[Tarantool-patches] [PATCH v6 1/1] applier: filter incoming synchro packets via transaction initiator

[Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Currently we use synchro packets filtration based on their contents,
in particular by their xrow->replica_id value. Still there was a
question if we can optimize this moment and rather filter out all
packets coming from non-leader replica.

Raft specification requires that only data from a current leader
should be applied to local WAL but doesn't put a concrete claim on
the data transport, ie how exactly rows are reaching replicas. This
implies that data propagation may reach replicas indirectly via transit
hops. Thus we drop applier->instance_id filtering and rely on
xrow->replica_id matching instead.

In the test (inspired by Serge Petrenko's test) we recreate the situation
where replica3 obtains master's node data (which is a raft leader)
indirectly via replica2 node.

Closes #6035

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 src/box/applier.cc                            |  27 ++--
 src/lib/raft/raft.h                           |   7 -
 .../gh-5445-leader-inconsistency.result       |  15 +++
 .../gh-5445-leader-inconsistency.test.lua     |   5 +
 .../replication/gh-6035-applier-filter.result | 120 ++++++++++++++++++
 .../gh-6035-applier-filter.test.lua           |  54 ++++++++
 test/replication/gh-6035-master.lua           |   1 +
 test/replication/gh-6035-node.lua             |  35 +++++
 test/replication/gh-6035-replica1.lua         |   1 +
 test/replication/gh-6035-replica2.lua         |   1 +
 test/replication/suite.cfg                    |   3 +
 11 files changed, 250 insertions(+), 19 deletions(-)
 create mode 100644 test/replication/gh-6035-applier-filter.result
 create mode 100644 test/replication/gh-6035-applier-filter.test.lua
 create mode 120000 test/replication/gh-6035-master.lua
 create mode 100644 test/replication/gh-6035-node.lua
 create mode 120000 test/replication/gh-6035-replica1.lua
 create mode 120000 test/replication/gh-6035-replica2.lua

diff --git a/src/box/applier.cc b/src/box/applier.cc
index 33181fdbf..d3430f582 100644
--- a/src/box/applier.cc
+++ b/src/box/applier.cc
@@ -1027,21 +1027,24 @@ nopify:;
  * Return 0 for success or -1 in case of an error.
  */
 static int
-applier_apply_tx(struct applier *applier, struct stailq *rows)
+applier_apply_tx(struct stailq *rows)
 {
 	/*
-	 * Rows received not directly from a leader are ignored. That is a
-	 * protection against the case when an old leader keeps sending data
-	 * around not knowing yet that it is not a leader anymore.
+	 * Initially we've been filtering out data if it came from
+	 * an applier which instance_id doesn't match raft->leader,
+	 * but this prevents from obtaining valid leader's data when
+	 * it comes from intermediate node. For example a series of
+	 * replica hops
 	 *
-	 * XXX: it may be that this can be fine to apply leader transactions by
-	 * looking at their replica_id field if it is equal to leader id. That
-	 * can be investigated as an 'optimization'. Even though may not give
-	 * anything, because won't change total number of rows sent in the
-	 * network anyway.
+	 *  master -> replica 1 -> replica 2
+	 *
+	 * where each replica carries master's initiated transaction
+	 * in xrow->replica_id field and master's data get propagated
+	 * indirectly.
+	 *
+	 * Finally we dropped such "sender" filtration and use transaction
+	 * "initiator" filtration via xrow->replica_id only.
 	 */
-	if (!raft_is_source_allowed(box_raft(), applier->instance_id))
-		return 0;
 	struct xrow_header *first_row = &stailq_first_entry(rows,
 					struct applier_tx_row, next)->row;
 	struct xrow_header *last_row;
@@ -1312,7 +1315,7 @@ applier_subscribe(struct applier *applier)
 					diag_raise();
 			}
 			applier_signal_ack(applier);
-		} else if (applier_apply_tx(applier, &rows) != 0) {
+		} else if (applier_apply_tx(&rows) != 0) {
 			diag_raise();
 		}
 
diff --git a/src/lib/raft/raft.h b/src/lib/raft/raft.h
index a8da564b0..fae30b03d 100644
--- a/src/lib/raft/raft.h
+++ b/src/lib/raft/raft.h
@@ -236,13 +236,6 @@ raft_is_ro(const struct raft *raft)
 	return raft->is_enabled && raft->state != RAFT_STATE_LEADER;
 }
 
