I tried System zip on compression level 6 and PclZip and I get similar error messages with both of them

If switching the compressor did not change the results then the next thing is to confirm if any backups can be created on your web server. Try creating a Sanity Check backup that includes only TXT files to see if that generates successfully.

Should the Sanity Check backup succeed then that indicates the issue might be related to resource consumption limits on your web server. Enable Filelist Analysis if the Sanity Check is successful and attempt to create a full backup of your website again to generate a log file which will show all of the large directories or files that are getting included in your backup. You can exclude the large directories or files and try generating another backup to see if that gets things working.

The log information you sent us shows that the backup process is terminating after about two minutes and increasing the PHP time limit in your web server configuration might also allow backups to complete successfully if there aren’t any large files or directories that you can exclude.

I ran a Sanity Check and it was successful.
I looked at the file list log and ran another backup excluding the largest files listed in the log but it still failed.

This is the end of the log file:

[2022-04-08 10:58:51 UTC] Finished analyzing filelist!
[2022-04-08 10:58:51 UTC] Memory usage - limit / current / peak memory usage: 1073741824 / 31232984 (29.79 MB) / 31782720 (30 MB)
[2022-04-08 10:58:59 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 10:58:59 UTC] Backup process running: Yes (pgid = 55801)
[2022-04-08 10:59:27 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 10:59:27 UTC] Backup process running: Yes (pgid = 55801)
[2022-04-08 10:59:50 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 10:59:50 UTC] Backup process running: Yes (pgid = 55801)
[2022-04-08 10:59:55 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 10:59:55 UTC] Backup process running: Yes (pgid = 55801)
[2022-04-08 11:00:42 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 11:00:42 UTC] Backup process running: Yes (pgid = 55801)
[2022-04-08 11:02:02 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 11:02:02 UTC] Backup process running: Yes (pgid = 55801)
[2022-04-08 11:04:00 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.
[2022-04-08 11:04:00 UTC] Backup process running: No
[2022-04-08 11:06:04 UTC] Cannot add signal handlers, pcntl_async_signals function does not exist.

That is great news about the Sanity Check backup, now we know that backups can work on your server!

Generally when Sanity Check backups works but Full backups fail it is because of the amount of media files getting included in the backup that causes the backup process to exceed the resource limitations on the server.

Could you share the section of the Filelist Analysis that shows the total file size based on the file extension type?

The next thing would be to try making a backup that excludes the uploads directory to see if a backup of the critical website files and database is successful. You can exclude the entire uploads directory by adding /wp-content/uploads to the Exclude field.

Hi redsoftdev-

It’s been a while since we heard back from you on this issue, so I’m marking the topic as “Resolved.” Please feel free to reply or create a new topic if you have any more questions!