聊聊flink的InputFormatSourceFunction

ApacheFlink · 發表 2018-12-04 13:09:27

摘要： final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment(); IteratorInputFormat iteratorInputFormat = new ...

final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
IteratorInputFormat iteratorInputFormat = new IteratorInputFormat<String>(new WordIterator());
env
//TypeInformation.of(new TypeHint<String>() {}
.createInput(iteratorInputFormat,TypeExtractor.createTypeInfo(String.class))
.setParallelism(1)
.print();
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這裡使用IteratorInputFormat呼叫env的createInput方法來建立SourceFunction

StreamExecutionEnvironment.createInput

flink-streaming-java_2.11-1.6.2-sources.jar!/org/apache/flink/streaming/api/environment/StreamExecutionEnvironment.java

@PublicEvolving
public <OUT> DataStreamSource<OUT> createInput(InputFormat<OUT, ?> inputFormat, TypeInformation<OUT> typeInfo) {
DataStreamSource<OUT> source;

if (inputFormat instanceof FileInputFormat) {
@SuppressWarnings("unchecked")
FileInputFormat<OUT> format = (FileInputFormat<OUT>) inputFormat;

source = createFileInput(format, typeInfo, "Custom File source",
FileProcessingMode.PROCESS_ONCE, -1);
} else {
source = createInput(inputFormat, typeInfo, "Custom Source");
}
return source;
}

private <OUT> DataStreamSource<OUT> createInput(InputFormat<OUT, ?> inputFormat,
TypeInformation<OUT> typeInfo,
String sourceName) {

InputFormatSourceFunction<OUT> function = new InputFormatSourceFunction<>(inputFormat, typeInfo);
return addSource(function, sourceName, typeInfo);
}
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StreamExecutionEnvironment.createInput在inputFormat不是FileInputFormat型別的時候建立的是InputFormatSourceFunction

InputFormatSourceFunction

/**
 * A {@link SourceFunction} that reads data using an {@link InputFormat}.
 */
@Internal
public class InputFormatSourceFunction<OUT> extends RichParallelSourceFunction<OUT> {
private static final long serialVersionUID = 1L;

private TypeInformation<OUT> typeInfo;
private transient TypeSerializer<OUT> serializer;

private InputFormat<OUT, InputSplit> format;

private transient InputSplitProvider provider;
private transient Iterator<InputSplit> splitIterator;

private volatile boolean isRunning = true;

@SuppressWarnings("unchecked")
public InputFormatSourceFunction(InputFormat<OUT, ?> format, TypeInformation<OUT> typeInfo) {
this.format = (InputFormat<OUT, InputSplit>) format;
this.typeInfo = typeInfo;
}

@Override
@SuppressWarnings("unchecked")
public void open(Configuration parameters) throws Exception {
StreamingRuntimeContext context = (StreamingRuntimeContext) getRuntimeContext();

if (format instanceof RichInputFormat) {
((RichInputFormat) format).setRuntimeContext(context);
}
format.configure(parameters);

provider = context.getInputSplitProvider();
serializer = typeInfo.createSerializer(getRuntimeContext().getExecutionConfig());
splitIterator = getInputSplits();
isRunning = splitIterator.hasNext();
}

@Override
public void run(SourceContext<OUT> ctx) throws Exception {
try {

Counter completedSplitsCounter = getRuntimeContext().getMetricGroup().counter("numSplitsProcessed");
if (isRunning && format instanceof RichInputFormat) {
((RichInputFormat) format).openInputFormat();
}

OUT nextElement = serializer.createInstance();
while (isRunning) {
format.open(splitIterator.next());

// for each element we also check if cancel
// was called by checking the isRunning flag

while (isRunning && !format.reachedEnd()) {
nextElement = format.nextRecord(nextElement);
if (nextElement != null) {
ctx.collect(nextElement);
} else {
break;
}
}
format.close();
completedSplitsCounter.inc();

if (isRunning) {
isRunning = splitIterator.hasNext();
}
}
} finally {
format.close();
if (format instanceof RichInputFormat) {
((RichInputFormat) format).closeInputFormat();
}
isRunning = false;
}
}

