updated docs on event

ndb/include/ndbapi/NdbEventOperation.hpp

@@ -24,73 +24,78 @@ class NdbEventOperationImpl;
  * @class NdbEventOperation
  * @brief Class of operations for getting change events from database.  
  *
- * An NdbEventOperation object is instantiated by 
- * Ndb::createEventOperation
- *
- * Prior to that an event must have been created in the Database through
- * NdbDictionary::createEvent
- * 
- * The instance is removed by Ndb::dropEventOperation
+ * Brief description on how to work with events:
+ *
+ * - An event i created in the Database through
+ *   NdbDictionary::Dictionary::createEvent() (note that this can be done 
+ *   by any application or thread and not necessarily by the "listener")
+ * - To listen to events, an NdbEventOperation object is instantiated by 
+ *   Ndb::createEventOperation()
+ * - execute() starts the event flow. Use Ndb::pollEvents() to wait
+ *   for an event to occur.  Use next() to iterate
+ *   through the events that have occured.
+ * - The instance is removed by Ndb::dropEventOperation()
  *
  * For more info see:
  * @ref ndbapi_event.cpp
  *
  * Known limitations:
  *
- * Maximum number of active NdbEventOperations are now set at compile time.
+ * - Maximum number of active NdbEventOperations are now set at compile time.
  * Today 100.  This will become a configuration parameter later.
- *
- * Maximum number of NdbEventOperations tied to same event are maximum 16
+ * - Maximum number of NdbEventOperations tied to same event are maximum 16
  * per process.
  *
  * Known issues:
  *
- * When several NdbEventOperation's are tied to the same event in the same
+ * - When several NdbEventOperation's are tied to the same event in the same
  * process they will share the circular buffer. The BufferLength will then
  * be the same for all and decided by the first NdbEventOperation 
  * instantiation. Just make sure to instantiate the "largest" one first.
- *
- * Today all events INSERT/DELETE/UPDATE and all changed attributes are
+ * - Today all events INSERT/DELETE/UPDATE and all changed attributes are
  * sent to the API, even if only specific attributes have been specified.
  * These are however hidden from the user and only relevant data is shown
  * after next().
- * However false exits from Ndb::pollEvents() may occur and thus
+ * - "False" exits from Ndb::pollEvents() may occur and thus
  * the subsequent next() will return zero,
  * since there was no available data. Just do Ndb::pollEvents() again.
- *
- * Event code does not check table schema version. Make sure to drop events
+ * - Event code does not check table schema version. Make sure to drop events
  * after table is dropped. Will be fixed in later
  * versions.
- *
- * If a node failure has occured not all events will be recieved
+ * - If a node failure has occured not all events will be recieved
  * anymore. Drop NdbEventOperation and Create again after nodes are up
  * again. Will be fixed in later versions.
  *
  * Test status:
- * Tests have been run on 1-node and 2-node systems
- *
- * Known bugs:
  *
- * None, except if we can call some of the "issues" above bugs
+ * - Tests have been run on 1-node and 2-node systems
  *
  * Useful API programs:
  *
- * ndb_select_all -d sys 'NDB$EVENTS_0'
- * Will show contents in the system table containing created events.
+ * - ndb_select_all -d sys 'NDB$EVENTS_0'
+ * shows contents in the system table containing created events.
  *
+ * @note this is an inteface to viewing events that is subject to change
  */
 class NdbEventOperation {
 public:
+  /**
+   * State of the NdbEventOperation object
+   */
+  enum State {
+    EO_CREATED,   ///< Created but execute() not called
+    EO_EXECUTING, ///< execute() called
+    EO_ERROR      ///< An error has occurred. Object unusable.
+  };
   /**
    * Retrieve current state of the NdbEventOperation object
    */
-  enum State {CREATED,EXECUTING,ERROR};
   State getState();
 
