libdb/lang/cxx/stl/dbstl_resource_manager.cpp

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2009, 2011 Oracle and/or its affiliates.  All rights reserved.
 *
 * $Id$
 */

#include <assert.h>
#include <utility>

#include "dbstl_resource_manager.h"
#include "dbstl_exception.h"
#include "dbstl_dbc.h"

START_NS(dbstl)

typedef struct {
	time_t	tv_sec;				/* seconds */
	long	tv_nsec;			/* nanoseconds */
} db_timespec;

extern "C"{
void __os_id (DB_ENV *, pid_t *, db_threadid_t*);
void __os_gettime(ENV *env, db_timespec *tp, int monotonic);
}

using std::pair;
using std::make_pair;

// Static data member definitions.
map<Db*, size_t> ResourceManager::open_dbs_;
map<DbEnv*, size_t> ResourceManager::open_envs_;
set<DbstlGlobalInnerObject *> ResourceManager::glob_objs_;
set<Db *> ResourceManager::deldbs; 
set<DbEnv *> ResourceManager::delenvs; 

DbEnv * ResourceManager::mtx_env_ = NULL;
db_mutex_t ResourceManager::mtx_handle_ = 0;
db_mutex_t ResourceManager::mtx_globj_ = 0;

#ifdef TLS_DEFN_MODIFIER
template <Typename T> TLS_DEFN_MODIFIER T *TlsWrapper<T>::tinst_ = NULL;
#elif defined(HAVE_PTHREAD_TLS)
static pthread_once_t once_control_ = PTHREAD_ONCE_INIT;
template <Typename T>
pthread_key_t TlsWrapper<T>::tls_key_;

template<Typename T>
void tls_init_once(void) {
	pthread_key_create(&TlsWrapper<T>::tls_key_, NULL);
}

template<Typename T>
TlsWrapper<T>::TlsWrapper()
{
	pthread_once(&once_control_, tls_init_once<T>);
}
#else
#error "No suitable thread-local storage model configured"
#endif

int ResourceManager::global_lock(db_mutex_t dbcontainer_mtx)
{
	int ret;

	ret = mtx_env_->mutex_lock(dbcontainer_mtx);
	dbstl_assert(ret == 0);
	return 0;
}

int ResourceManager::global_unlock(db_mutex_t dbcontainer_mtx)
{
	int ret;

	ret = mtx_env_->mutex_unlock(dbcontainer_mtx);
	dbstl_assert(ret == 0);
	return 0;
}

u_int32_t dbstl_strlen(const char *str)
{
	return (u_int32_t)strlen(str);
}

void dbstl_strcpy(char *dest, const char *src, size_t num)
{
	strncpy(dest, src, num);
}

int dbstl_strncmp(const char *s1, const char *s2, size_t num)
{
	return strncmp(s1, s2, num);
}

int dbstl_wcsncmp(const wchar_t *s1, const wchar_t *s2, size_t num)
{
	return wcsncmp(s1, s2, num);
}

int dbstl_strcmp(const char *s1, const char *s2)
{
	return strcmp(s1, s2);
}

int dbstl_wcscmp(const wchar_t *s1, const wchar_t *s2)
{
	return wcscmp(s1, s2);
}

u_int32_t dbstl_wcslen(const wchar_t *str)
{
	return (u_int32_t)wcslen(str);
}

void dbstl_wcscpy(wchar_t *dest, const wchar_t *src, size_t num)
{
	wcsncpy(dest, src, num);
}

// This function should be called in a single thread inside a process, before
// any use of dbstl. We don't want to rely on platform dependent mutex API,
// so we defer the synchronization to users.
void ResourceManager::global_startup()
{
	int ret;
	db_timespec tnow;

	if (mtx_env_ == NULL) {
		mtx_env_ = new DbEnv(DB_CXX_NO_EXCEPTIONS);
		// Set cache size to 32k, to save space.
		BDBOP(mtx_env_->set_cachesize(0, 32 * 1024, 1), ret);
		BDBOP(mtx_env_->mutex_set_max(DBSTL_MAX_MTX_ENV_MUTEX), ret);
		BDBOP2(mtx_env_->open(NULL, DB_PRIVATE | DB_CREATE, 0777),
		    ret, mtx_env_->close(0));
		BDBOP2(mtx_env_->mutex_alloc(DB_MUTEX_PROCESS_ONLY,
		    &mtx_handle_), ret, mtx_env_->mutex_free(mtx_handle_));
		BDBOP2(mtx_env_->mutex_alloc(DB_MUTEX_PROCESS_ONLY,
		    &mtx_globj_), ret, mtx_env_->mutex_free(mtx_globj_));
		__os_gettime(NULL, &tnow, 0);
		srand((unsigned int)tnow.tv_sec);
	}

