Cluster/afr: Don't treat all bricks having metadata pending as split-brain

Problem:
We currently don't have a roll-back/undoing of post-ops if quorum is not met.
Though the FOP is still unwound with failure, the xattrs remain on the disk.
Due to these partial post-ops and partial heals (healing only when 2 bricks
are up), we can end up in metadata split-brain purely from the afr xattrs
point of view i.e each brick is blamed by atleast one of the others for
metadata. These scenarios are hit when there is frequent connect/disconnect
of the client/shd to the bricks.

Fix:
Pick a source based on the xattr values. If 2 bricks blame one, the blamed
one must be treated as sink. If there is no majority, all are sources. Once
we pick a source, self-heal will then do the heal instead of erroring out
due to split-brain.
This patch also adds restriction of all the bricks to be up to perform
metadata heal to avoid any metadata loss.

Removed the test case tests/bugs/replicate/bug-1468279-source-not-blaming-sinks.t
as it was doing metadata heal even when only 2 of 3 bricks were up.

Change-Id: I07a9d62f84ceda329dcab1f02a33aeed258dcb09
fixes: bz#1717819
Signed-off-by: karthik-us <ksubrahm@redhat.com>

1 files changed, 130 insertions, 0 deletions

diff --git a/tests/bugs/replicate/bug-1717819-metadata-split-brain-detection.t b/tests/bugs/replicate/bug-1717819-metadata-split-brain-detection.t
new file mode 100644
index 00000000000..94b8bf3887e
--- /dev/null
+++ b/tests/bugs/replicate/bug-1717819-metadata-split-brain-detection.t
@@ -0,0 +1,130 @@
+#!/bin/bash
+
+. $(dirname $0)/../../include.rc
+. $(dirname $0)/../../volume.rc
+. $(dirname $0)/../../afr.rc
+
+cleanup;
+
+## Start and create a volume
+TEST glusterd;
+TEST pidof glusterd;
+TEST $CLI volume info;
+
+TEST $CLI volume create $V0 replica 3 $H0:$B0/${V0}{0,1,2};
+TEST $CLI volume start $V0;
+EXPECT 'Started' volinfo_field $V0 'Status';
+TEST $CLI volume heal $V0 disable
+TEST $GFS --volfile-id=/$V0 --volfile-server=$H0 $M0
+
+###############################################################################
+# Case of 2 bricks blaming the third and the third blaming the other two.
+
+TEST mkdir $M0/dir
+
+# B0 and B2 must blame B1
+TEST kill_brick $V0 $H0 $B0/$V0"1"
+TEST setfattr -n user.metadata -v 1 $M0/dir
+EXPECT "00000001" afr_get_specific_changelog_xattr $B0/${V0}0/dir trusted.afr.$V0-client-1 metadata
+EXPECT "00000001" afr_get_specific_changelog_xattr $B0/${V0}2/dir trusted.afr.$V0-client-1 metadata
+CLIENT_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $M0/dir)
+
+# B1 must blame B0 and B2
+setfattr -n trusted.afr.$V0-client-0 -v 0x000000000000000100000000 $B0/$V0"1"/dir
+setfattr -n trusted.afr.$V0-client-2 -v 0x000000000000000100000000 $B0/$V0"1"/dir
+
+# Launch heal
+TEST $CLI volume start $V0 force
+EXPECT_WITHIN $PROCESS_UP_TIMEOUT "^1$" brick_up_status $V0 $H0 $B0/${V0}1
+TEST $CLI volume heal $V0 enable
+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
+EXPECT_WITHIN $HEAL_TIMEOUT "^0$" get_pending_heal_count $V0
+
+B0_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}0/dir)
+B1_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}1/dir)
+B2_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}2/dir)
+
+TEST [ "$CLIENT_XATTR" == "$B0_XATTR" ]
