363 lines
11 KiB
C++
363 lines
11 KiB
C++
#include "lmdb-safe.hh"
|
||
|
||
#include <fcntl.h>
|
||
#include <sys/stat.h>
|
||
|
||
#include <cstring>
|
||
#include <map>
|
||
#include <memory>
|
||
#include <mutex>
|
||
|
||
using namespace std;
|
||
|
||
namespace LMDBSafe {
|
||
|
||
MDBDbi::MDBDbi(MDB_env *env, MDB_txn *txn, const string_view dbname, unsigned int flags)
|
||
{
|
||
(void)env;
|
||
// A transaction that uses this function must finish (either commit or abort) before any other transaction in the process may use this function.
|
||
|
||
if (const auto rc = mdb_dbi_open(txn, dbname.empty() ? 0 : &dbname[0], flags, &d_dbi))
|
||
throw LMDBError("Unable to open named database: ", rc);
|
||
|
||
// Database names are keys in the unnamed database, and may be read but not written.
|
||
}
|
||
|
||
MDBEnv::MDBEnv(const char *fname, unsigned int flags, mdb_mode_t mode, MDB_dbi maxDBs)
|
||
{
|
||
mdb_env_create(&d_env);
|
||
if (const auto rc = mdb_env_set_mapsize(d_env, 16ULL * 4096 * 244140ULL)) { // 4GB
|
||
throw LMDBError("Setting map size: ", rc);
|
||
}
|
||
// Various other options may also need to be set before opening the handle, e.g. mdb_env_set_mapsize(), mdb_env_set_maxreaders(), mdb_env_set_maxdbs(),
|
||
if (const auto rc = mdb_env_set_maxdbs(d_env, maxDBs)) {
|
||
throw LMDBError("Setting maxdbs: ", rc);
|
||
}
|
||
|
||
// we need MDB_NOTLS since we rely on its semantics
|
||
if (const auto rc = mdb_env_open(d_env, fname, flags | MDB_NOTLS, mode)) {
|
||
// If this function fails, mdb_env_close() must be called to discard the MDB_env handle.
|
||
mdb_env_close(d_env);
|
||
throw LMDBError("Unable to open database file " + std::string(fname) + ": ", rc);
|
||
}
|
||
}
|
||
|
||
void MDBEnv::incROTX()
|
||
{
|
||
std::lock_guard<std::mutex> l(d_countmutex);
|
||
++d_ROtransactionsOut[std::this_thread::get_id()];
|
||
}
|
||
|
||
void MDBEnv::decROTX()
|
||
{
|
||
std::lock_guard<std::mutex> l(d_countmutex);
|
||
--d_ROtransactionsOut[std::this_thread::get_id()];
|
||
}
|
||
|
||
void MDBEnv::incRWTX()
|
||
{
|
||
std::lock_guard<std::mutex> l(d_countmutex);
|
||
++d_RWtransactionsOut[std::this_thread::get_id()];
|
||
}
|
||
|
||
void MDBEnv::decRWTX()
|
||
{
|
||
std::lock_guard<std::mutex> l(d_countmutex);
|
||
--d_RWtransactionsOut[std::this_thread::get_id()];
|
||
}
|
||
|
||
int MDBEnv::getRWTX()
|
||
{
|
||
std::lock_guard<std::mutex> l(d_countmutex);
|
||
return d_RWtransactionsOut[std::this_thread::get_id()];
|
||
}
|
||
int MDBEnv::getROTX()
|
||
{
|
||
std::lock_guard<std::mutex> l(d_countmutex);
|
||
return d_ROtransactionsOut[std::this_thread::get_id()];
|
||
}
|
||
|
||
std::shared_ptr<MDBEnv> getMDBEnv(const char *fname, unsigned int flags, mdb_mode_t mode, MDB_dbi maxDBs)
|
||
{
|
||
struct Value {
|
