org.apache.flink.runtime.operators.BatchTask Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.operators;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.accumulators.Accumulator;
import org.apache.flink.api.common.distributions.DataDistribution;
import org.apache.flink.api.common.functions.DefaultOpenContext;
import org.apache.flink.api.common.functions.Function;
import org.apache.flink.api.common.functions.GroupCombineFunction;
import org.apache.flink.api.common.functions.OpenContext;
import org.apache.flink.api.common.functions.Partitioner;
import org.apache.flink.api.common.functions.util.FunctionUtils;
import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypeComparatorFactory;
import org.apache.flink.api.common.typeutils.TypeSerializerFactory;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.metrics.groups.OperatorMetricGroup;
import org.apache.flink.runtime.broadcast.BroadcastVariableMaterialization;
import org.apache.flink.runtime.execution.CancelTaskException;
import org.apache.flink.runtime.execution.Environment;
import org.apache.flink.runtime.io.disk.iomanager.IOManager;
import org.apache.flink.runtime.io.network.api.reader.MutableReader;
import org.apache.flink.runtime.io.network.api.reader.MutableRecordReader;
import org.apache.flink.runtime.io.network.api.writer.ChannelSelector;
import org.apache.flink.runtime.io.network.api.writer.RecordWriter;
import org.apache.flink.runtime.io.network.api.writer.RecordWriterBuilder;
import org.apache.flink.runtime.io.network.partition.consumer.IndexedInputGate;
import org.apache.flink.runtime.io.network.partition.consumer.UnionInputGate;
import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
import org.apache.flink.runtime.memory.MemoryManager;
import org.apache.flink.runtime.metrics.groups.InternalOperatorMetricGroup;
import org.apache.flink.runtime.operators.chaining.ChainedDriver;
import org.apache.flink.runtime.operators.chaining.ExceptionInChainedStubException;
import org.apache.flink.runtime.operators.resettable.SpillingResettableMutableObjectIterator;
import org.apache.flink.runtime.operators.shipping.OutputCollector;
import org.apache.flink.runtime.operators.shipping.OutputEmitter;
import org.apache.flink.runtime.operators.shipping.ShipStrategyType;
import org.apache.flink.runtime.operators.sort.ExternalSorter;
import org.apache.flink.runtime.operators.sort.Sorter;
import org.apache.flink.runtime.operators.util.CloseableInputProvider;
import org.apache.flink.runtime.operators.util.DistributedRuntimeUDFContext;
import org.apache.flink.runtime.operators.util.LocalStrategy;
import org.apache.flink.runtime.operators.util.ReaderIterator;
import org.apache.flink.runtime.operators.util.TaskConfig;
import org.apache.flink.runtime.plugable.DeserializationDelegate;
import org.apache.flink.runtime.plugable.SerializationDelegate;
import org.apache.flink.runtime.taskmanager.TaskManagerRuntimeInfo;
import org.apache.flink.util.Collector;
import org.apache.flink.util.InstantiationUtil;
import org.apache.flink.util.MutableObjectIterator;
import org.apache.flink.util.Preconditions;
import org.apache.flink.util.UserCodeClassLoader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import static java.util.Collections.emptyList;
/**
* The base class for all batch tasks. Encapsulated common behavior and implements the main
* life-cycle of the user code.
*/
public class BatchTask extends AbstractInvokable
implements TaskContext {
protected static final Logger LOG = LoggerFactory.getLogger(BatchTask.class);
// --------------------------------------------------------------------------------------------
/**
* The driver that invokes the user code (the stub implementation). The central driver in this
* task (further drivers may be chained behind this driver).
*/
protected volatile Driver driver;
/**
* The instantiated user code of this task's main operator (driver). May be null if the operator
* has no udf.
*/
protected S stub;
/** The udf's runtime context. */
protected DistributedRuntimeUDFContext runtimeUdfContext;
/**
* The collector that forwards the user code's results. May forward to a channel or to chained
* drivers within this task.
*/
protected Collector output;
/**
* The output writers for the data that this task forwards to the next task. The latest driver
* (the central, if no chained drivers exist, otherwise the last chained driver) produces its
* output to these writers.
*/
protected List> eventualOutputs;
/** The input readers of this task. */
protected MutableReader[] inputReaders;
/** The input readers for the configured broadcast variables for this task. */
protected MutableReader[] broadcastInputReaders;
/** The inputs reader, wrapped in an iterator. Prior to the local strategies, etc... */
protected MutableObjectIterator[] inputIterators;
/** The indices of the iterative inputs. Empty, if the task is not iterative. */
protected int[] iterativeInputs;
/** The indices of the iterative broadcast inputs. Empty, if non of the inputs is iterative. */
protected int[] iterativeBroadcastInputs;
/** The local strategies that are applied on the inputs. */
protected volatile CloseableInputProvider[] localStrategies;
/**
* The optional temp barriers on the inputs for dead-lock breaking. Are optionally resettable.
