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Mar 3, 2025
Merged

handle follower dying while being promoted to leader #15134

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893d5ae
handle follower dying while being promoted to leader
vporyadke Feb 27, 2025
e47265f
code review
vporyadke Mar 3, 2025
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58 changes: 40 additions & 18 deletions ydb/core/mind/hive/hive_ut.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3363,7 +3363,7 @@ Y_UNIT_TEST_SUITE(THiveTest) {
}
}

Y_UNIT_TEST(TestFollowerPromotion) {
void TestFollowerPromotion(bool killDuringPromotion) {
constexpr int NODES = 3;
TTestBasicRuntime runtime(NODES, false);
Setup(runtime, true);
Expand Down Expand Up @@ -3394,30 +3394,42 @@ Y_UNIT_TEST_SUITE(THiveTest) {
MakeSureTabletIsUp(runtime, tabletId, i, &pipeConfig, &tabletRolesBefore[i]);
}
int leaders = std::accumulate(tabletRolesBefore.begin(), tabletRolesBefore.end(), 0, [](int a, bool b) -> int { return b ? a + 1 : a; });
UNIT_ASSERT_VALUES_EQUAL(leaders, 1);
int leaderNode = std::find(tabletRolesBefore.begin(), tabletRolesBefore.end(), true) - tabletRolesBefore.begin();
// killing leader
SendKillLocal(runtime, leaderNode);
UNIT_ASSERT_VALUES_EQUAL(leaders, 1);
{
TDispatchOptions options;
options.FinalEvents.emplace_back(TEvLocal::EvTabletStatus);
runtime.DispatchEvents(options);
}
std::array<bool, NODES> tabletRolesIntermediate = {};
for (int i = 0; i < NODES; ++i) {
if (i != leaderNode) {
MakeSureTabletIsUp(runtime, tabletId, i, &pipeConfig, &tabletRolesIntermediate[i]);
} else {
tabletRolesIntermediate[i] = false;
TBlockEvents<TEvTablet::TEvPromoteToLeader> blockPromote(runtime);
// killing leader
SendKillLocal(runtime, leaderNode);

while (blockPromote.empty()) {
runtime.DispatchEvents({}, TDuration::MilliSeconds(100));
}

if (killDuringPromotion) {
for (int i = 0; i < NODES; ++i) {
if (i == leaderNode) {
continue;
}
TActorId sender = runtime.AllocateEdgeActor(i);
runtime.SendToPipe(tabletId, sender, new TEvents::TEvPoisonPill, i, pipeConfig);
}
}

runtime.DispatchEvents({}, TDuration::MilliSeconds(100));

blockPromote.Stop().Unblock();
}
{
TDispatchOptions options;
options.FinalEvents.emplace_back(TEvLocal::EvTabletStatus, killDuringPromotion ? 3 : 1);
runtime.DispatchEvents(options, TDuration::MilliSeconds(100));
}
leaders = std::accumulate(tabletRolesIntermediate.begin(), tabletRolesIntermediate.end(), 0, [](int a, bool b) -> int { return b ? a + 1 : a; });
int followers = std::accumulate(tabletRolesIntermediate.begin(), tabletRolesIntermediate.end(), 0, [](int a, bool b) -> int { return b ? a : a + 1; });
UNIT_ASSERT_VALUES_EQUAL(leaders, 1);
UNIT_ASSERT_VALUES_EQUAL(followers, 2);
std::unordered_set<std::pair<TTabletId, TFollowerId>> activeTablets;
TActorId senderA = runtime.AllocateEdgeActor();
for (int i = 0; i < NODES; ++i) {
if (i == leaderNode) {
continue;
}
TActorId whiteboard = NNodeWhiteboard::MakeNodeWhiteboardServiceId(runtime.GetNodeId(i));
runtime.Send(new IEventHandle(whiteboard, senderA, new NNodeWhiteboard::TEvWhiteboard::TEvTabletStateRequest()));
TAutoPtr<IEventHandle> handle;
Expand All @@ -3432,6 +3444,16 @@ Y_UNIT_TEST_SUITE(THiveTest) {
}
}
UNIT_ASSERT_VALUES_EQUAL(activeTablets.size(), 3);
leaders = std::count_if(activeTablets.begin(), activeTablets.end(), [](auto&& p) { return p.second == 0; });
UNIT_ASSERT_VALUES_EQUAL(leaders, 1);
}

Y_UNIT_TEST(TestFollowerPromotion) {
TestFollowerPromotion(false);
}

Y_UNIT_TEST(TestFollowerPromotionFollowerDies) {
TestFollowerPromotion(true);
}

Y_UNIT_TEST(TestManyFollowersOnOneNode) {
Expand Down
50 changes: 37 additions & 13 deletions ydb/core/mind/local.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -52,19 +52,19 @@ class TLocalNodeRegistrar : public TActorBootstrapped<TLocalNodeRegistrar> {
ui32 Generation;
TTabletTypes::EType TabletType;
NKikimrLocal::EBootMode BootMode;
ui32 FollowerId;

TTablet()
: Tablet()
, Generation(0)
, TabletType()
, BootMode(NKikimrLocal::EBootMode::BOOT_MODE_LEADER)
, FollowerId(0)
{}
};

struct TTabletEntry : TTablet {
TInstant From;
bool IsPromoting = false;
ui32 PromotingFromFollower = 0;