}

ResourceManager::ResourceManager(void)
{

	// Initialize process wide dbstl settings. If there are multiple 
	// threads, the global_startup should be called in a single thread 
	// before any use of dbstl.
	global_startup();
}

void ResourceManager::close_db(Db *pdb)
{
	bool berase = false;

	if (pdb == NULL)
		return;
	db_csr_map_t::iterator itr = all_csrs_.find(pdb);
	if (itr == all_csrs_.end())
		return;

	this->close_db_cursors(pdb);

	delete all_csrs_[pdb];
	all_csrs_.erase(itr);
	pdb->close(0);
	set<Db *>::iterator itrdb = deldbs.find(pdb);
	// If new'ed by open_db, delete it.
	if (itrdb != deldbs.end()) {
		delete *itrdb;
		berase = true;
	}

	global_lock(mtx_handle_);
	open_dbs_.erase(pdb);
	if (berase)
		deldbs.erase(itrdb);

	global_unlock(mtx_handle_);
}

void ResourceManager::close_all_db_envs()
{
	u_int32_t oflags;
	int ret;
	size_t txnstk_sz;

	global_lock(mtx_handle_);
	for (map<DbEnv*, size_t>::iterator i = open_envs_.begin();
	    i != open_envs_.end(); ++i) {
		BDBOP(i->first->get_open_flags(&oflags), ret);
		txnstk_sz = env_txns_[i->first].size();
		if (oflags & DB_INIT_CDB) {
			assert(txnstk_sz == 1);
			BDBOP(env_txns_[i->first].top()->commit(0), ret);
		} else
			assert(txnstk_sz == 0);

		i->first->close(0);
	}

	// Delete DbEnv objects new'ed by dbstl.
	set<DbEnv *>::iterator itr2 = delenvs.begin(); 
	for (; itr2 != delenvs.end(); ++itr2)
		delete *itr2;

	delenvs.clear();
	env_txns_.clear();
	open_envs_.clear();
	global_unlock(mtx_handle_);
}

void ResourceManager::close_db_env(DbEnv *penv)
{
	u_int32_t oflags;
	int ret;
	size_t txnstk_sz;
	bool berase = false;

	if (penv == NULL)
		return;
	map<DbEnv *, txnstk_t>::iterator itr = env_txns_.find(penv);
	if (itr == env_txns_.end())
		return;
	BDBOP(penv->get_open_flags(&oflags), ret);
	txnstk_sz = itr->second.size();
	if (oflags & DB_INIT_CDB) {
		assert(txnstk_sz == 1);
		BDBOP(itr->second.top()->commit(0), ret);
	} else
		assert(txnstk_sz == 0);
	env_txns_.erase(itr);
	penv->close(0);

	set<DbEnv *>::iterator itrdb = delenvs.find(penv);
	// If new'ed by open_db, delete it.
	if (itrdb != delenvs.end()) {
		delete penv;
		berase = true;
	}

	global_lock(mtx_handle_);
	open_envs_.erase(penv);
	if (berase)
		delenvs.erase(itrdb);
	global_unlock(mtx_handle_);
}

void ResourceManager::close_all_dbs()
{
	map<Db *, size_t>::iterator itr;
	set<Db *>::iterator itr2;
	Db *pdb;

	global_lock(mtx_handle_);
	for (itr = open_dbs_.begin(); itr != open_dbs_.end(); ++itr) {
		pdb = itr->first;
		this->close_db_cursors(pdb);

		delete all_csrs_[pdb];
		all_csrs_.erase(pdb);
		pdb->close(0);
	}

	// Delete Db objects new'ed by dbstl.
	for (itr2 = deldbs.begin(); itr2 != deldbs.end(); ++itr2)
		delete *itr2;

	deldbs.clear();
	open_dbs_.clear();

	global_unlock(mtx_handle_);
}

ResourceManager::~ResourceManager(void)
{
	u_int32_t oflags;
	int ret;
	set<Db *> dbs2del;
	set<DbEnv *> envs2del;

	global_lock(mtx_handle_);

