diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index fa7c1f83bac34c54fefa210c2b3913bcc11db118..ef9b079cfc53c5975a6f217546ebdfcdca1247d7 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -295,6 +295,10 @@ void taos_close(TAOS *taos) {
 
       tscDebug("%p HB is freed", pHb);
       taosReleaseRef(tscObjRef, pHb->self);
+#ifdef __APPLE__
+      // to satisfy later tsem_destroy in taos_free_result
+      tsem_init(&pHb->rspSem, 0, 0);
+#endif // __APPLE__
       taos_free_result(pHb);
     }
   }
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 8dcb7425a8c4671dd46fe5e4679c896d1eaf00e0..e1521b4aa139f1d4cdf3c076c4a542d4a81cfb05 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -1933,6 +1933,10 @@ SSqlObj* createSimpleSubObj(SSqlObj* pSql, __async_cb_func_t fp, void* param, in
   }
 
   if (tscAddSubqueryInfo(pCmd) != TSDB_CODE_SUCCESS) {
+#ifdef __APPLE__
+    // to satisfy later tsem_destroy in taos_free_result
+    tsem_init(&pNew->rspSem, 0, 0);
+#endif // __APPLE__
     tscFreeSqlObj(pNew);
     return NULL;
   }
diff --git a/src/os/src/darwin/darwinSemphone.c b/src/os/src/darwin/darwinSemphone.c
index d8e60cd2d55f4dc38834046bc8d7b702832ce8b1..a9e470bd7019c84d8c8c8368da242cbc4a1d618b 100644
--- a/src/os/src/darwin/darwinSemphone.c
+++ b/src/os/src/darwin/darwinSemphone.c
@@ -13,19 +13,76 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+// fail-fast or let-it-crash philosophy
+// https://en.wikipedia.org/wiki/Fail-fast
+// https://stackoverflow.com/questions/4393197/erlangs-let-it-crash-philosophy-applicable-elsewhere
+// experimentally, we follow log-and-crash here
+
 #define _DEFAULT_SOURCE
 #include "os.h"
 
+// #define SEM_USE_PTHREAD
+// #define SEM_USE_POSIX
+#define SEM_USE_SEM
+
+#ifdef SEM_USE_SEM
+#include <mach/mach_init.h>
+#include <mach/mach_error.h>
+#include <mach/semaphore.h>
+#include <mach/task.h>
+
+static pthread_t                 sem_thread;
+static pthread_once_t            sem_once;
+static task_t                    sem_port;
+static volatile int              sem_inited = 0;
+static semaphore_t               sem_exit;
+
+static void* sem_thread_routine(void *arg) {
+  (void)arg;
+  sem_port = mach_task_self();
+  kern_return_t ret = semaphore_create(sem_port, &sem_exit, SYNC_POLICY_FIFO, 0);
+  if (ret != KERN_SUCCESS) {
+    fprintf(stderr, "==%s[%d]%s()==failed to create sem_exit\n", basename(__FILE__), __LINE__, __func__);
+    sem_inited = -1;
+    return NULL;
+  }
+  sem_inited = 1;
+  semaphore_wait(sem_exit);
+  return NULL;
+}
+
+static void once_init(void) {
+  int r = 0;
+  r = pthread_create(&sem_thread, NULL, sem_thread_routine, NULL);
+  if (r) {
+    fprintf(stderr, "==%s[%d]%s()==failed to create thread\n", basename(__FILE__), __LINE__, __func__);
+    return;
+  }
+  while (sem_inited==0) {
+    ;
+  }
+}
+#endif
+
 struct tsem_s {
+#ifdef SEM_USE_PTHREAD
+  pthread_mutex_t              lock;
+  pthread_cond_t               cond;
+  volatile int64_t             val;
+#elif defined(SEM_USE_POSIX)
+  size_t                       id;
+  sem_t                       *sem;
+#elif defined(SEM_USE_SEM)
+  semaphore_t                  sem;
+#else // SEM_USE_PTHREAD
   dispatch_semaphore_t         sem;
+#endif // SEM_USE_PTHREAD
+
   volatile unsigned int        valid:1;
 };
 
