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Overview
| Comment: | Add a test case for a read-only transaction outlasting an entire read-write session. And a fix. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | read-only-clients |
| Files: | files | file ages | folders |
| SHA1: |
3f532582197266f734d837ba38326c00 |
| User & Date: | dan 2013-02-19 20:16:09 |
Context
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2013-02-20
| ||
| 16:03 | Instead of locking the CHECKPOINTER byte, have read-only connections take a SHARED lock on the ROTRANS byte when reading from a non-live db. Read-write connections may not recycle space within either the database or log files while such a lock is held, but may perform checkpoint operations. check-in: 3b2a50c089 user: dan tags: read-only-clients | |
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2013-02-19
| ||
| 20:16 | Add a test case for a read-only transaction outlasting an entire read-write session. And a fix. check-in: 3f53258219 user: dan tags: read-only-clients | |
| 19:35 | Changes to allow read-only clients to safely work with live databases. check-in: 08cc3604cf user: dan tags: read-only-clients | |
Changes
Changes to src/lsmInt.h.
900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 |
#ifdef LSM_DEBUG
void lsmShmHasLock(lsm_db *db, int iLock, int eOp);
#else
# define lsmShmHasLock(x,y,z)
#endif
int lsmReadlock(lsm_db *, i64 iLsm, u32 iShmMin, u32 iShmMax);
int lsmReleaseReadlock(lsm_db *);
int lsmLsmInUse(lsm_db *db, i64 iLsmId, int *pbInUse);
int lsmTreeInUse(lsm_db *db, u32 iLsmId, int *pbInUse);
int lsmFreelistAppend(lsm_env *pEnv, Freelist *p, int iBlk, i64 iId);
int lsmDbMultiProc(lsm_db *);
void lsmDbDeferredClose(lsm_db *, lsm_file *, LsmFile *);
|
< |
900 901 902 903 904 905 906 907 908 909 910 911 912 913 |
#ifdef LSM_DEBUG void lsmShmHasLock(lsm_db *db, int iLock, int eOp); #else # define lsmShmHasLock(x,y,z) #endif int lsmReadlock(lsm_db *, i64 iLsm, u32 iShmMin, u32 iShmMax); int lsmLsmInUse(lsm_db *db, i64 iLsmId, int *pbInUse); int lsmTreeInUse(lsm_db *db, u32 iLsmId, int *pbInUse); int lsmFreelistAppend(lsm_env *pEnv, Freelist *p, int iBlk, i64 iId); int lsmDbMultiProc(lsm_db *); void lsmDbDeferredClose(lsm_db *, lsm_file *, LsmFile *); |
Changes to src/lsm_main.c.
740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 |
/* Open a read transaction if one is not already open. */
assert_db_state(pDb);
if( pDb->pShmhdr==0 ){
assert( pDb->bReadonly );
rc = lsmBeginRoTrans(pDb);
}else{
assert( pDb->bRoTrans==0 );
rc = lsmBeginReadTrans(pDb);
}
/* Allocate the multi-cursor. */
if( rc==LSM_OK ) rc = lsmMCursorNew(pDb, &pCsr);
/* If an error has occured, set the output to NULL and delete any partially
|
< |
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/* Open a read transaction if one is not already open. */
assert_db_state(pDb);
if( pDb->pShmhdr==0 ){
assert( pDb->bReadonly );
rc = lsmBeginRoTrans(pDb);
}else{
rc = lsmBeginReadTrans(pDb);
}
/* Allocate the multi-cursor. */
if( rc==LSM_OK ) rc = lsmMCursorNew(pDb, &pCsr);
/* If an error has occured, set the output to NULL and delete any partially
|
Changes to src/lsm_shared.c.
