afr: don't treat all cases all bricks being blamed 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 split-brain purely from the afr
xattrs point of view i.e each brick is blamed by atleast one of the
others. These scenarios are hit when there is frequent
connect/disconnect of the client/shd to the bricks while I/O or heal
are in progress.

Fix:
Instead of undoing the post-op, 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.

Change-Id: I3d0224b883eb0945785ade0e9697a1c828aec0ae
BUG: 1539358
Signed-off-by: Ravishankar N <ravishankar@redhat.com>

2 files changed, 101 insertions, 0 deletions

diff --git a/tests/bugs/replicate/bug-1539358-split-brain-detection.t b/tests/bugs/replicate/bug-1539358-split-brain-detection.t
new file mode 100755
index 00000000000..7b71a7a9e7d
--- /dev/null
+++ b/tests/bugs/replicate/bug-1539358-split-brain-detection.t
@@ -0,0 +1,89 @@
+#!/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 set $V0 self-heal-daemon off
+TEST glusterfs --volfile-id=/$V0 --volfile-server=$H0 $M0 --attribute-timeout=0 --entry-timeout=0
+
+###############################################################################yy
+# Case of 2 bricks blaming the third and the third blaming the other two.
+
+TEST `echo "hello" >> $M0/file`
+
+# B0 and B2 must blame B1
+TEST kill_brick $V0 $H0 $B0/$V0"1"
+TEST `echo "append" >> $M0/file`
+EXPECT "00000001" afr_get_specific_changelog_xattr $B0/${V0}0/file trusted.afr.$V0-client-1 data
+EXPECT "00000001" afr_get_specific_changelog_xattr $B0/${V0}2/file trusted.afr.$V0-client-1 data
+CLIENT_MD5=$(md5sum $M0/file | cut -d\  -f1)
+
+# B1 must blame B0 and B2
+setfattr -n trusted.afr.$V0-client-0 -v 0x000000010000000000000000 $B0/$V0"1"/file
+setfattr -n trusted.afr.$V0-client-2 -v 0x000000010000000000000000 $B0/$V0"1"/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 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
+EXPECT_WITHIN $HEAL_TIMEOUT "^0$" get_pending_heal_count $V0
+B0_MD5=$(md5sum $B0/${V0}0/file | cut -d\  -f1)
+B1_MD5=$(md5sum $B0/${V0}1/file | cut -d\  -f1)
+B2_MD5=$(md5sum $B0/${V0}2/file | cut -d\  -f1)
+TEST [ "$CLIENT_MD5" == "$B0_MD5" ]
+TEST [ "$CLIENT_MD5" == "$B1_MD5" ]
+TEST [ "$CLIENT_MD5" == "$B2_MD5" ]
+
+TEST rm $M0/file
+
+###############################################################################yy
+# Case of each brick blaming the next one in a cyclic manner
+
+TEST `echo "hello" >> $M0/file`
+# Mark cyclic xattrs and modify file content directly on the bricks.
+TEST $CLI volume set $V0 self-heal-daemon off
+setfattr -n trusted.afr.$V0-client-1 -v 0x000000010000000000000000 $B0/$V0"0"/file
+setfattr -n trusted.afr.dirty -v 0x000000010000000000000000 $B0/$V0"0"/file
+setfattr -n trusted.afr.$V0-client-2 -v 0x000000010000000000000000 $B0/$V0"1"/file
+setfattr -n trusted.afr.dirty -v 0x000000010000000000000000 $B0/$V0"1"/file
+setfattr -n trusted.afr.$V0-client-0 -v 0x000000010000000000000000 $B0/$V0"2"/file
+setfattr -n trusted.afr.dirty -v 0x000000010000000000000000 $B0/$V0"2"/file
+
+TEST `echo "ab" >> $B0/$V0"0"/file`
+TEST `echo "cdef" >> $B0/$V0"1"/file`
+TEST `echo "ghi" >> $B0/$V0"2"/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"/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 set $V0 self-heal-daemon on
+TEST $CLI volume heal $V0
+EXPECT_WITHIN $HEAL_TIMEOUT "^0$" get_pending_heal_count $V0
+B0_MD5=$(md5sum $B0/${V0}0/file | cut -d\  -f1)
+B1_MD5=$(md5sum $B0/${V0}1/file | cut -d\  -f1)
+B2_MD5=$(md5sum $B0/${V0}2/file | cut -d\  -f1)
+TEST [ "$B0_MD5" == "$B1_MD5" ]
+TEST [ "$B0_MD5" == "$B2_MD5" ]
+###############################################################################yy
+cleanup
diff --git a/tests/bugs/replicate/bug-802417.t b/tests/bugs/replicate/bug-802417.t
index c5ba98b65fd..f213439401e 100755
--- a/tests/bugs/replicate/bug-802417.t
+++ b/tests/bugs/replicate/bug-802417.t
@@ -10,6 +10,18 @@ function write_file()
 }
 
 cleanup;
+
+#####################################################
+# We are currently not triggering data heal unless all bricks of the replica are
+# up. We will need to modify this .t once the fix for preventing stale reads
+# being served to clients for files in spurious split-brains is done. Spurious
+# split-brains here means afr xattrs indicates sbrain but it is actually not.
+# Self-heal will heal such files automatically but before the heal completes,
+# reads can be served which needs fixing.
+#G_TESTDEF_TEST_STATUS_NETBSD7=BAD_TEST,BUG=000000
+#G_TESTDEF_TEST_STATUS_CENTOS6=BAD_TEST,BUG=000000
+######################################################
+
 TEST glusterd
 TEST pidof glusterd
 TEST $CLI volume info;