+TEST [ "$CLIENT_XATTR" == "$B1_XATTR" ]
+TEST [ "$CLIENT_XATTR" == "$B2_XATTR" ]
+TEST setfattr -x user.metadata $M0/dir
+
+###############################################################################
+# Case of each brick blaming the next one in a cyclic manner
+
+TEST $CLI volume heal $V0 disable
+TEST `echo "hello" >> $M0/dir/file`
+# Mark cyclic xattrs and modify metadata directly on the bricks.
+setfattr -n trusted.afr.$V0-client-1 -v 0x000000000000000100000000 $B0/$V0"0"/dir/file
+setfattr -n trusted.afr.$V0-client-2 -v 0x000000000000000100000000 $B0/$V0"1"/dir/file
+setfattr -n trusted.afr.$V0-client-0 -v 0x000000000000000100000000 $B0/$V0"2"/dir/file
+
+setfattr -n user.metadata -v 1 $B0/$V0"0"/dir/file
+setfattr -n user.metadata -v 2 $B0/$V0"1"/dir/file
+setfattr -n user.metadata -v 3 $B0/$V0"2"/dir/file
+
+# Add entry to xattrop dir to trigger index heal.
+xattrop_dir0=$(afr_get_index_path $B0/$V0"0")
+base_entry_b0=`ls $xattrop_dir0`
+gfid_str=$(gf_gfid_xattr_to_str $(gf_get_gfid_xattr $B0/$V0"0"/dir/file))
+ln $xattrop_dir0/$base_entry_b0 $xattrop_dir0/$gfid_str
+EXPECT_WITHIN $HEAL_TIMEOUT "^1$" get_pending_heal_count $V0
+
+# Launch heal
+TEST $CLI volume heal $V0 enable
+TEST $CLI volume heal $V0
+EXPECT_WITHIN $HEAL_TIMEOUT "^0$" get_pending_heal_count $V0
+
+B0_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}0/dir/file)
+B1_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}1/dir/file)
+B2_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}2/dir/file)
+
+TEST [ "$B0_XATTR" == "$B1_XATTR" ]
+TEST [ "$B0_XATTR" == "$B2_XATTR" ]
+TEST rm -f $M0/dir/file
+
+###############################################################################
+# Case of 2 bricks having quorum blaming and the other having only one blaming.
+
+TEST $CLI volume heal $V0 disable
+TEST `echo "hello" >> $M0/dir/file`
+# B0 and B2 must blame B1
+TEST kill_brick $V0 $H0 $B0/$V0"1"
+TEST setfattr -n user.metadata -v 1 $M0/dir/file
+EXPECT "00000001" afr_get_specific_changelog_xattr $B0/${V0}0/dir/file trusted.afr.$V0-client-1 metadata
+EXPECT "00000001" afr_get_specific_changelog_xattr $B0/${V0}2/dir/file trusted.afr.$V0-client-1 metadata
+
+# B1 must blame B0 and B2
+setfattr -n trusted.afr.$V0-client-0 -v 0x000000000000000100000000 $B0/$V0"1"/dir/file
+setfattr -n trusted.afr.$V0-client-2 -v 0x000000000000000100000000 $B0/$V0"1"/dir/file
+
+# B0 must blame B2
+setfattr -n trusted.afr.$V0-client-2 -v 0x000000000000000100000000 $B0/$V0"0"/dir/file
+
+# Modify the metadata directly on the bricks B1 & B2.
+setfattr -n user.metadata -v 2 $B0/$V0"1"/dir/file
+setfattr -n user.metadata -v 3 $B0/$V0"2"/dir/file
+
+# Launch heal
+TEST $CLI volume start $V0 force
+EXPECT_WITHIN $PROCESS_UP_TIMEOUT "^1$" brick_up_status $V0 $H0 $B0/${V0}1
+TEST $CLI volume heal $V0 enable
+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 $V0 2
+
+B0_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}0/dir/file)
+B1_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}1/dir/file)
+B2_XATTR=$(getfattr -n 'user.metadata' --absolute-names --only-values $B0/${V0}2/dir/file)
+
+TEST [ "$B0_XATTR" == "$B1_XATTR" ]
+TEST [ "$B0_XATTR" == "$B2_XATTR" ]
+
+###############################################################################
+
+cleanup