*/
protected volatile TempBarrier[] tempBarriers;
/** The resettable inputs in the case where no temp barrier is needed. */
protected volatile SpillingResettableMutableObjectIterator[] resettableInputs;
/**
* The inputs to the operator. Return the readers' data after the application of the local
* strategy and the temp-table barrier.
*/
protected MutableObjectIterator[] inputs;
/** The serializers for the input data type. */
protected TypeSerializerFactory[] inputSerializers;
/** The serializers for the broadcast input data types. */
protected TypeSerializerFactory[] broadcastInputSerializers;
/** The comparators for the central driver. */
protected TypeComparator[] inputComparators;
/** The task configuration with the setup parameters. */
protected TaskConfig config;
/** A list of chained drivers, if there are any. */
protected ArrayList> chainedTasks;
/**
* Certain inputs may be excluded from resetting. For example, the initial partial solution in
* an iteration head must not be reset (it is read through the back channel), when all others
* are reset.
*/
private boolean[] excludeFromReset;
/** Flag indicating for each input whether it is cached and can be reset. */
private boolean[] inputIsCached;
/** flag indicating for each input whether it must be asynchronously materialized. */
private boolean[] inputIsAsyncMaterialized;
/** The amount of memory per input that is dedicated to the materialization. */
private int[] materializationMemory;
/** The flag that tags the task as still running. Checked periodically to abort processing. */
protected volatile boolean running = true;
/** The accumulator map used in the RuntimeContext. */
protected Map> accumulatorMap;
private InternalOperatorMetricGroup metrics;
// --------------------------------------------------------------------------------------------
// Constructor
// --------------------------------------------------------------------------------------------
/**
* Create an Invokable task and set its environment.
*
* @param environment The environment assigned to this invokable.
*/
public BatchTask(Environment environment) {
super(environment);
}
// --------------------------------------------------------------------------------------------
// Task Interface
// --------------------------------------------------------------------------------------------
/** The main work method. */
@Override
public void invoke() throws Exception {
// --------------------------------------------------------------------
// Initialize
// --------------------------------------------------------------------
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Start registering input and output."));
}
// obtain task configuration (including stub parameters)
Configuration taskConf = getTaskConfiguration();
this.config = new TaskConfig(taskConf);
// now get the operator class which drives the operation
final Class> driverClass = this.config.getDriver();
this.driver = InstantiationUtil.instantiate(driverClass, Driver.class);
String headName = getEnvironment().getTaskInfo().getTaskName().split("->")[0].trim();
this.metrics =
getEnvironment()
.getMetricGroup()
.getOrAddOperator(
headName.startsWith("CHAIN") ? headName.substring(6) : headName);
this.metrics.getIOMetricGroup().reuseInputMetricsForTask();
if (config.getNumberOfChainedStubs() == 0) {
this.metrics.getIOMetricGroup().reuseOutputMetricsForTask();
}
// initialize the readers.
// this does not yet trigger any stream consuming or processing.
initInputReaders();
initBroadcastInputReaders();
// initialize the writers.
initOutputs();
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Finished registering input and output."));
}
// --------------------------------------------------------------------
// Invoke
// --------------------------------------------------------------------
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Start task code."));
}
this.runtimeUdfContext = createRuntimeContext(metrics);
// whatever happens in this scope, make sure that the local strategies are cleaned up!
// note that the initialization of the local strategies is in the try-finally block as well,
// so that the thread that creates them catches its own errors that may happen in that
// process.
// this is especially important, since there may be asynchronous closes (such as through
// canceling).
