Endless loop in digest emailing

Hello all.

Our discourse server went into endless loop sending emails non stop. Here is shared/standalone/log/rails/production.log output:

Delivered mail 7db8eecd-c36a-419c-ae34-0561b08bae25@community.xx.cc (1322.2ms)
  Rendered user_notifications/digest.text.erb (Duration: 50.1ms | Allocations: 12577)
  Rendering user_notifications/digest.html.erb within layouts/email_template
  Rendered user_notifications/digest.html.erb within layouts/email_template (Duration: 139.5ms | Allocations: 26910)
  Rendering user_notifications/digest.text.erb
  Rendered user_notifications/digest.text.erb (Duration: 71.7ms | Allocations: 13505)
Delivered mail 5bbf2e54-96a8-437d-a032-69f98a00f22a@community.xx.cc (1485.2ms)
  Rendering user_notifications/digest.html.erb within layouts/email_template
  Rendered user_notifications/digest.html.erb within layouts/email_template (Duration: 70.9ms | Allocations: 20613)
  Rendering user_notifications/digest.text.erb
  Rendered user_notifications/digest.text.erb (Duration: 38.2ms | Allocations: 11390)

This started happen suddenly (probably when digest cron started:


Now 1 core is fully busy with sending digset email.

  • App rebuild doesn’t help;

  • Updated to the latest version - no change;

  • Turn on “Disable summary emails for all users.” and rebuiled the app - no change;

    #### Installed
    ### 2.4.0.beta5

What else can I do? How ca I stop this?
Thanks in advance.

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I could be wrong, but I think that what happened is that the summary emails got queued and now it’s delivering them. It’s going to keep going until it delivers them.

If I’m right, You can disable emails then find the table that has them and delete them. But it’s just going to happen again the next time that summary emails go out.

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Yes, but this happens for 3 days already. All other mails (register, for example are not delivered anymore. Community works, but all emailing - not).
I found very similar issue - Extreme memory usage due to bad mail credentials. So look like this is some kind of tricky bug.

The only way I found in order to stop this - I removed the auth token in my SMTP provider. Discourse start showing hundreds of errors and only after that load decreased. I restored the token and now all seems ok.

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Did you have bad email credentials?

@codinghorror I found the root cause of the issue. Our mail provider removed (for their own stupid reasons) verified host records for our account. The host records were used to provide from field in the email with our host. So after they did that - discourse went into endless loop. I think discourse flow has a bug as well for that case. Because it should report the error and stop load 1 core for 100%.

So account is correct. But mail provider returns an error on mail send “Wrong sending host” or something like that and this flow causes the issue.


I agree, this is a bad state to be in and we should handle it better.

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Is everything back to normal now?

Yes. After I changed credentials for mail.

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