[Tarantool-patches] [PATCH v5] 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 our 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>
---
issue https://github.com/tarantool/tarantool/issues/6035
branch gorcunov/gh-6035-applier-filter-5

Guys, take a look please, would such description be verbose enough?
Should we allow such configurations at all?

 src/box/applier.cc                            |  27 ++--
 src/lib/raft/raft.h                           |   7 -
 .../replication/gh-6035-applier-filter.result | 147 ++++++++++++++++++
 .../gh-6035-applier-filter.test.lua           |  66 ++++++++
 test/replication/gh6035master.lua             |   1 +
 test/replication/gh6035node.lua               |  35 +++++
 test/replication/gh6035replica1.lua           |   1 +
 test/replication/gh6035replica2.lua           |   1 +
 8 files changed, 266 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/gh6035master.lua
 create mode 100644 test/replication/gh6035node.lua
 create mode 120000 test/replication/gh6035replica1.lua
 create mode 120000 test/replication/gh6035replica2.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-6035-applier-filter.result b/test/replication/gh-6035-applier-filter.result
new file mode 100644
index 000000000..cf032c332
--- /dev/null
+++ b/test/replication/gh-6035-applier-filter.result
@@ -0,0 +1,147 @@
+-- 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).
+--
+
+local SOCKET_DIR = require('fio').cwd()
+ | ---
+ | ...
+local function unix_socket(name)                \
+    return SOCKET_DIR .. "/" .. name .. '.sock' \
+end
+ | ---
+ | ...
+
+env = require('test_run')
+ | ---
+ | ...
+test_run = env.new()
+ | ---
+ | ...
+engine = test_run:get_cfg('engine')
+ | ---
+ | ...
+
+test_run:cmd('create server gh6035master with script="replication/gh6035master.lua"')
+ | ---
+ | - true
+ | ...
+test_run:cmd('start server gh6035master with args="gh6035master"')
+ | ---
+ | - true
+ | ...
+
+test_run:cmd('create server gh6035replica1 with script="replication/gh6035replica1.lua"')
+ | ---
+ | - true
+ | ...
+test_run:cmd('start server gh6035replica1 with args="gh6035replica1"')
+ | ---
+ | - true
+ | ...
+
+test_run:cmd('create server gh6035replica2 with script="replication/gh6035replica2.lua"')
+ | ---
+ | - true
+ | ...
+test_run:cmd('start server gh6035replica2 with args="gh6035replica2"')
+ | ---
+ | - true
+ | ...
+
+--
+-- The gh6035master node connected to gh6035replica1 and gh6035replica2,
+-- where each of gh6035replicaX connected to the gh6035master only.
+--
+-- Lets reroute gh6035replica2 to gh6035replica1 so gh6035replica1 gonna
+-- be sending data to gh6035replica2 as a transit hop from gh6035master.
+test_run:cmd('switch gh6035replica2')
+ | ---
+ | - true
+ | ...
+box.cfg{replication = {unix_socket("gh6035replica1")}}
+ | ---
+ | ...
+
+--
+-- Make the gh6035master to be RAFT leader.
+test_run:cmd('switch gh6035master')
+ | ---
+ | - true
+ | ...
+box.cfg{                                    \
+    replication = {                         \
+        unix_socket("gh6035master"),        \
+        unix_socket("gh6035replica1"),      \
+    },                                      \
+    replication_synchro_quorum = 2,         \
+    election_mode = 'manual',               \
+}
+ | ---
+ | ...
+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 gh6035replica1.
+test_run:cmd('switch gh6035replica1')
+ | ---
+ | - true
+ | ...
+box.space.sync:select{}
+ | ---
+ | - - [1]
+ | ...
+
+-- And the second hop is gh6035replica2 where
+-- gh6035replica1 replicated the data to us.
+test_run:cmd('switch gh6035replica2')
+ | ---
+ | - true
+ | ...
+box.space.sync:select{}
+ | ---
+ | - - [1]
+ | ...
+
+test_run:cmd('switch default')
+ | ---
+ | - true
+ | ...
+test_run:cmd('stop server gh6035master')
+ | ---
+ | - true
+ | ...
+test_run:cmd('delete server gh6035master')
+ | ---
+ | - true
+ | ...
+test_run:cmd('stop server gh6035replica1')
+ | ---
+ | - true
+ | ...
+test_run:cmd('delete server gh6035replica1')
+ | ---
+ | - true
+ | ...
+test_run:cmd('stop server gh6035replica2')
+ | ---
+ | - true
+ | ...
