此示例演示 NDB API 事件处理。
该程序的源代码可以在 NDB Cluster 源代码树中的
storage/ndb/ndbapi-examples/ndbapi_event/ndbapi_event.cpp.
#include <NdbApi.hpp>
// Used for cout
#include <stdio.h>
#include <iostream>
#include <unistd.h>
#ifdef VM_TRACE
#include <my_global.h>
#endif
#ifndef assert
#include <assert.h>
#endif
/**
* Assume that there is a table which is being updated by
* another process (e.g. flexBench -l 0 -stdtables).
* We want to monitor what happens with column values.
*
* Or using the mysql client:
*
* $> mysql -u root
* mysql> create database ndb_examples;
* mysql> use ndb_examples;
* mysql> create table t0
(c0 int, c1 int, c2 char(4), c3 char(4), c4 text,
primary key(c0, c2)) engine ndb charset latin1;
*
* In another window start ndbapi_event, wait until properly started
insert into t0 values (1, 2, 'a', 'b', null);
insert into t0 values (3, 4, 'c', 'd', null);
update t0 set c3 = 'e' where c0 = 1 and c2 = 'a'; -- use pk
update t0 set c3 = 'f'; -- use scan
update t0 set c3 = 'F'; -- use scan update to 'same'
update t0 set c2 = 'g' where c0 = 1; -- update pk part
update t0 set c2 = 'G' where c0 = 1; -- update pk part to 'same'
update t0 set c0 = 5, c2 = 'H' where c0 = 3; -- update full PK
delete from t0;
insert ...; update ...; -- see events w/ same pk merged (if -m option)
delete ...; insert ...; -- there are 5 combinations ID IU DI UD UU
update ...; update ...;
-- text requires -m flag
set @a = repeat('a',256); -- inline size
set @b = repeat('b',2000); -- part size
set @c = repeat('c',2000*30); -- 30 parts
-- update the text field using combinations of @a, @b, @c ...
* you should see the data popping up in the example window
*
*/
#define APIERROR(error) \
{ std::cout << "Error in " << __FILE__ << ", line:" << __LINE__ << ", code:" \
<< error.code << ", msg: " << error.message << "." << std::endl; \
exit(-1); }
int myCreateEvent(Ndb* myNdb,
const char *eventName,
const char *eventTableName,
const char **eventColumnName,
const int noEventColumnName,
bool merge_events);
int main(int argc, char** argv)
{
if (argc < 3)
{
std::cout << "Arguments are <connect_string cluster> <timeout> [m(merge events)|d(debug)].\n";
exit(-1);
}
const char *connection_string = argv[1];
int timeout = atoi(argv[2]);
ndb_init();
bool merge_events = argc > 3 && strchr(argv[3], 'm') != 0;
#ifdef VM_TRACE
bool dbug = argc > 3 && strchr(argv[3], 'd') != 0;
if (dbug) DBUG_PUSH("d:t:");
if (dbug) putenv("API_SIGNAL_LOG=-");
#endif
Ndb_cluster_connection *cluster_connection=
new Ndb_cluster_connection(connection_string); // Object representing the cluster
int r= cluster_connection->connect(5 /* retries */,
3 /* delay between retries */,
1 /* verbose */);
if (r > 0)
{
std::cout
<< "Cluster connect failed, possibly resolved with more retries.\n";
exit(-1);
}
else if (r < 0)
{
std::cout
<< "Cluster connect failed.\n";
exit(-1);
}
if (cluster_connection->wait_until_ready(30,30))
{
std::cout << "Cluster was not ready within 30 secs." << std::endl;
exit(-1);
}
Ndb* myNdb= new Ndb(cluster_connection,
"ndb_examples"); // Object representing the database
if (myNdb->init() == -1) APIERROR(myNdb->getNdbError());
const char *eventName= "CHNG_IN_t0";
const char *eventTableName= "t0";
const int noEventColumnName= 5;
const char *eventColumnName[noEventColumnName]=
{"c0",
"c1",
"c2",
"c3",
"c4"
};
// Create events
myCreateEvent(myNdb,
eventName,
eventTableName,
eventColumnName,
noEventColumnName,
merge_events);
// Normal values and blobs are unfortunately handled differently..