||
weak_ptr<MDBEnv> wp;
|
||
unsigned int flags;
|
||
};
|
||
|
||
static std::map<tuple<dev_t, ino_t>, Value> s_envs;
|
||
static std::mutex mut;
|
||
|
||
struct stat statbuf;
|
||
if (stat(fname, &statbuf)) {
|
||
if (errno != ENOENT)
|
||
throw LMDBError("Unable to stat prospective mdb database: " + string(strerror(errno)));
|
||
else {
|
||
std::lock_guard<std::mutex> l(mut);
|
||
auto fresh = std::make_shared<MDBEnv>(fname, flags, mode, maxDBs);
|
||
if (stat(fname, &statbuf))
|
||
throw LMDBError("Unable to stat prospective mdb database: " + string(strerror(errno)));
|
||
auto key = std::tie(statbuf.st_dev, statbuf.st_ino);
|
||
s_envs[key] = { fresh, flags };
|
||
return fresh;
|
||
}
|
||
}
|
||
|
||
std::lock_guard<std::mutex> l(mut);
|
||
auto key = std::tie(statbuf.st_dev, statbuf.st_ino);
|
||
auto iter = s_envs.find(key);
|
||
if (iter != s_envs.end()) {
|
||
auto sp = iter->second.wp.lock();
|
||
if (sp) {
|
||
if (iter->second.flags != flags)
|
||
throw LMDBError("Can't open mdb with differing flags");
|
||
|
||
return sp;
|
||
} else {
|
||
s_envs.erase(iter); // useful if make_shared fails
|
||
}
|
||
}
|
||
|
||
auto fresh = std::make_shared<MDBEnv>(fname, flags, mode, maxDBs);
|
||
s_envs[key] = { fresh, flags };
|
||
|
||
return fresh;
|
||
}
|
||
|
||
MDBDbi MDBEnv::openDB(const string_view dbname, unsigned int flags)
|
||
{
|
||
unsigned int envflags;
|
||
mdb_env_get_flags(d_env, &envflags);
|
||
/*
|
||
This function must not be called from multiple concurrent transactions in the same process. A transaction that uses this function must finish (either commit or abort) before any other transaction in the process may use this function.
|
||
*/
|
||
std::lock_guard<std::mutex> l(d_openmut);
|
||
|
||
if (!(envflags & MDB_RDONLY)) {
|
||
auto rwt = getRWTransaction();
|
||
MDBDbi ret = rwt->openDB(dbname, flags);
|
||
rwt->commit();
|
||
return ret;
|
||
}
|
||
|
||
MDBDbi ret;
|
||
{
|
||
auto rwt = getROTransaction();
|
||
ret = rwt->openDB(dbname, flags);
|
||
}
|
||
return ret;
|
||
}
|
||
|
||
MDBRWTransactionImpl::MDBRWTransactionImpl(MDBEnv *parent, MDB_txn *txn)
|
||
: MDBROTransactionImpl(parent, txn)
|
||
|
||
{
|
||
}
|
||
|
||
MDB_txn *MDBRWTransactionImpl::openRWTransaction(MDBEnv *env, MDB_txn *parent, unsigned int flags)
|
||
{
|
||
MDB_txn *result;
|
||
if (env->getRWTX())
|
||
throw LMDBError("Duplicate RW transaction");
|
||
|
||
for (int tries = 0; tries < 3; ++tries) { // it might happen twice, who knows
|
||
if (int rc = mdb_txn_begin(env->d_env, parent, flags, &result)) {
|
||
if (rc == MDB_MAP_RESIZED && tries < 2) {
|
||
// "If the mapsize is increased by another process (..) mdb_txn_begin() will return MDB_MAP_RESIZED.
|
||
// call mdb_env_set_mapsize with a size of zero to adopt the new size."