try {
// initialize the remaining data structures on the input and trigger the local
// processing
// the local processing includes building the dams / caches
try {
int numInputs = driver.getNumberOfInputs();
int numComparators = driver.getNumberOfDriverComparators();
int numBroadcastInputs = this.config.getNumBroadcastInputs();
initInputsSerializersAndComparators(numInputs, numComparators);
initBroadcastInputsSerializers(numBroadcastInputs);
// set the iterative status for inputs and broadcast inputs
{
List iterativeInputs = new ArrayList<>();
for (int i = 0; i < numInputs; i++) {
final int numberOfEventsUntilInterrupt =
getTaskConfig().getNumberOfEventsUntilInterruptInIterativeGate(i);
if (numberOfEventsUntilInterrupt < 0) {
throw new IllegalArgumentException();
} else if (numberOfEventsUntilInterrupt > 0) {
this.inputReaders[i].setIterativeReader();
iterativeInputs.add(i);
if (LOG.isDebugEnabled()) {
LOG.debug(
formatLogString(
"Input ["
+ i
+ "] reads in supersteps with ["
+ numberOfEventsUntilInterrupt
+ "] event(s) till next superstep."));
}
}
}
this.iterativeInputs = asArray(iterativeInputs);
}
{
List iterativeBcInputs = new ArrayList<>();
for (int i = 0; i < numBroadcastInputs; i++) {
final int numberOfEventsUntilInterrupt =
getTaskConfig()
.getNumberOfEventsUntilInterruptInIterativeBroadcastGate(i);
if (numberOfEventsUntilInterrupt < 0) {
throw new IllegalArgumentException();
} else if (numberOfEventsUntilInterrupt > 0) {
this.broadcastInputReaders[i].setIterativeReader();
iterativeBcInputs.add(i);
if (LOG.isDebugEnabled()) {
LOG.debug(
formatLogString(
"Broadcast input ["
+ i
+ "] reads in supersteps with ["
+ numberOfEventsUntilInterrupt
+ "] event(s) till next superstep."));
}
}
}
this.iterativeBroadcastInputs = asArray(iterativeBcInputs);
}
initLocalStrategies(numInputs);
} catch (Exception e) {
throw new RuntimeException(
"Initializing the input processing failed"
+ (e.getMessage() == null ? "." : ": " + e.getMessage()),
e);
}
if (!this.running) {
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Task cancelled before task code was started."));
}
return;
}
// pre main-function initialization
initialize();
// read the broadcast variables. they will be released in the finally clause
for (int i = 0; i < this.config.getNumBroadcastInputs(); i++) {
final String name = this.config.getBroadcastInputName(i);
readAndSetBroadcastInput(
i, name, this.runtimeUdfContext, 1 /* superstep one for the start */);
}
// the work goes here
run();
} finally {
// clean up in any case!
closeLocalStrategiesAndCaches();
clearReaders(inputReaders);
clearWriters(eventualOutputs);
}
if (this.running) {
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Finished task code."));
}
} else {
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Task code cancelled."));
}
}
}
@Override
public void cancel() throws Exception {
this.running = false;
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Cancelling task code"));
}
try {
if (this.driver != null) {
this.driver.cancel();
}
} finally {
closeLocalStrategiesAndCaches();
}
}
// --------------------------------------------------------------------------------------------
// Main Work Methods
// --------------------------------------------------------------------------------------------
protected void initialize() throws Exception {
// create the operator
try {
this.driver.setup(this);
} catch (Throwable t) {
throw new Exception(
"The driver setup for '"
+ this.getEnvironment().getTaskInfo().getTaskName()
+ "' , caused an error: "
+ t.getMessage(),
t);
}
// instantiate the UDF
try {
final Class userCodeFunctionType = this.driver.getStubType();
// if the class is null, the driver has no user code
if (userCodeFunctionType != null) {
this.stub = initStub(userCodeFunctionType);
}
} catch (Exception e) {
throw new RuntimeException(
"Initializing the UDF" + (e.getMessage() == null ? "." : ": " + e.getMessage()),
e);
}
}
protected void readAndSetBroadcastInput(
int inputNum, String bcVarName, DistributedRuntimeUDFContext context, int superstep)
throws IOException {
if (LOG.isDebugEnabled()) {
LOG.debug(
formatLogString(
"Setting broadcast variable '"
+ bcVarName
+ "'"
+ (superstep > 1 ? ", superstep " + superstep : "")));
}
@SuppressWarnings("unchecked")
final TypeSerializerFactory serializerFactory =
(TypeSerializerFactory) this.broadcastInputSerializers[inputNum];
final MutableReader reader = this.broadcastInputReaders[inputNum];
BroadcastVariableMaterialization variable =
getEnvironment()
.getBroadcastVariableManager()
.materializeBroadcastVariable(
bcVarName, superstep, this, reader, serializerFactory);
context.setBroadcastVariable(bcVarName, variable);
}
protected void releaseBroadcastVariables(
String bcVarName, int superstep, DistributedRuntimeUDFContext context) {
if (LOG.isDebugEnabled()) {
LOG.debug(
formatLogString(
"Releasing broadcast variable '"
+ bcVarName
+ "'"
+ (superstep > 1 ? ", superstep " + superstep : "")));
}
getEnvironment().getBroadcastVariableManager().releaseReference(bcVarName, superstep, this);
context.clearBroadcastVariable(bcVarName);
}
protected void run() throws Exception {
// ---------------------------- Now, the actual processing starts ------------------------
// check for asynchronous canceling
if (!this.running) {
return;
}
boolean stubOpen = false;
try {
// run the data preparation
try {
this.driver.prepare();
} catch (Throwable t) {
// if the preparation caused an error, clean up
// errors during clean-up are swallowed, because we have already a root exception
throw new Exception(
"The data preparation for task '"
+ this.getEnvironment().getTaskInfo().getTaskName()
+ "' , caused an error: "
+ t.getMessage(),
t);
}
// check for canceling
if (!this.running) {
return;
}
// start all chained tasks
BatchTask.openChainedTasks(this.chainedTasks, this);
// open stub implementation
if (this.stub != null) {
try {
Configuration stubConfig = this.config.getStubParameters();
FunctionUtils.openFunction(this.stub, DefaultOpenContext.INSTANCE);
stubOpen = true;
} catch (Throwable t) {
throw new Exception(
"The user defined 'open()' method caused an exception: "
+ t.getMessage(),
t);
}
}
// run the user code
this.driver.run();
// close. We close here such that a regular close throwing an exception marks a task as
// failed.