@Override
public void cancel() {
isRunning = false;
}

@Override
public void close() throws Exception {
format.close();
if (format instanceof RichInputFormat) {
((RichInputFormat) format).closeInputFormat();
}
}

/**
 * Returns the {@code InputFormat}. This is only needed because we need to set the input
 * split assigner on the {@code StreamGraph}.
 */
public InputFormat<OUT, InputSplit> getFormat() {
return format;
}

private Iterator<InputSplit> getInputSplits() {

return new Iterator<InputSplit>() {

private InputSplit nextSplit;

private boolean exhausted;

@Override
public boolean hasNext() {
if (exhausted) {
return false;
}

if (nextSplit != null) {
return true;
}

final InputSplit split;
try {
split = provider.getNextInputSplit(getRuntimeContext().getUserCodeClassLoader());
} catch (InputSplitProviderException e) {
throw new RuntimeException("Could not retrieve next input split.", e);
}

if (split != null) {
this.nextSplit = split;
return true;
} else {
exhausted = true;
return false;
}
}

@Override
public InputSplit next() {
if (this.nextSplit == null && !hasNext()) {
throw new NoSuchElementException();
}

final InputSplit tmp = this.nextSplit;
this.nextSplit = null;
return tmp;
}

@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
}
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splitIterator

InputSplitProvider

flink-runtime_2.11-1.6.2-sources.jar!/org/apache/flink/runtime/jobgraph/tasks/InputSplitProvider.java

/**
 * An input split provider can be successively queried to provide a series of {@link InputSplit} objects a
 * task is supposed to consume in the course of its execution.
 */
@Public
public interface InputSplitProvider {

/**
 * Requests the next input split to be consumed by the calling task.
 *
 * @param userCodeClassLoader used to deserialize input splits
 * @return the next input split to be consumed by the calling task or <code>null</code> if the
 *task shall not consume any further input splits.
 * @throws InputSplitProviderException if fetching the next input split fails
 */
InputSplit getNextInputSplit(ClassLoader userCodeClassLoader) throws InputSplitProviderException;
}
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InputSplitProvider介面定義了getNextInputSplit方法，用於查詢nextInputSplit，它有兩個實現類，分別是RpcInputSplitProvider、TaskInputSplitProvider

RpcInputSplitProvider

flink-runtime_2.11-1.6.2-sources.jar!/org/apache/flink/runtime/taskexecutor/rpc/RpcInputSplitProvider.java

public class RpcInputSplitProvider implements InputSplitProvider {
private final JobMasterGateway jobMasterGateway;
private final JobVertexID jobVertexID;
private final ExecutionAttemptID executionAttemptID;
private final Time timeout;

public RpcInputSplitProvider(
JobMasterGateway jobMasterGateway,
JobVertexID jobVertexID,
ExecutionAttemptID executionAttemptID,
Time timeout) {
this.jobMasterGateway = Preconditions.checkNotNull(jobMasterGateway);
this.jobVertexID = Preconditions.checkNotNull(jobVertexID);
this.executionAttemptID = Preconditions.checkNotNull(executionAttemptID);
this.timeout = Preconditions.checkNotNull(timeout);
}


@Override
public InputSplit getNextInputSplit(ClassLoader userCodeClassLoader) throws InputSplitProviderException {
Preconditions.checkNotNull(userCodeClassLoader);

