org.apache.flink.streaming.connectors.twitter

Class TwitterSource

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.streaming.api.functions.source.RichSourceFunction<String>

org.apache.flink.streaming.connectors.twitter.TwitterSource

All Implemented Interfaces:

Serializable, Function, RichFunction, StoppableFunction, SourceFunction<String>

public class TwitterSource
extends RichSourceFunction<String>
implements StoppableFunction

Implementation of SourceFunction specialized to emit tweets from Twitter. This is not a parallel source because the Twitter API only allows two concurrent connections.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	TwitterSource.EndpointInitializer Implementing this interface allows users of this source to set a custom endpoint.

Nested classes/interfaces inherited from interface org.apache.flink.streaming.api.functions.source.SourceFunction

SourceFunction.SourceContext<T>

Field Summary

Fields

Modifier and Type	Field and Description
static String	CLIENT_BUFFER_SIZE
static String	CLIENT_HOSTS
static String	CLIENT_NAME
static String	CONSUMER_KEY
static String	CONSUMER_SECRET
static String	TOKEN
static String	TOKEN_SECRET

Constructor Summary

Constructors

Constructor and Description
TwitterSource(Properties properties) Create TwitterSource for streaming.

Method Summary

Modifier and Type	Method and Description
void	cancel() Cancels the source.
void	close() Tear-down method for the user code.
void	open(Configuration parameters) Initialization method for the function.
void	run(SourceFunction.SourceContext<String> ctx) Starts the source.
void	setCustomEndpointInitializer(TwitterSource.EndpointInitializer initializer) Set a custom endpoint initializer.
void	stop() Stops the source.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

getIterationRuntimeContext, getRuntimeContext, setRuntimeContext

Methods inherited from class java.lang.Object

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

Field Detail

CONSUMER_KEY

public static final String CONSUMER_KEY

See Also:

Constant Field Values

CONSUMER_SECRET

public static final String CONSUMER_SECRET

See Also:

Constant Field Values

TOKEN

public static final String TOKEN

See Also:

Constant Field Values

TOKEN_SECRET

public static final String TOKEN_SECRET

See Also:

Constant Field Values

CLIENT_NAME

public static final String CLIENT_NAME

See Also:

Constant Field Values

CLIENT_HOSTS

public static final String CLIENT_HOSTS

See Also:

Constant Field Values

CLIENT_BUFFER_SIZE

public static final String CLIENT_BUFFER_SIZE

See Also:

Constant Field Values

Constructor Detail

TwitterSource

public TwitterSource(Properties properties)

Create TwitterSource for streaming.

Parameters:

properties - For the source

Method Detail

setCustomEndpointInitializer

public void setCustomEndpointInitializer(TwitterSource.EndpointInitializer initializer)

Set a custom endpoint initializer.

open

public void open(Configuration parameters)
          throws Exception

Description copied from interface: RichFunction

Initialization method for the function. It is called before the actual working methods (like map or join) and thus suitable for one time setup work. For functions that are part of an iteration, this method will be invoked at the beginning of each iteration superstep.

The configuration object passed to the function can be used for configuration and initialization. The configuration contains all parameters that were configured on the function in the program composition.

 public class MyMapper extends FilterFunction<String> {
 
     private String searchString;
     
     public void open(Configuration parameters) {
         this.searchString = parameters.getString("foo");
     }
     
     public boolean filter(String value) {
         return value.equals(searchString);
     }
 }
 

By default, this method does nothing.

Specified by:

open in interface RichFunction

Overrides:

open in class AbstractRichFunction

Parameters:

parameters - The configuration containing the parameters attached to the contract.

Throws:

Exception - Implementations may forward exceptions, which are caught by the runtime. When the runtime catches an exception, it aborts the task and lets the fail-over logic decide whether to retry the task execution.

See Also:

Configuration

run

public void run(SourceFunction.SourceContext<String> ctx)
         throws Exception

Description copied from interface: SourceFunction

Starts the source. Implementations can use the SourceFunction.SourceContext emit elements.

Sources that implement CheckpointedFunction must lock on the checkpoint lock (using a synchronized block) before updating internal state and emitting elements, to make both an atomic operation:

  public class ExampleCountSource implements SourceFunction<Long>, CheckpointedFunction {
      private long count = 0L;
      private volatile boolean isRunning = true;

      private transient ListState<Long> checkpointedCount;

      public void run(SourceContext<T> ctx) {
          while (isRunning && count < 1000) {
              // this synchronized block ensures that state checkpointing,
              // internal state updates and emission of elements are an atomic operation
              synchronized (ctx.getCheckpointLock()) {
                  ctx.collect(count);
                  count++;
              }
          }
      }

      public void cancel() {
          isRunning = false;
      }

      public void initializeState(FunctionInitializationContext context) {
          this.checkpointedCount = context
              .getOperatorStateStore()
              .getListState(new ListStateDescriptor<>("count", Long.class));

          if (context.isRestored()) {
              for (Long count : this.checkpointedCount.get()) {
                  this.count = count;
              }
          }
      }

      public void snapshotState(FunctionSnapshotContext context) {
          this.checkpointedCount.clear();
          this.checkpointedCount.add(count);
      }
 }
 

Specified by:

run in interface SourceFunction<String>

Parameters:

ctx - The context to emit elements to and for accessing locks.

Throws:

Exception

close

public void close()

Description copied from interface: RichFunction

Tear-down method for the user code. It is called after the last call to the main working methods (e.g. map or join). For functions that are part of an iteration, this method will be invoked after each iteration superstep.

This method can be used for clean up work.

Specified by:

close in interface RichFunction

Overrides:

close in class AbstractRichFunction

cancel

public void cancel()

Description copied from interface: SourceFunction

Cancels the source. Most sources will have a while loop inside the SourceFunction.run(SourceContext) method. The implementation needs to ensure that the source will break out of that loop after this method is called.

A typical pattern is to have an "volatile boolean isRunning" flag that is set to false in this method. That flag is checked in the loop condition.

When a source is canceled, the executing thread will also be interrupted (via Thread.interrupt()). The interruption happens strictly after this method has been called, so any interruption handler can rely on the fact that this method has completed. It is good practice to make any flags altered by this method "volatile", in order to guarantee the visibility of the effects of this method to any interruption handler.

Specified by:

cancel in interface SourceFunction<String>

stop

public void stop()

Description copied from interface: StoppableFunction

Stops the source. In contrast to cancel() this is a request to the source function to shut down gracefully. Pending data can still be emitted and it is not required to stop immediately -- however, in the near future. The job will keep running until all emitted data is processed completely.

Most streaming sources will have a while loop inside the run() method. You need to ensure that the source will break out of this loop. This can be achieved by having a volatile field "isRunning" that is checked in the loop and that is set to false in this method.

The call to stop() should not block and not throw any exception.

Specified by:

stop in interface StoppableFunction