[Tarantool-patches] [PATCH v2 4/5] election: during bootstrap prefer candidates
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Sun Jul 18 19:53:28 MSK 2021
During cluster bootstrap the boot master election algorithm didn't
take into account election modes of the instances. It could be
that all nodes have box.cfg.read_only = false, none is booted,
all are read-only now. Then the node with the smallest UUID was
chosen even if it was a box.cfg.election_mode='voter' node.
It could neither boot nor register other nodes and the cluster
couldn't start.
The patch makes the boot master election prefer the instances
which can become a Raft leader. If all the other parameters didn't
help.
Part #6018
---
src/box/replication.cc | 11 ++-
.../gh-6018-election-boot-voter.result | 70 +++++++++++++++++++
.../gh-6018-election-boot-voter.test.lua | 38 ++++++++++
test/replication/gh-6018-master.lua | 17 +++++
test/replication/gh-6018-replica.lua | 15 ++++
test/replication/suite.cfg | 1 +
6 files changed, 150 insertions(+), 2 deletions(-)
create mode 100644 test/replication/gh-6018-election-boot-voter.result
create mode 100644 test/replication/gh-6018-election-boot-voter.test.lua
create mode 100644 test/replication/gh-6018-master.lua
create mode 100644 test/replication/gh-6018-replica.lua
diff --git a/src/box/replication.cc b/src/box/replication.cc
index a0b3e0186..45ad03dfd 100644
--- a/src/box/replication.cc
+++ b/src/box/replication.cc
@@ -978,12 +978,19 @@ replicaset_find_join_master(void)
* config is stronger because if it is configured as read-only,
* it is in read-only state for sure, until the config is
* changed.
+ *
+ * In a cluster with leader election enabled all instances might
+ * look equal by the scores above. Then must prefer the ones
+ * which can be elected as a leader, because only they would be
+ * able to boot themselves and register the others.
*/
if (ballot->is_booted)
- score += 10;
+ score += 1000;
if (!ballot->is_ro_cfg)
- score += 5;
+ score += 100;
if (!ballot->is_ro)
+ score += 10;
+ if (ballot->can_lead)
score += 1;
if (leader_score < score)
goto elect;
diff --git a/test/replication/gh-6018-election-boot-voter.result b/test/replication/gh-6018-election-boot-voter.result
new file mode 100644
index 000000000..6b05f0825
--- /dev/null
+++ b/test/replication/gh-6018-election-boot-voter.result
@@ -0,0 +1,70 @@
+-- test-run result file version 2
+--
+-- gh-6018: in an auto-election cluster nodes with voter state could be selected
+-- as bootstrap leaders. They should not, because a voter can't be ever writable
+-- and it can neither boot itself nor register other nodes.
+--
+test_run = require('test_run').new()
+ | ---
+ | ...
+
+function boot_with_master_election_mode(mode) \
+ test_run:cmd('create server master with '.. \
+ 'script="replication/gh-6018-master.lua"') \
+ test_run:cmd('start server master with wait=False, args="'..mode..'"') \
+ test_run:cmd('create server replica with '.. \
+ 'script="replication/gh-6018-replica.lua"') \
+ test_run:cmd('start server replica') \
+end
+ | ---
+ | ...
+
+function stop_cluster() \
+ test_run:cmd('stop server replica') \
+ test_run:cmd('stop server master') \
+ test_run:cmd('delete server replica') \
+ test_run:cmd('delete server master') \
+end
+ | ---
+ | ...
+
+--
+-- Candidate leader.
+--
+boot_with_master_election_mode('candidate')
+ | ---
+ | ...
+
+test_run:switch('master')
+ | ---
+ | - true
+ | ...
+test_run:wait_cond(function() return not box.info.ro end)
+ | ---
+ | - true
+ | ...
+assert(box.info.election.state == 'leader')
+ | ---
+ | - true
+ | ...
+
+test_run:switch('replica')
+ | ---
+ | - true
+ | ...
+assert(box.info.ro)
+ | ---
+ | - true
+ | ...
+assert(box.info.election.state == 'follower')
+ | ---
+ | - true
+ | ...
