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Added special lock for local data. Use read and write locking. Do not hold read lock during agency transactions. (#9277)

This commit is contained in:
Lars Maier 2019-06-21 14:27:21 +02:00 committed by Michael Hackstein
parent a6bf8028c7
commit 49fde75427
2 changed files with 44 additions and 32 deletions
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27
arangod/Cluster/FollowerInfo.cpp
View File

@ -30,14 +30,6 @@
using namespace arangodb;
////////////////////////////////////////////////////////////////////////////////
/// @brief get information about current followers of a shard.
////////////////////////////////////////////////////////////////////////////////
std::shared_ptr<std::vector<ServerID> const> FollowerInfo::get() const {
MUTEX_LOCKER(locker, _mutex);
return _followers;
}
////////////////////////////////////////////////////////////////////////////////
/// @brief change JSON under
@ -98,8 +90,13 @@ static VPackBuilder newShardEntry(VPackSlice oldValue, ServerID const& sid, bool
////////////////////////////////////////////////////////////////////////////////
void FollowerInfo::add(ServerID const& sid) {
MUTEX_LOCKER(locker, _mutex);
MUTEX_LOCKER(locker, _agencyMutex);
std::shared_ptr<std::vector<ServerID>> v;
{
WRITE_LOCKER(writeLocker, _dataLock);
// First check if there is anything to do:
for (auto const& s : *_followers) {
if (s == sid) {
@ -107,7 +104,7 @@ void FollowerInfo::add(ServerID const& sid) {
}
}
// Fully copy the vector:
auto v = std::make_shared<std::vector<ServerID>>(*_followers);
v = std::make_shared<std::vector<ServerID>>(*_followers);
v->push_back(sid); // add a single entry
_followers = v; // will cast to std::vector<ServerID> const
#ifdef DEBUG_SYNC_REPLICATION
@ -115,6 +112,7 @@ void FollowerInfo::add(ServerID const& sid) {
return;
}
#endif
}
// Now tell the agency, path is
// Current/Collections/<dbName>/<collectionID>/<shardID>
std::string path = "Current/Collections/";
@ -192,7 +190,10 @@ bool FollowerInfo::remove(ServerID const& sid) {
LOG_TOPIC("ce460", DEBUG, Logger::CLUSTER)
<< "Removing follower " << sid << " from " << _docColl->name();
MUTEX_LOCKER(locker, _mutex);
MUTEX_LOCKER(locker, _agencyMutex);
WRITE_LOCKER(writeLocker, _dataLock); // the data lock has to be locked until this function completes
// because if the agency communication does not work
// local data is modified again.
// First check if there is anything to do:
bool found = false;
@ -294,7 +295,7 @@ bool FollowerInfo::remove(ServerID const& sid) {
//////////////////////////////////////////////////////////////////////////////
void FollowerInfo::clear() {
MUTEX_LOCKER(locker, _mutex);
WRITE_LOCKER(writeLocker, _dataLock);
auto v = std::make_shared<std::vector<ServerID>>();
_followers = v; // will cast to std::vector<ServerID> const
}
@ -304,7 +305,7 @@ void FollowerInfo::clear() {
//////////////////////////////////////////////////////////////////////////////
bool FollowerInfo::contains(ServerID const& sid) const {
MUTEX_LOCKER(locker, _mutex);
READ_LOCKER(readLocker, _dataLock);
for (auto const& s : *_followers) {
if (s == sid) {
return true;

25
arangod/Cluster/FollowerInfo.h
View File

@ -26,6 +26,9 @@
#define ARANGOD_CLUSTER_FOLLOWER_INFO_H 1
#include "ClusterInfo.h"
#include "Basics/Mutex.h"
#include "Basics/ReadWriteLock.h"
#include "Basics/WriteLocker.h"
namespace arangodb {
@ -35,7 +38,12 @@ namespace arangodb {
class FollowerInfo {
std::shared_ptr<std::vector<ServerID> const> _followers;
mutable Mutex _mutex;
// The agencyMutex is used to synchronise access to the agency.
// the _dataLock is used to sync the access to local data.
// The agencyMutex is always locked before the _dataLock is locked.
mutable Mutex _agencyMutex;
mutable arangodb::basics::ReadWriteLock _dataLock;
arangodb::LogicalCollection* _docColl;
std::string _theLeader;
// if the latter is empty, then we are leading
@ -45,11 +53,14 @@ class FollowerInfo {
explicit FollowerInfo(arangodb::LogicalCollection* d)
: _followers(new std::vector<ServerID>()), _docColl(d), _theLeaderTouched(false) {}
//////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
/// @brief get information about current followers of a shard.
//////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
std::shared_ptr<std::vector<ServerID> const> get() const;
std::shared_ptr<std::vector<ServerID> const> get() const {
READ_LOCKER(readLocker, _dataLock);
return _followers;
}
//////////////////////////////////////////////////////////////////////////////
/// @brief add a follower to a shard, this is only done by the server side
@ -87,7 +98,7 @@ class FollowerInfo {
//////////////////////////////////////////////////////////////////////////////
void setTheLeader(std::string const& who) {
MUTEX_LOCKER(locker, _mutex);
WRITE_LOCKER(writeLocker, _dataLock);
_theLeader = who;
_theLeaderTouched = true;
}
@ -97,7 +108,7 @@ class FollowerInfo {
//////////////////////////////////////////////////////////////////////////////
std::string getLeader() const {
MUTEX_LOCKER(locker, _mutex);
READ_LOCKER(readLocker, _dataLock);
return _theLeader;
}
@ -106,7 +117,7 @@ class FollowerInfo {
//////////////////////////////////////////////////////////////////////////////
bool getLeaderTouched() const {
MUTEX_LOCKER(locker, _mutex);
READ_LOCKER(readLocker, _dataLock);
return _theLeaderTouched;
}
};