CompletableFuture<SerializedInputSplit> futureInputSplit = jobMasterGateway.requestNextInputSplit(
jobVertexID,
executionAttemptID);

try {
SerializedInputSplit serializedInputSplit = futureInputSplit.get(timeout.getSize(), timeout.getUnit());

if (serializedInputSplit.isEmpty()) {
return null;
} else {
return InstantiationUtil.deserializeObject(serializedInputSplit.getInputSplitData(), userCodeClassLoader);
}
} catch (Exception e) {
throw new InputSplitProviderException("Requesting the next input split failed.", e);
}
}
}
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RpcInputSplitProvider請求jobMasterGateway.requestNextInputSplit來獲取SerializedInputSplit(本例項的splitProvider為RpcInputSplitProvider )

TaskInputSplitProvider

flink-runtime_2.11-1.6.2-sources.jar!/org/apache/flink/runtime/taskmanager/TaskInputSplitProvider.java

/**
 * Implementation using {@link ActorGateway} to forward the messages.
 */
public class TaskInputSplitProvider implements InputSplitProvider {

private final ActorGateway jobManager;

private final JobID jobID;

private final JobVertexID vertexID;

private final ExecutionAttemptID executionID;

private final FiniteDuration timeout;


public TaskInputSplitProvider(
ActorGateway jobManager,
JobID jobID,
JobVertexID vertexID,
ExecutionAttemptID executionID,
FiniteDuration timeout) {

this.jobManager = Preconditions.checkNotNull(jobManager);
this.jobID = Preconditions.checkNotNull(jobID);
this.vertexID = Preconditions.checkNotNull(vertexID);
this.executionID = Preconditions.checkNotNull(executionID);
this.timeout = Preconditions.checkNotNull(timeout);
}

@Override
public InputSplit getNextInputSplit(ClassLoader userCodeClassLoader) throws InputSplitProviderException {
Preconditions.checkNotNull(userCodeClassLoader);

final Future<Object> response = jobManager.ask(
new JobManagerMessages.RequestNextInputSplit(jobID, vertexID, executionID),
timeout);

final Object result;

try {
result = Await.result(response, timeout);
} catch (Exception e) {
throw new InputSplitProviderException("Did not receive next input split from JobManager.", e);
}

if(result instanceof JobManagerMessages.NextInputSplit){
final JobManagerMessages.NextInputSplit nextInputSplit =
(JobManagerMessages.NextInputSplit) result;

byte[] serializedData = nextInputSplit.splitData();

if(serializedData == null) {
return null;
} else {
final Object deserialized;

try {
deserialized = InstantiationUtil.deserializeObject(serializedData,
userCodeClassLoader);
} catch (Exception e) {
throw new InputSplitProviderException("Could not deserialize the serialized input split.", e);
}

return (InputSplit) deserialized;
}
} else {
throw new InputSplitProviderException("RequestNextInputSplit requires a response of type " +
"NextInputSplit. Instead response is of type " + result.getClass() + '.');
}

}
}
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TaskInputSplitProvider請求jobManager.ask(new JobManagerMessages.RequestNextInputSplit(jobID, vertexID, executionID),timeout)來獲取SerializedInputSplit

InputSplit

flink-core-1.6.2-sources.jar!/org/apache/flink/core/io/InputSplit.java

/**
 * This interface must be implemented by all kind of input splits that can be assigned to input formats.
 * 
 * <p>Input splits are transferred in serialized form via the messages, so they need to be serializable
 * as defined by {@link java.io.Serializable}.</p>
 */
@Public
public interface InputSplit extends Serializable {

/**
 * Returns the number of this input split.
 * 
 * @return the number of this input split
 */
int getSplitNumber();
}
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InputSplit是所有型別的input splits必須實現的介面，它InputSplit繼承了Serializable，方便進行序列化傳輸；getSplitNumber返回的是當前split的編號
它有四個實現類，其中兩個實現類是直接實現該介面，分別是GenericInputSplit、LocatableInputSplit
另外兩個分別是繼承了LocatableInputSplit的FileInputSplit，以及繼承了FileInputSplit的TimestampedFileInputSplit

GenericInputSplit

flink-core-1.6.2-sources.jar!/org/apache/flink/core/io/GenericInputSplit.java

/**
 * A generic input split that has only a partition number.
 */
@Public
public class GenericInputSplit implements InputSplit, java.io.Serializable {

private static final long serialVersionUID = 1L;