-int tsem_wait(tsem_t *sem);
-int tsem_post(tsem_t *sem);
-int tsem_destroy(tsem_t *sem);
 int tsem_init(tsem_t *sem, int pshared, unsigned int value) {
-  fprintf(stderr, "==%s[%d]%s():[%p]==creating\n", basename(__FILE__), __LINE__, __func__, sem);
+  // fprintf(stderr, "==%s[%d]%s():[%p]==creating\n", basename(__FILE__), __LINE__, __func__, sem);
   if (*sem) {
     fprintf(stderr, "==%s[%d]%s():[%p]==already initialized\n", basename(__FILE__), __LINE__, __func__, sem);
     abort();
@@ -36,11 +93,61 @@ int tsem_init(tsem_t *sem, int pshared, unsigned int value) {
     abort();
   }
 
+#ifdef SEM_USE_PTHREAD
+  int r = pthread_mutex_init(&p->lock, NULL);
+  do {
+    if (r) break;
+    r = pthread_cond_init(&p->cond, NULL);
+    if (r) {
+      pthread_mutex_destroy(&p->lock);
+      break;
+    }
+    p->val = value;
+  } while (0);
+  if (r) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==not created\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+#elif defined(SEM_USE_POSIX)
+  static size_t tick = 0;
+  do {
+    size_t id = atomic_add_fetch_64(&tick, 1);
+    if (id==SEM_VALUE_MAX) {
+      atomic_store_64(&tick, 0);
+      id = 0;
+    }
+    char name[NAME_MAX-4];
+    snprintf(name, sizeof(name), "/t%ld", id);
+    p->sem = sem_open(name, O_CREAT|O_EXCL, pshared, value);
+    p->id  = id;
+    if (p->sem!=SEM_FAILED) break;
+    int e = errno;
+    if (e==EEXIST) continue;
+    if (e==EINTR) continue;
+    fprintf(stderr, "==%s[%d]%s():[%p]==not created[%d]%s\n", basename(__FILE__), __LINE__, __func__, sem, e, strerror(e));
+    abort();
+  } while (p->sem==SEM_FAILED);
+#elif defined(SEM_USE_SEM)
+  pthread_once(&sem_once, once_init);
+  if (sem_inited!=1) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal resource init failed\n", basename(__FILE__), __LINE__, __func__, sem);
+    errno = ENOMEM;
+    return -1;
+  }
+  kern_return_t ret = semaphore_create(sem_port, &p->sem, SYNC_POLICY_FIFO, 0);
+  if (ret != KERN_SUCCESS) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==semophore_create failed\n", basename(__FILE__), __LINE__, __func__, sem);
+    // we fail-fast here, because we have less-doc about semaphore_create for the moment
+    abort();
+  }
+#else // SEM_USE_PTHREAD
   p->sem = dispatch_semaphore_create(value);
   if (p->sem == NULL) {
     fprintf(stderr, "==%s[%d]%s():[%p]==not created\n", basename(__FILE__), __LINE__, __func__, sem);
     abort();
   }
+#endif // SEM_USE_PTHREAD
+
   p->valid = 1;
 