|
||
mdb_env_set_mapsize(env->d_env, 0);
|
||
continue;
|
||
}
|
||
throw LMDBError("Unable to start RW transaction: ", rc);
|
||
}
|
||
break;
|
||
}
|
||
env->incRWTX();
|
||
return result;
|
||
}
|
||
|
||
MDBRWTransactionImpl::MDBRWTransactionImpl(MDBEnv *parent, unsigned int flags)
|
||
: MDBRWTransactionImpl(parent, openRWTransaction(parent, nullptr, flags))
|
||
{
|
||
}
|
||
|
||
MDBRWTransactionImpl::~MDBRWTransactionImpl()
|
||
{
|
||
MDBRWTransactionImpl::abort();
|
||
}
|
||
|
||
void MDBRWTransactionImpl::commit()
|
||
{
|
||
closeRORWCursors();
|
||
if (!d_txn) {
|
||
return;
|
||
}
|
||
|
||
if (const auto rc = mdb_txn_commit(d_txn)) {
|
||
throw LMDBError("Committing transaction: ", rc);
|
||
}
|
||
environment().decRWTX();
|
||
d_txn = nullptr;
|
||
}
|
||
|
||
void MDBRWTransactionImpl::abort()
|
||
{
|
||
closeRORWCursors();
|
||
if (!d_txn) {
|
||
return;
|
||
}
|
||
|
||
mdb_txn_abort(d_txn);
|
||
// prevent the RO destructor from cleaning up the transaction itself
|
||
environment().decRWTX();
|
||
d_txn = nullptr;
|
||
}
|
||
|
||
MDBROTransactionImpl::MDBROTransactionImpl(MDBEnv *parent, MDB_txn *txn)
|
||
: d_parent(parent)
|
||
, d_cursors()
|
||
, d_txn(txn)
|
||
{
|
||
}
|
||
|
||
MDB_txn *MDBROTransactionImpl::openROTransaction(MDBEnv *env, MDB_txn *parent, unsigned int flags)
|
||
{
|
||
if (env->getRWTX())
|
||
throw LMDBError("Duplicate RO transaction");
|
||
|
||
/*
|
||
A transaction and its cursors must only be used by a single thread, and a thread may only have a single transaction at a time. If MDB_NOTLS is in use, this does not apply to read-only transactions. */
|
||
MDB_txn *result = nullptr;
|
||
for (int tries = 0; tries < 3; ++tries) { // it might happen twice, who knows
|
||
if (const auto rc = mdb_txn_begin(env->d_env, parent, MDB_RDONLY | flags, &result)) {
|
||
if (rc == MDB_MAP_RESIZED && tries < 2) {
|
||
// "If the mapsize is increased by another process (..) mdb_txn_begin() will return MDB_MAP_RESIZED.
|
||
// call mdb_env_set_mapsize with a size of zero to adopt the new size."
|
||
mdb_env_set_mapsize(env->d_env, 0);
|
||
continue;
|
||
}
|
||
throw LMDBError("Unable to start RO transaction: ", rc);
|
||
}
|
||
break;
|
||
}
|
||
env->incROTX();
|
||
|
||
return result;
|
||
}
|
||
|
||
void MDBROTransactionImpl::closeROCursors()
|
||
{
|
||
// we need to move the vector away to ensure that the cursors don’t mess with our iteration.
|
||
std::vector<MDBROCursor *> buf;
|
||
std::swap(d_cursors, buf);
|
||
for (auto &cursor : buf) {
|
||
cursor->close();
|
||
}
|
||
}
|
||
|
||
MDBROTransactionImpl::MDBROTransactionImpl(MDBEnv *parent, unsigned int flags)
|
||
: MDBROTransactionImpl(parent, openROTransaction(parent, nullptr, flags))
|
||
{
|
||
}
|
||
|
||
MDBROTransactionImpl::~MDBROTransactionImpl()
|
||
{
|
||
// this is safe because C++ will not call overrides of virtual methods in destructors.
|
||
MDBROTransactionImpl::commit();
|
||
}
|
||
|
||
void MDBROTransactionImpl::abort()
|
||
{
|
||
closeROCursors();
|
||
// if d_txn is non-nullptr here, either the transaction object was invalidated earlier (e.g. by moving from it), or it is an RW transaction which has already cleaned up the d_txn pointer (with an abort).
