[Tarantool-patches] [PATCH v3 08/10] Support manual elections in `box.ctl.clear_synchro_queue()`
Serge Petrenko
sergepetrenko at tarantool.org
Fri Apr 16 18:40:04 MSK 2021
16.04.2021 18:38, Serge Petrenko via Tarantool-patches пишет:
>
>
> 16.04.2021 02:30, Vladislav Shpilevoy пишет:
>>> diff --git a/src/box/raft.h b/src/box/raft.h
>>> index 15f4e80d9..8fce423e1 100644
>>> --- a/src/box/raft.h
>>> +++ b/src/box/raft.h
>>> @@ -97,6 +97,9 @@ box_raft_checkpoint_remote(struct raft_request *req);
>>> int
>>> box_raft_process(struct raft_request *req, uint32_t source);
>>> +void
>>> +box_raft_wait_leader_found();
>>> +
>>> void
>>> box_raft_init(void);
>>> diff --git a/src/lib/raft/raft.c b/src/lib/raft/raft.c
>>> index e9ce8cade..7b77e05ea 100644
>>> --- a/src/lib/raft/raft.c
>>> +++ b/src/lib/raft/raft.c
>>> @@ -846,7 +846,7 @@ raft_cfg_is_enabled(struct raft *raft, bool
>>> is_enabled)
>>> }
>>> void
>>> -raft_cfg_is_candidate(struct raft *raft, bool is_candidate)
>>> +raft_cfg_is_candidate(struct raft *raft, bool is_candidate, bool
>>> demote)
>> 5. I know it might lead to some code duplication, but probably
>> better move that to other functions. For example,
>>
>> raft_cfg_is_temporary_candidate()
>>
>> or something like that. Otherwise it appears surprisingly hard
>> to follow these 2 flags together. Although I might be wrong and
>> it would look worse. Did you try?
>>
>> Or another option:
>>
>> raft_cfg_is_candidate(box_raft(), true, false);
>> raft_cfg_is_candidate(box_raft(), false, false);
>>
>> turns into
>>
>> raft_start_candidate(box_raft())
>> raft_stop_candidate(box_raft())
>>
>> Also it would be good to have unit tests for the changes in raft.h
>> and raft.c.
>
> This variant sounds good. I'll implement in in a new commit.
The commit I was talking about:
=====================================================
commit 79940c7b20a4acefaa5984550fee2872a58fef0c
Author: Serge Petrenko <sergepetrenko at tarantool.org>
Date: Fri Apr 16 18:22:28 2021 +0300
raft: introduce raft_start/stop_candidate
Extract raft_start_candidate and raft_stop_candidate functions from
raft_cfg_is_candidate.
These functions will be used in manual elections.
Prerequisite #3055
diff --git a/src/lib/raft/raft.c b/src/lib/raft/raft.c
index e9ce8cade..8deb06eb5 100644
--- a/src/lib/raft/raft.c
+++ b/src/lib/raft/raft.c
@@ -848,38 +848,59 @@ raft_cfg_is_enabled(struct raft *raft, bool
is_enabled)
void
raft_cfg_is_candidate(struct raft *raft, bool is_candidate)
{
- bool old_is_candidate = raft->is_candidate;
raft->is_cfg_candidate = is_candidate;
- raft->is_candidate = is_candidate && raft->is_enabled;
- if (raft->is_candidate == old_is_candidate)
- return;
+ is_candidate = is_candidate && raft->is_enabled;
+ if (is_candidate)
+ raft_start_candidate(raft);
+ else
+ raft_stop_candidate(raft, true);
+}
- if (raft->is_candidate) {
- assert(raft->state == RAFT_STATE_FOLLOWER);
- if (raft->is_write_in_progress) {
- /*
- * If there is an on-going WAL write, it means there was
- * some node who sent newer data to this node. So it is
- * probably a better candidate. Anyway can't do anything
- * until the new state is fully persisted.
- */
- } else if (raft->leader != 0) {
- raft_sm_wait_leader_dead(raft);
- } else {
- raft_sm_wait_leader_found(raft);
- }
+void
+raft_start_candidate(struct raft *raft)
+{
+ if (raft->is_candidate)
+ return;
+ raft->is_candidate = true;
+ assert(raft->state == RAFT_STATE_FOLLOWER);
+ if (raft->is_write_in_progress) {
+ /*
+ * If there is an on-going WAL write, it means there was
+ * some node who sent newer data to this node. So it is
+ * probably a better candidate. Anyway can't do anything
+ * until the new state is fully persisted.