   *sem = p;
@@ -58,7 +165,30 @@ int tsem_wait(tsem_t *sem) {
     fprintf(stderr, "==%s[%d]%s():[%p]==already destroyed\n", basename(__FILE__), __LINE__, __func__, sem);
     abort();
   }
+#ifdef SEM_USE_PTHREAD
+  if (pthread_mutex_lock(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  p->val -= 1;
+  if (p->val < 0) {
+    if (pthread_cond_wait(&p->cond, &p->lock)) {
+      fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+      abort();
+    }
+  }
+  if (pthread_mutex_unlock(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  return 0;
+#elif defined(SEM_USE_POSIX)
+  return sem_wait(p->sem);
+#elif defined(SEM_USE_SEM)
+  return semaphore_wait(p->sem);
+#else // SEM_USE_PTHREAD
   return dispatch_semaphore_wait(p->sem, DISPATCH_TIME_FOREVER);
+#endif // SEM_USE_PTHREAD
 }
 
 int tsem_post(tsem_t *sem) {
@@ -71,21 +201,76 @@ int tsem_post(tsem_t *sem) {
     fprintf(stderr, "==%s[%d]%s():[%p]==already destroyed\n", basename(__FILE__), __LINE__, __func__, sem);
     abort();
   }
+#ifdef SEM_USE_PTHREAD
+  if (pthread_mutex_lock(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  p->val += 1;
+  if (p->val <= 0) {
+    if (pthread_cond_signal(&p->cond)) {
+      fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+      abort();
+    }
+  }
+  if (pthread_mutex_unlock(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  return 0;
+#elif defined(SEM_USE_POSIX)
+  return sem_post(p->sem);
+#elif defined(SEM_USE_SEM)
+  return semaphore_signal(p->sem);
+#else // SEM_USE_PTHREAD
   return dispatch_semaphore_signal(p->sem);
+#endif // SEM_USE_PTHREAD
 }
 
 int tsem_destroy(tsem_t *sem) {
-  fprintf(stderr, "==%s[%d]%s():[%p]==destroying\n", basename(__FILE__), __LINE__, __func__, sem);
+  // fprintf(stderr, "==%s[%d]%s():[%p]==destroying\n", basename(__FILE__), __LINE__, __func__, sem);
   if (!*sem) {
-    fprintf(stderr, "==%s[%d]%s():[%p]==not initialized\n", basename(__FILE__), __LINE__, __func__, sem);
-    abort();
+    // fprintf(stderr, "==%s[%d]%s():[%p]==not initialized\n", basename(__FILE__), __LINE__, __func__, sem);
+    // abort();
     return 0;
   }
   struct tsem_s *p = *sem;
   if (!p->valid) {
-    fprintf(stderr, "==%s[%d]%s():[%p]==already destroyed\n", basename(__FILE__), __LINE__, __func__, sem);
+    // fprintf(stderr, "==%s[%d]%s():[%p]==already destroyed\n", basename(__FILE__), __LINE__, __func__, sem);
+    // abort();
+    return 0;
+  }
+#ifdef SEM_USE_PTHREAD
+  if (pthread_mutex_lock(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  p->valid = 0;
+  if (pthread_cond_destroy(&p->cond)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  if (pthread_mutex_unlock(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+  if (pthread_mutex_destroy(&p->lock)) {
+    fprintf(stderr, "==%s[%d]%s():[%p]==internal logic error\n", basename(__FILE__), __LINE__, __func__, sem);
+    abort();
+  }
+#elif defined(SEM_USE_POSIX)
+  char name[NAME_MAX-4];
+  snprintf(name, sizeof(name), "/t%ld", p->id);
+  int r = sem_unlink(name);
+  if (r) {
+    int e = errno;
+    fprintf(stderr, "==%s[%d]%s():[%p]==unlink failed[%d]%s\n", basename(__FILE__), __LINE__, __func__, sem, e, strerror(e));
     abort();
   }
+#elif defined(SEM_USE_SEM)
+  semaphore_destroy(sem_port, p->sem);
+#else // SEM_USE_PTHREAD
+#endif // SEM_USE_PTHREAD
 
   p->valid = 0;
   free(p);
diff --git a/src/os/src/darwin/darwinTimer.c b/src/os/src/darwin/darwinTimer.c
index 121e2e9427a7e313db9f718883d5f21ff39c3dad..ee1becc91af5237296bb2a562982b33cc5c78f10 100644
--- a/src/os/src/darwin/darwinTimer.c
+++ b/src/os/src/darwin/darwinTimer.c
@@ -13,9 +13,82 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+// fail-fast or let-it-crash philosophy
+// https://en.wikipedia.org/wiki/Fail-fast
+// https://stackoverflow.com/questions/4393197/erlangs-let-it-crash-philosophy-applicable-elsewhere
+// experimentally, we follow log-and-crash here
+
 #define _DEFAULT_SOURCE
 #include "os.h"
 
