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本文主要研究一下nifi的BinlogEventListener
BinlogEventListener
nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/BinlogEventListener.java
public class BinlogEventListener implements BinaryLogClient.EventListener {
protected final AtomicBoolean stopNow = new AtomicBoolean(false);
private static final int QUEUE_OFFER_TIMEOUT_MSEC = 100;
private final BlockingQueue queue;
private final BinaryLogClient client;
public BinlogEventListener(BinaryLogClient client, BlockingQueue q) {
this.client = client;
this.queue = q;
}
public void start() {
stopNow.set(false);
}
public void stop() {
stopNow.set(true);
}
@Override
public void onEvent(Event event) {
while (!stopNow.get()) {
RawBinlogEvent ep = new RawBinlogEvent(event, client.getBinlogFilename());
try {
if (queue.offer(ep, QUEUE_OFFER_TIMEOUT_MSEC, TimeUnit.MILLISECONDS)) {
return;
} else {
throw new RuntimeException("Unable to add event to the queue");
}
} catch (InterruptedException e) {
throw new RuntimeException("Interrupted while adding event to the queue");
}
}
}
} - BinlogEventListener实现了BinaryLogClient.EventListener接口，其onEvent方法会将event包装为RawBinlogEvent，然后放到queue中
RawBinlogEvent
nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/event/RawBinlogEvent.java
public class RawBinlogEvent {
private Event event;
private String binlogFilename;
public RawBinlogEvent(Event event, String binlogFilename) {
this.event = event;
this.binlogFilename = binlogFilename;
}
public Event getEvent() {
return event;
}
public void setEvent(Event event) {
this.event = event;
}
public String getBinlogFilename() {
return binlogFilename;
}
}- RawBinlogEvent定义了event及binlogFilename两个属性
CaptureChangeMySQL
nifi-1.11.4/nifi-nar-bundles/nifi-cdc/nifi-cdc-mysql-bundle/nifi-cdc-mysql-processors/src/main/java/org/apache/nifi/cdc/mysql/processors/CaptureChangeMySQL.java
public class CaptureChangeMySQL extends AbstractSessionFactoryProcessor {
//......
public void outputEvents(ProcessSession session, StateManager stateManager, ComponentLog log) throws IOException {
RawBinlogEvent rawBinlogEvent;
// Drain the queue
while ((rawBinlogEvent = queue.poll()) != null && !doStop.get()) {
Event event = rawBinlogEvent.getEvent();
EventHeaderV4 header = event.getHeader();
long timestamp = header.getTimestamp();
EventType eventType = header.getEventType();
// Advance the current binlog position. This way if no more events are received and the processor is stopped, it will resume at the event about to be processed.
// We always get ROTATE and FORMAT_DESCRIPTION messages no matter where we start (even from the end), and they won't have the correct "next position" value, so only
// advance the position if it is not that type of event. ROTATE events don't generate output CDC events and have the current binlog position in a special field, which
// is filled in during the ROTATE case
if (eventType != ROTATE && eventType != FORMAT_DESCRIPTION) {
currentBinlogPosition = header.getPosition();
}
log.debug("Got message event type: {} ", new Object[]{header.getEventType().toString()});
switch (eventType) {
case TABLE_MAP:
// This is sent to inform which table is about to be changed by subsequent events
TableMapEventData data = event.getData();
// Should we skip this table? Yes if we've specified a DB or table name pattern and they don't match
skipTable = (databaseNamePattern != null && !databaseNamePattern.matcher(data.getDatabase()).matches())
|| (tableNamePattern != null && !tableNamePattern.matcher(data.getTable()).matches());
if (!skipTable) {
TableInfoCacheKey key = new TableInfoCacheKey(this.getIdentifier(), data.getDatabase(), data.getTable(), data.getTableId());
if (cacheClient != null) {
try {
currentTable = cacheClient.get(key, cacheKeySerializer, cacheValueDeserializer);
} catch (ConnectException ce) {
throw new IOException("Could not connect to Distributed Map Cache server to get table information", ce);
}
if (currentTable == null) {
// We don't have an entry for this table yet, so fetch the info from the database and populate the cache
try {
currentTable = loadTableInfo(key);
try {
cacheClient.put(key, currentTable, cacheKeySerializer, cacheValueSerializer);
} catch (ConnectException ce) {
throw new IOException("Could not connect to Distributed Map Cache server to put table information", ce);
}
} catch (SQLException se) {
// Propagate the error up, so things like rollback and logging/bulletins can be handled
throw new IOException(se.getMessage(), se);
}
}
}
} else {
// Clear the current table, to force a reload next time we get a TABLE_MAP event we care about
currentTable = null;
}
break;
case QUERY:
QueryEventData queryEventData = event.getData();
currentDatabase = queryEventData.getDatabase();
String sql = queryEventData.getSql();
// Is this the start of a transaction?
