First verify that the VIP used for outgoing traffic has a correct reverse DNS record:
host 195.54.62.XXFix it if necessary. Next, change the /etc/mailname on every VM. Value should be strictly identical to the reverse.
Last step, indicate to every MTA’s VM to use a custom EHLO value instead of the hostname. For exim simple create a file /etc/exim4/exim4.conf.localmacros with the following content:
REMOTE_SMTP_HELO_DATA=<reverse_value>Since version 1.3 Magento can use multiple layer of cache, for example a memcached for content cache and session, and a database for the rest. This mechanism work pretty well except when you have a connectivity problem.
If Magento is unable to load a session, the request processing will end immediately preventing Apache from logging it. The only information inside the error log will be an zend_mm_heap corrupted entry.
To ‘fix’ this behavior, you must increase the default timeout for the PHP session handler for a value greater than the TCP re-transmission delay. A 5 seconds value is good enough.