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rc = lsmShmLock(pDb, LSM_LOCK_DMS1, LSM_LOCK_EXCL, 1);
if( rc==LSM_OK ){
/* Try an exclusive lock on DMS2. If successful, this is the last
** connection to the database. In this case flush the contents of the
** in-memory tree to disk and write a checkpoint. */
rc = lsmShmTestLock(pDb, LSM_LOCK_DMS2, 1, LSM_LOCK_EXCL);
if( rc==LSM_OK ){
int bReadonly = 0; /* True if there exist read-only conns. */
/* Flush the in-memory tree, if required. If there is data to flush,
** this will create a new client snapshot in Database.pClient. The
** checkpoint (serialization) of this snapshot may be written to disk
** by the following block.
................................................................................
break;
}
}
return rc;
}
/*
** Argument bFlush is true if the contents of the in-memory tree has just
** been flushed to disk. The significance of this is that once the snapshot
** created to hold the updated state of the database is synced to disk, log
** file space can be recycled.
*/
................................................................................
int lsmBeginReadTrans(lsm_db *pDb){
const int MAX_READLOCK_ATTEMPTS = 10;
const int nMaxAttempt = (pDb->bRoTrans ? 1 : MAX_READLOCK_ATTEMPTS);
int rc = LSM_OK; /* Return code */
int iAttempt = 0;
assert( pDb->pWorker==0 );
while( rc==LSM_OK && pDb->iReader<0 && (iAttempt++)<nMaxAttempt ){
int iTreehdr = 0;
int iSnap = 0;
assert( pDb->pCsr==0 && pDb->nTransOpen==0 );
................................................................................
** checkpoint just loaded. TODO: This will be removed after
** lsm_sorted.c is changed to work directly from the serialized
** version of the snapshot. */
if( pDb->pClient==0 ){
rc = lsmCheckpointDeserialize(pDb, 0, pDb->aSnapshot,&pDb->pClient);
}
assert( (rc==LSM_OK)==(pDb->pClient!=0) );
assert( pDb->iReader>=0 || pDb->bRoTrans );
/* Check that the client has the right compression hooks loaded.
** If not, set rc to LSM_MISMATCH. */
if( rc==LSM_OK ){
rc = lsmCheckCompressionId(pDb, pDb->pClient->iCmpId);
}
}else{
rc = lsmReleaseReadlock(pDb);
}
}
if( rc==LSM_BUSY ){
rc = LSM_OK;
}
}
................................................................................
#endif
}
if( rc==LSM_OK ){
rc = lsmShmCacheChunks(pDb, pDb->treehdr.nChunk);
}
if( rc!=LSM_OK ){
lsmReleaseReadlock(pDb);
}
if( pDb->pClient==0 && rc==LSM_OK ) rc = LSM_BUSY;
return rc;
}
/*
** db is a read-only database handle in the disconnected state. This function
................................................................................
/* Worker connections should not be closing read transactions. And
** read transactions should only be closed after all cursors and write
** transactions have been closed. Finally pClient should be non-NULL
** only iff pDb->iReader>=0. */
assert( pDb->pWorker==0 );
assert( pDb->pCsr==0 && pDb->nTransOpen==0 );
lsmReleaseReadlock(pDb);
if( pDb->bRoTrans ){
int i;
for(i=0; i<pDb->nShm; i++){
lsmFree(pDb->pEnv, pDb->apShm[i]);
}
lsmFree(pDb->pEnv, pDb->apShm);
pDb->apShm = 0;
pDb->nShm = 0;
pDb->pShmhdr = 0;
lsmShmLock(pDb, LSM_LOCK_CHECKPOINTER, LSM_LOCK_UNLOCK, 0);
pDb->bRoTrans = 0;
}
}
/*
** Open a write transaction.
*/
int lsmBeginWriteTrans(lsm_db *pDb){
int rc; /* Return code */
ShmHeader *pShm = pDb->pShmhdr; /* Shared memory header */
assert( pDb->nTransOpen==0 );
assert( pDb->bDiscardOld==0 );
/* If there is no read-transaction open, open one now. */
rc = lsmBeginReadTrans(pDb);
/* Attempt to take the WRITER lock */
if( rc==LSM_OK ){
rc = lsmShmLock(pDb, LSM_LOCK_WRITER, LSM_LOCK_EXCL, 0);
................................................................................
