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one/include/RaftManager.h
Tino Vázquez 05d147c524
M #-: Bump version 6.10.0 
Also bump copyright year to 2024
2024-07-29 14:27:11 +02:00

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/* -------------------------------------------------------------------------- */
/* Copyright 2002-2024, OpenNebula Project, OpenNebula Systems */
/* */
/* 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 RAFT_MANAGER_H_
#define RAFT_MANAGER_H_
#include "Listener.h"
#include "ReplicaManager.h"
#include "ReplicaRequest.h"
#include "Template.h"
#include "ExecuteHook.h"
class LogDBRecord;
/* -------------------------------------------------------------------------- */
/* -------------------------------------------------------------------------- */
class RaftManager
{
public:
/**
* State of this server
*/
enum State
{
SOLO = 0,
CANDIDATE = 1,
FOLLOWER = 2,
LEADER = 3
};
/**
* Raft manager constructor
* @param server_id of this server
* @param leader_hook_mad to be executed when follower->leader
* @param follower_hook_mad to be executed when leader->follower
* @param log_purge period to purge logDB records
* @param bcast heartbeat broadcast timeout
* @param election timeout
* @param xmlrpc timeout for RAFT related xmlrpc API calls
**/
RaftManager(int server_id, const VectorAttribute * leader_hook_mad,
const VectorAttribute * follower_hook_mad, time_t log_purge,
long long bcast, long long election, time_t xmlrpc,
const std::string& remotes_location);
~RaftManager() = default;
// -------------------------------------------------------------------------
// Raft associated actions (synchronous)
// -------------------------------------------------------------------------
/**
* Follower successfully replicated a log entry:
* - Increment next entry to send to follower
* - Update match entry on follower
* - Evaluate majority to apply changes to DB
*/
void replicate_success(int follower_id);
/**
* Follower failed to replicate a log entry because an inconsistency was
* detected (same index, different term):
* - Decrease follower next_index
* - Retry (do not wait for replica events)
*/
void replicate_failure(int follower_id);
/**
* Triggers a REPLICATE event, it will notify the replica threads to
* send the log to the followers
*/
void replicate_log(ReplicaRequest * rr);
/**
* Allocate a replica request fot the given index.
* @param rindex of the record for the request
*/
void replicate_allocate(uint64_t rindex)
{
requests.allocate(rindex);
}
/**
* Termination function
*/
void finalize();
// -------------------------------------------------------------------------
// Raft state query functions
// -------------------------------------------------------------------------
/**
* Return the Raft status in XML format
* @return xml document with the raft state
*/
std::string& to_xml(std::string& state_xml);
/**
* Makes this server follower. Stop associated replication facilities
*/
void follower(unsigned int term);
static std::string state_to_str(State _state)
{
std::string st;
switch (_state)
{
case SOLO:
st = "SOLO";
break;
case CANDIDATE:
st = "CANDIDATE";
break;
case FOLLOWER:
st = "FOLLOWER";
break;
case LEADER:
st = "LEADER";
break;
}
return st;
}
State get_state()
{
std::lock_guard<std::mutex> lock(raft_mutex);
return state;
}
unsigned int get_term()
{
std::lock_guard<std::mutex> lock(raft_mutex);
return term;
}
uint64_t get_commit()
{
std::lock_guard<std::mutex> lock(raft_mutex);
return commit;
}
/**
* Update the commit index = min(leader_commit, log index).
* @param leader_commit index sent by leader in a replicate xml-rpc call
* @param index of the last record inserted in the database
* @return the updated commit index
*/
uint64_t update_commit(uint64_t leader_commit, uint64_t index);
/**
* Evaluates a vote request. It is granted if no vote has been granted in
* this term or it is requested by the same candidate.
* @param _votedfor the candidate id
* @return -1 if vote is not granted
*/
int update_votedfor(int _votedfor);
/**
* Update the last_heartbeat time recieved from server. It stores the id
* of the leader.
* @param leader_id id of server, -1 if there is no leader set (e.g.