   /**
    * Activates the NdbEventOperation to start receiving events. The
    * changed attribute values may be retrieved after next() has returned
-   * a value greater than zero. The getValue() methods below must be called
+   * a value greater than zero. The getValue() methods must be called
    * prior to execute().
    *
    * @return 0 if successful otherwise -1.
@@ -112,21 +117,21 @@ public:
    *       aligned appropriately.  The buffer is used directly
    *       (avoiding a copy penalty) only if it is aligned on a
    *       4-byte boundary and the attribute size in bytes
-   *       (i.e. NdbRecAttr::attrSize times NdbRecAttr::arraySize is
+   *       (i.e. NdbRecAttr::attrSize() times NdbRecAttr::arraySize() is
    *       a multiple of 4).
    *
-   * @note There are two versions, NdbOperation::getValue and
-   *       NdbOperation::getPreValue for retrieving the current and
+   * @note There are two versions, getValue() and
+   *       getPreValue() for retrieving the current and
    *       previous value repectively.
    *
    * @note This method does not fetch the attribute value from 
    *       the database!  The NdbRecAttr object returned by this method 
    *       is <em>not</em> readable/printable before the 
-   *       NdbEventConnection::execute has been made and
-   *       NdbEventConnection::next has returned a value greater than
+   *       execute() has been made and
+   *       next() has returned a value greater than
    *       zero. If a specific attribute has not changed the corresponding 
    *       NdbRecAttr will be in state UNDEFINED.  This is checked by 
-   *       NdbRecAttr::isNull which then returns -1.
+   *       NdbRecAttr::isNull() which then returns -1.
    *
    * @param anAttrName  Attribute name 
    * @param aValue      If this is non-NULL, then the attribute value 
@@ -143,11 +148,11 @@ public:
   /**
    * Retrieves event resultset if available, inserted into the NdbRecAttrs
    * specified in getValue() and getPreValue(). To avoid polling for
-   * a resultset, one can use Ndb::pollEvents
+   * a resultset, one can use Ndb::pollEvents()
    * which will wait on a mutex until an event occurs or the specified
    * timeout occurs.
    *
-   * @return >=0 if successful otherwise -1. Return value inicates number
+   * @return >=0 if successful otherwise -1. Return value indicates number
    * of available events. By sending pOverRun one may query for buffer
    * overflow and *pOverRun will indicate the number of events that have
    * overwritten.

ndb/src/ndbapi/Ndb.cpp

@@ -1177,7 +1177,14 @@ NdbEventOperation* Ndb::createEventOperation(const char* eventName,
 
   tOp = new NdbEventOperation(this, eventName, bufferLength);
 
-  if (tOp->getState() != NdbEventOperation::CREATED) {
+  if (tOp == 0)
+  {
+    theError.code= 4000;
+    return NULL;
+  }
+
+  if (tOp->getState() != NdbEventOperation::EO_CREATED) {
+    theError.code= tOp->getNdbError().code;
     delete tOp;
     tOp = NULL;
   }

ndb/src/ndbapi/NdbEventOperationImpl.cpp

@@ -55,9 +55,8 @@ NdbEventOperationImpl::NdbEventOperationImpl(NdbEventOperation &N,
 					     const char* eventName, 
 					     const int bufferLength) 
   : NdbEventOperation(*this), m_ndb(theNdb),
-    m_state(ERROR), m_bufferL(bufferLength)
+    m_state(EO_ERROR), m_bufferL(bufferLength)
 {
-
   m_eventId = 0;
   theFirstRecAttrs[0] = NULL;
   theCurrentRecAttrs[0] = NULL;
@@ -71,16 +70,15 @@ NdbEventOperationImpl::NdbEventOperationImpl(NdbEventOperation &N,
   // we should lookup id in Dictionary, TODO
   // also make sure we only have one listener on each event
 
-  if (!m_ndb) { ndbout_c("m_ndb=NULL"); return; }
+  if (!m_ndb) abort();
 