TTabletEntry()
: From(TInstant::MicroSeconds(0))
Expand Down Expand Up @@ -141,6 +141,10 @@ class TLocalNodeRegistrar : public TActorBootstrapped<TLocalNodeRegistrar> {
::NMonitoring::TDynamicCounters::TCounterPtr CounterCancelDemotedByBS;
::NMonitoring::TDynamicCounters::TCounterPtr CounterCancelUnknownReason;

static TTabletId LeaderId(TTabletId tabletId) {
return {tabletId.first, 0};
}

void Die(const TActorContext &ctx) override {
if (HivePipeClient) {
if (Connected) {
Expand Down Expand Up @@ -385,6 +389,24 @@ class TLocalNodeRegistrar : public TActorBootstrapped<TLocalNodeRegistrar> {
ScheduleSendTabletMetrics(ctx);
}

void StartPromotion(TTabletId tabletId, TOnlineTabletEntry& followerEntry, ui32 suggestedGen, TInstant now) {
TTabletId leaderId = LeaderId(tabletId);
TTabletEntry& leaderEntry = InbootTablets[leaderId];
followerEntry.IsPromoting = true;
leaderEntry = followerEntry;
leaderEntry.From = now;
leaderEntry.BootMode = NKikimrLocal::EBootMode::BOOT_MODE_LEADER;
leaderEntry.Generation = suggestedGen;
leaderEntry.PromotingFromFollower = tabletId.second;
}

void FinishPromotion(TTabletId tabletId, TTabletEntry& entry) {
TTabletId promotedTablet{tabletId.first, entry.PromotingFromFollower};
OnlineTablets.erase(promotedTablet);
entry.IsPromoting = false;
entry.PromotingFromFollower = 0;
}

void Handle(TEvLocal::TEvBootTablet::TPtr &ev, const TActorContext &ctx) {
NKikimrLocal::TEvBootTablet &record = ev->Get()->Record;
TIntrusivePtr<TTabletStorageInfo> info(TabletStorageInfoFromProto(record.GetInfo()));
Expand Down Expand Up @@ -427,18 +449,9 @@ class TLocalNodeRegistrar : public TActorBootstrapped<TLocalNodeRegistrar> {
if (it != OnlineTablets.end()) {
if (it->second.BootMode == NKikimrLocal::EBootMode::BOOT_MODE_FOLLOWER
&& record.GetBootMode() == NKikimrLocal::EBootMode::BOOT_MODE_LEADER) {
// promote to leader
it->second.BootMode = NKikimrLocal::EBootMode::BOOT_MODE_LEADER;
it->second.Generation = suggestedGen;
tabletId.second = 0; // FollowerId = 0
TTabletEntry &entry = InbootTablets[tabletId];
entry = it->second;
entry.From = ctx.Now();
entry.BootMode = NKikimrLocal::EBootMode::BOOT_MODE_LEADER;
entry.Generation = suggestedGen;
ctx.Send(entry.Tablet, new TEvTablet::TEvPromoteToLeader(suggestedGen, info));
StartPromotion(tabletId, it->second, suggestedGen, ctx.Now());
ctx.Send(it->second.Tablet, new TEvTablet::TEvPromoteToLeader(suggestedGen, info));
MarkDeadTablet(it->first, 0, TEvLocal::TEvTabletStatus::StatusSupersededByLeader, TEvTablet::TEvTabletDead::ReasonError, ctx);
OnlineTablets.erase(it);
LOG_DEBUG_S(ctx, NKikimrServices::LOCAL,
"TLocalNodeRegistrar::Handle TEvLocal::TEvBootTablet follower tablet " << tabletId << " promoted to leader");
return;
Expand Down Expand Up @@ -718,6 +731,9 @@ class TLocalNodeRegistrar : public TActorBootstrapped<TLocalNodeRegistrar> {
<< " marked as running at generation "
<< generation);
NTabletPipe::SendData(ctx, HivePipeClient, new TEvLocal::TEvTabletStatus(TEvLocal::TEvTabletStatus::StatusOk, tabletId, generation));
if (inbootIt->second.IsPromoting) {
FinishPromotion(tabletId, inbootIt->second);
}
OnlineTablets.emplace(tabletId, inbootIt->second);
InbootTablets.erase(inbootIt);
}
Expand Down Expand Up @@ -818,6 +834,14 @@ class TLocalNodeRegistrar : public TActorBootstrapped<TLocalNodeRegistrar> {
});
if (onlineIt != OnlineTablets.end()) { // from online list
MarkDeadTablet(onlineIt->first, generation, TEvLocal::TEvTabletStatus::StatusFailed, msg->Reason, ctx);
if (onlineIt->second.IsPromoting) {
TTabletId leader = LeaderId(onlineIt->first);
auto inbootIt = InbootTablets.find(leader);
if (inbootIt != InbootTablets.end()) {
MarkDeadTablet(leader, inbootIt->second.Generation, TEvLocal::TEvTabletStatus::StatusFailed, msg->Reason, ctx);
}
InbootTablets.erase(inbootIt);
}
OnlineTablets.erase(onlineIt);
UpdateEstimate();
return;
Expand Down
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