if (this.running && this.stub != null) {
FunctionUtils.closeFunction(this.stub);
stubOpen = false;
}
// close all chained tasks letting them report failure
BatchTask.closeChainedTasks(this.chainedTasks, this);
// close the output collector
this.output.close();
} catch (Exception ex) {
// close the input, but do not report any exceptions, since we already have another root
// cause
if (stubOpen) {
try {
FunctionUtils.closeFunction(this.stub);
} catch (Throwable t) {
// do nothing
}
}
// if resettable driver invoke teardown
if (this.driver instanceof ResettableDriver) {
final ResettableDriver resDriver = (ResettableDriver) this.driver;
try {
resDriver.teardown();
} catch (Throwable t) {
throw new Exception(
"Error while shutting down an iterative operator: " + t.getMessage(),
t);
}
}
BatchTask.cancelChainedTasks(this.chainedTasks);
ex = ExceptionInChainedStubException.exceptionUnwrap(ex);
if (ex instanceof CancelTaskException) {
// forward canceling exception
throw ex;
} else if (this.running) {
// throw only if task was not cancelled. in the case of canceling, exceptions are
// expected
BatchTask.logAndThrowException(ex, this);
}
} finally {
this.driver.cleanup();
}
}
protected void closeLocalStrategiesAndCaches() {
// make sure that all broadcast variable references held by this task are released
if (LOG.isDebugEnabled()) {
LOG.debug(formatLogString("Releasing all broadcast variables."));
}
getEnvironment().getBroadcastVariableManager().releaseAllReferencesFromTask(this);
if (runtimeUdfContext != null) {
runtimeUdfContext.clearAllBroadcastVariables();
}
// clean all local strategies and caches/pipeline breakers.
if (this.localStrategies != null) {
for (int i = 0; i < this.localStrategies.length; i++) {
if (this.localStrategies[i] != null) {
try {
this.localStrategies[i].close();
} catch (Throwable t) {
LOG.error("Error closing local strategy for input " + i, t);
}
}
}
}
if (this.tempBarriers != null) {
for (int i = 0; i < this.tempBarriers.length; i++) {
if (this.tempBarriers[i] != null) {
try {
this.tempBarriers[i].close();
} catch (Throwable t) {
LOG.error("Error closing temp barrier for input " + i, t);
}
}
}
}
if (this.resettableInputs != null) {
for (int i = 0; i < this.resettableInputs.length; i++) {
if (this.resettableInputs[i] != null) {
try {
this.resettableInputs[i].close();
} catch (Throwable t) {
LOG.error("Error closing cache for input " + i, t);
}
}
}
}
}
// --------------------------------------------------------------------------------------------
// Task Setup and Teardown
// --------------------------------------------------------------------------------------------
/** @return the last output collector in the collector chain */
@SuppressWarnings("unchecked")
protected Collector getLastOutputCollector() {
int numChained = this.chainedTasks.size();
return (numChained == 0)
? output
: (Collector) chainedTasks.get(numChained - 1).getOutputCollector();
}
/**
* Sets the last output {@link Collector} of the collector chain of this {@link BatchTask}.
*
* In case of chained tasks, the output collector of the last {@link ChainedDriver} is set.
* Otherwise it is the single collector of the {@link BatchTask}.