	for (map<Db*, size_t>::iterator i = open_dbs_.begin();
	    i != open_dbs_.end(); ++i) {
		this->close_db_cursors(i->first);
		(i->second)--;
		if (i->second == 0) {

			delete all_csrs_[i->first]; // Delete the cursor set.
			all_csrs_.erase(i->first);
			i->first->close(0);

			set<Db *>::iterator itrdb = deldbs.find(i->first);
			// If new'ed by open_db, delete it.
			if (itrdb != deldbs.end()) {
				delete *itrdb;
				deldbs.erase(itrdb);
			}
			dbs2del.insert(i->first);
		}
	}

	for (map<DbEnv*, size_t>::iterator i = open_envs_.begin();
	    i != open_envs_.end(); ++i) {
		BDBOP(i->first->get_open_flags(&oflags), ret);
		if (oflags & DB_INIT_CDB) {
			assert(env_txns_[i->first].size() == 1);
			BDBOP(env_txns_[i->first].top()->commit(0), ret);
			env_txns_[i->first].pop();
		}

		(i->second)--;
		if (i->second == 0) {
			assert(env_txns_[i->first].size() == 0);
			i->first->close(0);
			set<DbEnv *>::iterator itrdb = delenvs.find(i->first);
			// If new'ed by open_db, delete it.
			if (itrdb != delenvs.end()) {
				delete *itrdb;
				delenvs.erase(itrdb);
			}
			envs2del.insert(i->first);
		}
	}

	// Erase db/env entries that are just closed.
	for (set<Db *>::iterator i = dbs2del.begin(); i != dbs2del.end(); ++i)
		open_dbs_.erase(*i);
	for (set<DbEnv *>::iterator i = envs2del.begin(); 
	    i != envs2del.end(); ++i)
		open_envs_.erase(*i);

	global_unlock(mtx_handle_);

	for (db_csr_map_t::iterator itr3 = all_csrs_.begin(); 
	    itr3 != all_csrs_.end(); ++itr3)
	{
		// Delete the cursor set. Above code may not have a chance to
		// delete this set because the db(itr3->first) was already 
		// closed by another thread.
		delete itr3->second; 
	}
	// Don't bother to clear all_csrs_ since it is being destructed.

// Don't handle transactions, leave them alone, because autocommit
// transactions must have been committed/aborted, and outside transactions
// should be handled by user code, and if they are not handled yet,
// the DbEnv::close will fail.
// Only handle the transaction for CDS mode---an DB_TXN* handle is opened
// at environment registration/creation by cdsgroup_begin, so we need to commit
// that transaction.
//
}

Db* ResourceManager::open_db (
    DbEnv*penv, const char* filename, DBTYPE dbtype,
    u_int32_t oflags, u_int32_t set_flags1, int mode, DbTxn* txn,
    u_int32_t cflags, const char* dbname)
{
	int ret, ci = 0;
	u_int32_t envf = 0, envoflags = 0;
	DbTxn *ptxn = NULL;
	Db *pdb = new Db(penv, cflags | DB_CXX_NO_EXCEPTIONS);

	if (penv) {
		BDBOP(penv->get_open_flags(&envoflags), ret);
		BDBOP(penv->get_flags(&envf), ret);
	}
	if (set_flags1)
		BDBOP(pdb->set_flags(set_flags1), ret);
	// If no transaction is specified and we really need one, begin a
	// transaction and commit it before return, we don't commit
	// passed-in transaction.
	//
	if (penv && ((envf & DB_AUTO_COMMIT) ||
	    (envoflags & DB_INIT_TXN)) && txn == 0){
		ptxn = current_txn(penv);
		BDBOP2(penv->txn_begin(ptxn, &txn, 0), ret, txn->abort());
		ci = 1;
	}
	if (txn == NULL)
		BDBOP2(pdb->open(txn, filename, dbname,
		    dbtype, oflags, mode),
		    ret, (pdb->close(0)));
	else
		BDBOP2(pdb->open(txn, filename, dbname,
		    dbtype, oflags, mode),
		    ret, (pdb->close(0), txn->abort()));
	if (ci && txn)
		BDBOP(txn->commit(0), ret);
	global_lock(mtx_handle_);
	open_dbs_.insert(make_pair(pdb, 1u));
	pair<set<Db *>::iterator, bool> delinsret = deldbs.insert(pdb);
	assert(delinsret.second);
	global_unlock(mtx_handle_);
	csrset_t *mycsrs = new csrset_t();
	all_csrs_.insert(make_pair(pdb, mycsrs));

	return pdb;
}

// Only called if the user does not supply an environment handle.
DbEnv* ResourceManager::open_env(const char* env_home, u_int32_t set_flags1,
    u_int32_t oflags, u_int32_t cachesize, int mode, u_int32_t cflags)
{
	int ret;