-/** See if the instance can accept rows from an instance with the given ID. */
-static inline bool
-raft_is_source_allowed(const struct raft *raft, uint32_t source_id)
-{
-	return !raft->is_enabled || raft->leader == source_id;
-}
-
 /** Check if Raft is enabled. */
 static inline bool
 raft_is_enabled(const struct raft *raft)
diff --git a/test/replication/gh-5445-leader-inconsistency.result b/test/replication/gh-5445-leader-inconsistency.result
index 5c6169f50..38d0b097c 100644
--- a/test/replication/gh-5445-leader-inconsistency.result
+++ b/test/replication/gh-5445-leader-inconsistency.result
@@ -175,9 +175,17 @@ test_run:cmd('stop server '..leader)
  | ---
  | - true
  | ...
+-- And other node as well so it would notice new term on restart.
 is_possible_leader[leader_nr] = false
  | ---
  | ...
+test_run:cmd('stop server '..other)
+ | ---
+ | - true
+ | ...
+is_possible_leader[other_nr] = false
+ | ---
+ | ...
 
 -- Emulate a situation when next_leader wins the elections. It can't do that in
 -- this configuration, obviously, because it's behind the 'other' node, so set
@@ -195,6 +203,13 @@ assert(get_leader(is_possible_leader) == next_leader_nr)
  | ---
  | - true
  | ...
+test_run:cmd('start server '..other..' with args="1 0.4 voter 2"')
+ | ---
+ | - true
+ | ...
+is_possible_leader[other_nr] = true
+ | ---
+ | ...
 test_run:switch(other)
  | ---
  | - true
diff --git a/test/replication/gh-5445-leader-inconsistency.test.lua b/test/replication/gh-5445-leader-inconsistency.test.lua
index e7952f5fa..fad101881 100644
--- a/test/replication/gh-5445-leader-inconsistency.test.lua
+++ b/test/replication/gh-5445-leader-inconsistency.test.lua
@@ -81,7 +81,10 @@ test_run:wait_cond(function() return box.space.test:get{2} ~= nil end)
 -- Old leader is gone.
 test_run:switch('default')
 test_run:cmd('stop server '..leader)
+-- And other node as well so it would notice new term on restart.
 is_possible_leader[leader_nr] = false
+test_run:cmd('stop server '..other)
+is_possible_leader[other_nr] = false
 