typedef union { NdbRecAttr* ra; NdbBlob* bh; } RA_BH;
int i, j, k, l;
j = 0;
while (j < timeout) {
// Start "transaction" for handling events
NdbEventOperation* op;
printf("create EventOperation\n");
if ((op = myNdb->createEventOperation(eventName)) == NULL)
APIERROR(myNdb->getNdbError());
op->mergeEvents(merge_events);
printf("get values\n");
RA_BH recAttr[noEventColumnName];
RA_BH recAttrPre[noEventColumnName];
// primary keys should always be a part of the result
for (i = 0; i < noEventColumnName; i++) {
if (i < 4) {
recAttr[i].ra = op->getValue(eventColumnName[i]);
recAttrPre[i].ra = op->getPreValue(eventColumnName[i]);
} else if (merge_events) {
recAttr[i].bh = op->getBlobHandle(eventColumnName[i]);
recAttrPre[i].bh = op->getPreBlobHandle(eventColumnName[i]);
}
}
// set up the callbacks
printf("execute\n");
// This starts changes to "start flowing"
if (op->execute())
APIERROR(op->getNdbError());
NdbEventOperation* the_op = op;
i= 0;
while (i < timeout) {
// printf("now waiting for event...\n");
int r = myNdb->pollEvents(1000); // wait for event or 1000 ms
if (r > 0) {
// printf("got data! %d\n", r);
while ((op= myNdb->nextEvent())) {
assert(the_op == op);
i++;
switch (op->getEventType()) {
case NdbDictionary::Event::TE_INSERT:
printf("%u INSERT", i);
break;
case NdbDictionary::Event::TE_DELETE:
printf("%u DELETE", i);
break;
case NdbDictionary::Event::TE_UPDATE:
printf("%u UPDATE", i);
break;
default:
abort(); // should not happen
}
printf(" gci=%d\n", (int)op->getGCI());
for (k = 0; k <= 1; k++) {
printf(k == 0 ? "post: " : "pre : ");
for (l = 0; l < noEventColumnName; l++) {
if (l < 4) {
NdbRecAttr* ra = k == 0 ? recAttr[l].ra : recAttrPre[l].ra;
if (ra->isNULL() >= 0) { // we have a value
if (ra->isNULL() == 0) { // we have a non-null value
if (l < 2)
printf("%-5u", ra->u_32_value());
else
printf("%-5.4s", ra->aRef());
} else
printf("%-5s", "NULL");
} else
printf("%-5s", "-"); // no value
} else if (merge_events) {
int isNull;
NdbBlob* bh = k == 0 ? recAttr[l].bh : recAttrPre[l].bh;
bh->getDefined(isNull);
if (isNull >= 0) { // we have a value
if (! isNull) { // we have a non-null value
Uint64 length = 0;
bh->getLength(length);
// read into buffer
unsigned char* buf = new unsigned char [length];
memset(buf, 'X', length);
Uint32 n = length;
bh->readData(buf, n); // n is in/out
assert(n == length);
// pretty-print
bool first = true;
Uint32 i = 0;
while (i < n) {
unsigned char c = buf[i++];
Uint32 m = 1;
while (i < n && buf[i] == c)
i++, m++;
if (! first)
printf("+");
printf("%u%c", m, c);
first = false;
}
printf("[%u]", n);
delete [] buf;
} else
printf("%-5s", "NULL");
} else
printf("%-5s", "-"); // no value
}
}
printf("\n");
}
}
} // else printf("timed out (%i)\n", timeout);
}
// don't want to listen to events anymore
if (myNdb->dropEventOperation(the_op)) APIERROR(myNdb->getNdbError());
the_op = 0;
j++;
}
{
NdbDictionary::Dictionary *myDict = myNdb->getDictionary();
if (!myDict) APIERROR(myNdb->getNdbError());
// remove event from database
if (myDict->dropEvent(eventName)) APIERROR(myDict->getNdbError());
}
delete myNdb;
delete cluster_connection;
ndb_end(0);
return 0;
}
int myCreateEvent(Ndb* myNdb,
const char *eventName,
const char *eventTableName,
const char **eventColumnNames,
const int noEventColumnNames,
bool merge_events)
{
NdbDictionary::Dictionary *myDict= myNdb->getDictionary();
if (!myDict) APIERROR(myNdb->getNdbError());
const NdbDictionary::Table *table= myDict->getTable(eventTableName);
if (!table) APIERROR(myDict->getNdbError());
NdbDictionary::Event myEvent(eventName, *table);
myEvent.addTableEvent(NdbDictionary::Event::TE_ALL);
// myEvent.addTableEvent(NdbDictionary::Event::TE_INSERT);
// myEvent.addTableEvent(NdbDictionary::Event::TE_UPDATE);
// myEvent.addTableEvent(NdbDictionary::Event::TE_DELETE);
myEvent.addEventColumns(noEventColumnNames, eventColumnNames);
myEvent.mergeEvents(merge_events);
// Add event to database
if (myDict->createEvent(myEvent) == 0)
myEvent.print();
else if (myDict->getNdbError().classification ==
NdbError::SchemaObjectExists) {
printf("Event creation failed, event exists\n");
printf("dropping Event...\n");
if (myDict->dropEvent(eventName)) APIERROR(myDict->getNdbError());
// try again
// Add event to database
if ( myDict->createEvent(myEvent)) APIERROR(myDict->getNdbError());
} else
APIERROR(myDict->getNdbError());
return 0;
}