public class NiFiSource extends RichParallelSourceFunction<NiFiDataPacket> implements StoppableFunction
SourceFunction.SourceContext<T>| 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.
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NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig,
long waitTimeMs)
Constructs a new NiFiSource using the given client config and wait time.
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| 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.
|
void |
stop()
Stops the source.
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getIterationRuntimeContext, getRuntimeContext, setRuntimeContextpublic NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig)
clientConfig - the configuration for building a NiFi SiteToSiteClientpublic NiFiSource(org.apache.nifi.remote.client.SiteToSiteClientConfig clientConfig,
long waitTimeMs)
clientConfig - the configuration for building a NiFi SiteToSiteClientwaitTimeMs - the amount of time to wait (in milliseconds) if no data is available to pull from NiFipublic void open(Configuration parameters) throws Exception
RichFunctionThe 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.
open in interface RichFunctionopen in class AbstractRichFunctionparameters - The configuration containing the parameters attached to the contract.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.Configurationpublic void run(SourceFunction.SourceContext<NiFiDataPacket> ctx) throws Exception
SourceFunctionSourceFunction.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);
}
}
run in interface SourceFunction<NiFiDataPacket>ctx - The context to emit elements to and for accessing locks.Exceptionpublic void cancel()
SourceFunctionSourceFunction.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.
cancel in interface SourceFunction<NiFiDataPacket>public void close()
throws Exception
RichFunctionThis method can be used for clean up work.
close in interface RichFunctionclose in class AbstractRichFunctionException - 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.public void stop()
StoppableFunctioncancel() 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.
stop in interface StoppableFunctionCopyright © 2014–2020 The Apache Software Foundation. All rights reserved.