+#if 1
+#include <sys/event.h>
+
+static void (*timer_callback)(int);
+static int           timer_ms = 0;
+static pthread_t     timer_thread;
+static int           timer_kq = -1;
+static volatile int  timer_stop = 0;
+
+static void* timer_routine(void *arg) {
+  (void)arg;
+
+  int r = 0;
+  struct timespec to = {0};
+  to.tv_sec    = timer_ms / 1000;
+  to.tv_nsec   = (timer_ms % 1000) * 1000000;
+  while (!timer_stop) {
+    struct kevent64_s kev[10] = {0};
+    r = kevent64(timer_kq, NULL, 0, kev, sizeof(kev)/sizeof(kev[0]), 0, &to);
+    if (r!=0) {
+      fprintf(stderr, "==%s[%d]%s()==kevent64 failed\n", basename(__FILE__), __LINE__, __func__);
+      abort();
+    }
+    timer_callback(SIGALRM); // just mock
+  }
+
+  return NULL;
+}
+
+int taosInitTimer(void (*callback)(int), int ms) {
+  int r = 0;
+  timer_ms       = ms;
+  timer_callback = callback;
+
+  timer_kq = kqueue();
+  if (timer_kq==-1) {
+    fprintf(stderr, "==%s[%d]%s()==failed to create timer kq\n", basename(__FILE__), __LINE__, __func__);
+    // since no caller of this func checks the return value for the moment
+    abort();
+  }
+
+  r = pthread_create(&timer_thread, NULL, timer_routine, NULL);
+  if (r) {
+    fprintf(stderr, "==%s[%d]%s()==failed to create timer thread\n", basename(__FILE__), __LINE__, __func__);
+    // since no caller of this func checks the return value for the moment
+    abort();
+  }
+  return 0;
+}
+
+void taosUninitTimer() {
+  int r = 0;
+  timer_stop = 1;
+  r = pthread_join(timer_thread, NULL);
+  if (r) {
+    fprintf(stderr, "==%s[%d]%s()==failed to join timer thread\n", basename(__FILE__), __LINE__, __func__);
+    // since no caller of this func checks the return value for the moment
+    abort();
+  }
+  close(timer_kq);
+  timer_kq = -1;
+}
+
+void taos_block_sigalrm(void) {
+  // we don't know if there's any specific API for SIGALRM to deliver to specific thread
+  // this implementation relies on kqueue rather than SIGALRM
+}
+#else
 int taosInitTimer(void (*callback)(int), int ms) {
   signal(SIGALRM, callback);
 
@@ -46,4 +119,5 @@ void taos_block_sigalrm(void) {
     already_set = 1;
   }
 }
+#endif
 
diff --git a/src/os/src/darwin/eok.c b/src/os/src/darwin/eok.c
index 9c6a263a40c593cd2484faac8381eb529303b1f7..f731aaf330cb8618aa8a2dc51401ac45ecdc5440 100644
--- a/src/os/src/darwin/eok.c
+++ b/src/os/src/darwin/eok.c
@@ -13,13 +13,18 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+// fail-fast or let-it-crash philosophy
+// https://en.wikipedia.org/wiki/Fail-fast
+// https://stackoverflow.com/questions/4393197/erlangs-let-it-crash-philosophy-applicable-elsewhere
+// experimentally, we follow log-and-crash here
+
 #include "eok.h"
 
 #include "os.h"
 
