From 7c466e53f0e7a55e28ad343e8556934e54c31b15 Mon Sep 17 00:00:00 2001 From: James Rouzier Date: Wed, 25 Oct 2017 19:41:28 -0400 Subject: [PATCH] Add the ability to not block when opening a write transaction --- mdbx.h | 14 ++++++++++++-- src/bits.h | 3 ++- src/lck-posix.c | 18 +++++++++++++++++- src/lck-windows.c | 10 ++++++++++ src/mdbx.c | 6 ++++-- src/osal.h | 1 + 6 files changed, 46 insertions(+), 6 deletions(-) diff --git a/mdbx.h b/mdbx.h index 4d95ae25..d8453d05 100644 --- a/mdbx.h +++ b/mdbx.h @@ -327,6 +327,10 @@ typedef int(MDBX_cmp_func)(const MDBX_val *a, const MDBX_val *b); /* Store multiple data items in one call. Only for MDBX_DUPFIXED. */ #define MDBX_MULTIPLE 0x80000u +/* Transaction Flags*/ +/* Do not block when starting a write transaction */ +#define MDBX_TRYTXN 0x10000000u + /* Copy Flags */ /* Compacting copy: Omit free space from copy, and renumber all * pages sequentially. */ @@ -420,8 +424,10 @@ typedef enum MDBX_cursor_op { #define MDBX_BAD_DBI (-30780) /* Unexpected problem - txn should abort */ #define MDBX_PROBLEM (-30779) +/* Unexpected problem - txn should abort */ +#define MDBX_BUSY (-30778) /* The last defined error code */ -#define MDBX_LAST_ERRCODE MDBX_PROBLEM +#define MDBX_LAST_ERRCODE MDBX_BUSY /* The mdbx_put() or mdbx_replace() was called for key, that has more that one associated value. */ @@ -953,6 +959,9 @@ LIBMDBX_API int mdbx_env_set_assert(MDBX_env *env, MDBX_assert_func *func); * - MDBX_RDONLY * This transaction will not perform any write operations. * + * - MDBX_TRYTXN + * Do not block when starting a write transaction + * * [out] txn Address where the new MDBX_txn handle will be stored * * Returns A non-zero error value on failure and 0 on success, some @@ -964,7 +973,8 @@ LIBMDBX_API int mdbx_env_set_assert(MDBX_env *env, MDBX_assert_func *func); * as well. See mdbx_env_set_mapsize(). * - MDBX_READERS_FULL - a read-only transaction was requested and the reader * lock table is full. See mdbx_env_set_maxreaders(). - * - MDBX_ENOMEM - out of memory. */ + * - MDBX_ENOMEM - out of memory. + * - MDBX_BUSY - a write transaction is already started. */ LIBMDBX_API int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags, MDBX_txn **txn); diff --git a/src/bits.h b/src/bits.h index 43c02ed7..88a8032d 100644 --- a/src/bits.h +++ b/src/bits.h @@ -553,7 +553,8 @@ struct MDBX_txn { /* Transaction Flags */ /* mdbx_txn_begin() flags */ -#define MDBX_TXN_BEGIN_FLAGS (MDBX_NOMETASYNC | MDBX_NOSYNC | MDBX_RDONLY) +#define MDBX_TXN_BEGIN_FLAGS_PERSISTENT (MDBX_NOMETASYNC | MDBX_NOSYNC | MDBX_RDONLY) +#define MDBX_TXN_BEGIN_FLAGS (MDBX_TXN_BEGIN_FLAGS_PERSISTENT | MDBX_TRYTXN) #define MDBX_TXN_NOMETASYNC \ MDBX_NOMETASYNC /* don't sync meta for this txn on commit */ #define MDBX_TXN_NOSYNC MDBX_NOSYNC /* don't sync this txn on commit */ diff --git a/src/lck-posix.c b/src/lck-posix.c index 5b882b0d..0c8cb41b 100644 --- a/src/lck-posix.c +++ b/src/lck-posix.c @@ -184,6 +184,13 @@ static int mdbx_robust_lock(MDBX_env *env, pthread_mutex_t *mutex) { return rc; } +static int mdbx_robust_trylock(MDBX_env *env, pthread_mutex_t *mutex) { + int rc = pthread_mutex_trylock(mutex); + if (unlikely(rc != 0)) + rc = mdbx_mutex_failed(env, mutex, rc); + return rc; +} + static int mdbx_robust_unlock(MDBX_env *env, pthread_mutex_t *mutex) { int rc = pthread_mutex_unlock(mutex); if (unlikely(rc != 0)) @@ -213,6 +220,13 @@ int mdbx_txn_lock(MDBX_env *env) { return MDBX_IS_ERROR(rc) ? rc : MDBX_SUCCESS; } +int mdbx_txn_trylock(MDBX_env *env) { + mdbx_trace(">>"); + int rc = mdbx_robust_trylock(env, &env->me_lck->mti_wmutex); + mdbx_trace("<< rc %d", rc); + return MDBX_IS_ERROR(rc) ? rc : MDBX_SUCCESS; +} + void mdbx_txn_unlock(MDBX_env *env) { mdbx_trace(">>"); int rc = mdbx_robust_unlock(env, &env->me_lck->mti_wmutex); @@ -313,7 +327,9 @@ static int __cold mdbx_mutex_failed(MDBX_env *env, pthread_mutex_t *mutex, #endif /* MDBX_USE_ROBUST */ mdbx_error("mutex (un)lock failed, %s", mdbx_strerror(rc)); - if (rc != EDEADLK) { + if (rc == EBUSY) { + rc = MDBX_BUSY; + } else if (rc != EDEADLK && rc != EBUSY) { env->me_flags |= MDBX_FATAL_ERROR; rc = MDBX_PANIC; } diff --git a/src/lck-windows.c b/src/lck-windows.c index 66591db9..d3340d58 100644 --- a/src/lck-windows.c +++ b/src/lck-windows.c @@ -132,6 +132,16 @@ int mdbx_txn_lock(MDBX_env *env) { return GetLastError(); } +int mdbx_txn_trylock(MDBX_env *env) { + if (flock(env->me_fd, LCK_EXCLUSIVE | LCK_DONTWAIT, LCK_BODY)) + return MDBX_SUCCESS; + int rc = GetLastError(); + if (rc == ERROR_LOCK_VIOLATION) { + rc = MDBX_BUSY; + } + return rc; +} + void mdbx_txn_unlock(MDBX_env *env) { if (!funlock(env->me_fd, LCK_BODY)) mdbx_panic("%s failed: errcode %u", mdbx_func_, GetLastError()); diff --git a/src/mdbx.c b/src/mdbx.c index f510c4ee..a74c9376 100644 --- a/src/mdbx.c +++ b/src/mdbx.c @@ -708,6 +708,7 @@ static const char *__mdbx_strerr(int errnum) { "DUPFIXED size", "MDBX_BAD_DBI: The specified DBI handle was closed/changed unexpectedly", "MDBX_PROBLEM: Unexpected problem - txn should abort", + "MDBX_BUSY: Another write transation is started", }; if (errnum >= MDBX_KEYEXIST && errnum <= MDBX_LAST_ERRCODE) { @@ -2562,7 +2563,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) { } else { /* Not yet touching txn == env->me_txn0, it may be active */ mdbx_jitter4testing(false); - rc = mdbx_txn_lock(env); + rc = F_ISSET(flags, MDBX_TRYTXN) ? mdbx_txn_trylock(env) : mdbx_txn_lock(env); if (unlikely(rc)) return rc; @@ -2664,6 +2665,7 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags, MDBX_txn **ret) { MDBX_txn *txn; MDBX_ntxn *ntxn; + //unsigned pflags; int rc, size, tsize; if (unlikely(!env || !ret)) @@ -2718,7 +2720,7 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags, txn->mt_dbxs = env->me_dbxs; /* static */ txn->mt_dbs = (MDBX_db *)((char *)txn + tsize); txn->mt_dbflags = (uint8_t *)txn + size - env->me_maxdbs; - txn->mt_flags = flags; + txn->mt_flags = flags & MDBX_TXN_BEGIN_FLAGS_PERSISTENT; txn->mt_env = env; if (parent) { diff --git a/src/osal.h b/src/osal.h index 4216a534..ad9fd275 100644 --- a/src/osal.h +++ b/src/osal.h @@ -506,6 +506,7 @@ int mdbx_rdt_lock(MDBX_env *env); void mdbx_rdt_unlock(MDBX_env *env); int mdbx_txn_lock(MDBX_env *env); +int mdbx_txn_trylock(MDBX_env *env); void mdbx_txn_unlock(MDBX_env *env); int mdbx_rpid_set(MDBX_env *env);