/** The number of this split. */
private final int partitionNumber;

/** The total number of partitions */
private final int totalNumberOfPartitions;

// --------------------------------------------------------------------------------------------

/**
 * Creates a generic input split with the given split number.
 * 
 * @param partitionNumber The number of the split's partition.
 * @param totalNumberOfPartitions The total number of the splits (partitions).
 */
public GenericInputSplit(int partitionNumber, int totalNumberOfPartitions) {
this.partitionNumber = partitionNumber;
this.totalNumberOfPartitions = totalNumberOfPartitions;
}

//......

public String toString() {
return "GenericSplit (" + this.partitionNumber + '/' + this.totalNumberOfPartitions + ')';
}
}
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GenericInputSplit比較簡單，只有兩個屬性，分別是partitionNumber、totalNumberOfPartitions(本例項的InputSplit為GenericInputSplit型別 )

LocatableInputSplit

flink-core-1.6.2-sources.jar!/org/apache/flink/core/io/LocatableInputSplit.java

/**
 * A locatable input split is an input split referring to input data which is located on one or more hosts.
 */
@Public
public class LocatableInputSplit implements InputSplit, java.io.Serializable {

private static final long serialVersionUID = 1L;

private static final String[] EMPTY_ARR = new String[0];

/** The number of the split. */
private final int splitNumber;

/** The names of the hosts storing the data this input split refers to. */
private final String[] hostnames;

// --------------------------------------------------------------------------------------------

/**
 * Creates a new locatable input split that refers to a multiple host as its data location.
 * 
 * @param splitNumber The number of the split
 * @param hostnames The names of the hosts storing the data this input split refers to.
 */
public LocatableInputSplit(int splitNumber, String[] hostnames) {
this.splitNumber = splitNumber;
this.hostnames = hostnames == null ? EMPTY_ARR : hostnames;
}

/**
 * Creates a new locatable input split that refers to a single host as its data location.
 *
 * @param splitNumber The number of the split.
 * @param hostname The names of the host storing the data this input split refers to.
 */
public LocatableInputSplit(int splitNumber, String hostname) {
this.splitNumber = splitNumber;
this.hostnames = hostname == null ? EMPTY_ARR : new String[] { hostname };
}

//......

@Override
public String toString() {
return "Locatable Split (" + splitNumber + ") at " + Arrays.toString(this.hostnames);
}
}
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LocatableInputSplit是可定位的input split，它有兩個屬性，分別是splitNumber以及該split對應的資料所在的hostnames

IteratorInputFormat

flink-java-1.6.2-sources.jar!/org/apache/flink/api/java/io/IteratorInputFormat.java

/**
 * An input format that returns objects from an iterator.
 */
@PublicEvolving
public class IteratorInputFormat<T> extends GenericInputFormat<T> implements NonParallelInput {

private static final long serialVersionUID = 1L;

private Iterator<T> iterator; // input data as serializable iterator

public IteratorInputFormat(Iterator<T> iterator) {
if (!(iterator instanceof Serializable)) {
throw new IllegalArgumentException("The data source iterator must be serializable.");
}

this.iterator = iterator;
}

@Override
public boolean reachedEnd() {
return !this.iterator.hasNext();
}

@Override
public T nextRecord(T record) {
return this.iterator.next();
}
}
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IteratorInputFormat主要是對Iterator進行了包裝，實現了reachedEnd、nextRecord介面；它繼承了GenericInputFormat

GenericInputFormat

flink-core-1.6.2-sources.jar!/org/apache/flink/api/common/io/GenericInputFormat.java

/**
 * Generic base class for all Rich inputs that are not based on files.
 */
@Public
public abstract class GenericInputFormat<OT> extends RichInputFormat<OT, GenericInputSplit> {

private static final long serialVersionUID = 1L;