if ("BEGIN".equals(sql)) {
// If we're already in a transaction, something bad happened, alert the user
if (inTransaction) {
throw new IOException("BEGIN event received while already processing a transaction. This could indicate that your binlog position is invalid.");
}
// Mark the current binlog position in case we have to rollback the transaction (if the processor is stopped, e.g.)
xactBinlogFile = currentBinlogFile;
xactBinlogPosition = currentBinlogPosition;
xactSequenceId = currentSequenceId.get();
if (includeBeginCommit && (databaseNamePattern == null || databaseNamePattern.matcher(currentDatabase).matches())) {
BeginTransactionEventInfo beginEvent = new BeginTransactionEventInfo(currentDatabase, timestamp, currentBinlogFile, currentBinlogPosition);
currentSequenceId.set(beginEventWriter.writeEvent(currentSession, transitUri, beginEvent, currentSequenceId.get(), REL_SUCCESS));
}
inTransaction = true;
} else if ("COMMIT".equals(sql)) {
if (!inTransaction) {
throw new IOException("COMMIT event received while not processing a transaction (i.e. no corresponding BEGIN event). "
+ "This could indicate that your binlog position is invalid.");
}
// InnoDB generates XID events for "commit", but MyISAM generates Query events with "COMMIT", so handle that here
if (includeBeginCommit && (databaseNamePattern == null || databaseNamePattern.matcher(currentDatabase).matches())) {
CommitTransactionEventInfo commitTransactionEvent = new CommitTransactionEventInfo(currentDatabase, timestamp, currentBinlogFile, currentBinlogPosition);
currentSequenceId.set(commitEventWriter.writeEvent(currentSession, transitUri, commitTransactionEvent, currentSequenceId.get(), REL_SUCCESS));
}
// Commit the NiFi session
session.commit();
inTransaction = false;
currentTable = null;
} else {
// Check for DDL events (alter table, e.g.). Normalize the query to do string matching on the type of change
String normalizedQuery = sql.toLowerCase().trim().replaceAll(" {2,}", " ");
if (normalizedQuery.startsWith("alter table")
|| normalizedQuery.startsWith("alter ignore table")
|| normalizedQuery.startsWith("create table")
|| normalizedQuery.startsWith("truncate table")
|| normalizedQuery.startsWith("rename table")
|| normalizedQuery.startsWith("drop table")
|| normalizedQuery.startsWith("drop database")) {
if (includeDDLEvents && (databaseNamePattern == null || databaseNamePattern.matcher(currentDatabase).matches())) {
// If we don't have table information, we can still use the database name
TableInfo ddlTableInfo = (currentTable != null) ? currentTable : new TableInfo(currentDatabase, null, null, null);
DDLEventInfo ddlEvent = new DDLEventInfo(ddlTableInfo, timestamp, currentBinlogFile, currentBinlogPosition, sql);
currentSequenceId.set(ddlEventWriter.writeEvent(currentSession, transitUri, ddlEvent, currentSequenceId.get(), REL_SUCCESS));
}
// Remove all the keys from the cache that this processor added
if (cacheClient != null) {
cacheClient.removeByPattern(this.getIdentifier() + ".*");
}
// If not in a transaction, commit the session so the DDL event(s) will be transferred
if (includeDDLEvents && !inTransaction) {
session.commit();
}
}
}
break;
case XID:
if (!inTransaction) {
throw new IOException("COMMIT event received while not processing a transaction (i.e. no corresponding BEGIN event). "
+ "This could indicate that your binlog position is invalid.");
}
