Re: [libvirt-users] method for communication between containers
Dear Daniel,
Thank you for your email.
According to your suggestion, I tried to use the shared memory filesystem for data
exchange between the host machine and the container. The steps are as follows:
1) create an empty file in the host machine (/tmp1/file1).
2) run #chmod 777 /tmp1 and #chmod 777 /tmp1/file1.
3) expose /tmp1 to the container by configuring the container with the following XML
scripts.
<filesystem type="mount" accessmode="passthrough">
<source dir="/tmp1"/>
<target dir="/tmp1"/>
</filesystem>
4) write two programs: program1 writes a string to the shared memory
program2 reads the string from the shared memory
and compile both programs in the host machine.
both of the two programs use ftok() and shmget() to obtain the shmfs id.
5) a. if we run both program1 and program2 in the host machine, the program2 can read the
string that program1 has written.
b. if we run both program1 and program2 in the container, both programs also work well.
c. if we run program1 in the host and run program2 in the container, program2 fails. the
ftok() function can return the expected value, but shmget(...,0,0) fails and prompts
"No such files". It seems that the exposed file cannot be recognized by shmget()
function, although ftok() can work and return the value.
Do you have an idea?
Best wishes.
Cheng Wang
-----Original Message-----
From: Daniel P. Berrange [mailto:berrange@redhat.com]
Sent: 2014年2月27日 18:30
To: WANG Cheng D
Cc: libvirt-users(a)redhat.com
Subject: Re: [libvirt-users] method for communication between containers
On Thu, Feb 27, 2014 at 06:28:46AM +0000, WANG Cheng D wrote:
Dear all,
In my system, two containers need to exchange data as quick as
possible and the two containers are hosted by the same physical
machine, I wonder if socket is the only method for communication between containers?
If you have an area of filesystem that is shared + writable to both containers, they could
create UNIX sockets in that filesystem, rather than TCP sockets. Also they could create
named FIFO pipes.
Another option would be to create a shared memory backed file in shmfs or hugepagefs and
expose it to both containers.
Regards,
Daniel
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