foundationdb/fdbserver/CoordinationInterface.h

/*
 * CoordinationInterface.h
 *
 * 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.
 */

#ifndef FDBSERVER_COORDINATIONINTERFACE_H
#define FDBSERVER_COORDINATIONINTERFACE_H
#pragma once

#include "fdbclient/CoordinationInterface.h"

struct GenerationRegInterface {
	RequestStream< struct GenerationRegReadRequest > read;
	RequestStream< struct GenerationRegWriteRequest > write;

	// read(key,gen2) returns (value,gen,rgen).
	//   If there was no prior write(_,_,0) or a data loss fault, 
	//     returns (Optional(),0,0)   //< FIXME: The returned rgen is not zero, but >= gen2!  (Specification bug)
	//   Else
	//     There was some earlier or concurrent write(key,value,gen).
	//     There was some earlier or concurrent read(key,rgen).
	//     If there is a write(key,_,gen1)=>gen1 s.t. gen1 < gen2 OR the write completed before this read started, then gen >= gen1.
	//     If there is a read(key,gen1) that completed before this read started, then rgen >= gen1
	// write(key,value,gen) returns gen1.
	//   If gen>0 and there was no prior write(_,_,0) or a data loss fault, throws not_created()?
	//   (gen1==gen is considered a "successful" write)
	//   There is some earlier or concurrent read(key,gen1) or write(key,_,gen1).  (In the successful case, the concurrent write is this one)
	
	// All instances of the pattern
	//    read(key, g)=>v1 and write(key, v2, g)=>true
	// thus form a totally ordered sequence of modifications, in which
	// the v2 of the previous generation is the v1 of the next.

	GenerationRegInterface() {}
	GenerationRegInterface( NetworkAddress remote );
	GenerationRegInterface( INetwork* local );
};

struct UniqueGeneration {
	uint64_t generation;
	UID uid;
	UniqueGeneration() : generation(0) {}
	UniqueGeneration( uint64_t generation, UID uid ) : generation(generation), uid(uid) {}
	bool operator < (UniqueGeneration const& r) const {
		if (generation < r.generation) return true;
		if (r.generation < generation) return false;
		return uid < r.uid;
	}
	bool operator == (UniqueGeneration const& r) const {
		return generation == r.generation && uid == r.uid;
	}
	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, generation, uid);
	}
};

struct GenerationRegReadRequest {
	Key key;
	UniqueGeneration gen;
	ReplyPromise<struct GenerationRegReadReply> reply;
	GenerationRegReadRequest(){}
	GenerationRegReadRequest( Key key, UniqueGeneration gen ) : key(key), gen(gen) {}
	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, key, gen, reply);
	}
};

struct GenerationRegReadReply {
	Optional<Value> value;
	UniqueGeneration gen, rgen;
	GenerationRegReadReply() {}
	GenerationRegReadReply( Optional<Value> value, UniqueGeneration gen, UniqueGeneration rgen ) : value(value), gen(gen), rgen(rgen) {}
	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, value, gen, rgen);
	}
};

struct GenerationRegWriteRequest {
	KeyValue kv;
	UniqueGeneration gen;
	ReplyPromise< UniqueGeneration > reply;
	GenerationRegWriteRequest() {}
	GenerationRegWriteRequest(KeyValue kv, UniqueGeneration gen) : kv(kv), gen(gen) {}
	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, kv, gen, reply);
	}
};

struct LeaderElectionRegInterface : ClientLeaderRegInterface {
	RequestStream< struct CandidacyRequest > candidacy;
	RequestStream< struct LeaderHeartbeatRequest > leaderHeartbeat;
	RequestStream< struct ForwardRequest > forward;

	LeaderElectionRegInterface() {}
	LeaderElectionRegInterface(NetworkAddress remote);
	LeaderElectionRegInterface(INetwork* local);
};

struct CandidacyRequest {
	Key key;
	LeaderInfo myInfo;
	UID knownLeader, prevChangeID;
	ReplyPromise<Optional<LeaderInfo>> reply;

	CandidacyRequest() {}
	CandidacyRequest(Key key, LeaderInfo const& myInfo, UID const& knownLeader, UID const& prevChangeID) : key(key), myInfo(myInfo), knownLeader(knownLeader), prevChangeID(prevChangeID) {}

	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, key, myInfo, knownLeader, prevChangeID, reply);
	}
};

struct LeaderHeartbeatRequest {
	Key key;
	LeaderInfo myInfo;
	UID prevChangeID;
	ReplyPromise<bool> reply;

	LeaderHeartbeatRequest() {}
	explicit LeaderHeartbeatRequest( Key key, LeaderInfo const& myInfo, UID prevChangeID ) : key(key), myInfo(myInfo), prevChangeID(prevChangeID) {}

	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, key, myInfo, prevChangeID, reply);
	}
};

struct ForwardRequest {
	Key key;
	Value conn;  // a cluster connection string
	ReplyPromise<Void> reply;

	ForwardRequest() {}
	ForwardRequest( Key key, Value conn ) : key(key), conn(conn) {}

	template <class Ar>
	void serialize(Ar& ar) {
		serializer(ar, key, conn, reply);
	}
};

class ServerCoordinators : public ClientCoordinators {
public:
	explicit ServerCoordinators( Reference<ClusterConnectionFile> );

	vector<LeaderElectionRegInterface> leaderElectionServers;
	vector<GenerationRegInterface> stateServers;
};

Future<Void> coordinationServer( std::string const& dataFolder );

#endif