feat: using thread local buffer to improve performance at scale

src/client/inc/tscBulkWrite.h

@@ -16,23 +16,29 @@
 #ifndef TDENGINE_TSCBULKWRITE_H
 #define TDENGINE_TSCBULKWRITE_H
 
+#include <pthread.h>
+#include <stdlib.h>
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include "tlist.h"
 #include "tarray.h"
+#include "tlist.h"
 #include "tthread.h"
 
+/**
+ * SAsyncBulkWriteDispatcher is an async batching dispatcher(for writing), it can buffer insertion statements, batch
+ * and merge them into single statement.
+ */
 typedef struct SAsyncBulkWriteDispatcher {
-  // the mpmc queue to store the insertion statements. equivalent to SList<SSqlObj*>.
+  // the buffer to store the insertion statements. equivalent to SList<SSqlObj*>.
   SList* buffer;
 
   // the mutex to protect the buffer.
   pthread_mutex_t mutex;
 
   // the background thread to manage batching timeout.
-  pthread_t* background;
+  pthread_t background;
 
   // the maximum number of insertion rows in a batch.
   int32_t batchSize;
@@ -55,6 +61,7 @@ typedef struct SAsyncBulkWriteDispatcher {
 
 // forward declaration.
 typedef struct SSqlObj SSqlObj;
+
 /**
  * Merge the statements into single SSqlObj.
  *
@@ -125,6 +132,44 @@ bool tscSupportBulkInsertion(SSqlObj* pSql);
  */
 bool dispatcherTryBatching(SAsyncBulkWriteDispatcher* dispatcher, SSqlObj* pSql);
 
+/**
+ * A thread local version of SAsyncBulkWriteDispatcher.
+ */
+typedef struct SThreadLocalDispatcher {
+  pthread_key_t key;
+
+  // the maximum number of insertion rows in a batch.
+  int32_t batchSize;
+
+  // the batching timeout in milliseconds.
+  int32_t timeoutMs;
+
+} SThreadLocalDispatcher;
+
+/**
+ * Create a thread local SAsyncBulkWriteDispatcher variable.
+ *
+ * @param batchSize     the batchSize of SAsyncBulkWriteDispatcher.
+ * @param timeoutMs     the timeoutMs of SAsyncBulkWriteDispatcher.
+ * @return the thread local SAsyncBulkWriteDispatcher.
+ */
+SThreadLocalDispatcher* createThreadLocalDispatcher(int32_t batchSize, int32_t timeoutMs);
+
+/**
+ * Destroy the thread local SAsyncBulkWriteDispatcher variable.
+ * (will destroy all the instances of SAsyncBulkWriteDispatcher in the thread local variable)
+ *
+ * @param dispatcher  the thread local SAsyncBulkWriteDispatcher variable.
+ */
+void destroyThreadLocalDispatcher(SThreadLocalDispatcher* dispatcher);
+
+/**
+ * Get the thread local instance of SAsyncBulkWriteDispatcher.
+ * @param dispatcher  the thread local SAsyncBulkWriteDispatcher variable.
+ * @return the thread local SAsyncBulkWriteDispatcher.
+ */
+SAsyncBulkWriteDispatcher* dispatcherThreadLocal(SThreadLocalDispatcher* dispatcher);
+
 #ifdef __cplusplus
 }
 #endif

src/client/inc/tsclient.h

@@ -546,8 +546,8 @@ extern SHashObj  *tscTableMetaMap;
 extern SCacheObj *tscVgroupListBuf;
 
 // forward declaration.
-typedef struct SAsyncBulkWriteDispatcher SAsyncBulkWriteDispatcher;
-extern SAsyncBulkWriteDispatcher* tscDispatcher;
+typedef struct SThreadLocalDispatcher    SThreadLocalDispatcher;
+extern SThreadLocalDispatcher           *tscDispatcher;
 extern int   tscObjRef;
 extern void *tscTmr;
 extern void *tscQhandle;

src/client/src/tscAsync.c

@@ -397,11 +397,14 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, __async_cb_func_t fp, void* para
     return;
   }
   
-  if (tscDispatcher != NULL && dispatcherTryBatching(tscDispatcher, pSql)) {
+  if (tscDispatcher != NULL) {
+    SAsyncBulkWriteDispatcher* dispatcher = dispatcherThreadLocal(tscDispatcher);
+    if (dispatcherTryBatching(dispatcher, pSql)) {
       taosReleaseRef(tscObjRef, pSql->self);
       tscDebug("sql obj %p has been buffer in insert buffer", pSql);
       return;
     }
+  }
   
   SQueryInfo *pQueryInfo = tscGetQueryInfo(pCmd);
   executeQuery(pSql, pQueryInfo);

src/client/src/tscBulkWrite.c

@@ -151,8 +151,7 @@ SArray* dispatcherPollAll(SAsyncBulkWriteDispatcher* dispatcher) {
   }
   
   pthread_mutex_lock(&dispatcher->mutex);
-
-  SArray* statements = taosArrayInit(atomic_load_32(&dispatcher->bufferSize), sizeof(SSqlObj*));
+  SArray* statements = taosArrayInit(0, sizeof(SSqlObj*));
   if (statements == NULL) {
     pthread_mutex_unlock(&dispatcher->mutex);
     tscError("failed to poll all items: out of memory");
@@ -160,7 +159,7 @@ SArray* dispatcherPollAll(SAsyncBulkWriteDispatcher* dispatcher) {
   }
 
