org.apache.flink.streaming.connectors.nifi

Class NiFiSource

java.lang.Object

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

org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction<NiFiDataPacket>

org.apache.flink.streaming.connectors.nifi.NiFiSource

All Implemented Interfaces:

Serializable, Function, RichFunction, ParallelSourceFunction<NiFiDataPacket>, SourceFunction<NiFiDataPacket>

public class NiFiSource
extends RichParallelSourceFunction<NiFiDataPacket>

A source that pulls data from Apache NiFi using the NiFi Site-to-Site client. This source produces NiFiDataPackets which encapsulate the content and attributes of a NiFi FlowFile.

See Also:

Serialized Form

Nested Class Summary

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

SourceFunction.SourceContext<T>

Constructor Summary

Constructors

Constructor and Description
NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig) Constructs a new NiFiSource using the given client config and the default wait time of 1000 ms.
NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig, long waitTimeMs) Constructs a new NiFiSource using the given client config and wait time.

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<NiFiDataPacket> ctx) Starts 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

Constructor Detail

NiFiSource

public NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig)

Constructs a new NiFiSource using the given client config and the default wait time of 1000 ms.

Parameters:

clientConfig - the configuration for building a NiFi SiteToSiteClient

NiFiSource

public NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig,
                  long waitTimeMs)

Constructs a new NiFiSource using the given client config and wait time.

Parameters:

clientConfig - the configuration for building a NiFi SiteToSiteClient

waitTimeMs - the amount of time to wait (in milliseconds) if no data is available to pull from NiFi

Method Detail

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 MyFilter extends RichFilterFunction<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<NiFiDataPacket> ctx)
         throws Exception

Description copied from interface: SourceFunction

Starts the source. Implementations use the SourceFunction.SourceContext to emit elements. Sources that checkpoint their state for fault tolerance should use the SourceFunction.SourceContext.getCheckpointLock() checkpoint lock} to ensure consistency between the bookkeeping and emitting the elements.

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

Refer to the top-level class docs for an example.

Parameters:

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

Throws:

Exception

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.

In case of an ungraceful shutdown (cancellation of the source operator, possibly for failover), the thread that calls SourceFunction.run(SourceContext) will also be interrupted) by the Flink runtime, in order to speed up the cancellation (to ensure threads exit blocking methods fast, like I/O, blocking queues, etc.). The interruption happens strictly after this method has been called, so any interruption handler can rely on the fact that this method has completed (for example to ignore exceptions that happen after cancellation).

During graceful shutdown (for example stopping a job with a savepoint), the program must cleanly exit the SourceFunction.run(SourceContext) method soon after this method was called. The Flink runtime will NOT interrupt the source thread during graceful shutdown. Source implementors must ensure that no thread interruption happens on any thread that emits records through the SourceContext from the SourceFunction.run(SourceContext) method; otherwise the clean shutdown may fail when threads are interrupted while processing the final records.

Because the SourceFunction cannot easily differentiate whether the shutdown should be graceful or ungraceful, we recommend that implementors refrain from interrupting any threads that interact with the SourceContext at all. You can rely on the Flink runtime to interrupt the source thread in case of ungraceful cancellation. Any additionally spawned threads that directly emit records through the SourceContext should use a shutdown method that does not rely on thread interruption.

close

public void close()
           throws Exception

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

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.