features/changelog: Consider only changelog on/off as changelog breakage

Earlier, both chagelog on/off and brick restart were considered
to be changelog breakage and treated as changelog not being
continuous. As a result, new HTIME.TSTAMP file was created on
both the above cases. Now the change is made such that only
on changelog enable/disable, the changelog is considered to be
discontinuous. New HTIME.TSTAMP file is not created on brick
restart, the changelogs files are appended to last HTIME.TSTAMP
file.

Treating changelog as continuous in above scenario is important
as changelog history API will fail otherwise. It can successfully
get changes between start and end timestamps only when changelog
is continuous (Changelogs in single HTIME.TSTAMP file are treated
as continuous). Without this change, changelog history API would
fail, and it would become necessary to fallback to other mechanisms
like xsync FSCrawl in case geo-rep to detect changes in this time
window. But Xsync FSCrawl would not be applicable to other
consumers like glusterfind.

Rationale:
1. In plain distributed volume, if brick goes down, no I/O can
   happen onto the brick. Hence changelog is intact with data
   on disk.
2. In distributed replicate volume, if brick goes down, since
   self-heal traffic is captured in changelog. Eventually,
   I/O happened whend brick down is captured in changelog.

BUG: 1217944
Change-Id: Ifa6d932818fe1a3a914e87ac84f1d2ded01c1288
Signed-off-by: Kotresh HR <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/10222
Reviewed-on: http://review.gluster.org/10507
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Aravinda VK <avishwan@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

3 files changed, 57 insertions, 0 deletions

diff --git a/tests/bugs/changelog/bug-1211327.t b/tests/bugs/changelog/bug-1211327.t
new file mode 100644
index 00000000000..19d6e76ecab
--- /dev/null
+++ b/tests/bugs/changelog/bug-1211327.t
@@ -0,0 +1,48 @@
+#!/bin/bash
+
+#Testcase:
+#On brick restart, new HTIME.TSTAMP file should not be created.
+#But on changelog disable/enable HTIME.TSTAMP should be created.
+
+. $(dirname $0)/../../include.rc
+. $(dirname $0)/../../volume.rc
+. $(dirname $0)/../../changelog.rc
+cleanup;
+
+## Start and create a volume
+TEST glusterd;
+TEST pidof glusterd;
+TEST $CLI volume create $V0 $H0:$B0/$V0"1";
+
+## Verify volume is is created
+EXPECT "$V0" volinfo_field $V0 'Volume Name';
+EXPECT 'Created' volinfo_field $V0 'Status';
+
+## Start volume and verify
+TEST $CLI volume start $V0;
+EXPECT 'Started' volinfo_field $V0 'Status';
+
+TEST $CLI volume set $V0 changelog.changelog on;
+##Let changelog init complete before killing gluster processes
+sleep 1
+
+TEST killall_gluster;
+sleep 1
+EXPECT 0 online_brick_count;
+
+TEST glusterd;
+TEST pidof glusterd;
+##Let the brick processes starts
+sleep 1;
+
+EXPECT 1 online_brick_count;
+
+##On brick restart only one HTIME should be found.
+EXPECT 1 count_htime_files;
+
+##On changelog disable/enable, new HTIME should be created.
+TEST $CLI volume set $V0 changelog.changelog off;
+TEST $CLI volume set $V0 changelog.changelog on;
+EXPECT 2 count_htime_files;
+
+cleanup;
diff --git a/tests/changelog.rc b/tests/changelog.rc
new file mode 100644
index 00000000000..e3b040226ec
--- /dev/null
+++ b/tests/changelog.rc
@@ -0,0 +1,4 @@
+
+function count_htime_files {
+    ls -l $B0/$V0"1"/.glusterfs/changelogs/htime/ | grep HTIME | wc -l
+}
diff --git a/tests/volume.rc b/tests/volume.rc
index f2a56888fb8..75e244f3cc4 100644
--- a/tests/volume.rc
+++ b/tests/volume.rc
@@ -410,6 +410,11 @@ function volume_exists() {
 	fi
 }
 
+function killall_gluster() {
+        pkill gluster
+        sleep 1
+}
+
 function afr_get_index_count {
         local brick=$1
         ls $1/.glusterfs/indices/xattrop | grep -v xattrop | wc -l