+ */
+ } else if (raft->leader != 0) {
+ raft_sm_wait_leader_dead(raft);
} else {
- if (raft->state != RAFT_STATE_LEADER) {
- /* Do not wait for anything while being a voter. */
- raft_ev_timer_stop(raft_loop(), &raft->timer);
- }
- if (raft->state != RAFT_STATE_FOLLOWER) {
- if (raft->state == RAFT_STATE_LEADER)
- raft->leader = 0;
- raft->state = RAFT_STATE_FOLLOWER;
- /* State is visible and changed - broadcast. */
- raft_schedule_broadcast(raft);
+ raft_sm_wait_leader_found(raft);
+ }
+}
+
+void
+raft_stop_candidate(struct raft *raft, bool demote)
+{
+ if (!raft->is_candidate)
+ return;
+ raft->is_candidate = false;
+ if (raft->state != RAFT_STATE_LEADER) {
+ /* Do not wait for anything while being a voter. */
+ raft_ev_timer_stop(raft_loop(), &raft->timer);
+ }
+ if (raft->state != RAFT_STATE_FOLLOWER) {
+ if (raft->state == RAFT_STATE_LEADER) {
+ if (!demote) {
+ /*
+ * Remain leader until someone
+ * triggers new elections.
+ */
+ return;
+ }
+ raft->leader = 0;
}
+ raft->state = RAFT_STATE_FOLLOWER;
+ /* State is visible and changed - broadcast. */
+ raft_schedule_broadcast(raft);
}
}
diff --git a/src/lib/raft/raft.h b/src/lib/raft/raft.h
index a5f7e08d9..69dec63c6 100644
--- a/src/lib/raft/raft.h
+++ b/src/lib/raft/raft.h
@@ -327,6 +327,19 @@ raft_cfg_is_enabled(struct raft *raft, bool
is_enabled);
void
raft_cfg_is_candidate(struct raft *raft, bool is_candidate);
+/**
+ * Make the instance a candidate.
+ */
+void
+raft_start_candidate(struct raft *raft);
+
+/**
+ * Make the instance stop taking part in new elections.
+ * @param demote whether to stop being a leader immediately or not.
+ */
+void
+raft_stop_candidate(struct raft *raft, bool demote);
+
/** Configure Raft leader election timeout. */
void
raft_cfg_election_timeout(struct raft *raft, double timeout);
diff --git a/test/unit/raft.c b/test/unit/raft.c
index 0306cefcd..575886932 100644
--- a/test/unit/raft.c
+++ b/test/unit/raft.c
@@ -1296,15 +1296,43 @@ raft_test_term_filter(void)
ok(!raft_is_node_outdated(&node.raft, 3), "node doesn't become "
"outdated");
-
raft_node_destroy(&node);
raft_finish_test();
}
+static void
+raft_test_start_stop_candidate(void)
+{
+ raft_start_test(4);
+ struct raft_node node;
+ raft_node_create(&node);
+
+ raft_node_cfg_is_candidate(&node, false);
+ raft_node_cfg_election_quorum(&node, 1);
+
+ raft_start_candidate(&node.raft);
+ raft_run_next_event();
+ is(node.raft.state, RAFT_STATE_LEADER, "became leader after "
+ "start_candidate");
+ raft_stop_candidate(&node.raft, false);
+ raft_run_for(node.cfg_death_timeout);
+ is(node.raft.state, RAFT_STATE_LEADER, "remain leader after "
+ "stop_candidate");
+
+ is(raft_node_send_vote_request(&node,
+ 3 /* Term. */,
+ "{}" /* Vclock. */,
+ 2 /* Source. */
+ ), 0, "vote request from 2");
+ is(node.raft.state, RAFT_STATE_FOLLOWER, "demote once new election "
+ "starts");
+ raft_finish_test();
+}
+
static int
main_f(va_list ap)
{
- raft_start_test(14);
+ raft_start_test(15);
(void) ap;
fakeev_init();
@@ -1323,6 +1351,7 @@ main_f(va_list ap)
raft_test_enable_disable();
raft_test_too_long_wal_write();
raft_test_term_filter();
+ raft_test_start_stop_candidate();
fakeev_free();
diff --git a/test/unit/raft.result b/test/unit/raft.result
index ecb962e42..bb799936b 100644
--- a/test/unit/raft.result
+++ b/test/unit/raft.result
@@ -1,5 +1,5 @@
*** main_f ***
-1..14
+1..15
*** raft_test_leader_election ***
1..24
ok 1 - 1 pending message at start
@@ -233,4 +233,12 @@ ok 13 - subtests
ok 9 - node doesn't become outdated
ok 14 - subtests
*** raft_test_term_filter: done ***
+ *** raft_test_start_stop_candidate ***
+ 1..4
+ ok 1 - became leader after start_candidate
+ ok 2 - remain leader after stop_candidate
+ ok 3 - vote request from 2
+ ok 4 - demote once new election starts
+ok 15 - subtests
+ *** raft_test_start_stop_candidate: done ***
*** main_f: done ***
--
Serge Petrenko
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