+
+test_run:switch('default')
+ | ---
+ | - true
+ | ...
+stop_cluster()
+ | ---
+ | ...
diff --git a/test/replication/gh-6018-election-boot-voter.test.lua b/test/replication/gh-6018-election-boot-voter.test.lua
new file mode 100644
index 000000000..7222beb19
--- /dev/null
+++ b/test/replication/gh-6018-election-boot-voter.test.lua
@@ -0,0 +1,38 @@
+--
+-- gh-6018: in an auto-election cluster nodes with voter state could be selected
+-- as bootstrap leaders. They should not, because a voter can't be ever writable
+-- and it can neither boot itself nor register other nodes.
+--
+test_run = require('test_run').new()
+
+function boot_with_master_election_mode(mode) \
+ test_run:cmd('create server master with '.. \
+ 'script="replication/gh-6018-master.lua"') \
+ test_run:cmd('start server master with wait=False, args="'..mode..'"') \
+ test_run:cmd('create server replica with '.. \
+ 'script="replication/gh-6018-replica.lua"') \
+ test_run:cmd('start server replica') \
+end
+
+function stop_cluster() \
+ test_run:cmd('stop server replica') \
+ test_run:cmd('stop server master') \
+ test_run:cmd('delete server replica') \
+ test_run:cmd('delete server master') \
+end
+
+--
+-- Candidate leader.
+--
+boot_with_master_election_mode('candidate')
+
+test_run:switch('master')
+test_run:wait_cond(function() return not box.info.ro end)
+assert(box.info.election.state == 'leader')
+
+test_run:switch('replica')
+assert(box.info.ro)
+assert(box.info.election.state == 'follower')
+
+test_run:switch('default')
+stop_cluster()
diff --git a/test/replication/gh-6018-master.lua b/test/replication/gh-6018-master.lua
new file mode 100644
index 000000000..1192204ff
--- /dev/null
+++ b/test/replication/gh-6018-master.lua
@@ -0,0 +1,17 @@
+#!/usr/bin/env tarantool
+
+require('console').listen(os.getenv('ADMIN'))
+
+box.cfg({
+ listen = 'unix/:./gh-6018-master.sock',
+ replication = {
+ 'unix/:./gh-6018-master.sock',
+ 'unix/:./gh-6018-replica.sock',
+ },
+ election_mode = arg[1],
+ instance_uuid = 'cbf06940-0790-498b-948d-042b62cf3d29',
+ replication_timeout = 0.1,
+})
+
+box.ctl.wait_rw()
+box.schema.user.grant('guest', 'super')
diff --git a/test/replication/gh-6018-replica.lua b/test/replication/gh-6018-replica.lua
new file mode 100644
index 000000000..71e669141
--- /dev/null
+++ b/test/replication/gh-6018-replica.lua
@@ -0,0 +1,15 @@
+#!/usr/bin/env tarantool
+
+require('console').listen(os.getenv('ADMIN'))
+
+box.cfg({
+ listen = 'unix/:./gh-6018-replica.sock',
+ replication = {
+ 'unix/:./gh-6018-master.sock',
+ 'unix/:./gh-6018-replica.sock',
+ },
+ election_mode = 'voter',
+ -- Smaller than master UUID.
+ instance_uuid = 'cbf06940-0790-498b-948d-042b62cf3d28',
+ replication_timeout = 0.1,
+})
diff --git a/test/replication/suite.cfg b/test/replication/suite.cfg
index 69f2f3511..2bfc3b845 100644
--- a/test/replication/suite.cfg
+++ b/test/replication/suite.cfg
@@ -45,6 +45,7 @@
"gh-5536-wal-limit.test.lua": {},
"gh-5566-final-join-synchro.test.lua": {},
"gh-5613-bootstrap-prefer-booted.test.lua": {},
+ "gh-6018-election-boot-voter.test.lua": {},
"gh-6027-applier-error-show.test.lua": {},
"gh-6032-promote-wal-write.test.lua": {},
"gh-6057-qsync-confirm-async-no-wal.test.lua": {},
--
2.24.3 (Apple Git-128)
More information about the Tarantool-patches
mailing list