*
* @param newOutputCollector new output collector to set as last collector
*/
protected void setLastOutputCollector(Collector newOutputCollector) {
int numChained = this.chainedTasks.size();
if (numChained == 0) {
output = newOutputCollector;
return;
}
chainedTasks.get(numChained - 1).setOutputCollector(newOutputCollector);
}
public TaskConfig getLastTasksConfig() {
int numChained = this.chainedTasks.size();
return (numChained == 0) ? config : chainedTasks.get(numChained - 1).getTaskConfig();
}
protected S initStub(Class stubSuperClass) throws Exception {
try {
ClassLoader userCodeClassLoader = getUserCodeClassLoader();
S stub =
config.getStubWrapper(userCodeClassLoader)
.getUserCodeObject(stubSuperClass, userCodeClassLoader);
// check if the class is a subclass, if the check is required
if (stubSuperClass != null && !stubSuperClass.isAssignableFrom(stub.getClass())) {
throw new RuntimeException(
"The class '"
+ stub.getClass().getName()
+ "' is not a subclass of '"
+ stubSuperClass.getName()
+ "' as is required.");
}
FunctionUtils.setFunctionRuntimeContext(stub, this.runtimeUdfContext);
return stub;
} catch (ClassCastException ccex) {
throw new Exception(
"The stub class is not a proper subclass of " + stubSuperClass.getName(), ccex);
}
}
/**
* Creates the record readers for the number of inputs as defined by {@link
* #getNumTaskInputs()}. This method requires that the task configuration, the driver, and the
* user-code class loader are set.
*/
protected void initInputReaders() throws Exception {
final int numInputs = getNumTaskInputs();
final MutableReader[] inputReaders = new MutableReader[numInputs];
int currentReaderOffset = 0;
for (int i = 0; i < numInputs; i++) {
// ---------------- create the input readers ---------------------
// in case where a logical input unions multiple physical inputs, create a union reader
final int groupSize = this.config.getGroupSize(i);
if (groupSize == 1) {
// non-union case
inputReaders[i] =
new MutableRecordReader<>(
getEnvironment().getInputGate(currentReaderOffset),
getEnvironment().getTaskManagerInfo().getTmpDirectories());
} else if (groupSize > 1) {
// union case
IndexedInputGate[] readers = new IndexedInputGate[groupSize];
for (int j = 0; j < groupSize; ++j) {
readers[j] = getEnvironment().getInputGate(currentReaderOffset + j);
}
inputReaders[i] =
new MutableRecordReader<>(
new UnionInputGate(readers),
getEnvironment().getTaskManagerInfo().getTmpDirectories());
} else {
throw new Exception("Illegal input group size in task configuration: " + groupSize);
}
currentReaderOffset += groupSize;
}
this.inputReaders = inputReaders;
// final sanity check
if (currentReaderOffset != this.config.getNumInputs()) {
throw new Exception(
"Illegal configuration: Number of input gates and group sizes are not consistent.");
}
}
/**
* Creates the record readers for the extra broadcast inputs as configured by {@link
* TaskConfig#getNumBroadcastInputs()}. This method requires that the task configuration, the
* driver, and the user-code class loader are set.
*/
protected void initBroadcastInputReaders() throws Exception {
final int numBroadcastInputs = this.config.getNumBroadcastInputs();
final MutableReader[] broadcastInputReaders = new MutableReader[numBroadcastInputs];
int currentReaderOffset = config.getNumInputs();
for (int i = 0; i < this.config.getNumBroadcastInputs(); i++) {
// ---------------- create the input readers ---------------------
// in case where a logical input unions multiple physical inputs, create a union reader
final int groupSize = this.config.getBroadcastGroupSize(i);
if (groupSize == 1) {
// non-union case
broadcastInputReaders[i] =
new MutableRecordReader<>(
getEnvironment().getInputGate(currentReaderOffset),
getEnvironment().getTaskManagerInfo().getTmpDirectories());
} else if (groupSize > 1) {
// union case
IndexedInputGate[] readers = new IndexedInputGate[groupSize];
for (int j = 0; j < groupSize; ++j) {
readers[j] = getEnvironment().getInputGate(currentReaderOffset + j);
}
broadcastInputReaders[i] =
new MutableRecordReader<>(
new UnionInputGate(readers),
getEnvironment().getTaskManagerInfo().getTmpDirectories());
