java.lang.Object
- io.debezium.connector.mysql.legacy.ChainedReader

All Implemented Interfaces:

Reader
```
@ThreadSafe
public final class ChainedReader
extends Object
implements Reader
```
A Reader implementation that runs one or more other Readers in a consistently, completely, and sequentially. This reader ensures that all records generated by one of its contained Readers are all passed through to callers via polling before the next reader is started. And, when this reader is stopped, this class ensures that current reader is stopped and that no additional readers will be started.

Author:

Randall Hauch

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class ChainedReader.Builder
- Nested classes/interfaces inherited from interface io.debezium.connector.mysql.legacy.Reader
  Reader.State

Field Summary

Fields
Modifier and Type	Field	Description
`private AtomicBoolean`	`completed`
`private String`	`completionMessage`
`private AtomicReference<Reader>`	`currentReader`
`private org.slf4j.Logger`	`logger`
`private List<Reader>`	`readers`
`private LinkedList<Reader>`	`remainingReaders`
`private AtomicBoolean`	`running`
`private AtomicReference<Runnable>`	`uponCompletion`

Constructor Summary

Constructors
Modifier Constructor Description

private ChainedReader(List<Reader> readers, String completionMessage)
Create a new chained reader.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`destroy()`	After the reader has stopped, there may still be some resources we want left available until the connector task is destroyed.
`void`	`initialize()`	Perform any initialization of the reader before being started.
`String`	`name()`	Get the name of this reader.
`List<org.apache.kafka.connect.source.SourceRecord>`	`poll()`	Poll for the next batch of source records.
`private void`	`readerCompletedPolling()`	Called when the previously-started reader has returned all of its records via `polling`.
`void`	`start()`	Start the reader and return immediately.
`private boolean`	`startNextReader()`	Start the next reader.
`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.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - logger
```
private final org.slf4j.Logger logger
```
  - readers
```
private final List<Reader> readers
```
  - completionMessage
```
private final String completionMessage
```
  - remainingReaders
```
private final LinkedList<Reader> remainingReaders
```
  - running
```
private final AtomicBoolean running
```
  - completed
```
private final AtomicBoolean completed
```
  - currentReader
```
private final AtomicReference<Reader> currentReader
```
  - uponCompletion
```
private final AtomicReference<Runnable> uponCompletion
```
- Constructor Detail
  - ChainedReader
```
private ChainedReader(List<Reader> readers,
                      String completionMessage)
```
    Create a new chained reader.
- Method Detail
  - uponCompletion
```
public void uponCompletion(Runnable handler)
```
    Description copied from interface: Reader
    
    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.
    
    Specified by:
    
    uponCompletion in interface Reader
    
    Parameters:
    
    handler - the function; may not be null
  - initialize
```
public void initialize()
```
    Description copied from interface: Reader
    
    Perform any initialization of the reader before being started. This method should be called exactly once before Reader.start() is called, and it should block until all initialization is completed.
    
    Specified by:
    
    initialize in interface Reader
  - destroy
```
public void destroy()
```
    Description copied from interface: Reader
    
    After the reader has stopped, there may still be some resources we want left available until the connector task is destroyed. This method is used to clean up those remaining resources upon shutdown. This method is effectively the opposite of Reader.initialize(), performing any de-initialization of the reader entity before shutdown. This method should be called exactly once after Reader.stop() is called, and it should block until all de-initialization is completed.
    
    Specified by:
    
    destroy in interface Reader
  - start
```
public void start()
```
    Description copied from interface: Reader
    
    Start the reader and return immediately. Once started, the SourceRecords generated by the reader can be obtained by periodically calling Reader.poll() until that method returns null.
    This method does nothing if it is already running.
    
    Specified by:
    
    start in interface Reader
  - stop
```
public void stop()
```
    Description copied from interface: Reader
    
    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.
    
    Specified by:
    
    stop in interface Reader
  - state
```
public Reader.State state()
```
    Description copied from interface: Reader
    
    Get the current state of this reader.
    
    Specified by:
    
    state in interface Reader
    
    Returns:
    
    the state; never null
  - poll
```
public List<org.apache.kafka.connect.source.SourceRecord> poll()
                                                        throws InterruptedException
```
    Description copied from interface: Reader
    
    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.
    
    Specified by:
    
    poll in interface Reader
    
    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
  - readerCompletedPolling
```
private void readerCompletedPolling()
```
    Called when the previously-started reader has returned all of its records via polling. Only when this method is called is the now-completed reader removed as the current reader, and this is what guarantees that all records produced by the now-completed reader have been polled.
  - startNextReader
```
private boolean startNextReader()
```
    Start the next reader.
    
    Returns:
    
    true if the next reader was started, or false if there are no more readers
  - name
```
public String name()
```
    Description copied from interface: Reader
    
    Get the name of this reader.
    
    Specified by:
    
    name in interface Reader
    
    Returns:
    
    the reader's name; never null

Class ChainedReader

Nested Class Summary

Nested classes/interfaces inherited from interface io.debezium.connector.mysql.legacy.Reader

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

logger

readers

completionMessage

remainingReaders

running

completed

currentReader

uponCompletion

Constructor Detail

ChainedReader

Method Detail

uponCompletion

initialize

destroy

start

stop

state

poll

readerCompletedPolling

startNextReader

name