fix: very long string serialization problem

source/libs/nodes/src/nodesMsgFuncs.c

@@ -90,12 +90,12 @@ static void endTlvEncode(STlvEncoder* pEncoder, char** pMsg, int32_t* pLen) {
 static int32_t tlvEncodeImpl(STlvEncoder* pEncoder, int16_t type, const void* pValue, int32_t len) {
   int32_t tlvLen = sizeof(STlv) + len;
   if (pEncoder->offset + tlvLen > pEncoder->allocSize) {
-    void* pNewBuf = taosMemoryRealloc(pEncoder->pBuf, pEncoder->allocSize * 2);
+    pEncoder->allocSize = TMAX(pEncoder->allocSize * 2, pEncoder->allocSize + pEncoder->offset + tlvLen);
+    void* pNewBuf = taosMemoryRealloc(pEncoder->pBuf, pEncoder->allocSize);
     if (NULL == pNewBuf) {
       return TSDB_CODE_OUT_OF_MEMORY;
     }
     pEncoder->pBuf = pNewBuf;
-    pEncoder->allocSize = pEncoder->allocSize * 2;
   }
   STlv* pTlv = (STlv*)(pEncoder->pBuf + pEncoder->offset);
   pTlv->type = htons(type);