} else {
throw new Exception("Illegal input group size in task configuration: " + groupSize);
}
currentReaderOffset += groupSize;
}
this.broadcastInputReaders = broadcastInputReaders;
}
/** Creates all the serializers and comparators. */
protected void initInputsSerializersAndComparators(int numInputs, int numComparators) {
this.inputSerializers = new TypeSerializerFactory[numInputs];
this.inputComparators = numComparators > 0 ? new TypeComparator[numComparators] : null;
this.inputIterators = new MutableObjectIterator[numInputs];
ClassLoader userCodeClassLoader = getUserCodeClassLoader();
for (int i = 0; i < numInputs; i++) {
final TypeSerializerFactory serializerFactory =
this.config.getInputSerializer(i, userCodeClassLoader);
this.inputSerializers[i] = serializerFactory;
this.inputIterators[i] =
createInputIterator(this.inputReaders[i], this.inputSerializers[i]);
}
// ---------------- create the driver's comparators ---------------------
for (int i = 0; i < numComparators; i++) {
if (this.inputComparators != null) {
final TypeComparatorFactory comparatorFactory =
this.config.getDriverComparator(i, userCodeClassLoader);
this.inputComparators[i] = comparatorFactory.createComparator();
}
}
}
/** Creates all the serializers and iterators for the broadcast inputs. */
protected void initBroadcastInputsSerializers(int numBroadcastInputs) {
this.broadcastInputSerializers = new TypeSerializerFactory[numBroadcastInputs];
ClassLoader userCodeClassLoader = getUserCodeClassLoader();
for (int i = 0; i < numBroadcastInputs; i++) {
// ---------------- create the serializer first ---------------------
final TypeSerializerFactory serializerFactory =
this.config.getBroadcastInputSerializer(i, userCodeClassLoader);
this.broadcastInputSerializers[i] = serializerFactory;
}
}
/**
* NOTE: This method must be invoked after the invocation of {@code #initInputReaders()} and
* {@code #initInputSerializersAndComparators(int)}!
*/
protected void initLocalStrategies(int numInputs) throws Exception {
final MemoryManager memMan = getMemoryManager();
final IOManager ioMan = getIOManager();
this.localStrategies = new CloseableInputProvider[numInputs];
this.inputs = new MutableObjectIterator[numInputs];
this.excludeFromReset = new boolean[numInputs];
this.inputIsCached = new boolean[numInputs];
this.inputIsAsyncMaterialized = new boolean[numInputs];
this.materializationMemory = new int[numInputs];
// set up the local strategies first, such that the can work before any temp barrier is
// created
for (int i = 0; i < numInputs; i++) {
initInputLocalStrategy(i);
}
// we do another loop over the inputs, because we want to instantiate all
// sorters, etc before requesting the first input (as this call may block)
// we have two types of materialized inputs, and both are replayable (can act as a cache)
// The first variant materializes in a different thread and hence
// acts as a pipeline breaker. this one should only be there, if a pipeline breaker is
// needed.
// the second variant spills to the side and will not read unless the result is also
// consumed
// in a pipelined fashion.
this.resettableInputs = new SpillingResettableMutableObjectIterator[numInputs];
this.tempBarriers = new TempBarrier[numInputs];
for (int i = 0; i < numInputs; i++) {
final int memoryPages;
final boolean async = this.config.isInputAsynchronouslyMaterialized(i);
final boolean cached = this.config.isInputCached(i);
this.inputIsAsyncMaterialized[i] = async;
this.inputIsCached[i] = cached;
if (async || cached) {
memoryPages =
memMan.computeNumberOfPages(
this.config.getRelativeInputMaterializationMemory(i));
if (memoryPages <= 0) {
throw new Exception(
"Input marked as materialized/cached, but no memory for materialization provided.");
}
this.materializationMemory[i] = memoryPages;
} else {
memoryPages = 0;
}
if (async) {
@SuppressWarnings({"unchecked", "rawtypes"})
TempBarrier barrier =
new TempBarrier(
this,
getInput(i),
this.inputSerializers[i],
memMan,
ioMan,
memoryPages,
emptyList());
barrier.startReading();
this.tempBarriers[i] = barrier;
this.inputs[i] = null;
} else if (cached) {
@SuppressWarnings({"unchecked", "rawtypes"})
