cluster/afr: Prevent split-brain when bricks are brought off and on in cyclic order

When the bricks are brought offline and then online in cyclic
order while writes are in progress on a file, thanks to inode
refresh in write txns, AFR will mostly fail the write attempt
when the only good copy is offline. However, there is still a
remote possibility that the file will run into split-brain if
the brick that has the lone good copy goes offline *after* the
inode refresh but *before* the write txn completes (I call it
in-flight split-brain in the patch for ease of reference),
requiring intervention from admin to resolve the split-brain
before the IO can resume normally on the file. To get around this,
the patch does the following things:
i) retains the dirty xattrs on the file
ii) avoids marking the last of the good copies as bad (or accused)
    in case it is the one to go down during the course of a write.
iii) fails that particular write with the appropriate errno.

This way, we still have one good copy left despite the split-brain situation
which when it is back online, will be chosen as source to do the heal.

Change-Id: I9ca634b026ac830b172bac076437cc3bf1ae7d8a
BUG: 1363721
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/15080
Tested-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Smoke: Gluster Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-by: Oleksandr Natalenko <oleksandr@natalenko.name>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>

1 files changed, 112 insertions, 0 deletions

diff --git a/tests/bugs/replicate/bug-1363721.t b/tests/bugs/replicate/bug-1363721.t
new file mode 100644
index 00000000000..ec39889b27e
--- /dev/null
+++ b/tests/bugs/replicate/bug-1363721.t
@@ -0,0 +1,112 @@
+#!/bin/bash
+
+. $(dirname $0)/../../include.rc
+. $(dirname $0)/../../volume.rc
+
+FILE_UPDATE_TIMEOUT=20
+cleanup
+
+function size_increased {
+        local file=$1
+        local size=$2
+        local new_size=$(stat -c%s $file)
+        if [ $new_size -gt $size ];
+        then
+                echo "Y"
+        else
+                echo "N"
+        fi
+}
+
+TEST glusterd
+TEST pidof glusterd
+TEST $CLI volume create $V0 replica 3 $H0:$B0/${V0}{0,1,2}
+TEST $CLI volume set $V0 performance.write-behind off
+TEST $CLI volume set $V0 cluster.self-heal-daemon off
+TEST $CLI volume set $V0 cluster.data-self-heal off
+TEST $CLI volume set $V0 cluster.metadata-self-heal off
+TEST $CLI volume set $V0 cluster.entry-self-heal off
+TEST $CLI volume start $V0
+TEST $GFS --volfile-id=$V0 --volfile-server=$H0 $M0 --direct-io-mode=enable
+
+cd $M0
+
+# Start writing to a file.
+(dd if=/dev/urandom of=$M0/file1 bs=1k 2>/dev/null 1>/dev/null)&
+dd_pid=$!
+
+# Let IO happen
+EXPECT_WITHIN $FILE_UPDATE_TIMEOUT "Y" size_increased file1 0
+
+# Now kill the zeroth brick
+kill_brick $V0 $H0 $B0/${V0}0
+
+# Let IO continue
+EXPECT_WITHIN $FILE_UPDATE_TIMEOUT "Y" size_increased file1 $(stat -c%s file1)
+
+# Now bring the brick back up
+TEST $CLI volume start $V0 force
+EXPECT_WITHIN $CHILD_UP_TIMEOUT "1" afr_child_up_status $V0 0
+
+# Let IO continue
+EXPECT_WITHIN $FILE_UPDATE_TIMEOUT "Y" size_increased file1 $(stat -c%s file1)
+
+# Now kill the first brick
+kill_brick $V0 $H0 $B0/${V0}1
+
+# Let IO continue
+EXPECT_WITHIN $FILE_UPDATE_TIMEOUT "Y" size_increased file1 $(stat -c%s file1)
+
+# Now bring the brick back up
+TEST $CLI volume start $V0 force
+EXPECT_WITHIN $CHILD_UP_TIMEOUT "1" afr_child_up_status $V0 1
+
+# Let IO continue for 3 seconds
+sleep 3
+
+# Now kill the second brick
+kill_brick $V0 $H0 $B0/${V0}2
+
+# At this point the write should have been failed. But make sure that the second
+# brick is never an accused.
+
+md5sum_2=$(md5sum $B0/${V0}2/file1 | awk '{print $1}')
+
+EXPECT_NOT "$md5sum_2" echo `md5sum $B0/${V0}0/file1 | awk '{print $1}'`
+EXPECT_NOT "$md5sum_2" echo `md5sum $B0/${V0}1/file1 | awk '{print $1}'`
+
+EXPECT_NOT "00000000" afr_get_specific_changelog_xattr $B0/${V0}0/file1 trusted.afr.dirty data
+EXPECT_NOT "00000000" afr_get_specific_changelog_xattr $B0/${V0}1/file1 trusted.afr.dirty data
+
+EXPECT "00000000" afr_get_specific_changelog_xattr $B0/${V0}0/file1 trusted.afr.$V0-client-2 data
+EXPECT "00000000" afr_get_specific_changelog_xattr $B0/${V0}1/file1 trusted.afr.$V0-client-2 data
+EXPECT "00000000" afr_get_specific_changelog_xattr $B0/${V0}2/file1 trusted.afr.$V0-client-2 data
+EXPECT "00000000" afr_get_specific_changelog_xattr $B0/${V0}0/file1 trusted.afr.$V0-client-2 metadata
+EXPECT "00000000" afr_get_specific_changelog_xattr $B0/${V0}1/file1 trusted.afr.$V0-client-2 metadata
+EXPECT "00000000" afr_get_specific_changelog_xattr $B0/${V0}2/file1 trusted.afr.$V0-client-2 metadata
+
+# Now bring the brick back up
+TEST $CLI volume start $V0 force
+EXPECT_WITHIN $CHILD_UP_TIMEOUT "1" afr_child_up_status $V0 2
+
+# Enable shd
+TEST $CLI volume set $V0 self-heal-daemon on
+EXPECT_WITHIN $PROCESS_UP_TIMEOUT "Y" glustershd_up_status
+EXPECT_WITHIN $CHILD_UP_TIMEOUT "1" afr_child_up_status_in_shd $V0 0
+EXPECT_WITHIN $CHILD_UP_TIMEOUT "1" afr_child_up_status_in_shd $V0 1
+EXPECT_WITHIN $CHILD_UP_TIMEOUT "1" afr_child_up_status_in_shd $V0 2
+
+TEST $CLI volume heal $V0
+
+# Wait for heal to complete
+EXPECT_WITHIN $HEAL_TIMEOUT "^0$" get_pending_heal_count $V0
+
+EXPECT "$md5sum_2" echo `md5sum $B0/${V0}0/file1 | awk '{print $1}'`
+EXPECT "$md5sum_2" echo `md5sum $B0/${V0}1/file1 | awk '{print $1}'`
+EXPECT "$md5sum_2" echo `md5sum $B0/${V0}2/file1 | awk '{print $1}'`
+
+cd ~
+
+EXPECT_WITHIN $UMOUNT_TIMEOUT "Y" force_umount $M0
+
+cleanup