	DbEnv *penv = new DbEnv(cflags | DB_CXX_NO_EXCEPTIONS);
	if (set_flags1)
		BDBOP(penv->set_flags(set_flags1, 1), ret);
	BDBOP(penv->set_cachesize(0, cachesize, 1), ret);
	BDBOP(penv->set_lk_max_lockers(2000), ret);
	BDBOP(penv->set_lk_max_locks(2000), ret);
	BDBOP(penv->set_lk_max_objects(2000), ret);
	BDBOP2(penv->open(env_home, oflags, mode), ret, penv->close(0));

	stack<DbTxn*> stk;
	DbTxn *ptxn = NULL;
	if (oflags & DB_INIT_CDB) {
		BDBOP2(penv->cdsgroup_begin(&ptxn), ret, ptxn->commit(0));
		stk.push(ptxn);
	}

	env_txns_.insert(make_pair(penv, stk));
	global_lock(mtx_handle_);
	open_envs_.insert(make_pair(penv, 1u));
	delenvs.insert(penv);
	global_unlock(mtx_handle_);
	return penv;
}

DbTxn* ResourceManager::current_txn(DbEnv*env)
{
	if (env_txns_.count(env) <= 0)
		return NULL;

	stack<DbTxn*> &pstk = env_txns_[env];
	return pstk.size() != 0 ? pstk.top() : NULL;
}

void ResourceManager::thread_exit()
{
	ResourceManager *pinst;

	pinst = ResourceManager::instance();
	if (pinst == NULL) // Already deleted.
		return;

	global_lock(mtx_globj_);
	glob_objs_.erase(pinst);
	global_unlock(mtx_globj_);
	TlsWrapper<ResourceManager>::set_tls_obj(NULL);

	// Can't put this line between the lock and unlock pair above,
	// because the destructor also locks the same mutex, there 
	// would be a self lock.
	delete pinst;
}

void ResourceManager::set_global_callbacks()
{
	DbstlElemTraits<char> * cstarinst = 
	    DbstlElemTraits<char>::instance();
	cstarinst->set_sequence_len_function(dbstl_strlen);
	cstarinst->set_sequence_copy_function(dbstl_strcpy);
	cstarinst->set_sequence_compare_function(dbstl_strcmp);
	cstarinst->set_sequence_n_compare_function(dbstl_strncmp);

	DbstlElemTraits<wchar_t> *wcstarinst = 
	    DbstlElemTraits<wchar_t>::instance();
	wcstarinst->set_sequence_copy_function(dbstl_wcscpy);
	wcstarinst->set_sequence_len_function(dbstl_wcslen);
	wcstarinst->set_sequence_compare_function(dbstl_wcscmp);
	wcstarinst->set_sequence_n_compare_function(dbstl_wcsncmp);
}

ResourceManager* ResourceManager::instance()
{
	ResourceManager *pinst = NULL;
#ifdef HAVE_PTHREAD_TLS
	// Initialize the tls key.
	pthread_once(&once_control_, tls_init_once<ResourceManager>);
#endif

	if ((pinst = TlsWrapper<ResourceManager>::get_tls_obj()) == NULL){
		TlsWrapper<ResourceManager>::set_tls_obj(
		    pinst = new ResourceManager());
		register_global_object(pinst);
		set_global_callbacks();
	}
	return pinst;
}

int ResourceManager::open_cursor(DbCursorBase *dcbcsr,
    Db *pdb, int flags)
{
	u_int32_t oflags = 0;
	int ret;

	if (!pdb || !dcbcsr)
		return 0;

	csrset_t::iterator csitr;
	Dbc* csr = NULL;
	dcbcsr->set_owner_db(pdb);

	DbTxn *ptxn = NULL;
	DbTxn *ptxn2 = this->current_txn(pdb->get_env());
	if (ptxn2) {
		ptxn = ptxn2;
		dcbcsr->set_owner_txn(ptxn);
	}

	if (pdb->get_env() != NULL){
		ret = pdb->get_env()->get_open_flags(&oflags);
		dbstl_assert(ret == 0);
	}

