[Users] Sharing Unix Domain Sockets between VEs in devel version

Stefan Siegel contact+openvz at sdas.de
Sat Aug 23 19:17:32 EDT 2008


Hello,

Currently I have a Linux-VServer setup using the official Debian Etch 
binaries with MySQL socket sharing similar to what is described in the 
"Shared webhosting" article in the OpenVZ Wiki (it works the same with 
Linux-VServer). Now that there probably will be official Debian Lenny 
kernel images patched with OpenVZ support, I consider switching to 
OpenVZ. The 2.6.26 images currently in Sid are very promising. But there 
is a problem:

When I try to setup socket sharing as described in 
http://wiki.openvz.org/Shared_webhosting#MySQL_socket_sharing (or just 
starting my Linux-VServer virtual machines in OpenVZ) I cannot connect 
to a socket listening in a different VE. Only when I connect from the 
same VE the connection succeeds. I tried:
- hardlinking the socket
- bind mounting the containing directory
- directly connecting from/to VE0
I tried both MySQL and simply creating/connecting to the socket using 
Netcat (the OpenBSD version works with Unix Domain Sockets). Related 
strace output:

[...]
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
connect(3, {sa_family=AF_FILE, path="testdir/testsocket"...}, 20)
                                = -1 ECONNREFUSED (Connection refused)
close(3)                                = 0
[...]

Using linux-image-2.6.24-openvz-24-004.1d1-686_004.1d1_i386.deb from 
download.openvz.org doesn't change anything, but when using the stable 
linux-image-2.6.18-openvz-18-53.5d1-k7_028.53.5d1_i386.deb, I can 
connect without problems.

Am I missing something? Is the devel OpenVZ broken, or is it supposed to 
be a feature and the stable version behavior is deprecated? Is it 
configurable or is there a workaround? If the devel version's behavior 
is correct, then the Wiki article should probably be changed to mention 
that (and I would be forced to postpone my migration to OpenVZ). On the 
article's discussion page there is a user who also failed getting this 
to work.

Greetings,
Stefan Siegel



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