 #include <sys/event.h>
 
-#define LET_IT_BE
+// #define BALANCE_CHECK_WHEN_CLOSE
 
 #ifdef ENABLE_LOG
 #define D(fmt, ...) fprintf(stderr, "%s[%d]%s(): " fmt "\n", basename(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
@@ -99,16 +104,16 @@ struct eok_event_s {
 typedef struct eoks_s                      eoks_t;
 struct eoks_s {
   pthread_mutex_t      lock;
-  ep_over_kq_t       **eoks;       // note: this memory leaks when process terminates
-  int                  neoks;      //       we can add an extra api to let user clean
-  ep_over_kq_t        *eoks_free;  //       currently, we just keep it simple stupid
+  ep_over_kq_t       **eoks;            // note: this memory leaks when process terminates
+  int                  neoks;           //       we can add an extra api to let user clean
+  ep_over_kq_t        *eoks_free_list;  //       currently, we just keep it simple stupid
 };
 
 static eoks_t          eoks = {
-  .lock           = PTHREAD_MUTEX_INITIALIZER,
-  .eoks           = NULL,
-  .neoks          = 0,
-  .eoks_free      = NULL,
+  .lock                = PTHREAD_MUTEX_INITIALIZER,
+  .eoks                = NULL,
+  .neoks               = 0,
+  .eoks_free_list      = NULL,
 };
 
 #ifdef ENABLE_LOG
@@ -760,9 +765,9 @@ static ep_over_kq_t* eoks_alloc(void) {
 
   A(0==pthread_mutex_lock(&eoks.lock), "");
   do {
-    if (eoks.eoks_free) {
-      eok = eoks.eoks_free;
-      eoks.eoks_free = eok->next;
+    if (eoks.eoks_free_list) {
+      eok = eoks.eoks_free_list;
+      eoks.eoks_free_list = eok->next;
       A(eoks.eoks, "internal logic error");
       A(eok->idx>=0 && eok->idx<eoks.neoks, "internal logic error");
       A(*(eoks.eoks + eok->idx)==NULL, "internal logic error");
@@ -820,10 +825,12 @@ static void eoks_free(ep_over_kq_t *eok) {
 
     A(eok->waiting==0, "internal logic error");
     eok_event_t *ev = eok->evs_head;
+    int sv_closed = 0;
     while (ev) {
       eok_event_t *next = ev->next;
       if (ev->fd==eok->sv[0]) {
         // fd is critical system resource
+        A(sv_closed==0, "internal logic error");
         close(eok->sv[0]);
         eok->sv[0] = -1;
         close(eok->sv[1]);
@@ -832,11 +839,11 @@ static void eoks_free(ep_over_kq_t *eok) {
       } else {
         // user forget calling epoll_ctl(EPOLL_CTL_DEL) before calling epoll_close/close?
         // calling close(ev->fd) here smells really bad
-#ifdef LET_IT_BE
+#ifndef BALANCE_CHECK_WHEN_CLOSE
         // we just let it be and reclaim ev
         eok_free_ev(eok, ev);
 #else
-        // panic otherwise, if LET_IT_BE not defined
+        // panic otherwise, if BALANCE_CHECK_WHEN_CLOSE is defined
         A(eok->evs_head==NULL && eok->evs_tail==NULL && eok->evs_count==0,
           "epfd[%d] fd[%d]: internal logic error: have you epoll_ctl(EPOLL_CTL_DEL) everything before calling epoll_close?",
           eok->idx, ev->fd);
@@ -861,8 +868,8 @@ static void eoks_free(ep_over_kq_t *eok) {
       close(eok->kq);
       eok->kq = -1;
     }
-    eok->next = eoks.eoks_free;
-    eoks.eoks_free = eok;
+    eok->next = eoks.eoks_free_list;
+    eoks.eoks_free_list = eok;
     *(eoks.eoks + eok->idx) = NULL;
   } while (0);
   A(0==pthread_mutex_unlock(&eoks.lock), "");