Receiver (Spark 2.3.3 JavaDoc)

Object
- org.apache.spark.streaming.receiver.Receiver<T>

All Implemented Interfaces:: java.io.Serializable

public abstract class Receiver<T>
extends Object
implements scala.Serializable

:: DeveloperApi :: Abstract class of a receiver that can be run on worker nodes to receive external data. A custom receiver can be defined by defining the functions onStart() and onStop(). onStart() should define the setup steps necessary to start receiving data, and onStop() should define the cleanup steps necessary to stop receiving data. Exceptions while receiving can be handled either by restarting the receiver with restart(...) or stopped completely by stop(...).

A custom receiver in Scala would look like this.


  class MyReceiver(storageLevel: StorageLevel) extends NetworkReceiver[String](storageLevel) {
      def onStart() {
          // Setup stuff (start threads, open sockets, etc.) to start receiving data.
          // Must start new thread to receive data, as onStart() must be non-blocking.

          // Call store(...) in those threads to store received data into Spark's memory.

          // Call stop(...), restart(...) or reportError(...) on any thread based on how
          // different errors need to be handled.

          // See corresponding method documentation for more details
      }

      def onStop() {
          // Cleanup stuff (stop threads, close sockets, etc.) to stop receiving data.
      }
  }

A custom receiver in Java would look like this.


 class MyReceiver extends Receiver<String> {
     public MyReceiver(StorageLevel storageLevel) {
         super(storageLevel);
     }

     public void onStart() {
          // Setup stuff (start threads, open sockets, etc.) to start receiving data.
          // Must start new thread to receive data, as onStart() must be non-blocking.

          // Call store(...) in those threads to store received data into Spark's memory.

          // Call stop(...), restart(...) or reportError(...) on any thread based on how
          // different errors need to be handled.

          // See corresponding method documentation for more details
     }

     public void onStop() {
          // Cleanup stuff (stop threads, close sockets, etc.) to stop receiving data.
     }
 }

See Also:: Serialized Form

Constructor Summary

Constructors
Constructor and Description

Receiver(StorageLevel storageLevel)

Constructors
Constructor and Description
`Receiver(StorageLevel storageLevel)`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`isStarted()` Check if the receiver has started or not.
`boolean`	`isStopped()` Check if receiver has been marked for stopping.
`abstract void`	`onStart()` This method is called by the system when the receiver is started.
`abstract void`	`onStop()` This method is called by the system when the receiver is stopped.
`scala.Option<String>`	`preferredLocation()` Override this to specify a preferred location (hostname).
`void`	`reportError(String message, Throwable throwable)` Report exceptions in receiving data.
`void`	`restart(String message)` Restart the receiver.
`void`	`restart(String message, Throwable error)` Restart the receiver.
`void`	`restart(String message, Throwable error, int millisecond)` Restart the receiver.
`void`	`stop(String message)` Stop the receiver completely.
`void`	`stop(String message, Throwable error)` Stop the receiver completely due to an exception
`StorageLevel`	`storageLevel()`
`void`	`store(scala.collection.mutable.ArrayBuffer<T> dataBuffer)` Store an ArrayBuffer of received data as a data block into Spark's memory.
`void`	`store(scala.collection.mutable.ArrayBuffer<T> dataBuffer, Object metadata)` Store an ArrayBuffer of received data as a data block into Spark's memory.
`void`	`store(java.nio.ByteBuffer bytes)` Store the bytes of received data as a data block into Spark's memory.
`void`	`store(java.nio.ByteBuffer bytes, Object metadata)` Store the bytes of received data as a data block into Spark's memory.
`void`	`store(scala.collection.Iterator<T> dataIterator)` Store an iterator of received data as a data block into Spark's memory.
`void`	`store(java.util.Iterator<T> dataIterator)` Store an iterator of received data as a data block into Spark's memory.
`void`	`store(java.util.Iterator<T> dataIterator, Object metadata)` Store an iterator of received data as a data block into Spark's memory.
`void`	`store(scala.collection.Iterator<T> dataIterator, Object metadata)` Store an iterator of received data as a data block into Spark's memory.
`void`	`store(T dataItem)` Store a single item of received data to Spark's memory.
`int`	`streamId()` Get the unique identifier the receiver input stream that this receiver is associated with.

Methods inherited from class Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Receiver
```
public Receiver(StorageLevel storageLevel)
```
- Method Detail
  - storageLevel
```
public StorageLevel storageLevel()
```
  - onStart
```
public abstract void onStart()
```
    This method is called by the system when the receiver is started. This function must initialize all resources (threads, buffers, etc.) necessary for receiving data. This function must be non-blocking, so receiving the data must occur on a different thread. Received data can be stored with Spark by calling store(data).
    If there are errors in threads started here, then following options can be done (i) reportError(...) can be called to report the error to the driver. The receiving of data will continue uninterrupted. (ii) stop(...) can be called to stop receiving data. This will call onStop() to clear up all resources allocated (threads, buffers, etc.) during onStart(). (iii) restart(...) can be called to restart the receiver. This will call onStop() immediately, and then onStart() after a delay.
  - onStop
```
public abstract void onStop()
```
    This method is called by the system when the receiver is stopped. All resources (threads, buffers, etc.) set up in onStart() must be cleaned up in this method.
  - preferredLocation
```
public scala.Option<String> preferredLocation()
```
    Override this to specify a preferred location (hostname).
  - store
```
public void store(T dataItem)
```
    Store a single item of received data to Spark's memory. These single items will be aggregated together into data blocks before being pushed into Spark's memory.
    