   NdbDictionary::Dictionary *myDict = m_ndb->getDictionary();
-  if (!myDict) { ndbout_c("getDictionary=NULL"); return; }
+  if (!myDict) { m_error.code= m_ndb->getNdbError().code; return; }
 
   const NdbDictionary::Event *myEvnt = myDict->getEvent(eventName);
-  if (!myEvnt) { ndbout_c("getEvent()=NULL"); return; }
+  if (!myEvnt) { m_error.code= myDict->getNdbError().code; return; }
 
   m_eventImpl = &myEvnt->m_impl;
-  if (!m_eventImpl) { ndbout_c("m_impl=NULL"); return; }
 
   m_bufferHandle = m_ndb->getGlobalEventBufferHandle();
   if (m_bufferHandle->m_bufferL > 0) 
@@ -88,7 +86,7 @@ NdbEventOperationImpl::NdbEventOperationImpl(NdbEventOperation &N,
   else
     m_bufferHandle->m_bufferL = m_bufferL;
 
-  m_state = CREATED;
+  m_state = EO_CREATED;
 }
 
 NdbEventOperationImpl::~NdbEventOperationImpl()
@@ -106,7 +104,7 @@ NdbEventOperationImpl::~NdbEventOperationImpl()
       p = p_next;
     }
   }
-  if (m_state == NdbEventOperation::EXECUTING) {
+  if (m_state == EO_EXECUTING) {
     stop();
     // m_bufferHandle->dropSubscribeEvent(m_bufferId);
     ; // We should send stop signal here
@@ -122,7 +120,7 @@ NdbEventOperationImpl::getState()
 NdbRecAttr*
 NdbEventOperationImpl::getValue(const char *colName, char *aValue, int n)
 {
-  if (m_state != NdbEventOperation::CREATED) {
+  if (m_state != EO_CREATED) {
     ndbout_c("NdbEventOperationImpl::getValue may only be called between instantiation and execute()");
     return NULL;
   }
@@ -211,8 +209,8 @@ NdbEventOperationImpl::execute()
 {
   NdbDictionary::Dictionary *myDict = m_ndb->getDictionary();
   if (!myDict) {
-    ndbout_c("NdbEventOperation::execute(): getDictionary=NULL");
-    return 0;
+    m_error.code= m_ndb->getNdbError().code;
+    return -1;
   }
 
   if (theFirstRecAttrs[0] == NULL) { // defaults to get all
@@ -245,14 +243,14 @@ NdbEventOperationImpl::execute()
     if (r) {
       //Error
       m_bufferHandle->unprepareAddSubscribeEvent(m_bufferId);
-      m_state = NdbEventOperation::ERROR;
+      m_state = EO_ERROR;
     } else {
       m_bufferHandle->addSubscribeEvent(m_bufferId, this);
-      m_state = NdbEventOperation::EXECUTING;
+      m_state = EO_EXECUTING;
     }
   } else {
     //Error
-    m_state = NdbEventOperation::ERROR;
+    m_state = EO_ERROR;
   }
   return r;
 }
@@ -261,14 +259,14 @@ int
 NdbEventOperationImpl::stop()
 {
   DBUG_ENTER("NdbEventOperationImpl::stop");
-  if (m_state != NdbEventOperation::EXECUTING)
+  if (m_state != EO_EXECUTING)
     DBUG_RETURN(-1);
 
   //  ndbout_c("NdbEventOperation::stopping()");
 
   NdbDictionary::Dictionary *myDict = m_ndb->getDictionary();
   if (!myDict) {
-    ndbout_c("NdbEventOperation::stop(): getDictionary=NULL");
+    m_error.code= m_ndb->getNdbError().code;
     DBUG_RETURN(-1);
   }
 
@@ -299,13 +297,13 @@ NdbEventOperationImpl::stop()
     //Error
     m_bufferHandle->unprepareDropSubscribeEvent(m_bufferId);
     m_error.code= myDictImpl.m_error.code;
-    m_state = NdbEventOperation::ERROR;
+    m_state = EO_ERROR;
   } else {
 #ifdef EVENT_DEBUG
     ndbout_c("NdbEventOperation::dropping()");
 #endif
     m_bufferHandle->dropSubscribeEvent(m_bufferId);
-    m_state = NdbEventOperation::CREATED;
+    m_state = EO_CREATED;
   }
 
   DBUG_RETURN(r);