Saturday, July 19, 2014

Enable / Disable SetCronJob DNS cache

This is an update to SetCronJob DNS cache. Since the day SetCronJob DNS cache was created, it is enabled by default and you can't make any change to it. This solves and generates some problems, so we should let you enable or disable it on your own.

How to enable/disable SetCronJob DNS cache?

To change it, click Edit cronjob, More options, you'll see the DNS cache option below the Name field.
The DNS cache option (click Edit cronjob, More options to see)
To enable it, check the box, and Save cronjob. To disable it, uncheck (clear) the box and Save cronjob.

You can also select multiple cronjobs, then click With selected: Edit cronjobs, and select desired DNS cache option.

You won't see any different after enable or disable the DNS cache.

When to enable SetCronJob DNS cache

Our DNS cache is enabled by default, and it's recommended to do so. So if your cronjobs work fine with DNS cache enabled, just leave it there. There are some benefits:
  • It get rids of name lookup, thus makes your script executed quicker.
  • It also minimizes lookup errors e.g. in case your name server doesn't respond, we still have the cache.
  • It ignores DNS records' TTL (not a good practice), so if your name server is down and your domain name is unreachable, your scheduled scripts in your web server are still running fine.

When to disable SetCronJob DNS cache

SetCronJob DNS cache may make some problems, and in these cases below you should disable it:
  • Your website is under SSL (HTTPS), and SSL error occurs when we try to execute your cronjob. Maybe your SSL certificate is used for multiple domain name with the same IP address, while SetCronJob DNS cache will disable the SNI feature, thus it doesn't work.
  • Your website is using IPv6 only. Our DNS cache doesn't work with IPv6, while our library works fine. Disabling the DNS cache will let our library choose which IP version to connect, and it seems it prefer IPv6 though. See updated info below.
  • Your website IP addresses are updated frequently.
UPDATED on Dec 20, 2014:
From now on, if you want us to send HTTP requests to your IPv6 address, please click Edit cronjob, More options, then select our IPv6 in the Server IP list.
The IPv6 test. SetCronJob's IPv6 is 2600:3c01::f03c:91ff:fe56:75d1, and whatismyv6's IPv6 is 2001:4810::110
If you have any question, please feel free to email me.