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authorhari gowtham <hgowtham@redhat.com>2016-09-16 13:24:22 +0530
committerAtin Mukherjee <amukherj@redhat.com>2017-01-16 20:49:21 -0800
commit8390e313aeb09c7eca756690b7297a5dfa68ad4c (patch)
treea06c93a0639c8b1985778d439083e10b6d5632be /under_review
parentd6288d24f955f5b36394cfa1a952cc91cf57440a (diff)
Tier: Tier as a daemon under service framework.
Change-Id: Idab9cafbed076b33f63db83a16aa040d66d05a5a Signed-off-by: hari gowtham <hgowtham@redhat.com> Reviewed-on: http://review.gluster.org/15519 Reviewed-by: Atin Mukherjee <amukherj@redhat.com> Tested-by: Atin Mukherjee <amukherj@redhat.com>
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+Feature
+-------
+
+Tier as a daemon with the service framework of gluster.
+
+Summary
+-------
+
+Current tier process uses the same dht code. If any change is made to DHT
+it affects tier and vice versa. On an attempt to support add brick on tiered
+volume, we need a rebalance daemon. So the current tier daemon has to be
+separated from DHT. And so the new Daemon has been split from DHT and comes
+under the service framework.
+
+Owners
+------
+
+Dan Lambright <dlambrig@redhat.com>
+
+Hari Gowtham <hgowtham@redhatcom>
+
+Current status
+--------------
+
+In the current code, it doesn't fall under the service framework and this
+makes it hard for gluster to manage the daemon. Moving it into the gluster's
+service framework makes it easier to be managed.
+
+Related Feature Requests and Bugs
+---------------------------------
+
+[BUG] https://bugzilla.redhat.com/show_bug.cgi?id=1313838
+
+Detailed Description
+--------------------
+
+This change is similar to the other daemons that come under service framework.
+The service framework takes care of :
+
+*) Spawning the daemon, killing it and other such processes.
+*) Volume set options.
+*) Restarting the daemon at two points
+ 1) when gluster goes down and comes up.
+ 2) to stop detach tier.
+*) Reconfigure is used to make volfile changes. The reconfigure checks if the
+daemons needs a restart or not and then does it as per the requirement.
+By doing this, we don’t restart the daemon everytime.
+*) Volume status lists the status of tier daemon as a process instead of
+a task.
+*) remove-brick and detach tier are separated from code level.
+
+With this patch the log, pid, and volfile are separated and put into respective
+directories.
+
+
+Benefit to GlusterFS
+--------------------
+
+Improved Stability, helps the glusterd to manage the daemon during situations
+like update, node down, and restart.
+
+Scope
+-----
+
+#### Nature of proposed change
+
+A new service will be made available. The existing code will be removed in a
+while to make DHT rebalance easy to maintain as the DHT and tier code are
+separated.
+
+#### Implications on manageability
+
+The older gluster commands are designed to be compatible with this change.
+
+#### Implications on presentation layer
+
+None.
+
+#### Implications on persistence layer
+
+None.
+
+#### Implications on 'GlusterFS' backend
+
+Remains the same as for Tier.
+
+#### Modification to GlusterFS metadata
+
+None.
+
+#### Implications on 'glusterd'
+
+The data related to tier is made persistent (will be available after reboot).
+The brick op phase being different for Tier (brick op phase was earlier used
+to communicate with the daemon instead of bricks) has been implemented in
+the commit phase.
+The volfile changes for setting the options are also take care of using the
+service framework.
+
+How To Test
+-----------
+
+The basic tier commands need to be tested as it doesn't change much
+in the user perspective. The same test (like attaching tier, detaching it,
+status) used for testing tier have to be used.
+
+User Experience
+---------------
+
+No changes.
+
+Dependencies
+------------
+
+None.
+
+Documentation
+-------------
+
+https://docs.google.com/document/d/1_iyjiwTLnBJlCiUgjAWnpnPD801h5LNxLhHmN7zmk1o/edit?usp=sharing
+
+Status
+------
+
+Code being reviewed.
+
+Comments and Discussion
+-----------------------
+
+*Follow here*