rootfs/.md

## .md

      
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              .md
            
          
    Use DaemonSet to Mount Filesystems on Host

                 +- - - - - - - - - - - - - - - - - - +
                 '                   Master           '
                 '                                    '
                 '          +-----------------------+ '
                 '          |       ConfigMap       | '
                 '          +-----------------------+ '
                 '                                    '
                 +- - - - - - - - - - - - - - - - - - +
                              ^
                              | 1. get REST API path
                              |
                 +- - - - - - - - - - - - - - - - - - +
                 '                   Kubelet          '
                 '                                    '
                 '          +-----------------------+ '
                 '          |        Mounter        | ' <+
                 '          +-----------------------+ '  |
                 '                                    '  |
                 +- - - - - - - - - - - - - - - - - - +  |
                              |                          |
                              | 2. mount REST call       | 5. mount REST success
                              v                          |
+ - - - - - - - - - - - - - - - - - - - - - - - - - - +  |
'                 DaemonSet                           '  |
'                                                     '  |
'                           +-----------------------+ '  |
'   +---------------------> |        Daemon         | ' -+
'   |                       +-----------------------+ '
'   |                         |                       '
'   | 4. success              | 3. exec               '
'   |                         v                       '
'   |                       +-----------------------+ '
'   +---------------------- | /sbin/mount.glusterfs | '
'                           +-----------------------+ '
'                                                     '
+ - - - - - - - - - - - - - - - - - - - - - - - - - - +


Requirement

Needs mount namespace propagation from Docker >= 1.10
Feedbacks from Storage SIG on Mar 17th


One monolithic daemonset with all mount binaries or one daemon set that orchestrates multiple imagaes, each of which support certain types of filesystem.

Rolling upgrade of daemonset doesn't exist.
If new volume mount is absent in the daemonset, how to load it on the hosts without bringing down the existing mounts.


(pmorie) in-kernel vs in-user space mounters don't have the same resource usage profile. Long running mounts like FUSE need to be subject to quota control.


(saad) What is in the ConfigMap? REST API path for individual filesystems.


Is pod-running-inside-kubelet approach more resource efficient?

(sami) running a pod to mount by kubelet
(sami) daemonset needs a REST API redirection on all hosts, seemingly inefficient.
(hchen) running-pod-inside-kubelet needs to manage pod lifecycle, and ensure pod executes the mount (meaning watching apiserver)


(sami and pmorie) How to ensure mount namespace propagation to be set in a Pod (not Docker API)


(nelluri) How to ensure daemonset reacheable only by kubelet? Do other user containers able to access the daemonset to execute mount?