ShmHeader *pShm = db->pShmhdr;
int i;
assert( db->iReader<0 );
assert( shm_sequence_ge(iShmMax, iShmMin) );
/* This is a no-op if the read-only transaction flag is set. */
if( db->bRoTrans ) return LSM_OK;
/* Search for an exact match. */
for(i=0; db->iReader<0 && rc==LSM_OK && i<LSM_LOCK_NREADER; i++){
ShmReader *p = &pShm->aReader[i];
if( p->iLsmId==iLsm && p->iTreeId==iShmMax ){
rc = lsmShmLock(db, LSM_LOCK_READER(i), LSM_LOCK_SHARED, 0);
if( rc==LSM_OK && p->iLsmId==iLsm && p->iTreeId==iShmMax ){
................................................................................
if( db->pClient && db->pClient->iId<=iLsmId ){
*pbInUse = 1;
return LSM_OK;
}
return isInUse(db, iLsmId, 0, pbInUse);
}
/*
** Release the read-lock currently held by connection db.
*/
int lsmReleaseReadlock(lsm_db *db){
int rc = LSM_OK;
if( db->iReader>=0 ){
rc = lsmShmLock(db, LSM_LOCK_READER(db->iReader), LSM_LOCK_UNLOCK, 0);
db->iReader = -1;
}
return rc;
}
/*
** This function may only be called after a successful call to
** lsmDbDatabaseConnect(). It returns true if the connection is in
** multi-process mode, or false otherwise.
*/
int lsmDbMultiProc(lsm_db *pDb){
return pDb->pDatabase && pDb->pDatabase->bMultiProc;
|
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rc = lsmShmLock(pDb, LSM_LOCK_DMS1, LSM_LOCK_EXCL, 1);
if( rc==LSM_OK ){
/* Try an exclusive lock on DMS2. If successful, this is the last
** connection to the database. In this case flush the contents of the
** in-memory tree to disk and write a checkpoint. */
rc = lsmShmTestLock(pDb, LSM_LOCK_DMS2, 1, LSM_LOCK_EXCL);
if( rc==LSM_OK ){
rc = lsmShmTestLock(pDb, LSM_LOCK_CHECKPOINTER, 1, LSM_LOCK_EXCL);
}
if( rc==LSM_OK ){
int bReadonly = 0; /* True if there exist read-only conns. */
/* Flush the in-memory tree, if required. If there is data to flush,
** this will create a new client snapshot in Database.pClient. The
** checkpoint (serialization) of this snapshot may be written to disk
** by the following block.
................................................................................
break;
}
}
return rc;
}
/*
** Release the read-lock currently held by connection db.
*/
int dbReleaseReadlock(lsm_db *db){
int rc = LSM_OK;
if( db->iReader>=0 ){
rc = lsmShmLock(db, LSM_LOCK_READER(db->iReader), LSM_LOCK_UNLOCK, 0);
db->iReader = -1;
}
db->bRoTrans = 0;
return rc;
}
/*
** Argument bFlush is true if the contents of the in-memory tree has just
** been flushed to disk. The significance of this is that once the snapshot
** created to hold the updated state of the database is synced to disk, log
** file space can be recycled.
*/
................................................................................
int lsmBeginReadTrans(lsm_db *pDb){
const int MAX_READLOCK_ATTEMPTS = 10;
const int nMaxAttempt = (pDb->bRoTrans ? 1 : MAX_READLOCK_ATTEMPTS);
int rc = LSM_OK; /* Return code */
int iAttempt = 0;
assert( pDb->pWorker==0 );
while( rc==LSM_OK && pDb->iReader<0 && (iAttempt++)<nMaxAttempt ){
int iTreehdr = 0;
int iSnap = 0;
assert( pDb->pCsr==0 && pDb->nTransOpen==0 );
................................................................................
** checkpoint just loaded. TODO: This will be removed after
** lsm_sorted.c is changed to work directly from the serialized
** version of the snapshot. */
if( pDb->pClient==0 ){
rc = lsmCheckpointDeserialize(pDb, 0, pDb->aSnapshot,&pDb->pClient);
}
assert( (rc==LSM_OK)==(pDb->pClient!=0) );
assert( pDb->iReader>=0 );
/* Check that the client has the right compression hooks loaded.
** If not, set rc to LSM_MISMATCH. */
if( rc==LSM_OK ){
rc = lsmCheckCompressionId(pDb, pDb->pClient->iCmpId);
}
}else{
rc = dbReleaseReadlock(pDb);
}
}
if( rc==LSM_BUSY ){
rc = LSM_OK;
}
}
................................................................................
