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Overview
Comment: | Changes which attempt to address an obscure SQLITE_PROTOCOL error. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | wal-trace-375 |
Files: | files | file ages | folders |
SHA1: |
1725aa7501fa97283a397d4c7cf206f3 |
User & Date: | drh 2011-02-19 14:19:17.314 |
Context
2011-02-19
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14:19 | Changes which attempt to address an obscure SQLITE_PROTOCOL error. (Leaf check-in: 1725aa7501 user: drh tags: wal-trace-375) | |
2011-01-18
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17:34 | Pull over all the latest trunk changes. (check-in: ca86d04be1 user: drh tags: wal-trace-375) | |
Changes
Changes to src/wal.c.
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1968 1969 1970 1971 1972 1973 1974 | u32 mxReadMark; /* Largest aReadMark[] value */ int mxI; /* Index of largest aReadMark[] value */ int i; /* Loop counter */ int rc = SQLITE_OK; /* Return code */ assert( pWal->readLock<0 ); /* Not currently locked */ | | > > > > > > > > > > > > > > > > > > | | 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 | u32 mxReadMark; /* Largest aReadMark[] value */ int mxI; /* Index of largest aReadMark[] value */ int i; /* Loop counter */ int rc = SQLITE_OK; /* Return code */ assert( pWal->readLock<0 ); /* Not currently locked */ /* Take steps to avoid spinning forever if there is a protocol error. ** ** Circumstances that cause a RETRY should only last for the briefest ** instances of time. No I/O or other system calls are done while the ** locks are held, so the locks should not be held for very long. But ** if we are unlucky, another process that is holding a lock might get ** paged out or take a page-fault that is time-consuming to resolve, ** during the few nanoseconds that it is holding the lock. In that case, ** it might take longer than normal for the lock to free. ** ** After 5 RETRYs, we begin calling sqlite3OsSleep(). The first few ** calls to sqlite3OsSleep() have a delay of 1 microsecond. Really this ** is more of a scheduler yield than an actual delay. But on the 10th ** an subsequent retries, the delays start becoming longer and longer, ** so that on the 100th (and last) RETRY we delay for 21 milliseconds. ** The total delay time before giving up is less than 1 second. */ if( cnt>5 ){ int nDelay = 1; /* Pause time in microseconds */ walTrace("cnt=%d",cnt); if( cnt>100 ) return SQLITE_PROTOCOL; if( cnt>=10 ) nDelay = (cnt-9)*238; /* Max delay 21ms. Total delay 996ms */ sqlite3OsSleep(pWal->pVfs, nDelay); } if( !useWal ){ rc = walIndexReadHdr(pWal, pChanged); if( rc==SQLITE_BUSY ){ /* If there is not a recovery running in another thread or process ** then convert BUSY errors to WAL_RETRY. If recovery is known to |
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2056 2057 2058 2059 2060 2061 2062 | u32 thisMark = pInfo->aReadMark[i]; if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){ assert( thisMark!=READMARK_NOT_USED ); mxReadMark = thisMark; mxI = i; } } | | < < < < < < < < < < < < < < < < > | > > > > > | 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 | u32 thisMark = pInfo->aReadMark[i]; if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){ assert( thisMark!=READMARK_NOT_USED ); mxReadMark = thisMark; mxI = i; } } /* There was once an "if" here. The extra "{" is to preserve indentation. */ { if( mxReadMark < pWal->hdr.mxFrame || mxI==0 ){ for(i=1; i<WAL_NREADER; i++){ rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1); if( rc==SQLITE_OK ){ mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame; mxI = i; walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1); break; }else if( rc!=SQLITE_BUSY ){ walTrace("walLockExclusive(%d):%d", i, rc); return rc; } } } if( mxI==0 ){ assert( rc==SQLITE_BUSY ); walTrace("all readlocks busy: cannot set read mark"); return WAL_RETRY; } rc = walLockShared(pWal, WAL_READ_LOCK(mxI)); if( rc ){ walTrace("walLockShared(mxI=%d):%d", mxI, rc); return rc==SQLITE_BUSY ? WAL_RETRY : rc; } /* Now that the read-lock has been obtained, check that neither the |
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2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 | int rc = SQLITE_OK; int cnt; if( pWal->readLock==0 ){ volatile WalCkptInfo *pInfo = walCkptInfo(pWal); assert( pInfo->nBackfill==pWal->hdr.mxFrame ); if( pInfo->nBackfill>0 ){ rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1); if( rc==SQLITE_OK ){ /* If all readers are using WAL_READ_LOCK(0) (in other words if no ** readers are currently using the WAL), then the transactions ** frames will overwrite the start of the existing log. Update the ** wal-index header to reflect this. ** ** In theory it would be Ok to update the cache of the header only ** at this point. But updating the actual wal-index header is also ** safe and means there is no special case for sqlite3WalUndo() ** to handle if this transaction is rolled back. */ int i; /* Loop counter */ u32 *aSalt = pWal->hdr.aSalt; /* Big-endian salt values */ pWal->nCkpt++; pWal->hdr.mxFrame = 0; sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0])); | > > | | 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 | int rc = SQLITE_OK; int cnt; if( pWal->readLock==0 ){ volatile WalCkptInfo *pInfo = walCkptInfo(pWal); assert( pInfo->nBackfill==pWal->hdr.mxFrame ); if( pInfo->nBackfill>0 ){ u32 salt1; sqlite3_randomness(4, &salt1); rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1); if( rc==SQLITE_OK ){ /* If all readers are using WAL_READ_LOCK(0) (in other words if no ** readers are currently using the WAL), then the transactions ** frames will overwrite the start of the existing log. Update the ** wal-index header to reflect this. ** ** In theory it would be Ok to update the cache of the header only ** at this point. But updating the actual wal-index header is also ** safe and means there is no special case for sqlite3WalUndo() ** to handle if this transaction is rolled back. */ int i; /* Loop counter */ u32 *aSalt = pWal->hdr.aSalt; /* Big-endian salt values */ pWal->nCkpt++; pWal->hdr.mxFrame = 0; sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0])); aSalt[1] = salt1; walIndexWriteHdr(pWal); pInfo->nBackfill = 0; for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED; assert( pInfo->aReadMark[0]==0 ); walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1); }else if( rc!=SQLITE_BUSY ){ return rc; |
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