Bug 1475399

+++ This bug was initially created as a clone of Bug #1457985 +++

+++ This bug was initially created as a clone of Bug #1454602 +++

Description of problem:
=======================
On a cifs mount having a dataset of empty directories+ directories with files, started removing few bricks. When issued remove-brick status command, rebalance estimate time shows negative values. 

I have issued status for almost 21 times during remove-brick rebalance and every time it showed negative values. At the 22nd attempt, the rebalance estimate time showed positive values (at the point, rebalance ran for almost 24 mins) 

[root@server1 samba]# gluster v remove-brick distrep server1:/bricks/brick6/b6 server2:/bricks/brick6/b6 server3:/bricks/brick6/b6 server4:/bricks/brick6/b6 status
                                    Node Rebalanced-files          size       scanned      failures       skipped               status  run time in h:m:s
                               ---------      -----------   -----------   -----------   -----------   -----------         ------------     --------------
                               localhost                2         9.5KB             6             0             0            completed        0:15:16
       server1.redhat.com                0        0Bytes             0             0             0          in progress        0:21:32
        server2.redhat.com                0        0Bytes             0             0             0          in progress        0:00:00
       server3.redhat.com                0        0Bytes             0             0             0          in progress        0:21:21
Estimated time left for rebalance to complete : 2023406814:-21:-32


Version-Release number of selected component (if applicable):
3.8.4-25.el7rhgs.x86_64

How reproducible:
=================
1/1

Steps to Reproduce:
===================
1) Create a distributed-replicate volume and start it.
2) cifs mount the volume on a client.
3) Create a data set of empty directories+ directories with files.
4) Remove few bricks.
5) Keep running remove-brick status command and check "Estimated time left for rebalance to complete " output.

Actual results:
===============
Rebalance estimate time sometimes shows negative values.

Expected results:
=================
Rebalance estimate time should not show negative values.


From distrep-rebalance.log in sosreport-sysreg-prod.negativevalues-20170523062944:  


[2017-05-23 05:54:01.319951] I [dht-rebalance.c:4425:gf_defrag_status_get] 0-glusterfs: TIME: num_files_lookedup=0,elapsed time = 51.000000,rate_lookedup=0.000000
[2017-05-23 05:54:01.320001] I [dht-rebalance.c:4428:gf_defrag_status_get] 0-glusterfs: TIME: Estimated total time to complete = 0 seconds
[2017-05-23 05:54:01.320012] I [dht-rebalance.c:4431:gf_defrag_status_get] 0-glusterfs: TIME: Seconds left = 18446744073709551565 seconds


This skews the results causing the weird result seen.

Easily reproducible by running rebalance on a volume with only dirs (no files).

--- Additional comment from Worker Ant on 2017-06-01 13:00:56 EDT ---

REVIEW: https://review.gluster.org/17448 (cluster/dht: Include dirs in rebalance estimates) posted (#1) for review on master by N Balachandran (nbalacha)

--- Additional comment from Worker Ant on 2017-06-07 00:02:27 EDT ---

COMMIT: https://review.gluster.org/17448 committed in master by Raghavendra G (rgowdapp) 
------
commit c9860430a77f20ddfec532819542bb1d0187c06e
Author: N Balachandran <nbalacha>
Date:   Thu Jun 1 22:13:41 2017 +0530

    cluster/dht: Include dirs in rebalance estimates
    
    Empty directories were not being considered while
    calculating rebalance estimates leading to negative
    time-left values being displayed as part of the
    rebalance status.
    
    Change-Id: I48d41d702e72db30af10e6b87b628baa605afa98
    BUG: 1457985
    Signed-off-by: N Balachandran <nbalacha>
    Reviewed-on: https://review.gluster.org/17448
    Smoke: Gluster Build System <jenkins.org>
    NetBSD-regression: NetBSD Build System <jenkins.org>
    CentOS-regression: Gluster Build System <jenkins.org>
    Reviewed-by: Amar Tumballi <amarts>
    Reviewed-by: Raghavendra G <rgowdapp>

--- Additional comment from Nithya Balachandran on 2017-06-19 02:09:06 EDT ---

Moving this back to Post as there is one more patch required.

--- Additional comment from Worker Ant on 2017-06-19 02:26:48 EDT ---

REVIEW: https://review.gluster.org/17564 (cluster/dht: Additional checks for rebalance estimates) posted (#1) for review on master by N Balachandran (nbalacha)

--- Additional comment from Worker Ant on 2017-06-20 08:31:51 EDT ---

COMMIT: https://review.gluster.org/17564 committed in master by Jeff Darcy (jeff.us) 
------
commit 426c2908aee4addd36d925ee93e56c9b2688ec1b
Author: N Balachandran <nbalacha>
Date:   Mon Jun 19 11:50:28 2017 +0530

    cluster/dht: Additional checks for rebalance estimates
    
    The rebalance estimates calculation was not handling
    calculations correctly when no files had been processed,
    i.e., when rate_lookedup was 0.
    
    Now, the estimated time is set to 0 in such scenarios as
    there is no way for rebalance to figure out how long the
    process will take to complete without knowing the rate at
    which the files are being processed.
    
    Change-Id: I7b6378e297e1ba139852bcb2239adf2477336b5b
    BUG: 1457985
    Signed-off-by: N Balachandran <nbalacha>
    Reviewed-on: https://review.gluster.org/17564
    Smoke: Gluster Build System <jenkins.org>
    NetBSD-regression: NetBSD Build System <jenkins.org>
    CentOS-regression: Gluster Build System <jenkins.org>
    Reviewed-by: Amar Tumballi <amarts>
    Reviewed-by: Raghavendra G <rgowdapp>

--- Additional comment from Worker Ant on 2017-07-24 09:05:14 EDT ---

REVIEW: https://review.gluster.org/17863 (cluster/dht: Fix negative rebalance estimates) posted (#1) for review on master by N Balachandran (nbalacha)

--- Additional comment from Worker Ant on 2017-07-25 13:03:05 EDT ---

REVIEW: https://review.gluster.org/17863 (cluster/dht: Fix negative rebalance estimates) posted (#2) for review on master by N Balachandran (nbalacha)

--- Additional comment from Worker Ant on 2017-07-26 05:25:03 EDT ---

COMMIT: https://review.gluster.org/17863 committed in master by Atin Mukherjee (amukherj) 
------
commit e21c915679244ddc1fae886e52badf02b4d95efc
Author: N Balachandran <nbalacha>
Date:   Mon Jul 24 18:27:39 2017 +0530

    cluster/dht: Fix negative rebalance estimates
    
    The calculation of the rebalance estimates will start
    after the rebalance operation has been running for 10
    minutes. This patch also changes the cli rebalance status
    code to use unsigned variables for the time calculations.
    
    Change-Id: Ic76f517c59ad938a407f1cf5e3b9add571690a6c
    BUG: 1457985
    Signed-off-by: N Balachandran <nbalacha>
    Reviewed-on: https://review.gluster.org/17863
    Reviewed-by: Amar Tumballi <amarts>
    Smoke: Gluster Build System <jenkins.org>
    Reviewed-by: Atin Mukherjee <amukherj>
    CentOS-regression: Gluster Build System <jenkins.org>