I don't know why SELinux problems seem so frustrating. The problem almost certainly is related to the fact that there is frequently no error message. This is exactly the problem I ran into while turning up a new Apache web server on Red Hat Enterprise Linux 6 (RHEL6) with SELinux enabled.
The problem is that SELinux prevents Apache from making network connections by
default. This is defined by the SELinux boolean
In order to change this value, issue the following command:
setsebool -P httpd_can_network_connect_db true
-P indicates the command is persistent and that the setting should survive
For reference, here is a list of all httpd-related SELinux booleans and their default values in RHEL6:
# getsebool -a | egrep '^httpd' httpd_builtin_scripting --> on httpd_can_check_spam --> off httpd_can_network_connect --> off httpd_can_network_connect_cobbler --> off httpd_can_network_connect_db --> off httpd_can_network_memcache --> off httpd_can_network_relay --> off httpd_can_sendmail --> off httpd_dbus_avahi --> on httpd_enable_cgi --> on httpd_enable_ftp_server --> off httpd_enable_homedirs --> off httpd_execmem --> off httpd_manage_ipa --> off httpd_read_user_content --> off httpd_setrlimit --> off httpd_ssi_exec --> off httpd_tmp_exec --> off httpd_tty_comm --> on httpd_unified --> on httpd_use_cifs --> off httpd_use_gpg --> off httpd_use_nfs --> off httpd_use_openstack --> off