SpillingResettableMutableObjectIterator iter =
new SpillingResettableMutableObjectIterator(
getInput(i),
this.inputSerializers[i].getSerializer(),
getMemoryManager(),
getIOManager(),
memoryPages,
this);
this.resettableInputs[i] = iter;
this.inputs[i] = iter;
}
}
}
protected void resetAllInputs() throws Exception {
// first we need to make sure that caches consume remaining data
// NOTE: we need to do this before closing the local strategies
for (int i = 0; i < this.inputs.length; i++) {
if (this.inputIsCached[i] && this.resettableInputs[i] != null) {
this.resettableInputs[i].consumeAndCacheRemainingData();
}
}
// close all local-strategies. they will either get re-initialized, or we have
// read them now and their data is cached
for (int i = 0; i < this.localStrategies.length; i++) {
if (this.localStrategies[i] != null) {
this.localStrategies[i].close();
this.localStrategies[i] = null;
}
}
final MemoryManager memMan = getMemoryManager();
final IOManager ioMan = getIOManager();
// reset the caches, or re-run the input local strategy
for (int i = 0; i < this.inputs.length; i++) {
if (this.excludeFromReset[i]) {
if (this.tempBarriers[i] != null) {
this.tempBarriers[i].close();
this.tempBarriers[i] = null;
} else if (this.resettableInputs[i] != null) {
this.resettableInputs[i].close();
this.resettableInputs[i] = null;
}
} else {
// make sure the input is not available directly, but are lazily fetched again
this.inputs[i] = null;
if (this.inputIsCached[i]) {
if (this.tempBarriers[i] != null) {
this.inputs[i] = this.tempBarriers[i].getIterator();
} else if (this.resettableInputs[i] != null) {
this.resettableInputs[i].reset();
this.inputs[i] = this.resettableInputs[i];
} else {
throw new RuntimeException(
"Found a resettable input, but no temp barrier and no resettable iterator.");
}
} else {
// close the async barrier if there is one
List allocated =
tempBarriers[i] == null
? emptyList()
: tempBarriers[i].closeAndGetLeftoverMemory();
tempBarriers[i] = null;
try {
initInputLocalStrategy(i);
if (this.inputIsAsyncMaterialized[i]) {
final int pages = this.materializationMemory[i];
Preconditions.checkState(
allocated.size()
<= pages); // pages shouldn't change, but some segments
// might have been consumed
@SuppressWarnings({"unchecked", "rawtypes"})
TempBarrier barrier =
new TempBarrier(
this,
getInput(i),
this.inputSerializers[i],
memMan,
ioMan,
pages,
allocated);
barrier.startReading();
this.tempBarriers[i] = barrier;
this.inputs[i] = null;
} else {
memMan.release(allocated);
}
} catch (Exception exception) {
try {
memMan.release(allocated);
} catch (Exception releaseException) {
exception.addSuppressed(releaseException);
}
throw exception;
}
}
}
}
}
protected void excludeFromReset(int inputNum) {
this.excludeFromReset[inputNum] = true;
}
private void initInputLocalStrategy(int inputNum) throws Exception {
// check if there is already a strategy
if (this.localStrategies[inputNum] != null) {
throw new IllegalStateException();
}
// now set up the local strategy
final LocalStrategy localStrategy = this.config.getInputLocalStrategy(inputNum);
if (localStrategy != null) {
switch (localStrategy) {
case NONE:
// the input is as it is
this.inputs[inputNum] = this.inputIterators[inputNum];
break;
case SORT:
@SuppressWarnings({"rawtypes", "unchecked"})
Sorter sorter =
ExternalSorter.newBuilder(
getMemoryManager(),
this,
this.inputSerializers[inputNum].getSerializer(),
getLocalStrategyComparator(inputNum))
.maxNumFileHandles(this.config.getFilehandlesInput(inputNum))
.enableSpilling(
getIOManager(),
this.config.getSpillingThresholdInput(inputNum))
.memoryFraction(this.config.getRelativeMemoryInput(inputNum))
.objectReuse(this.getExecutionConfig().isObjectReuseEnabled())
.largeRecords(this.getTaskConfig().getUseLargeRecordHandler())
.build((MutableObjectIterator) this.inputIterators[inputNum]);
// set the input to null such that it will be lazily fetched from the input
// strategy
this.inputs[inputNum] = null;
this.localStrategies[inputNum] = sorter;
break;
case COMBININGSORT:
// sanity check this special case!
// this still breaks a bit of the abstraction!