+test_run:cmd('delete server gh6035replica2')
+ | ---
+ | - 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..280ae4bae
--- /dev/null
+++ b/test/replication/gh-6035-applier-filter.test.lua
@@ -0,0 +1,66 @@
+--
+-- 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).
+--
+
+local SOCKET_DIR = require('fio').cwd()
+local function unix_socket(name)                \
+    return SOCKET_DIR .. "/" .. name .. '.sock' \
+end
+
+env = require('test_run')
+test_run = env.new()
+engine = test_run:get_cfg('engine')
+
+test_run:cmd('create server gh6035master with script="replication/gh6035master.lua"')
+test_run:cmd('start server gh6035master with args="gh6035master"')
+
+test_run:cmd('create server gh6035replica1 with script="replication/gh6035replica1.lua"')
+test_run:cmd('start server gh6035replica1 with args="gh6035replica1"')
+
+test_run:cmd('create server gh6035replica2 with script="replication/gh6035replica2.lua"')
+test_run:cmd('start server gh6035replica2 with args="gh6035replica2"')
+
+--
+-- The gh6035master node connected to gh6035replica1 and gh6035replica2,
+-- where each of gh6035replicaX connected to the gh6035master only.
+--
+-- Lets reroute gh6035replica2 to gh6035replica1 so gh6035replica1 gonna
+-- be sending data to gh6035replica2 as a transit hop from gh6035master.
+test_run:cmd('switch gh6035replica2')
+box.cfg{replication = {unix_socket("gh6035replica1")}}
+
+--
+-- Make the gh6035master to be RAFT leader.
+test_run:cmd('switch gh6035master')
+box.cfg{                                    \
+    replication = {                         \
+        unix_socket("gh6035master"),        \
+        unix_socket("gh6035replica1"),      \
+    },                                      \
+    replication_synchro_quorum = 2,         \
+    election_mode = 'manual',               \
+}
+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 gh6035replica1.
+test_run:cmd('switch gh6035replica1')
+box.space.sync:select{}
+
+-- And the second hop is gh6035replica2 where
+-- gh6035replica1 replicated the data to us.
+test_run:cmd('switch gh6035replica2')
+box.space.sync:select{}
+
+test_run:cmd('switch default')
+test_run:cmd('stop server gh6035master')
+test_run:cmd('delete server gh6035master')
+test_run:cmd('stop server gh6035replica1')
+test_run:cmd('delete server gh6035replica1')
+test_run:cmd('stop server gh6035replica2')
+test_run:cmd('delete server gh6035replica2')
diff --git a/test/replication/gh6035master.lua b/test/replication/gh6035master.lua
new file mode 120000
index 000000000..43b20c2cc
--- /dev/null
+++ b/test/replication/gh6035master.lua
@@ -0,0 +1 @@
+gh6035node.lua
\ No newline at end of file
diff --git a/test/replication/gh6035node.lua b/test/replication/gh6035node.lua
new file mode 100644
index 000000000..2fb1ce86f
--- /dev/null
+++ b/test/replication/gh6035node.lua
@@ -0,0 +1,35 @@
+local SOCKET_DIR = require('fio').cwd()
+local node_name = arg[1]
+
+function unix_socket(name)
+    return SOCKET_DIR .. "/" .. name .. '.sock';
+end
+
+require('console').listen(os.getenv('ADMIN'))
+
+if node_name == "gh6035master" then
+    box.cfg({
+        listen = unix_socket("gh6035master"),
+    })
+elseif node_name == "gh6035replica1" then
+    box.cfg({
+        listen = unix_socket("gh6035replica1"),
+        replication = {
+            unix_socket("gh6035master"),
+            unix_socket("gh6035replica1")
+        },
+        election_mode = 'voter'
+    })
+else
+    assert(node_name == "gh6035replica2")
+    box.cfg({
+        replication = {
+            unix_socket("gh6035master"),
+        },
+        election_mode = 'voter'
+    })
+end
+
+box.once("bootstrap", function()
+    box.schema.user.grant('guest', 'super')
+end)
diff --git a/test/replication/gh6035replica1.lua b/test/replication/gh6035replica1.lua
new file mode 120000
index 000000000..43b20c2cc
--- /dev/null
+++ b/test/replication/gh6035replica1.lua
@@ -0,0 +1 @@
+gh6035node.lua
\ No newline at end of file
diff --git a/test/replication/gh6035replica2.lua b/test/replication/gh6035replica2.lua
new file mode 120000
index 000000000..43b20c2cc
--- /dev/null
+++ b/test/replication/gh6035replica2.lua
@@ -0,0 +1 @@
+gh6035node.lua
\ No newline at end of file
-- 
2.31.1