/**
 * The partition of this split.
 */
protected int partitionNumber;

// --------------------------------------------------------------------------------------------

@Override
public void configure(Configuration parameters) {
//nothing by default
}

@Override
public BaseStatistics getStatistics(BaseStatistics cachedStatistics) throws IOException {
// no statistics available, by default.
return cachedStatistics;
}

@Override
public GenericInputSplit[] createInputSplits(int numSplits) throws IOException {
if (numSplits < 1) {
throw new IllegalArgumentException("Number of input splits has to be at least 1.");
}

numSplits = (this instanceof NonParallelInput) ? 1 : numSplits;
GenericInputSplit[] splits = new GenericInputSplit[numSplits];
for (int i = 0; i < splits.length; i++) {
splits[i] = new GenericInputSplit(i, numSplits);
}
return splits;
}

@Override
public DefaultInputSplitAssigner getInputSplitAssigner(GenericInputSplit[] splits) {
return new DefaultInputSplitAssigner(splits);
}

// --------------------------------------------------------------------------------------------

@Override
public void open(GenericInputSplit split) throws IOException {
this.partitionNumber = split.getSplitNumber();
}

@Override
public void close() throws IOException {}
}
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從vertex.getSplitAssigner()獲取
根據numTaskVertices來分割

DefaultInputSplitAssigner

flink-core-1.6.2-sources.jar!/org/apache/flink/api/common/io/DefaultInputSplitAssigner.java

/**
 * This is the default implementation of the {@link InputSplitAssigner} interface. The default input split assigner
 * simply returns all input splits of an input vertex in the order they were originally computed.
 */
@Internal
public class DefaultInputSplitAssigner implements InputSplitAssigner {

/** The logging object used to report information and errors. */
private static final Logger LOG = LoggerFactory.getLogger(DefaultInputSplitAssigner.class);

/** The list of all splits */
private final List<InputSplit> splits = new ArrayList<InputSplit>();


public DefaultInputSplitAssigner(InputSplit[] splits) {
Collections.addAll(this.splits, splits);
}

public DefaultInputSplitAssigner(Collection<? extends InputSplit> splits) {
this.splits.addAll(splits);
}


@Override
public InputSplit getNextInputSplit(String host, int taskId) {
InputSplit next = null;

// keep the synchronized part short
synchronized (this.splits) {
if (this.splits.size() > 0) {
next = this.splits.remove(this.splits.size() - 1);
}
}

if (LOG.isDebugEnabled()) {
if (next == null) {
LOG.debug("No more input splits available");
} else {
LOG.debug("Assigning split " + next + " to " + host);
}
}
return next;
}
}
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DefaultInputSplitAssigner僅僅是按順序返回InputSplit

小結

InputFormatSourceFunction是一個使用InputFormat來讀取資料的SourceFunction，它繼承了RichParallelSourceFunction，新增了帶有2個引數的構造器，一個是InputFormat，一個是TypeInformation
本例項使用的IteratorInputFormat繼承了GenericInputFormat，後者提供了兩個重要的方法，一個是createInputSplits(這裡是根據numTaskVertices來分割 )，一個是getInputSplitAssigner(這裡建立的是DefaultInputSplitAssigner，即按順序返回分割好的InputSplit )
InputFormatSourceFunction的run方法主要是挨個呼叫splitIterator.next()，並用InputFormat去open該InputSplit，然後呼叫format.nextRecord來挨個讀取該InputSplit的每個record，最後使用SourceContext的emit方法發射出去

可以看到整個大的邏輯就是GenericInputFormat提供將input分割為InputSplit的方法，同時提供InputSplitAssigner，然後InputFormatSourceFunction就是挨個遍歷分割好的屬於自己(Task )的InputSplit(通過InputSplitAssigner獲取 )，然後通過InputFormat讀取InputSplit來挨個獲取這個InputSplit的每個元素，然後通過SourceContext的emit方法發射出去