io.debezium.connector.sqlserver

Class SqlServerStreamingChangeEventSource

java.lang.Object

io.debezium.connector.sqlserver.SqlServerStreamingChangeEventSource

All Implemented Interfaces:

ChangeEventSource, StreamingChangeEventSource

public class SqlServerStreamingChangeEventSource
extends Object
implements StreamingChangeEventSource

A StreamingChangeEventSource based on SQL Server change data capture functionality. A main loop polls database DDL change and change data tables and turns them into change events.

The connector uses CDC functionality of SQL Server that is implemented as as a process that monitors source table and write changes from the table into the change table.

The main loop keeps a pointer to the LSN of changes that were already processed. It queries all change tables and get result set of changes. It always finds the smallest LSN across all tables and the change is converted into the event message and sent downstream. The process repeats until all result sets are empty. The LSN is marked and the procedure repeats.

The schema changes detection follows the procedure recommended by SQL Server CDC documentation. The database operator should create one more capture process (and table) when a table schema is updated. The code detects presence of two change tables for a single source table. It decides which table is the new one depending on LSNs stored in them. The loop streams changes from the older table till there are events in new table with the LSN larger than in the old one. Then the change table is switched and streaming is executed from the new one.

Author:

Jiri Pechanec

Nested Class Summary

Nested classes/interfaces inherited from interface io.debezium.pipeline.source.spi.ChangeEventSource

ChangeEventSource.ChangeEventSourceContext

Field Summary

Fields

Modifier and Type	Field and Description
private Clock	clock
private SqlServerConnectorConfig	connectorConfig
private SqlServerConnection	dataConnection Connection used for reading CDC tables.
private EventDispatcher<TableId>	dispatcher
private ErrorHandler	errorHandler
private static org.slf4j.Logger	LOGGER
private SqlServerConnection	metadataConnection A separate connection for retrieving timestamps; without it, adaptive buffering will not work.
private static Pattern	MISSING_CDC_FUNCTION_CHANGES_ERROR
private SqlServerOffsetContext	offsetContext
private Duration	pollInterval
private SqlServerDatabaseSchema	schema

Constructor Summary

Constructors

Constructor and Description
SqlServerStreamingChangeEventSource(SqlServerConnectorConfig connectorConfig, SqlServerOffsetContext offsetContext, SqlServerConnection dataConnection, SqlServerConnection metadataConnection, EventDispatcher<TableId> dispatcher, ErrorHandler errorHandler, Clock clock, SqlServerDatabaseSchema schema)

Method Summary

Modifier and Type	Method and Description
void	execute(ChangeEventSource.ChangeEventSourceContext context)
private SqlServerChangeTable[]	getCdcTablesToQuery()
private void	migrateTable(Queue<SqlServerChangeTable> schemaChangeCheckpoints)
private SqlServerChangeTable[]	processErrorFromChangeTableQuery(SQLException exception, SqlServerChangeTable[] currentChangeTables)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.debezium.pipeline.source.spi.StreamingChangeEventSource

commitOffset

Field Detail

MISSING_CDC_FUNCTION_CHANGES_ERROR

private static final Pattern MISSING_CDC_FUNCTION_CHANGES_ERROR

LOGGER

private static final org.slf4j.Logger LOGGER

dataConnection

private final SqlServerConnection dataConnection

Connection used for reading CDC tables.

metadataConnection

private final SqlServerConnection metadataConnection

A separate connection for retrieving timestamps; without it, adaptive buffering will not work.

See Also:

https://docs.microsoft.com/en-us/sql/connect/jdbc/using-adaptive-buffering?view=sql-server-2017#guidelines-for-using-adaptive-buffering

dispatcher

private final EventDispatcher<TableId> dispatcher

errorHandler

private final ErrorHandler errorHandler

clock

private final Clock clock

schema

private final SqlServerDatabaseSchema schema

offsetContext

private final SqlServerOffsetContext offsetContext

pollInterval

private final Duration pollInterval

connectorConfig

private final SqlServerConnectorConfig connectorConfig

Constructor Detail

SqlServerStreamingChangeEventSource

public SqlServerStreamingChangeEventSource(SqlServerConnectorConfig connectorConfig,
                                           SqlServerOffsetContext offsetContext,
                                           SqlServerConnection dataConnection,
                                           SqlServerConnection metadataConnection,
                                           EventDispatcher<TableId> dispatcher,
                                           ErrorHandler errorHandler,
                                           Clock clock,
                                           SqlServerDatabaseSchema schema)

Method Detail

execute

public void execute(ChangeEventSource.ChangeEventSourceContext context)
             throws InterruptedException

Specified by:

execute in interface StreamingChangeEventSource

Throws:

InterruptedException

migrateTable

private void migrateTable(Queue<SqlServerChangeTable> schemaChangeCheckpoints)
                   throws InterruptedException,
                          SQLException

Throws:

InterruptedException

SQLException

processErrorFromChangeTableQuery

private SqlServerChangeTable[] processErrorFromChangeTableQuery(SQLException exception,
                                                                SqlServerChangeTable[] currentChangeTables)
                                                         throws Exception

Throws:

Exception

getCdcTablesToQuery

private SqlServerChangeTable[] getCdcTablesToQuery()
                                            throws SQLException,
                                                   InterruptedException

Throws:

SQLException

InterruptedException