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foundationdb/fdbserver/CoordinatedState.actor.cpp

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/*
* CoordinatedState.actor.cpp
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "fdbserver/CoordinatedState.h"
#include "fdbserver/CoordinationInterface.h"
#include "fdbserver/Knobs.h"
#include "flow/ActorCollection.h"
#include "fdbserver/LeaderElection.h"
#include "flow/actorcompiler.h" // has to be last include
ACTOR Future<GenerationRegReadReply> waitAndSendRead( RequestStream<GenerationRegReadRequest> to, GenerationRegReadRequest req ) {
if( SERVER_KNOBS->BUGGIFY_ALL_COORDINATION || BUGGIFY )
wait( delay( SERVER_KNOBS->BUGGIFIED_EVENTUAL_CONSISTENCY*g_random->random01() ) );
state GenerationRegReadReply reply = wait( retryBrokenPromise( to, req ) );
if( SERVER_KNOBS->BUGGIFY_ALL_COORDINATION || BUGGIFY )
wait( delay( SERVER_KNOBS->BUGGIFIED_EVENTUAL_CONSISTENCY*g_random->random01() ) );
return reply;
}
ACTOR Future<UniqueGeneration> waitAndSendWrite(RequestStream<GenerationRegWriteRequest> to, GenerationRegWriteRequest req) {
if( SERVER_KNOBS->BUGGIFY_ALL_COORDINATION || BUGGIFY )
wait( delay( SERVER_KNOBS->BUGGIFIED_EVENTUAL_CONSISTENCY*g_random->random01() ) );
state UniqueGeneration reply = wait( retryBrokenPromise( to, req ) );
if( SERVER_KNOBS->BUGGIFY_ALL_COORDINATION || BUGGIFY )
wait( delay( SERVER_KNOBS->BUGGIFIED_EVENTUAL_CONSISTENCY*g_random->random01() ) );
return reply;
}
ACTOR Future<GenerationRegReadReply> emptyToNever( Future<GenerationRegReadReply> f ) {
state GenerationRegReadReply r = wait(f);
if (r.gen.generation == 0)
wait( Future<Void>(Never()) );
return r;
}
ACTOR Future<GenerationRegReadReply> nonemptyToNever( Future<GenerationRegReadReply> f ) {
state GenerationRegReadReply r = wait(f);
if (r.gen.generation != 0)
wait( Future<Void>(Never()) );
return r;
}
struct CoordinatedStateImpl {
ServerCoordinators coordinators;
int stage;
UniqueGeneration gen;
uint64_t conflictGen;
bool doomed;
ActorCollection ac; //Errors are not reported
bool initial;
CoordinatedStateImpl( ServerCoordinators const& c ) : coordinators(c), stage(0), conflictGen(0), doomed(false), ac(false), initial(false) {}
uint64_t getConflict() { return conflictGen; }
bool isDoomed( GenerationRegReadReply const& rep ) {
return rep.gen > gen // setExclusive is doomed, because there was a write at least started at a higher generation, which means a read completed at that higher generation
// || rep.rgen > gen // setExclusive isn't absolutely doomed, but it may/probably will fail
;
}
ACTOR static Future<Value> read( CoordinatedStateImpl* self ) {
ASSERT( self->stage == 0 );
{
self->stage = 1;
GenerationRegReadReply rep = wait( self->replicatedRead( self, GenerationRegReadRequest( self->coordinators.clusterKey, UniqueGeneration() ) ) );
self->conflictGen = std::max( self->conflictGen, std::max(rep.gen.generation, rep.rgen.generation) ) + 1;
self->gen = UniqueGeneration( self->conflictGen, g_random->randomUniqueID() );
}
{
self->stage = 2;
GenerationRegReadReply rep = wait( self->replicatedRead( self, GenerationRegReadRequest( self->coordinators.clusterKey, self->gen ) ) );
self->stage = 3;
self->conflictGen = std::max(self->conflictGen, std::max( rep.gen.generation, rep.rgen.generation ));
if (self->isDoomed(rep))
self->doomed = true;
self->initial = rep.gen.generation == 0;
self->stage = 4;
return rep.value.present() ? rep.value.get() : Value();
}
}
ACTOR static Future<Void> onConflict( CoordinatedStateImpl* self ) {
ASSERT( self->stage == 4 );
if (self->doomed) return Void();
loop {
wait( delay( SERVER_KNOBS->COORDINATED_STATE_ONCONFLICT_POLL_INTERVAL ) );
GenerationRegReadReply rep = wait( self->replicatedRead( self, GenerationRegReadRequest( self->coordinators.clusterKey, UniqueGeneration() ) ) );
if (self->stage > 4) break;
self->conflictGen = std::max(self->conflictGen, std::max( rep.gen.generation, rep.rgen.generation ));
if (self->isDoomed(rep))
return Void();
}
wait( Future<Void>(Never()) );
return Void();
}
ACTOR static Future<Void> setExclusive( CoordinatedStateImpl* self, Value v ) {
ASSERT( self->stage == 4 );
self->stage = 5;