if (includeBeginCommit && (databaseNamePattern == null || databaseNamePattern.matcher(currentDatabase).matches())) {
CommitTransactionEventInfo commitTransactionEvent = new CommitTransactionEventInfo(currentDatabase, timestamp, currentBinlogFile, currentBinlogPosition);
currentSequenceId.set(commitEventWriter.writeEvent(currentSession, transitUri, commitTransactionEvent, currentSequenceId.get(), REL_SUCCESS));
}
// Commit the NiFi session
session.commit();
inTransaction = false;
currentTable = null;
currentDatabase = null;
break;
case WRITE_ROWS:
case EXT_WRITE_ROWS:
case PRE_GA_WRITE_ROWS:
case UPDATE_ROWS:
case EXT_UPDATE_ROWS:
case PRE_GA_UPDATE_ROWS:
case DELETE_ROWS:
case EXT_DELETE_ROWS:
case PRE_GA_DELETE_ROWS:
// If we are skipping this table, then don't emit any events related to its modification
if (skipTable) {
break;
}
if (!inTransaction) {
// These events should only happen inside a transaction, warn the user otherwise
log.warn("Table modification event occurred outside of a transaction.");
break;
}
if (currentTable == null && cacheClient != null) {
// No Table Map event was processed prior to this event, which should not happen, so throw an error
throw new RowEventException("No table information is available for this event, cannot process further.");
}
if (eventType == WRITE_ROWS
|| eventType == EXT_WRITE_ROWS
|| eventType == PRE_GA_WRITE_ROWS) {
InsertRowsEventInfo eventInfo = new InsertRowsEventInfo(currentTable, timestamp, currentBinlogFile, currentBinlogPosition, event.getData());
currentSequenceId.set(insertRowsWriter.writeEvent(currentSession, transitUri, eventInfo, currentSequenceId.get(), REL_SUCCESS));
} else if (eventType == DELETE_ROWS
|| eventType == EXT_DELETE_ROWS
|| eventType == PRE_GA_DELETE_ROWS) {
DeleteRowsEventInfo eventInfo = new DeleteRowsEventInfo(currentTable, timestamp, currentBinlogFile, currentBinlogPosition, event.getData());
currentSequenceId.set(deleteRowsWriter.writeEvent(currentSession, transitUri, eventInfo, currentSequenceId.get(), REL_SUCCESS));
} else {
// Update event
UpdateRowsEventInfo eventInfo = new UpdateRowsEventInfo(currentTable, timestamp, currentBinlogFile, currentBinlogPosition, event.getData());
currentSequenceId.set(updateRowsWriter.writeEvent(currentSession, transitUri, eventInfo, currentSequenceId.get(), REL_SUCCESS));
}
break;
case ROTATE:
// Update current binlog filename
RotateEventData rotateEventData = event.getData();
currentBinlogFile = rotateEventData.getBinlogFilename();
currentBinlogPosition = rotateEventData.getBinlogPosition();
break;
default:
break;
}
// Advance the current binlog position. This way if no more events are received and the processor is stopped, it will resume after the event that was just processed.
// We always get ROTATE and FORMAT_DESCRIPTION messages no matter where we start (even from the end), and they won't have the correct "next position" value, so only
// advance the position if it is not that type of event.
if (eventType != ROTATE && eventType != FORMAT_DESCRIPTION) {
currentBinlogPosition = header.getNextPosition();
}
}
}
//......
}- CaptureChangeMySQL的outputEvents方法会使用while循环不断执行queue.poll()，之后根据eventType来做不同处理，创建对应的BeginTransactionEventInfo、CommitTransactionEventInfo、DDLEventInfo、InsertRowsEventInfo、DeleteRowsEventInfo、UpdateRowsEventInfo，写入到对应的writer
小结
BinlogEventListener实现了BinaryLogClient.EventListener接口，其onEvent方法会将event包装为RawBinlogEvent，然后放到queue中