All Known Implementing Classes:

AbstractReader, BinlogReader, BlockingReader, ChainedReader, ParallelSnapshotReader, ReconcilingBinlogReader, SnapshotReader, TimedBlockingReader
```
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 {@value State#STOPPING stopping} 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 Description

static class Reader.State
The possible states of a reader.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`default void`	`destroy()`	After the reader has stopped, there may still be some resources we want left available until the connector task is destroyed.
`default 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.
`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
  - initialize
```
default void initialize()
```
    Perform any initialization of the reader before being started. This method should be called exactly once before start() is called, and it should block until all initialization is completed.
  - destroy
```
default void destroy()
```
    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 initialize(), performing any de-initialization of the reader entity before shutdown. This method should be called exactly once after stop() is called, and it should block until all de-initialization is completed.
  - start
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void start()
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    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

Interface Reader

Nested Class Summary

Method Summary

Method Detail

name

state

uponCompletion

initialize

destroy

start

stop

poll