UniqueGeneration wgen = wait( self->replicatedWrite( self, GenerationRegWriteRequest( KeyValueRef(self->coordinators.clusterKey, v), self->gen ) ) );
self->stage = 6;
TraceEvent("CoordinatedStateSet").detail("Gen", self->gen.generation).detail("Wgen", wgen.generation)
.detail("Genu", self->gen.uid).detail("Wgenu", wgen.uid)
.detail("Cgen", self->conflictGen);
if (wgen == self->gen)
return Void();
else {
self->conflictGen = std::max(self->conflictGen, wgen.generation);
throw coordinated_state_conflict();
}
}
ACTOR static Future<GenerationRegReadReply> replicatedRead( CoordinatedStateImpl* self, GenerationRegReadRequest req ) {
state std::vector<GenerationRegInterface> &replicas = self->coordinators.stateServers;
state vector< Future<GenerationRegReadReply> > rep_empty_reply;
state vector< Future<GenerationRegReadReply> > rep_reply;
for(int i=0; i<replicas.size(); i++) {
Future<GenerationRegReadReply> reply = waitAndSendRead( replicas[i].read, GenerationRegReadRequest(req.key, req.gen) );
rep_empty_reply.push_back( nonemptyToNever( reply ) );
rep_reply.push_back( emptyToNever( reply ) );
self->ac.add( success( reply ) );
}
state Future<Void> majorityEmpty = quorum( rep_empty_reply, (replicas.size()+1)/2 ); //enough empty to ensure we cannot achieve a majority non-empty
wait( quorum( rep_reply, replicas.size()/2 + 1 ) || majorityEmpty );
if( majorityEmpty.isReady() ) {
int best = -1;
for(int i=0; i<rep_empty_reply.size(); i++)
if (rep_empty_reply[i].isReady() && !rep_empty_reply[i].isError()) {
if (best < 0 || rep_empty_reply[i].get().rgen > rep_empty_reply[best].get().rgen )
best = i;
}
ASSERT( best >= 0 );
auto result = rep_empty_reply[best].get();
return result;
} else {
int best = -1;
for(int i=0; i<rep_reply.size(); i++)
if (rep_reply[i].isReady() && !rep_reply[i].isError()) {
if (best < 0 ||
rep_reply[i].get().gen > rep_reply[best].get().gen ||
( rep_reply[i].get().gen == rep_reply[best].get().gen && rep_reply[i].get().rgen > rep_reply[best].get().rgen ) )
best = i;
}
ASSERT( best >= 0 );
auto result = rep_reply[best].get();
return result;
}
}
ACTOR static Future<UniqueGeneration> replicatedWrite( CoordinatedStateImpl* self, GenerationRegWriteRequest req ) {
state std::vector<GenerationRegInterface> &replicas = self->coordinators.stateServers;
state vector< Future<UniqueGeneration> > wrep_reply;
for(int i=0; i<replicas.size(); i++) {
Future<UniqueGeneration> reply = waitAndSendWrite( replicas[i].write, GenerationRegWriteRequest( req.kv, req.gen ) );
wrep_reply.push_back( reply );
self->ac.add( success( reply ) );
}
wait( quorum( wrep_reply, self->initial ? replicas.size() : replicas.size()/2 + 1 ) );
UniqueGeneration maxGen;
for(int i=0; i<wrep_reply.size(); i++)
if (wrep_reply[i].isReady())
maxGen = std::max(maxGen, wrep_reply[i].get());
return maxGen;
}
};
CoordinatedState::CoordinatedState( ServerCoordinators const& coord ) : impl( new CoordinatedStateImpl(coord) ) { }
CoordinatedState::~CoordinatedState() { delete impl; }
Future<Value> CoordinatedState::read() { return CoordinatedStateImpl::read(impl); }
Future<Void> CoordinatedState::onConflict() { return CoordinatedStateImpl::onConflict(impl); }
Future<Void> CoordinatedState::setExclusive(Value v) { return CoordinatedStateImpl::setExclusive(impl,v); }
uint64_t CoordinatedState::getConflict() { return impl->getConflict(); }
struct MovableValue {
enum MoveState {
MaybeTo = 1,
Active = 2,
MovingFrom = 3
};
Value value;
int32_t mode;
Optional<Value> other; // a cluster connection string
MovableValue() : mode( Active ) {}
MovableValue( Value const& v, int mode, Optional<Value> other = Optional<Value>() ) : value( v ), mode( mode ), other( other ) {}
template <class Ar>
void serialize(Ar& ar) {
ASSERT( ar.protocolVersion() >= 0x0FDB00A2000D0001LL );
serializer(ar, value, mode, other);
}
};
struct MovableCoordinatedStateImpl {
ServerCoordinators coordinators;
CoordinatedState cs;
Optional<Value> lastValue, // The value passed to setExclusive()
lastCSValue; // The value passed to cs.setExclusive()
MovableCoordinatedStateImpl( ServerCoordinators const& c ) : coordinators(c), cs(c) {}
ACTOR static Future<Value> read( MovableCoordinatedStateImpl* self ) {
state MovableValue moveState;
