public final class SocketSourceFunction extends RichSourceFunction<RowData> implements ResultTypeQueryable<RowData>
SocketSourceFunction
opens a socket and consumes bytes.
It splits records by the given byte delimiter (`\n` by default) and delegates the decoding to
a pluggable DeserializationSchema
.
Note: This is only an example and should not be used in production. The source function is not fault-tolerant and can only work with a parallelism of 1.
SourceFunction.SourceContext<T>
Constructor and Description |
---|
SocketSourceFunction(String hostname,
int port,
byte byteDelimiter,
DeserializationSchema<RowData> deserializer) |
Modifier and Type | Method and Description |
---|---|
void |
cancel()
Cancels the source.
|
TypeInformation<RowData> |
getProducedType()
Gets the data type (as a
TypeInformation ) produced by this function or input format. |
void |
open(Configuration parameters)
Initialization method for the function.
|
void |
run(SourceFunction.SourceContext<RowData> ctx)
Starts the source.
|
close, getIterationRuntimeContext, getRuntimeContext, setRuntimeContext
public SocketSourceFunction(String hostname, int port, byte byteDelimiter, DeserializationSchema<RowData> deserializer)
public TypeInformation<RowData> getProducedType()
ResultTypeQueryable
TypeInformation
) produced by this function or input format.getProducedType
in interface ResultTypeQueryable<RowData>
public void open(Configuration parameters) throws Exception
RichFunction
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.
open
in interface RichFunction
open
in class AbstractRichFunction
parameters
- 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.Configuration
public void run(SourceFunction.SourceContext<RowData> ctx) throws Exception
SourceFunction
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);
}
}
run
in interface SourceFunction<RowData>
ctx
- The context to emit elements to and for accessing locks.Exception
public void cancel()
SourceFunction
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.
cancel
in interface SourceFunction<RowData>
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