   // get all the sql statements from the buffer.
-  while (atomic_load_32(&dispatcher->bufferSize)) {
+  while (true) {
     SListNode* node = tdListPopHead(dispatcher->buffer);
     if (!node) {
       break;
@@ -172,7 +171,6 @@ SArray* dispatcherPollAll(SAsyncBulkWriteDispatcher* dispatcher) {
     listNodeFree(node);
     atomic_fetch_sub_32(&dispatcher->bufferSize, 1);
     atomic_fetch_sub_32(&dispatcher->currentSize, statementGetInsertionRows(item));
-
     taosArrayPush(statements, &item);
   }
   
@@ -285,8 +283,7 @@ SAsyncBulkWriteDispatcher* createAsyncBulkWriteDispatcher(int32_t batchSize, int
   pthread_mutex_init(&dispatcher->mutex, NULL);
 
   // init background thread.
-  dispatcher->background = taosCreateThread(dispatcherTimeoutCallback, dispatcher);
-  if (!dispatcher->background) {
+  if (pthread_create(&dispatcher->background, NULL, dispatcherTimeoutCallback, dispatcher)) {
     tdListFree(dispatcher->buffer);
     tfree(dispatcher);
     return NULL;
@@ -300,17 +297,18 @@ void destroyAsyncDispatcher(SAsyncBulkWriteDispatcher* dispatcher) {
     return;
   }
   
+  // mark shutdown.
   atomic_store_8(&dispatcher->shutdown, true);
   
+  // make sure the timeout thread exit.
+  pthread_join(dispatcher->background, NULL);
+  
   // poll and send all the statements in the buffer.
   while (atomic_load_32(&dispatcher->bufferSize)) {
     SArray* statements = dispatcherPollAll(dispatcher);
     dispatcherExecute(statements);
   }
   
-  // make sure the thread exit.
-  taosDestroyThread(dispatcher->background);
-
   // destroy the buffer.
   tdListFree(dispatcher->buffer);
 
@@ -375,3 +373,54 @@ bool dispatcherTryBatching(SAsyncBulkWriteDispatcher* dispatcher, SSqlObj* pSql)
   }
   return true;
 }
+
+/**
+ * Destroy the SAsyncBulkWriteDispatcher create by SThreadLocalDispatcher.
+ * @param arg 
+ */
+static void destroyDispatcher(void* arg) {
+  SAsyncBulkWriteDispatcher* dispatcher = arg;
+  if (!dispatcher) {
+    return;
+  }
+  
+  destroyAsyncDispatcher(dispatcher);
+}
+
+SThreadLocalDispatcher* createThreadLocalDispatcher(int32_t batchSize, int32_t timeoutMs) {
+  SThreadLocalDispatcher* dispatcher = calloc(1, sizeof(SThreadLocalDispatcher));
+  if (!dispatcher) {
+    return NULL;
+  }
+
+  dispatcher->batchSize = batchSize;
+  dispatcher->timeoutMs = timeoutMs;
+
+  if (pthread_key_create(&dispatcher->key, destroyDispatcher)) {
+    free(dispatcher);
+    return NULL;
+  }
+  return dispatcher;
+}
+
+SAsyncBulkWriteDispatcher* dispatcherThreadLocal(SThreadLocalDispatcher* dispatcher) {
+  SAsyncBulkWriteDispatcher* value = pthread_getspecific(dispatcher->key);
+  if (value) {
+    return value;
+  }
+
+  value = createAsyncBulkWriteDispatcher(dispatcher->batchSize, dispatcher->timeoutMs);
+  if (value) {
+    pthread_setspecific(dispatcher->key, value);
+    return value;
+  }
+
+  return NULL;
+}
+
+void destroyThreadLocalDispatcher(SThreadLocalDispatcher* dispatcher) {
+  if (dispatcher) {
+    pthread_key_delete(dispatcher->key);
+    free(dispatcher);
+  }
+}

src/client/src/tscSystem.c

@@ -50,7 +50,7 @@ void      *tscRpcCache;            // cache to keep rpc obj
 int32_t    tscNumOfThreads = 1;     // num of rpc threads
 char       tscLogFileName[] = "taoslog";
 int        tscLogFileNum = 10;
-SAsyncBulkWriteDispatcher* tscDispatcher = NULL;
+SThreadLocalDispatcher * tscDispatcher = NULL;
 
 static pthread_mutex_t rpcObjMutex; // mutex to protect open the rpc obj concurrently
 static pthread_once_t  tscinit = PTHREAD_ONCE_INIT;
@@ -60,20 +60,20 @@ static pthread_mutex_t setConfMutex = PTHREAD_MUTEX_INITIALIZER;
 static volatile int tscInitRes = 0;
 
 /**
- * Init the taosc async bulk write dispatcher.
+ * Init the thread local async bulk write dispatcher.
  * 
  * @param batchSize  the batchSize of async bulk write dispatcher.
  * @param timeoutMs  the timeout of batching in milliseconds.
  */
 void tscInitAsyncDispatcher(int32_t batchSize, int32_t timeoutMs) {
-  tscDispatcher = createAsyncBulkWriteDispatcher(batchSize, timeoutMs);
+  tscDispatcher = createThreadLocalDispatcher(batchSize, timeoutMs);
 }
 
 /**
- * Destroy the taosc async bulk write dispatcher.
+ * Destroy the thread local async bulk write dispatcher.
  */
 void tscDestroyAsyncDispatcher() {
-  destroyAsyncDispatcher(tscDispatcher);
+  destroyThreadLocalDispatcher(tscDispatcher);
   tscDispatcher = NULL;
 }