    Parameters:
    
    dataItem - (undocumented)
  - store
```
public void store(scala.collection.mutable.ArrayBuffer<T> dataBuffer)
```
    Store an ArrayBuffer of received data as a data block into Spark's memory.
  - store
```
public void store(scala.collection.mutable.ArrayBuffer<T> dataBuffer,
                  Object metadata)
```
    Store an ArrayBuffer of received data as a data block into Spark's memory. The metadata will be associated with this block of data for being used in the corresponding InputDStream.
    
    Parameters:
    
    dataBuffer - (undocumented)
    
    metadata - (undocumented)
  - store
```
public void store(scala.collection.Iterator<T> dataIterator)
```
    Store an iterator of received data as a data block into Spark's memory.
  - store
```
public void store(java.util.Iterator<T> dataIterator,
                  Object metadata)
```
    Store an iterator of received data as a data block into Spark's memory. The metadata will be associated with this block of data for being used in the corresponding InputDStream.
    
    Parameters:
    
    dataIterator - (undocumented)
    
    metadata - (undocumented)
  - store
```
public void store(java.util.Iterator<T> dataIterator)
```
    Store an iterator of received data as a data block into Spark's memory.
  - store
```
public void store(scala.collection.Iterator<T> dataIterator,
                  Object metadata)
```
    Store an iterator of received data as a data block into Spark's memory. The metadata will be associated with this block of data for being used in the corresponding InputDStream.
    
    Parameters:
    
    dataIterator - (undocumented)
    
    metadata - (undocumented)
  - store
```
public void store(java.nio.ByteBuffer bytes)
```
    Store the bytes of received data as a data block into Spark's memory. Note that the data in the ByteBuffer must be serialized using the same serializer that Spark is configured to use.
    
    Parameters:
    
    bytes - (undocumented)
  - store
```
public void store(java.nio.ByteBuffer bytes,
                  Object metadata)
```
    Store the bytes of received data as a data block into Spark's memory. The metadata will be associated with this block of data for being used in the corresponding InputDStream.
    
    Parameters:
    
    bytes - (undocumented)
    
    metadata - (undocumented)
  - reportError
```
public void reportError(String message,
                        Throwable throwable)
```
    Report exceptions in receiving data.
  - restart
```
public void restart(String message)
```
    Restart the receiver. This method schedules the restart and returns immediately. The stopping and subsequent starting of the receiver (by calling onStop() and onStart()) is performed asynchronously in a background thread. The delay between the stopping and the starting is defined by the Spark configuration spark.streaming.receiverRestartDelay. The message will be reported to the driver.
    
    Parameters:
    
    message - (undocumented)
  - restart
```
public void restart(String message,
                    Throwable error)
```
    Restart the receiver. This method schedules the restart and returns immediately. The stopping and subsequent starting of the receiver (by calling onStop() and onStart()) is performed asynchronously in a background thread. The delay between the stopping and the starting is defined by the Spark configuration spark.streaming.receiverRestartDelay. The message and exception will be reported to the driver.
    
    Parameters:
    
    message - (undocumented)
    
    error - (undocumented)
  - restart
```
public void restart(String message,
                    Throwable error,
                    int millisecond)
```
    Restart the receiver. This method schedules the restart and returns immediately. The stopping and subsequent starting of the receiver (by calling onStop() and onStart()) is performed asynchronously in a background thread.
    
    Parameters:
    
    message - (undocumented)
    
    error - (undocumented)
    
    millisecond - (undocumented)
  - stop
```
public void stop(String message)
```
    Stop the receiver completely.
  - stop
```
public void stop(String message,
                 Throwable error)
```
    Stop the receiver completely due to an exception
  - isStarted
```
public boolean isStarted()
```
    Check if the receiver has started or not.
  - isStopped
```
public boolean isStopped()
```
    Check if receiver has been marked for stopping. Use this to identify when the receiving of data should be stopped.
    
    Returns:
    
    (undocumented)
  - streamId
```
public int streamId()
```
    Get the unique identifier the receiver input stream that this receiver is associated with.
    
    Returns:
    
    (undocumented)

Class Receiver<T>

Constructor Summary

Method Summary

Methods inherited from class Object

Constructor Detail

Receiver

Method Detail

storageLevel

onStart

onStop

preferredLocation

store

store

store

store

store

store

store

store

store

reportError

restart

restart

restart

stop

stop

isStarted

isStopped

streamId