	// Call Dbc->cursor only if there is no active open cursor in the
	// current thread, otherwise duplicate one from the existing cursor
	// and use the locks already held in this thread.
	//
	csrset_t *pcsrset = NULL;
	db_csr_map_t::iterator itrpcsrset = all_csrs_.find(pdb);
	if (itrpcsrset == all_csrs_.end()) { // No such pair in current thread.
		pcsrset = new csrset_t;
		pair<db_csr_map_t::iterator, bool> insret0 = 
		    all_csrs_.insert(make_pair(pdb, pcsrset));
		assert(insret0.second);
	} else
		pcsrset = itrpcsrset->second;

	assert(pcsrset != NULL);
	if (pcsrset->size() == 0) {
newcursor:
		BDBOP2(pdb->cursor(ptxn, &csr, flags), ret,
		    ((csr != NULL ? csr->close() : 1),
		    this->abort_txn(pdb->get_env())));
	} else {
		// We have some open cursors, so try to dup from one. If we are
		// in CDS mode, and trying to open a write cursor, we should
		// duplicate from a write cursor.
		csitr = pcsrset->begin();
		Dbc *csr22 = (*csitr)->get_cursor();
		assert(csr22 != NULL);
		assert(!((oflags & DB_INIT_TXN) && (flags & DB_WRITECURSOR)));
		// If opening a CDS write cursor, must find a write cursor
		// to duplicate from.
		if (((flags & DB_WRITECURSOR) != 0)) {
			for (;csitr != pcsrset->end(); ++csitr) {
				csr22 = (*csitr)->get_cursor();
				if (((DBC*)csr22)->flags & DBC_WRITECURSOR) {
					// No need to abortTxn on fail in CDS.
					BDBOP2(csr22->dup(&csr, DB_POSITION),
					     ret, csr->close());
					goto done;
				}
			}
			goto newcursor; // No write cursor, create a new one.

		} else if (((oflags & DB_INIT_TXN) == 0) || 
		    pdb->get_transactional() == 0) {
			// We are opening a DS or CDS read cursor, or 
			// opening a cursor in 
			// a transactional environment from a database not 
			// transactionally created.
			BDBOP2(csr22->dup(&csr, DB_POSITION), ret,
			    (csr->close(), this->abort_txn(pdb->get_env())));
			goto done;
		} else  {
			// We are opening a transactional cursor, duplicate
			// from a transactional one.
			// We don't remove (close) the non-transactional ones,
			// they are in use.
			// Hold the locks already held in this thread,
			// so need DB_POSITION flag.
			//
			DbTxn *ptxn3 = NULL;
			DbCursorBase *dcbcursor = NULL;
			csrset_t::iterator itr3, itr4;
			int got_rg = 0;

			// Opening a cursor in a transactional environment
			// with no transaction specified. This should not
			// happen in the first place.
			if (ptxn == NULL)
				THROW(InvalidArgumentException, ("DbTxn*",
"Opening a cursor in a transactional environment but no transaction \
is started specified"));
			// When we check that there must be a valid transaction
			// handle ptxn when opening a cursor in a
			// transactional environment, the following code
			// to delete cursors with no transaction
			// is not required and never reached,
			// but we will leave it there.
			for (;csitr != pcsrset->end();) {
				dcbcursor = *csitr;
				ptxn3 = dcbcursor->get_owner_txn();
				if (ptxn3 == NULL) {
					BDBOP(dcbcursor->close(), ret);
					if (!got_rg){
						got_rg++;
						itr3 = csitr;
					}
				} else if (got_rg) {
					got_rg = 0;
					itr4 = csitr;
					pcsrset->erase(itr3, itr4);
					csitr = pcsrset->begin();
					continue;
				}

				if (ptxn3 == ptxn)  {
					csr22 = dcbcursor->get_cursor();
					BDBOP2(csr22->dup(&csr, DB_POSITION),
					    ret, (csr->close(), this->
					    abort_txn(pdb->get_env())));
					goto done;
				}
				++csitr;

			}
			if (got_rg) {
				pcsrset->erase(itr3, pcsrset->end());
				got_rg = 0;
			}

			goto newcursor;

		} // else oflags & DB_INIT_TXN
	} // else pcsrset->size()
done:
	// Insert into current thread's db-cursor map and txn_csrs_ map,
	// for later duplication.
	//
	dcbcsr->set_cursor(csr);
	this->add_cursor(pdb, dcbcsr);
	return 0;
}

void ResourceManager::add_cursor(Db* dbp, DbCursorBase* dcbcsr)
{
	if (!dbp || !dcbcsr)
		return;
	assert(dcbcsr->get_cursor() != NULL);

