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Cannot send emails - cron job is hanging
  • Hi,
    When I am trying to send out emails, the cron process freezes without actually sending anything. I did some debugging and found that the process (scheduled.php) is getting stuck while doing multithreaded cURL (Lines 231 – 258 in includes/helpers/class.amazonses.php). We run Sendy off AWS instance. PHP version 5.3.18.

    Can you please help us with this issues? It's a holiday season and we do need to start emailing customers ASAP.

    -- Aleksey
  • Vote Up0Vote Down BenBen
    Posts: 3,643Sendy support
    Hi Aleksey, can you clarify what you mean by 'getting stuck'?

    Also, how many emails are you sending to? What is your send rate and what tier are you on?

  • Hi Ben,
    What I mean is the following:
    From UI, it looks like the campaign quickly (once the cron job starts running) gets into "sending" state, and stays in it forever (well, for more than an hour). Since I am trying to send a test batch to 10 recipients, this time seemed to me wrong, and I tried launching the cron script manually. It never ended. Then I opened your source (I am a PHP developer myself), and added several debug echo statements, which showed me that the script loops forever in class.amazonses.php. We are on production tier, daily quota 10,000 emails, 5 emails/sec.
  • Vote Up0Vote Down BenBen
    Posts: 3,643Sendy support
    Thanks for clarifying. Strange because many of our users are running Sendy on EC2 with no problems. I've also setup a micro instance with Apache/Linux before to test and was able to send successfully.

    Are you using Apache/Linux? Some used Ubuntu and was able to work as well.
  • We use Amazon Linux AMI release 2012.09 with Apache.
  • Looks like I solved the problem. I changed the following line in class.amazonses.php:
    $q2 = 'SELECT id, query_str, subscriber_id FROM queue WHERE campaign_id = '.$this->CampaignID.' LIMIT '.$ses_send_rate;


    $q2 = 'SELECT id, query_str, subscriber_id FROM queue WHERE campaign_id = '.$this->CampaignID.' LIMIT '.($ses_send_rate -1 );

  • No, scratch that - it only made it deliver some emails... Ben, can you please help us to fix this issue?
  • I think I - finally! - found the root of the problem. Looks like with certain combinations of OS versions/ PHP versions the call curl_multi_select behaves strangely - it always returns -1. This caused the loop in the class.amazonses.php to be executed forever. The official recommendation is that if the call returns -1, the caller should sleep for 0.1 second and then proceed as if the call was successful. I implemented it and it looks like the code is working now. Will know for sure tomorrow after some testing.

    Oh, and, BTW, I found some more bugs in Sendy. Let me know if you are interested :)
  • Vote Up0Vote Down BenBen
    Posts: 3,643Sendy support
    Hi @alinetskiy Glad that you nailed down the problem! I just checked and it turns out not to be a bug with Sendy, but an issue with PHP 5.3.18.

    I just launched an Amazon AMI micro instance with Apache/Linux and installed Sendy on it. I had exactly the same issue as you, curl_multi_select always returning -1. The PHP version is 5.3.18.

    I then checked my other Sendy installation on MediaTemple with PHP version 5.3.5, curl_multi_select returns the correct number of threads.

    I searched the web for this issue and found that others were having similar issue with curl_multi_select always returning -1 with PHP 5.3.18:

    Yes, let the script sleep for 100 milliseconds when curl_multi_select fails - works. :)

    I've updated the current build on

    Thanks and sorry that you have to discover this. My kudos to you for your unrelentless quest in nailing down the issue. :)
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