* during a election because a vote request was received)
*/
void update_last_heartbeat(int leader_id);
/**
* @return true if the server is the leader of the zone, runs in solo mode
* or is a follower
*/
bool is_leader()
{
return test_state(LEADER);
}
bool is_follower()
{
return test_state(FOLLOWER);
}
bool is_candidate()
{
return test_state(CANDIDATE);
}
bool is_solo()
{
return test_state(SOLO);
}
bool is_reconciling()
{
bool _reconciling;
std::lock_guard<std::mutex> lock(raft_mutex);
_reconciling = reconciling;
return _reconciling;
}
/**
* Get next index to send to the follower
* @param follower server id
* @return UINT64_MAX on failure, the next index if success
*/
uint64_t get_next_index(int follower_id)
{
uint64_t _index = UINT64_MAX;
std::lock_guard<std::mutex> lock(raft_mutex);
auto it = next.find(follower_id);
if ( it != next.end() )
{
_index = it->second;
}
return _index;
}
/**
* Gets the endpoint for xml-rpc calls of the current leader
* @param endpoint
* @return 0 on success, -1 if no leader found
*/
int get_leader_endpoint(std::string& endpoint);
// -------------------------------------------------------------------------
// XML-RPC Raft API calls
// -------------------------------------------------------------------------
/**
* Calls the follower xml-rpc method
* @param follower_id to make the call
* @param lr the record to replicate
* @param success of the xml-rpc method
* @param ft term in the follower as returned by the replicate call
* @param error describing error if any
* @return -1 if a XMl-RPC (network) error occurs, 0 otherwise
*/
int xmlrpc_replicate_log(int follower_id, LogDBRecord * lr, bool& success,
unsigned int& ft, std::string& error);
/**
* Calls the request vote xml-rpc method
* @param follower_id to make the call
* @param lindex highest last log index
* @param lterm highest last log term
* @param success of the xml-rpc method
* @param ft term in the follower as returned by the replicate call
* @param error describing error if any
* @return -1 if a XMl-RPC (network) error occurs, 0 otherwise
*/
int xmlrpc_request_vote(int follower_id, uint64_t lindex,
unsigned int lterm, bool& success, unsigned int& fterm,
std::string& error);
// -------------------------------------------------------------------------
// Server related interface
// -------------------------------------------------------------------------
/**
* Adds a new server to the follower list and starts associated replica
* thread.
* @param follower_id id of new server
* @param xmlep xmlrpc endpoint for new server
*/
void add_server(int follower_id, const std::string& xmlep);
/**
* Deletes a new server to the follower list and stops associated replica
* thread.
* @param follower_id id of server
*/
void delete_server(int follower_id);
/**
* Reset index for a follower.
* @param follower_id id of server
*/
void reset_index(int follower_id);
private:
std::mutex raft_mutex;
/**
* Clients waiting for a log replication
*/
ReplicaRequestMap requests;
// -------------------------------------------------------------------------
// Raft state
// -------------------------------------------------------------------------
/**
* Server state
*/
State state;
/**
* Server id
*/
int server_id;
/**
* Current term
*/
unsigned int term;
/**
* Number of servers in zone
*/
unsigned int num_servers;
/**
* Time when the last heartbeat was sent (LEADER) or received (FOLLOWER)
*/
struct timespec last_heartbeat;
/**
* ID of the last candidate we voted for ( -1 if none )
*/
int votedfor;
/**
* ID of leader for the current term
*/
int leader_id;
/**
* This is the raft persistent state: votedfor and current term. It is
* stored along the log in a special record (0, -1 , TEMPLATE, 0)
*/
Template raft_state;
/**
* Value for name column in system_attributes table for raft state.
*/
static const std::string raft_state_name;
/**
* After becoming a leader it is replicating and applying any pending
* log entry.
*/
bool reconciling;
//--------------------------------------------------------------------------
// Timers
// - timer_period_ms. Base timer to wake up the manager (10ms)
// - purge_period_ms. How often the LogDB is purged (600s)
// - xmlrpc_timeout. To timeout xml-rpc api calls to replicate log
// - election_timeout. Timeout leader heartbeats (followers)
// - broadcast_timeout. To send heartbeat to followers (leader)
//--------------------------------------------------------------------------
static const time_t timer_period_ms;
time_t purge_period_ms;
time_t xmlrpc_timeout_ms;
struct timespec election_timeout;
struct timespec broadcast_timeout;
/**
* Timer action async execution
*/
Timer timer_thread;
Timer purge_thread;
//--------------------------------------------------------------------------
// Volatile log index variables
// - commit, highest log known to be committed
// - applied, highest log applied to DB (in LogDB)
//
//---------------------------- LEADER VARIABLES ----------------------------
//
// - next, next log to send to each follower <follower, next>
// - match, highest log replicated in this server <follower, match>
// - servers, list of servers in zone and xml-rpc edp <follower, edp>
// -------------------------------------------------------------------------
RaftReplicaManager replica_manager;
HeartBeatManager heartbeat_manager;
uint64_t commit;
std::map<int, uint64_t> next;
std::map<int, uint64_t> match;
std::map<int, std::string> servers;
// -------------------------------------------------------------------------
// Hooks
// -------------------------------------------------------------------------
std::unique_ptr<ExecuteHook> leader_hook;
std::unique_ptr<ExecuteHook> follower_hook;
// -------------------------------------------------------------------------
// Internal Raft functions
// -------------------------------------------------------------------------
/**
* This function is executed periodically to vote leader
*/
void timer_action();
/**
* This function is executed periodically to purge the state log
*/
void purge_action();
/**
* @param s the state to check
* @return true if the server states matches the provided one
*/
bool test_state(State s)
{
bool _is_state;
std::lock_guard<std::mutex> lock(raft_mutex);
_is_state = state == s;
return _is_state;
}
/**
* Request votes of followers
*/
void request_vote();
/**
* Makes this server leader, and start replica threads
*/
void leader();
/**
* Init the raft state status row.
*/
int init_raft_state(const std::string& raft_xml);
};
#endif /*RAFT_MANAGER_H_*/
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