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Subject [Bug 61791] New: make mod_proxy 'honor DNS ttl' with enablereuse on (dnsttl, addressTTL ?)
Date Mon, 20 Nov 2017 16:36:29 GMT

            Bug ID: 61791
           Summary: make mod_proxy 'honor DNS ttl' with enablereuse on
                    (dnsttl, addressTTL ?)
           Product: Apache httpd-2
           Version: 2.5-HEAD
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: mod_proxy
  Target Milestone: ---

Created attachment 35541
diff to add dnsttl parameter to ProxyPass

When ProxyPass backend is a hostname and enablereuse is On, the DNS resolution
is done at child startup only.

It may be an issue in environments with auto-scaling, e.g. AWS : 
   * 'disablereuse on' is not a good solution for perfs.
   * MaxConnectionsPerChild is not precise enough to make child restart

Idea is to have parameter 'dnsttl' added to ProxyPass.
If an IP change is detected after a dnsttl : update worker->cp->addr with new
New connections are made to new addr, old stay unchanged ( e.g. for AWS grace
period )

Attached is a very simple patch [*] to summ-up the idea.
[*] patch done on httpd-2.4.29 for very simple testing only (not prod ready!)

Similar has been discussed in mailing lists several times.  
Latest seen :

@Yann, maybe your 'addressTTL' patch does answer the need.

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