 -- Emulate a situation when next_leader wins the elections. It can't do that in
 -- this configuration, obviously, because it's behind the 'other' node, so set
@@ -93,6 +96,8 @@ is_possible_leader[leader_nr] = false
 -- a situation when some rows from the old leader were not received).
 test_run:cmd('start server '..next_leader..' with args="1 0.4 candidate 1"')
 assert(get_leader(is_possible_leader) == next_leader_nr)
+test_run:cmd('start server '..other..' with args="1 0.4 voter 2"')
+is_possible_leader[other_nr] = true
 test_run:switch(other)
 -- New leader didn't know about the unconfirmed rows but still rolled them back.
 test_run:wait_cond(function() return box.space.test:get{2} == nil end)
diff --git a/test/replication/gh-6035-applier-filter.result b/test/replication/gh-6035-applier-filter.result
new file mode 100644
index 000000000..fd270de64
--- /dev/null
+++ b/test/replication/gh-6035-applier-filter.result
@@ -0,0 +1,120 @@
+-- test-run result file version 2
+--
+-- gh-6035: verify synchronous rows filtration in applier,
+-- we need to be sure that filtering synchronous rows is
+-- done via transaction initiator not sender (iow via
+-- xrow->replica_id).
+--
+test_run = require('test_run').new()
+ | ---
+ | ...
+
+--
+-- Prepare a scheme with transitional node
+--
+--  master <=> replica1 => replica2
+--
+-- such as transaction initiated on the master node would
+-- be replicated to the replica2 via interim replica1 node.
+--
+
+test_run:cmd('create server master with script="replication/gh-6035-master.lua"')
+ | ---
+ | - true
+ | ...
+test_run:cmd('create server replica1 with script="replication/gh-6035-replica1.lua"')
+ | ---
+ | - true
+ | ...
+test_run:cmd('create server replica2 with script="replication/gh-6035-replica2.lua"')
+ | ---
+ | - true
+ | ...
+
+test_run:cmd('start server master')
+ | ---
+ | - true
+ | ...
+test_run:cmd('start server replica1')
+ | ---
+ | - true
+ | ...
+test_run:cmd('start server replica2')
+ | ---
+ | - true
+ | ...
+
+--
+-- Make the master to be RAFT leader.
+test_run:switch('master')
+ | ---
+ | - true
+ | ...
+box.ctl.promote()
+ | ---
+ | ...
+_ = box.schema.space.create("sync", {is_sync = true})
+ | ---
+ | ...
+_ = box.space.sync:create_index("pk")
+ | ---
+ | ...
+box.space.sync:insert{1}
+ | ---
+ | - [1]
+ | ...
+
+--
+-- The first hop is replica1.
+test_run:switch('replica1')
+ | ---
+ | - true
+ | ...
+box.space.sync:select{}
+ | ---
+ | - - [1]
+ | ...
+
+--
+-- And the second hop is replica2 where
+-- replica1 replicated the data to us.
+test_run:switch('replica2')
+ | ---
+ | - true
+ | ...
+test_run:wait_cond(function()                   \
+    return box.space.sync:select{} ~= nil and   \
+           box.space.sync:select{}[1][1] == 1   \
+    end, 100)
+ | ---
+ | - true
+ | ...
+
+test_run:switch('default')
+ | ---
+ | - true
+ | ...
+test_run:cmd('stop server master')
+ | ---
+ | - true
+ | ...
+test_run:cmd('delete server master')
+ | ---
+ | - true
+ | ...
+test_run:cmd('stop server replica1')
+ | ---
+ | - true
+ | ...
+test_run:cmd('delete server replica1')
+ | ---
+ | - true
+ | ...
+test_run:cmd('stop server replica2')
+ | ---
+ | - true
+ | ...
+test_run:cmd('delete server replica2')
+ | ---
+ | - true
+ | ...
diff --git a/test/replication/gh-6035-applier-filter.test.lua b/test/replication/gh-6035-applier-filter.test.lua
new file mode 100644
index 000000000..5a1ca3fd3
--- /dev/null
+++ b/test/replication/gh-6035-applier-filter.test.lua
@@ -0,0 +1,54 @@
+--
+-- gh-6035: verify synchronous rows filtration in applier,
+-- we need to be sure that filtering synchronous rows is
+-- done via transaction initiator not sender (iow via
+-- xrow->replica_id).
+--
+test_run = require('test_run').new()
+
+--
+-- Prepare a scheme with transitional node