	(all_csrs_[dbp])->insert(dcbcsr);
	// Register to txncsrs_, we suppose current transaction is the context
	// of this operation.
	//
	this->add_txn_cursor(dcbcsr, dbp->get_env());
}

// Close dbp's all open cursors opened in current thread, do not close
// those of dbp opened in other threads, Db::truncate requires dbp's
// all cursors of all threads should be closed, and it is user's duty
// to make sure other threads all close dbp's cursor, because if we
// close them here, it is also an error---multi-threaded access to the same
// Dbc* cursor should be serialized, we can't serialize with user code
// anyway.
//
size_t ResourceManager::close_db_cursors(Db* dbp1)
{
	int ret;
	Db* dbp;
	DbTxn *ptxn, *ptxn2;
	csrset_t *pcset_txn;

	if (dbp1 == NULL)
		return 0;

	dbp = dbp1;
	db_csr_map_t::iterator itr0;
	csrset_t::iterator itr;

	itr0 = all_csrs_.find(dbp1);
	if (itr0 == all_csrs_.end())
		return 0;

	csrset_t *pcset = itr0->second;

	pcset_txn = NULL;
	ptxn2 = ptxn = NULL;
	size_t txncsr_sz = txn_csrs_.size();

	for (itr = pcset->begin(), ret = 0; itr != pcset->end();
	    ++itr, ret++) {

		BDBOP((*itr)->close(), ret);
		if (txncsr_sz > 0) {
			if (pcset_txn == NULL || ptxn !=
			    (ptxn2 = (*itr)->get_owner_txn())) {
				ptxn = ptxn2 ? ptxn2 : (*itr)->get_owner_txn();
				if (ptxn != NULL)
					pcset_txn = txn_csrs_[ptxn];
			}
			if (pcset_txn)
				pcset_txn->erase(*itr);
		}

	}

	// Don't delete the pcset or itr0 because this dbp1 may be used
	// by other containers in this thread.
	pcset->clear();
	// We don't delete the DbCursorBase object, it is still
	// referenced by others.
	return ret;
}

// Close the cursor of csr and remove the entry containing csr from
// txn_csrs_ and all_csrs_.
int ResourceManager::remove_cursor(DbCursorBase*csr,
    bool remove_from_txncsrs)
{
	int ret;

	if (csr == NULL)
		return 0;
	BDBOP(csr->close(), ret);

	if (remove_from_txncsrs) {
		DbTxn *ptxn = csr->get_owner_txn();
		if (ptxn != NULL) {
			txncsr_t::iterator itr = txn_csrs_.find(ptxn);
			if (itr != txn_csrs_.end())
				itr->second->erase(csr);
		}
	}

	Db *pdb = csr->get_owner_db();
	if (pdb != NULL)
		all_csrs_[pdb]->erase(csr);

	return ret;
}

/*
 * Remove cursors opened in transaction txn's context, should be called before
 * commiting/aborting a transaction.
 * Note that here we should remove the cursor from all_csrs_ too,
 * by calling remove_cursor() function.
 */
void ResourceManager::remove_txn_cursor(DbTxn* txn)
{
	int ret;

	if (!txn)
		return;

	txncsr_t::iterator itr0;
	csrset_t::iterator itr;
	itr0 = txn_csrs_.find(txn);
	if (itr0 == txn_csrs_.end())
		return; // No cursor opened in this txn.

	csrset_t *pcsrs = itr0->second;
	DbCursorBase *csr;

	// Remove(close and remove from csr registry) cursors
	// opened in the transaction txn's context.
	for (itr = pcsrs->begin(); itr != pcsrs->end(); ++itr) {
		// This cursor should be closed now and removed
		// from csr registry.
		csr = *itr;
		BDBOP(csr->close(), ret);
		all_csrs_[csr->get_owner_db()]->erase(csr);
	}

	delete pcsrs;
	// Erase csrs belonging to txn.
	txn_csrs_.erase(itr0);
}

// Begin a new transaction from the specified environment env.
// When outtxn is non-zero, it supports nested txn,
// so the new transaction is started as a child transaction of the
// current one, and we push it into env1's transaction stack;
// Otherwise, we are starting an internal transaction for autocommit,
// no new transaction will be started, but current transaction's reference
// count will be incremented.
DbTxn* ResourceManager::begin_txn(u_int32_t flags, DbEnv*env1, int outtxn)
{
	DbEnv *env = env1;
	DbTxn *ptxn, *txn = NULL;
	int ret;

	if (!env1)
		return NULL;

	assert(env_txns_.count(env1) > 0);

	stack<DbTxn*>&stk = env_txns_[env1];

