It is not possible to mount glusterfs on a custom (non-default and even specified default) port in a Docker environment.

reproduced on client - server pairs:
glusterfs 3.5.9 built on Mar 28 2016 07:10:14 - glusterfs 3.5.7 built on Dec 15 2015 07:19:25
glusterfs 3.6.9 built on Mar  2 2016 18:21:14 - glusterfs 3.5.7 built on Dec 15 2015 07:19:25
glusterfs 3.7.9 built on Mar 20 2016 12:12:16 - glusterfs 3.7.9 built on Mar 20 2016 12:12:16

Environment: dockerized in Ubuntu 14.04.3 LTS; 1 container for client and 1 for server
images are based off phusion/baseimage:0.9.17 and use ppa:gluster/glusterfs-3.X

How reproducible: easy

Steps to Reproduce:

1. mounting while relying on default port (24007):
root@5eaec083e5a4:/# mount -t glusterfs 172.17.2.53:www-volume /foo
server log:
[2016-03-30 09:54:00.556880] I [server-handshake.c:575:server_setvolume] 0-www-volume-server: accepted client from 5eaec083e5a4-510-2016/03/30-09:54:00:548380-www-volume-client-0-0-0 (version: 3.5.9)
-> OK

2. mounting while specifying the default port:
root@5eaec083e5a4:/# mount -t glusterfs 172.17.2.53:24007:www-volume /bar
Mount failed. Please check the log file for more details.
root@5eaec083e5a4:/# cat /var/log/glusterfs/bar.log 
[2016-03-30 09:55:09.140076] I [glusterfsd.c:1959:main] 0-/usr/sbin/glusterfs: Started running /usr/sbin/glusterfs version 3.5.9 (/usr/sbin/glusterfs --volfile-server=172.17.2.53:24007 --volfile-id=www-volume /bar)
[2016-03-30 09:55:09.140944] I [socket.c:3645:socket_init] 0-glusterfs: SSL support is NOT enabled
[2016-03-30 09:55:09.140958] I [socket.c:3660:socket_init] 0-glusterfs: using system polling thread
[2016-03-30 09:55:09.141015] E [common-utils.c:223:gf_resolve_ip6] 0-resolver: getaddrinfo failed (Name or service not known)
[2016-03-30 09:55:09.141023] E [name.c:249:af_inet_client_get_remote_sockaddr] 0-glusterfs: DNS resolution failed on host 172.17.2.53:24007
[2016-03-30 09:55:09.141039] E [glusterfsd-mgmt.c:1601:mgmt_rpc_notify] 0-glusterfsd-mgmt: failed to connect with remote-host: 172.17.2.53:24007 (Success)
[2016-03-30 09:55:09.141044] I [glusterfsd-mgmt.c:1607:mgmt_rpc_notify] 0-glusterfsd-mgmt: Exhausted all volfile servers
[2016-03-30 09:55:09.141116] W [glusterfsd.c:1095:cleanup_and_exit] (-->/usr/sbin/glusterfs(glusterfs_mgmt_init+0x155) [0x7f8ec1cf3755] (-->/usr/lib/x86_64-linux-gnu/libgfrpc.so.0(rpc_clnt_start+0x12) [0x7f8ec162d3d2] (-->/usr/sbin/glusterfs(+0xcf13) [0x7f8ec1cf3f13]))) 0-: received signum (1), shutting down
[2016-03-30 09:55:09.141125] I [fuse-bridge.c:5520:fini] 0-fuse: Unmounting '/bar'.
server: no log (i.e. no connection attempt)

Actual results: client fails to mount when ip + port combination is given

Expected results: mount to succeed

Docker set up:

client:
docker run --privileged=true -ti phusion/baseimage:0.9.17 bash
(inside container) add-apt-repository ppa:gluster/glusterfs-3.7 -y && apt-get update -yqq && apt-get install glusterfs-client -yqq

server:
docker run --privileged=true -ti phusion/baseimage:0.9.17 bash
add-apt-repository ppa:gluster/glusterfs-3.7 -y && apt-get update -yqq && apt-get install glusterfs-server -yqq
glusterd
ip=$(ip route get 8.8.8.8 | awk '{print $NF; exit}') 
GLUSTER_VOLUMES='www-volume /data/disk0'
mkdir -p /data/disk0 
mkdir -p /data/disk1 
GLUSTER_VOLUMES=($GLUSTER_VOLUMES) 
for ((i=0; i< ${#GLUSTER_VOLUMES[@]}; i = i + 2)); do 
    gluster volume create ${GLUSTER_VOLUMES[$i]} transport tcp $ip:${GLUSTER_VOLUMES[$i+1]} force 
    gluster volume start ${GLUSTER_VOLUMES[$i]} 
done