+--
+--  master <=> replica1 => replica2
+--
+-- such as transaction initiated on the master node would
+-- be replicated to the replica2 via interim replica1 node.
+--
+
+test_run:cmd('create server master with script="replication/gh-6035-master.lua"')
+test_run:cmd('create server replica1 with script="replication/gh-6035-replica1.lua"')
+test_run:cmd('create server replica2 with script="replication/gh-6035-replica2.lua"')
+
+test_run:cmd('start server master')
+test_run:cmd('start server replica1')
+test_run:cmd('start server replica2')
+
+--
+-- Make the master to be RAFT leader.
+test_run:switch('master')
+box.ctl.promote()
+_ = box.schema.space.create("sync", {is_sync = true})
+_ = box.space.sync:create_index("pk")
+box.space.sync:insert{1}
+
+--
+-- The first hop is replica1.
+test_run:switch('replica1')
+box.space.sync:select{}
+
+--
+-- And the second hop is replica2 where
+-- replica1 replicated the data to us.
+test_run:switch('replica2')
+test_run:wait_cond(function()                   \
+    return box.space.sync:select{} ~= nil and   \
+           box.space.sync:select{}[1][1] == 1   \
+    end, 100)
+
+test_run:switch('default')
+test_run:cmd('stop server master')
+test_run:cmd('delete server master')
+test_run:cmd('stop server replica1')
+test_run:cmd('delete server replica1')
+test_run:cmd('stop server replica2')
+test_run:cmd('delete server replica2')
diff --git a/test/replication/gh-6035-master.lua b/test/replication/gh-6035-master.lua
new file mode 120000
index 000000000..f7ede7ef2
--- /dev/null
+++ b/test/replication/gh-6035-master.lua
@@ -0,0 +1 @@
+gh-6035-node.lua
\ No newline at end of file
diff --git a/test/replication/gh-6035-node.lua b/test/replication/gh-6035-node.lua
new file mode 100644
index 000000000..e3819471a
--- /dev/null
+++ b/test/replication/gh-6035-node.lua
@@ -0,0 +1,35 @@
+local SOCKET_DIR = require('fio').cwd()
+local INSTANCE_ID = string.match(arg[0], "gh%-6035%-(.+)%.lua")
+
+local function unix_socket(name)
+    return SOCKET_DIR .. "/" .. name .. '.sock';
+end
+
+require('console').listen(os.getenv('ADMIN'))
+
+if INSTANCE_ID == "master" then
+    box.cfg({
+        listen = unix_socket("master"),
+    })
+elseif INSTANCE_ID == "replica1" then
+    box.cfg({
+        listen = unix_socket("replica1"),
+        replication = {
+            unix_socket("master"),
+            unix_socket("replica1")
+        },
+        election_mode = 'voter'
+    })
+else
+    assert(INSTANCE_ID == "replica2")
+    box.cfg({
+        replication = {
+            unix_socket("master"),
+        },
+        election_mode = 'voter'
+    })
+end
+
+box.once("bootstrap", function()
+    box.schema.user.grant('guest', 'super')
+end)
diff --git a/test/replication/gh-6035-replica1.lua b/test/replication/gh-6035-replica1.lua
new file mode 120000
index 000000000..f7ede7ef2
--- /dev/null
+++ b/test/replication/gh-6035-replica1.lua
@@ -0,0 +1 @@
+gh-6035-node.lua
\ No newline at end of file
diff --git a/test/replication/gh-6035-replica2.lua b/test/replication/gh-6035-replica2.lua
new file mode 120000
index 000000000..f7ede7ef2
--- /dev/null
+++ b/test/replication/gh-6035-replica2.lua
@@ -0,0 +1 @@
+gh-6035-node.lua
\ No newline at end of file
diff --git a/test/replication/suite.cfg b/test/replication/suite.cfg
index 27eab20c2..55ec022ff 100644
--- a/test/replication/suite.cfg
+++ b/test/replication/suite.cfg
@@ -47,6 +47,9 @@
     "gh-6032-promote-wal-write.test.lua": {},
     "gh-6057-qsync-confirm-async-no-wal.test.lua": {},
     "gh-6094-rs-uuid-mismatch.test.lua": {},
+    "gh-6035-applier-filter.test.lua": {
+        "memtx": {"engine": "memtx"}
+    },
     "*": {
         "memtx": {"engine": "memtx"},
         "vinyl": {"engine": "vinyl"}
-- 
2.31.1