	// Not an outside transaction, so if there is transaction in stack,
	// use it and increment its reference count.
	if (outtxn == 0) {
		// We have a transaction in stack, increment its reference
		// count.
		if (stk.size() > 0) {
			txn = stk.top();
			// The txn was created externally, now we internally
			// use it, so the reference count is 2.
			map<DbTxn *, size_t>::iterator itr12;
			if ((itr12 = txn_count_.find(txn)) == txn_count_.end())
				txn_count_.insert(make_pair(txn, 2u));
			else
				txn_count_[txn]++;
		} else {
	// Empty stack, create a transaction and set reference count to 1.
			BDBOP(env->txn_begin(NULL, &txn, flags), ret);
			stk.push(txn);
			txn_count_[txn] = 1;// the first to use it
			txn_csrs_.insert(make_pair(txn, new csrset_t()));
		}

	} else { // Creating a transaction by user, used outside of dbstl.
		ptxn = stk.size() > 0 ? stk.top() : NULL;

		BDBOP(env->txn_begin(ptxn, &txn, flags), ret);

		// txn now is the current txn
		stk.push(txn);
		txn_csrs_.insert(make_pair(txn, new csrset_t()));
	}

	return txn;
}

void ResourceManager::commit_txn(DbEnv *env, u_int32_t flags)
{
	int ret;
	DbTxn *ptxn;

	if (!env)
		return;

	assert(env_txns_.count(env) > 0);
	stack<DbTxn*> &stk = env_txns_[env];
	ptxn = stk.top();
	assert(ptxn != NULL);
	size_t txncnt = txn_count_[ptxn];

	if (txncnt > 1) // used internally
		txn_count_[ptxn]--;
	else {
		txn_count_.erase(ptxn);
		this->remove_txn_cursor(ptxn);
		stk.pop();
		BDBOP(ptxn->commit(flags), ret);

	}

}

void ResourceManager::commit_txn(DbEnv *env, DbTxn *txn, u_int32_t flags)
{
	DbTxn *ptxn = NULL;
	int ret;

	if (env == NULL || txn == NULL)
		return;

	stack<DbTxn*> &stk = env_txns_[env];
	while (stk.size() > 0 && (ptxn = stk.top()) != txn) {
		stk.pop();
		txn_count_.erase(ptxn);// may be in the txn_count_ map
		this->remove_txn_cursor(ptxn);
		// Child txns could be committed by parent txn, but c++ API 
		// can't delete the new'ed child txns when committing the 
		// parent txn, so have to commit them explicitly.
		ptxn->commit(flags);
	}
	if (stk.size() == 0)
		THROW(InvalidArgumentException, (
		    "No such transaction created by dbstl"));
	else {
		stk.pop();
		txn_count_.erase(txn);// may be in the txn_count_ map
		this->remove_txn_cursor(txn);
		if (ptxn){
			BDBOP(ptxn->commit(flags), ret);
		} else // could never happen
			THROW(InvalidArgumentException, (
			    "No such transaction created by dbstl"));

	}
}

void ResourceManager::abort_txn(DbEnv *env, DbTxn *txn)
{
	int ret;
	DbTxn *ptxn = NULL;
	u_int32_t oflags;

	if (env == NULL || txn == NULL)
		return;

	BDBOP (env->get_open_flags(&oflags), ret);
	stack<DbTxn*> &stk = env_txns_[env];
	while (stk.size() > 0 && (ptxn = stk.top()) != txn) {
		txn_count_.erase(ptxn);// may be in the txn_count_ map
		this->remove_txn_cursor(ptxn);
		stk.pop();
		// Child txns could be aborted by parent txn, but c++ API 
		// can't delete the new'ed child txns when aborting the 
		// parent txn, so have to abort them explicitly.
		ptxn->abort();
	}
	if (stk.size() == 0)
		THROW(InvalidArgumentException, (
		    "No such transaction created by dbstl"));
	else {
		stk.pop();
		txn_count_.erase(txn);// may be in the txn_count_ map
		this->remove_txn_cursor(txn);
		if (ptxn){
			if ((oflags & DB_INIT_CDB) == 0)
				BDBOP(ptxn->abort(), ret);
		} else // could never happen
			THROW(InvalidArgumentException, (
			    "No such transaction created by dbstl"));

