We organized Docker Global Hack Day at Red Hat Office on 19th Sep’15. Though there were lots RSVPs, the turn up for the event was less than expected. We started the day by showing the recording of kick-off event.
The teams here worked on four different ideas, out of which two submitted to the Global Hack github page. The four ideas on which teams worked on are:-
Archit was winner of Docker Global Hack Day #2 as well for the same project. He updated the same project in this hackathon. His project is about crowd source analysis by using distributed computing through Docker.
Visualizing Docker Networking – Himanshu Roy
Himanshu was exploring the idea of visualizing multi-host Docker networking.
Spreading and collating containers on GlusterFS with runC -Mohamed Ashiq Liyazudeen, Hari Gowtham
By looking at runC demo in the kick-off video, we thought it would be good if we can run containers on GlusterFS and use it move containers around by saving and restoring the containers on shared volume.
I did not work on specific idea but I was helping teams and other attendees with their questions. I also worked on my upcoming tutorial at Linux Con, Europe on Data and Networking management with containers.
May be because of long weekend and other events we got less participation. Hopefully we do better next time.
bash-4.2# gluster volume create vol 172.17.0.3:/mnt/brick/ force
but I got following error:-
volume create: vol: failed: Glusterfs is not supported on brick: 172.17.0.3:/mnt/brick.
Setting extended attributes failed, reason: Operation not permitted.
From above error it looked as setting up extended attributes are not supported, which is a basic need to use GlusteFS. So I tried to test them manually. I was able to set extended attributes in user namespace but not in trusted namespace.
bash-4.2# yum install attr -y
bash-4.2# setfattr -n user.foo1 -v "bar" a
bash-4.2# touch a; setfattr -n trusted.foo1 -v "bar" a
setfattr: a: Operation not permitted
With some internet search I figured out that CAP_SYS_ADMIN is needed for setting up extended attributes in trusted namespace and to get that inside docker we need to run an image with –privileged=true option like
$ docker run --privileged=true -i -t mattdm/fedora /bin/bash
With that I was able to create the volume and start it
But when I tried to mount the volume I got following error:-
E [mount.c:267:gf_fuse_mount] 0-glusterfs-fuse: cannot open /dev/fuse (No such file or directory)
this turned out to be image specific problem, which I am using (mattdm/fedora). I had to mknod for /dev/fuse
bash-4.2# mknod /dev/fuse c 10 229
and after that I was able to mount volume.
On Fedroa 20 for docker version 0.7.6 the default storage driver for docker is device-mapper on which extended attributes are supported. AUFS storage driver does not support extended attributes as of now.I have tried with btrfs storage driver with docker 0.8 as well and was able to use GlusterFS. To use btrfs storage driver, we need to start docker daemon with following command :-
$ docker -d -s btrfs
Above will only work if Docker is running on a btrfs partition already prepared by the host system.
Last Saturday on 14th September’13 I gave on GlusterFS presentation at LSPE-IN. The title for the presentation was Performance Characterization in Large distributed file system with GlusterFS . Few days before the talk I looked at the attendee list to get the feel of the audience. I felt that not many of them have used GlusterFS by now. So I decided rather than covering lots of performance part I should cover the concepts of GlusterFS and talk about the performance challenges which can be there by design like file-system in user-space etc.
I am glad I did that as there were only 4 folks from ~70 attendees who have used GlusterFS before.
By going through the concepts the audience were able to compare GlusterFS with other solutions in the market. They asked interesting question about hashing algorithm, replication etc.
I attended the meetup till lunch. Other than giving the presentation I attended a keynote on Challenges in scaling cloud storage by Srivibhavan (Vibhav) Balaram in which he talked about the challenges in cloud storage and QoS in cloud environment. I also attended “Scaling using event driven programming with Perl, A tutorial” Aveek Mishra.
This was again a very informative and well managed event. I’ll look forward to attend and present in future meet-ups.