Value rawValue = wait( self->cs.read() );
if( rawValue.size() ) {
BinaryReader r( rawValue, IncludeVersion() );
if (r.protocolVersion() < 0x0FDB00A2000D0001LL) {
// Old coordinated state, not a MovableValue
moveState.value = rawValue;
} else
r >> moveState;
}
// SOMEDAY: If moveState.mode == MovingFrom, read (without locking) old state and assert that it corresponds with our state and is ReallyTo(coordinators)
if (moveState.mode == MovableValue::MaybeTo) {
TEST(true);
ASSERT( moveState.other.present() );
wait( self->moveTo( self, &self->cs, ClusterConnectionString( moveState.other.get().toString() ), moveState.value ) );
}
return moveState.value;
}
Future<Void> onConflict() {
return cs.onConflict();
}
Future<Void> setExclusive( Value v ) {
lastValue=v;
lastCSValue=BinaryWriter::toValue( MovableValue( v, MovableValue::Active ), IncludeVersion() );
return cs.setExclusive( lastCSValue.get() );
}
ACTOR static Future<Void> move( MovableCoordinatedStateImpl* self, ClusterConnectionString nc ) {
// Call only after setExclusive returns. Attempts to move the coordinated state
// permanently to the new ServerCoordinators, which must be uninitialized. Returns when the process has
// reached the point where a leader elected by the new coordinators should be doing the rest of the work
// (and therefore the caller should die).
state CoordinatedState cs( self->coordinators );
state CoordinatedState nccs( ServerCoordinators( Reference<ClusterConnectionFile>( new ClusterConnectionFile(nc) ) ) );
state Future<Void> creationTimeout = delay(30);
ASSERT( self->lastValue.present() && self->lastCSValue.present() );
TraceEvent("StartMove").detail("ConnectionString", nc.toString() );
choose {
when (wait(creationTimeout)) { throw new_coordinators_timed_out(); }
when (Value ncInitialValue = wait( nccs.read() )) {
ASSERT( !ncInitialValue.size() ); // The new coordinators must be uninitialized!
}
}
TraceEvent("FinishedRead").detail("ConnectionString", nc.toString() );
choose {
when (wait(creationTimeout)) { throw new_coordinators_timed_out(); }
when ( wait( nccs.setExclusive( BinaryWriter::toValue( MovableValue( self->lastValue.get(), MovableValue::MovingFrom, self->coordinators.ccf->getConnectionString().toString() ), IncludeVersion() ) ) ) ) {}
}
if (BUGGIFY) wait(delay(5));
Value oldQuorumState = wait( cs.read() );
if ( oldQuorumState != self->lastCSValue.get() ) {
TEST(true); // Quorum change aborted by concurrent write to old coordination state
TraceEvent("QuorumChangeAbortedByConcurrency");
throw coordinated_state_conflict();
}
wait( self->moveTo( self, &cs, nc, self->lastValue.get() ) );
throw coordinators_changed();
}
ACTOR static Future<Void> moveTo( MovableCoordinatedStateImpl* self, CoordinatedState* coordinatedState, ClusterConnectionString nc, Value value ) {
wait( coordinatedState->setExclusive( BinaryWriter::toValue( MovableValue( value, MovableValue::MaybeTo, nc.toString() ), IncludeVersion() ) ) );
if (BUGGIFY) wait( delay(5) );
// SOMEDAY: If we are worried about someone magically getting the new cluster ID and interfering, do a second cs.setExclusive( encode( ReallyTo, ... ) )
TraceEvent("ChangingQuorum").detail("ConnectionString", nc.toString());
wait( changeLeaderCoordinators( self->coordinators, StringRef(nc.toString()) ) );
TraceEvent("ChangedQuorum").detail("ConnectionString", nc.toString());
throw coordinators_changed();
}
};
void MovableCoordinatedState::operator=(MovableCoordinatedState&& av) {
if(impl) {
delete impl;
}
impl = av.impl;
av.impl = 0;
}
MovableCoordinatedState::MovableCoordinatedState( class ServerCoordinators const& coord ) : impl( new MovableCoordinatedStateImpl(coord) ) {}
MovableCoordinatedState::~MovableCoordinatedState() {
if(impl) {
delete impl;
}
}
Future<Value> MovableCoordinatedState::read() { return MovableCoordinatedStateImpl::read(impl); }
Future<Void> MovableCoordinatedState::onConflict() { return impl->onConflict(); }
Future<Void> MovableCoordinatedState::setExclusive(Value v) { return impl->setExclusive(v); }
Future<Void> MovableCoordinatedState::move( ClusterConnectionString const& nc ) { return MovableCoordinatedStateImpl::move(impl, nc); }
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