	}
}

// Abort current txn, close/remove its cursors and reference count.
void ResourceManager::abort_txn(DbEnv*env)
{
	int ret;
	DbTxn *ptxn;
	u_int32_t oflags;

	if (!env)
		return;
	env_txns_t::iterator itr(env_txns_.find(env));
	if (itr == env_txns_.end())
		return;

	stack<DbTxn*> &stk = itr->second;
	if (stk.size() == 0)
		return;
	ptxn = stk.top();
	if (ptxn == NULL)
		return;
	this->remove_txn_cursor(ptxn);
	BDBOP (env->get_open_flags(&oflags), ret);

	// Transactions handles created via cdsgroup_begin can not be aborted
	// because they are not really transactions, they just borrow the
	// DB_TXN structure to store a locker id.
	if ((oflags & DB_INIT_CDB) == 0) 
		BDBOP(ptxn->abort(), ret);
	txn_count_.erase(ptxn);
	stk.pop();
}

DbTxn* ResourceManager::set_current_txn_handle(DbEnv *env, DbTxn *newtxn)
{
	assert(env_txns_.count(env) > 0);
	stack<DbTxn*> &stk = env_txns_[env];
	DbTxn *ptxn = stk.top();
	stk.pop();
	stk.push(newtxn);
	return ptxn;
}

void ResourceManager::add_txn_cursor(DbCursorBase *dcbcsr, DbEnv *env)
{
	if (!env || !dcbcsr)
		return;

	DbTxn *ptxn = this->current_txn(env);
	if (ptxn == NULL)
		return;

	u_int32_t oflags;
	int ret;

	BDBOP(env->get_open_flags(&oflags), ret);
	if ((oflags & DB_INIT_TXN) == 0)
		return;

	txncsr_t::iterator itr;
	csrset_t *pset;

	itr = txn_csrs_.find(ptxn);
	pair<txncsr_t::iterator, bool> insret;

	if (itr == txn_csrs_.end()) {
		insret = txn_csrs_.insert(make_pair(ptxn, new csrset_t()));
		assert(insret.second);
		itr = insret.first;
	}
	pset = itr->second;
	pset->insert(dcbcsr);
}

void ResourceManager::register_db(Db*pdb1)
{
	if (!pdb1)
		return;
	global_lock(mtx_handle_);
	if (open_dbs_.count(pdb1) == 0)
		open_dbs_.insert(make_pair(pdb1, 1u));
	else
		open_dbs_[pdb1]++;
	global_unlock(mtx_handle_);
	csrset_t *pcsrset = new csrset_t();
	pair<db_csr_map_t::iterator, bool> insret = all_csrs_.insert(
	    make_pair(pdb1, pcsrset));
	if (!insret.second)
		delete pcsrset;

}

void ResourceManager::register_db_env(DbEnv*env1)
{
	u_int32_t oflags = 0;
	DbTxn *ptxn = NULL;
	int ret;

	if (!env1)
		return;

	stack<DbTxn*> stk;
	BDBOP(env1->get_open_flags(&oflags), ret);

	if (oflags & DB_INIT_CDB) {
		env1->cdsgroup_begin(&ptxn);
		stk.push(ptxn);
	}

	env_txns_.insert(make_pair(env1, stk));

	global_lock(mtx_handle_);
	if (open_envs_.count(env1) == 0)
		open_envs_.insert(make_pair(env1, 1u));
	else
		open_envs_[env1]++;
	global_unlock(mtx_handle_);
}

// Delete registered DbstlGlobalInnerObject objects.
void ResourceManager::global_exit()
{
	set<DbstlGlobalInnerObject *>::iterator itr;
	global_lock(mtx_globj_);
	for (itr = glob_objs_.begin(); itr != glob_objs_.end(); ++itr)
		delete *itr;
	global_unlock(mtx_globj_);

	mtx_env_->mutex_free(mtx_globj_);
	mtx_env_->mutex_free(mtx_handle_);
	delete mtx_env_;
}

void ResourceManager::register_global_object(DbstlGlobalInnerObject *gio)
{
	global_lock(mtx_globj_);
	glob_objs_.insert(gio);
	global_unlock(mtx_globj_);
}

END_NS