#endif
}
if( rc==LSM_OK ){
rc = lsmShmCacheChunks(pDb, pDb->treehdr.nChunk);
}
if( rc!=LSM_OK ){
dbReleaseReadlock(pDb);
}
if( pDb->pClient==0 && rc==LSM_OK ) rc = LSM_BUSY;
return rc;
}
/*
** db is a read-only database handle in the disconnected state. This function
................................................................................
/* Worker connections should not be closing read transactions. And
** read transactions should only be closed after all cursors and write
** transactions have been closed. Finally pClient should be non-NULL
** only iff pDb->iReader>=0. */
assert( pDb->pWorker==0 );
assert( pDb->pCsr==0 && pDb->nTransOpen==0 );
if( pDb->bRoTrans ){
int i;
for(i=0; i<pDb->nShm; i++){
lsmFree(pDb->pEnv, pDb->apShm[i]);
}
lsmFree(pDb->pEnv, pDb->apShm);
pDb->apShm = 0;
pDb->nShm = 0;
pDb->pShmhdr = 0;
lsmShmLock(pDb, LSM_LOCK_CHECKPOINTER, LSM_LOCK_UNLOCK, 0);
}
dbReleaseReadlock(pDb);
}
/*
** Open a write transaction.
*/
int lsmBeginWriteTrans(lsm_db *pDb){
int rc; /* Return code */
ShmHeader *pShm = pDb->pShmhdr; /* Shared memory header */
assert( pDb->nTransOpen==0 );
assert( pDb->bDiscardOld==0 );
assert( pDb->bReadonly==0 );
/* If there is no read-transaction open, open one now. */
rc = lsmBeginReadTrans(pDb);
/* Attempt to take the WRITER lock */
if( rc==LSM_OK ){
rc = lsmShmLock(pDb, LSM_LOCK_WRITER, LSM_LOCK_EXCL, 0);
................................................................................
ShmHeader *pShm = db->pShmhdr;
int i;
assert( db->iReader<0 );
assert( shm_sequence_ge(iShmMax, iShmMin) );
/* This is a no-op if the read-only transaction flag is set. */
if( db->bRoTrans ){
db->iReader = 0;
return LSM_OK;
}
/* Search for an exact match. */
for(i=0; db->iReader<0 && rc==LSM_OK && i<LSM_LOCK_NREADER; i++){
ShmReader *p = &pShm->aReader[i];
if( p->iLsmId==iLsm && p->iTreeId==iShmMax ){
rc = lsmShmLock(db, LSM_LOCK_READER(i), LSM_LOCK_SHARED, 0);
if( rc==LSM_OK && p->iLsmId==iLsm && p->iTreeId==iShmMax ){
................................................................................
if( db->pClient && db->pClient->iId<=iLsmId ){
*pbInUse = 1;
return LSM_OK;
}
return isInUse(db, iLsmId, 0, pbInUse);
}
/*
** This function may only be called after a successful call to
** lsmDbDatabaseConnect(). It returns true if the connection is in
** multi-process mode, or false otherwise.
*/
int lsmDbMultiProc(lsm_db *pDb){
return pDb->pDatabase && pDb->pDatabase->bMultiProc;
|
Changes to test/lsm5.test.
174 175 176 177 178 179 180 181 182 183 |
# Now close the read-only connection. The system is now non-live, but the
# *-shm remains in the file-system (the readonly connection cannot unlink it).
do_test 3.8 {
db close
list [file exists test.db-log] [file exists test.db-shm]
} {0 1}
finish_test
|
> > > > > > > > > > > > > > > > > > > |
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# Now close the read-only connection. The system is now non-live, but the
# *-shm remains in the file-system (the readonly connection cannot unlink it).
do_test 3.8 {
db close
list [file exists test.db-log] [file exists test.db-shm]
} {0 1}
#-------------------------------------------------------------------------
#
do_test 4.1 {
create_abc_log test.db
list [file size test.db] [file size test.db-log]
} {0 56}
do_test 4.2 {
lsm_open db test.db {readonly 1}
db csr_open T
list [db_fetch db a] [db_fetch db b] [db_fetch db c]
} {alpha bravo charlie}
do_test 4.3 {
lsm_open db_rw test.db
db_rw close
list [file size test.db] [file size test.db-log]
} {0 56}
finish_test
|