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Initial revision of NDB Cluster files
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ndb/include/ndbapi/NdbEventOperation.hpp
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ndb/include/ndbapi/NdbEventOperation.hpp
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/* Copyright (C) 2003 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/*****************************************************************************
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* Name: NdbEventOperation.hpp
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* Include:
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* Link:
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* Author: Tomas Ulin MySQL AB
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* Date: 2003-11-21
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* Version: 0.1
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* Description: Event support
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* Documentation:
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* Adjust: 2003-11-21 Tomas Ulin First version.
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* Adjust: 2003-12-11 Tomas Ulin Alpha Release.
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****************************************************************************/
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#ifndef NdbEventOperation_H
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#define NdbEventOperation_H
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class NdbGlobalEventBuffer;
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class NdbEventOperationImpl;
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/**
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* @class NdbEventOperation
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* @brief Class of operations for getting change events from database.
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*
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* An NdbEventOperation object is instantiated by
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* NdbEventOperation *Ndb::createEventOperation(const char *eventName,
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* int bufferLength)
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*
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* Prior to that an event must have been created in the Database through
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* int NdbDictionary::createEvent(NdbDictionary::Event)
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*
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* bufferLength indicates size of circular buffer to store event info as
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* they occur.
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*
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* The instance is removed by Ndb::dropEventOperation(NdbEventOperation*)
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*
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* For more info see:
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* ndbapi_example5.cpp
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* Ndb.hpp
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* NdbDictionary.hpp
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*
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* Known limitations:
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*
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* Maximum number of active NdbEventOperations are now set at compile time.
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* Today 100. This will become a configuration parameter later.
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*
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* Maximum number of NdbEventOperations tied to same event are maximum 16
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* per process.
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*
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* Known issues:
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*
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* When several NdbEventOperation s are tied to the same event in the same
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* process they will share the circular buffer. The BufferLength will then
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* be the same for all and decided by the first NdbEventOperation
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* instantiation. Just make sure to instantiate the "largest" one first.
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*
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* Today all events INSERT/DELETE/UPDATE and all changed attributes are
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* sent to the API, even if only specific attributes have been specified.
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* These are however hidden from the user and only relevant data is shown
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* after next(). However false exits from pollEvents() may occur and thus
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* the subsequent next() will return zero, since there was no available
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* data. Just do pollEvents() again. Will be fixed in later versions.
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*
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* Event code does not check table schema version. Make sure to drop events
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* after table is dropped. Will be fixed in later
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* versions.
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*
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* On a replicated system one will receive each event 2 times, one for each
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* replica. If a node fails events will not be received twice anymore
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* for data in corresponding fragment. Will be optimized in later versions.
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*
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* If a nodefailiure has occured not all events will be recieved
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* anymore. Drop NdbEventOperation and Create again after nodes are up
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* again. Will be fixed in later versions.
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*
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* Test status:
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* Tests have been run on 1-node and 2-node systems
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*
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* Known bugs:
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*
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* None, except if we can call some of the "isses" above bugs
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*
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* Useful API programs:
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*
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* select_all -d sys 'NDB$EVENTS_0'
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* Will show contents in the system table containing created events.
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*
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*/
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class NdbEventOperation {
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public:
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enum State {CREATED,EXECUTING,ERROR};
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State getState();
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/**
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* Activates the NdbEventOperation to start receiving events. The
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* changed attribute values may be retrieved after next() has returned
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* a value greater than zero. The getValue() methods below must be called
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* prior to execute().
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*
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* @return 0 if successful otherwise -1.
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*/
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int execute();
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// about the event operation
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// getting data
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// NdbResultSet* getResultSet();
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/**
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* Defines a retrieval operation of an attribute value.
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* The NDB API allocate memory for the NdbRecAttr object that
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* will hold the returned attribute value.
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*
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* @note Note that it is the applications responsibility
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* to allocate enough memory for aValue (if non-NULL).
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* The buffer aValue supplied by the application must be
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* aligned appropriately. The buffer is used directly
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* (avoiding a copy penalty) only if it is aligned on a
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* 4-byte boundary and the attribute size in bytes
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* (i.e. NdbRecAttr::attrSize times NdbRecAttr::arraySize is
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* a multiple of 4).
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*
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* @note There are two versions, NdbOperation::getValue and
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* NdbOperation::getPreValue for retrieving the current and
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* previous value repectively.
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*
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* @note This method does not fetch the attribute value from
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* the database! The NdbRecAttr object returned by this method
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* is <em>not</em> readable/printable before the
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* NdbEventConnection::execute has been made and
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* NdbEventConnection::next has returned a value greater than
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* zero. If a specific attribute has not changed the corresponding
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* NdbRecAttr will be in state UNDEFINED. This is checked by
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* NdbRecAttr::isNull which then returns -1.
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*
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* @param anAttrName Attribute name
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* @param aValue If this is non-NULL, then the attribute value
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* will be returned in this parameter.<br>
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* If NULL, then the attribute value will only
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* be stored in the returned NdbRecAttr object.
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* @return An NdbRecAttr object to hold the value of
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* the attribute, or a NULL pointer
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* (indicating error).
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*/
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NdbRecAttr *getValue(const char *anAttrName, char *aValue = NULL);
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NdbRecAttr *getPreValue(const char *anAttrName, char *aValue = NULL);
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/**
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* Retrieves event resultset if available, inserted into the NdbRecAttrs
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* specified in getValue() and getPreValue(). To avoid polling for
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* a resultset, one can use Ndb::pollEvents(int millisecond_timeout)
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* which will wait on a mutex until an event occurs or the specified
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* timeout occurs.
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*
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* @return >=0 if successful otherwise -1. Return value inicates number
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* of available events. By sending pOverRun one may query for buffer
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* overflow and *pOverRun will indicate the number of events that have
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* overwritten.
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*/
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int next(int *pOverRun=NULL);
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/**
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* In the current implementation a nodefailiure may cause loss of events,
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* in which case isConsistent() will return false
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*/
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bool isConsistent();
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/**
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* Query for occured event type.
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* NdbDictionary::Event::{TE_INSERT,TE_UPDATE,TE_DELETE}
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* Only valid after next() has returned value >= 0
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*/
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NdbDictionary::Event::TableEvent getEventType();
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Uint32 getGCI();
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Uint32 getLatestGCI();
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void print();
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private:
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friend class NdbEventOperationImpl;
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friend class Ndb;
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NdbEventOperation(Ndb *theNdb, const char* eventName,int bufferLength);
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~NdbEventOperation();
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static int wait(void *p, int aMillisecondNumber);
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class NdbEventOperationImpl &m_impl;
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NdbEventOperation(NdbEventOperationImpl& impl);
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};
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typedef void (* NdbEventCallback)(NdbEventOperation*, Ndb*, void*);
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#endif
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