io.debezium.connector.mysql

Interface Reader

All Known Implementing Classes:

AbstractReader, BinlogReader, ChainedReader, SnapshotReader

public interface Reader

A component that reads a portion of the MySQL server history or current state.

A reader starts out in the stopped state, and when started transitions to a Reader.State.RUNNING state. The reader may either complete its work or be explicitly stopped, at which point the reader transitions to a state until all already-generated SourceRecords are consumed by the client via the poll method. Only after all records are consumed does the reader transition to the stopped state and call the uponCompletion(Runnable) method.

See ChainedReader if multiple Reader implementations are to be run in-sequence while keeping the correct start, stop, and completion semantics.

Author:

Randall Hauch

See Also:

ChainedReader

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Reader.State The possible states of a reader.

Method Summary

Modifier and Type	Method and Description
String	name() Get the name of this reader.
List<org.apache.kafka.connect.source.SourceRecord>	poll() Poll for the next batch of source records.
void	start() Start the reader and return immediately.
Reader.State	state() Get the current state of this reader.
void	stop() Stop the reader from running and transition to the Reader.State.STOPPING state until all remaining records are consumed, at which point its state transitions to Reader.State.STOPPED.
void	uponCompletion(Runnable handler) Set the function that should be called when this reader transitions from the Reader.State.STOPPING to Reader.State.STOPPED state, which is after all generated records have been consumed via the poll method.

Method Detail

name

String name()

Get the name of this reader.

Returns:

the reader's name; never null

state

Reader.State state()

Get the current state of this reader.

Returns:

the state; never null

uponCompletion

void uponCompletion(Runnable handler)

Set the function that should be called when this reader transitions from the Reader.State.STOPPING to Reader.State.STOPPED state, which is after all generated records have been consumed via the poll method.

This method should only be called while the reader is in the Reader.State.STOPPED state.

Parameters:

handler - the function; may not be null

start

void start()

Start the reader and return immediately. Once started, the SourceRecords generated by the reader can be obtained by periodically calling poll() until that method returns null.

This method does nothing if it is already running.

stop

void stop()

Stop the reader from running and transition to the Reader.State.STOPPING state until all remaining records are consumed, at which point its state transitions to Reader.State.STOPPED.

poll

List<org.apache.kafka.connect.source.SourceRecord> poll()
                                                 throws InterruptedException

Poll for the next batch of source records. This method returns null only when all records generated by this reader have been processed, following the natural or explicit stopping of this reader. Note that this method may block if no additional records are available but the reader may produce more, thus callers should call this method continually until this method returns null.

Returns:

the list of source records that may or may not be empty; or null when there will be no more records because the reader has completely Reader.State.STOPPED.

Throws:

InterruptedException - if this thread is interrupted while waiting for more records

org.apache.kafka.connect.errors.ConnectException - if there is an error while this reader is running