|
||
if (d_txn) {
|
||
d_parent->decROTX();
|
||
mdb_txn_abort(d_txn); // this appears to work better than abort for r/o database opening
|
||
d_txn = nullptr;
|
||
}
|
||
}
|
||
|
||
void MDBROTransactionImpl::commit()
|
||
{
|
||
closeROCursors();
|
||
// if d_txn is non-nullptr here, either the transaction object was invalidated earlier (e.g. by moving from it), or it is an RW transaction which has already cleaned up the d_txn pointer (with an abort).
|
||
if (d_txn) {
|
||
d_parent->decROTX();
|
||
if (const auto rc = mdb_txn_commit(d_txn)) { // this appears to work better than abort for r/o database opening
|
||
throw LMDBError("Error committing transaction: ", rc);
|
||
}
|
||
d_txn = nullptr;
|
||
}
|
||
}
|
||
|
||
void MDBRWTransactionImpl::clear(MDB_dbi dbi)
|
||
{
|
||
if (const auto rc = mdb_drop(d_txn, dbi, 0)) {
|
||
throw LMDBError("Error clearing database: ", rc);
|
||
}
|
||
}
|
||
|
||
MDBRWCursor MDBRWTransactionImpl::getRWCursor(const MDBDbi &dbi)
|
||
{
|
||
MDB_cursor *cursor;
|
||
;
|
||
if (const auto rc = mdb_cursor_open(d_txn, dbi, &cursor)) {
|
||
throw LMDBError("Error creating RO cursor: ", rc);
|
||
}
|
||
return MDBRWCursor(d_rw_cursors, cursor);
|
||
}
|
||
|
||
MDBRWCursor MDBRWTransactionImpl::getCursor(const MDBDbi &dbi)
|
||
{
|
||
return getRWCursor(dbi);
|
||
}
|
||
|
||
MDBRWTransaction MDBRWTransactionImpl::getRWTransaction()
|
||
{
|
||
MDB_txn *txn;
|
||
if (const auto rc = mdb_txn_begin(environment(), *this, 0, &txn)) {
|
||
throw LMDBError("Failed to start child transaction: ", rc);
|
||
}
|
||
// we need to increase the counter here because commit/abort on the child transaction will decrease it
|
||
environment().incRWTX();
|
||
return MDBRWTransaction(new MDBRWTransactionImpl(&environment(), txn));
|
||
}
|
||
|
||
MDBROTransaction MDBRWTransactionImpl::getROTransaction()
|
||
{
|
||
return getRWTransaction();
|
||
}
|
||
|
||
MDBROTransaction MDBEnv::getROTransaction()
|
||
{
|
||
return MDBROTransaction(new MDBROTransactionImpl(this));
|
||
}
|
||
MDBRWTransaction MDBEnv::getRWTransaction()
|
||
{
|
||
return MDBRWTransaction(new MDBRWTransactionImpl(this));
|
||
}
|
||
|
||
void MDBRWTransactionImpl::closeRWCursors()
|
||
{
|
||
decltype(d_rw_cursors) buf;
|
||
std::swap(d_rw_cursors, buf);
|
||
for (auto &cursor : buf) {
|
||
cursor->close();
|
||
}
|
||
}
|
||
|
||
MDBROCursor MDBROTransactionImpl::getCursor(const MDBDbi &dbi)
|
||
{
|
||
return getROCursor(dbi);
|
||
}
|
||
|
||
MDBROCursor MDBROTransactionImpl::getROCursor(const MDBDbi &dbi)
|
||
{
|
||
MDB_cursor *cursor;
|
||
if (const auto rc = mdb_cursor_open(d_txn, dbi, &cursor)) {
|
||
throw LMDBError("Error creating RO cursor: ", rc);
|
||
}
|
||
return MDBROCursor(d_cursors, cursor);
|
||
}
|
||
|
||
} // namespace LMDBSafe
|