// we should have nested configurations for the local strategies to solve that
if (inputNum != 0) {
throw new IllegalStateException(
"Performing combining sort outside a (group)reduce task!");
}
// instantiate ourselves a combiner. we should not use the stub, because the
// sort and the
// subsequent (group)reduce would otherwise share it multi-threaded
final Class userCodeFunctionType = this.driver.getStubType();
if (userCodeFunctionType == null) {
throw new IllegalStateException(
"Performing combining sort outside a reduce task!");
}
final S localStub;
try {
localStub = initStub(userCodeFunctionType);
} catch (Exception e) {
throw new RuntimeException(
"Initializing the user code and the configuration failed"
+ (e.getMessage() == null ? "." : ": " + e.getMessage()),
e);
}
if (!(localStub instanceof GroupCombineFunction)) {
throw new IllegalStateException(
"Performing combining sort outside a reduce task!");
}
@SuppressWarnings({"rawtypes", "unchecked"})
Sorter cSorter =
ExternalSorter.newBuilder(
getMemoryManager(),
this,
this.inputSerializers[inputNum].getSerializer(),
getLocalStrategyComparator(inputNum))
.maxNumFileHandles(this.config.getFilehandlesInput(inputNum))
.withCombiner(
(GroupCombineFunction) localStub,
this.config.getStubParameters())
.enableSpilling(
getIOManager(),
this.config.getSpillingThresholdInput(inputNum))
.memoryFraction(this.config.getRelativeMemoryInput(inputNum))
.objectReuse(this.getExecutionConfig().isObjectReuseEnabled())
.largeRecords(this.getTaskConfig().getUseLargeRecordHandler())
.build(this.inputIterators[inputNum]);
// set the input to null such that it will be lazily fetched from the input
// strategy
this.inputs[inputNum] = null;
this.localStrategies[inputNum] = cSorter;
break;
default:
throw new Exception(
"Unrecognized local strategy provided: " + localStrategy.name());
}
} else {
// no local strategy in the config
this.inputs[inputNum] = this.inputIterators[inputNum];
}
}
private TypeComparator getLocalStrategyComparator(int inputNum) throws Exception {
TypeComparatorFactory compFact =
this.config.getInputComparator(inputNum, getUserCodeClassLoader());
if (compFact == null) {
throw new Exception(
"Missing comparator factory for local strategy on input " + inputNum);
}
return compFact.createComparator();
}
protected MutableObjectIterator createInputIterator(
MutableReader inputReader, TypeSerializerFactory serializerFactory) {
@SuppressWarnings("unchecked")
MutableReader> reader =
(MutableReader>) inputReader;
@SuppressWarnings({"unchecked", "rawtypes"})
final MutableObjectIterator iter =
new ReaderIterator(reader, serializerFactory.getSerializer());
return iter;
}
protected int getNumTaskInputs() {
return this.driver.getNumberOfInputs();
}
/**
* Creates a writer for each output. Creates an OutputCollector which forwards its input to all
* writers. The output collector applies the configured shipping strategies for each writer.
*/
protected void initOutputs() throws Exception {
this.chainedTasks = new ArrayList<>();
this.eventualOutputs = new ArrayList<>();
this.accumulatorMap = getEnvironment().getAccumulatorRegistry().getUserMap();
this.output =
initOutputs(
this,
getEnvironment().getUserCodeClassLoader(),
this.config,
this.chainedTasks,
this.eventualOutputs,
this.getExecutionConfig(),
this.accumulatorMap);
}
public DistributedRuntimeUDFContext createRuntimeContext(OperatorMetricGroup metrics) {
Environment env = getEnvironment();
return new DistributedRuntimeUDFContext(
env.getJobInfo(),
env.getTaskInfo(),
env.getUserCodeClassLoader(),
getExecutionConfig(),
env.getDistributedCacheEntries(),
this.accumulatorMap,
metrics,
env.getExternalResourceInfoProvider());
}
// --------------------------------------------------------------------------------------------
// Task Context Signature
// -------------------------------------------------------------------------------------------
@Override
public TaskConfig getTaskConfig() {
return this.config;
}
@Override
public TaskManagerRuntimeInfo getTaskManagerInfo() {
return getEnvironment().getTaskManagerInfo();
}
@Override
public MemoryManager getMemoryManager() {
return getEnvironment().getMemoryManager();
}
@Override
public IOManager getIOManager() {
return getEnvironment().getIOManager();
}
@Override
public S getStub() {
return this.stub;
}
@Override
public Collector getOutputCollector() {
return this.output;
}
@Override
public AbstractInvokable getContainingTask() {
return this;
}
@Override
public String formatLogString(String message) {
return constructLogString(message, getEnvironment().getTaskInfo().getTaskName(), this);
}
@Override
public OperatorMetricGroup getMetricGroup() {
return metrics;
}
@Override
public MutableObjectIterator getInput(int index) {
if (index < 0 || index > this.driver.getNumberOfInputs()) {
throw new IndexOutOfBoundsException();
}
// check for lazy assignment from input strategies
if (this.inputs[index] != null) {
@SuppressWarnings("unchecked")
MutableObjectIterator in = (MutableObjectIterator) this.inputs[index];
return in;
} else {
final MutableObjectIterator in;
try {
if (this.tempBarriers[index] != null) {
@SuppressWarnings("unchecked")
MutableObjectIterator iter =
(MutableObjectIterator) this.tempBarriers[index].getIterator();
in = iter;
} else if (this.localStrategies[index] != null) {
@SuppressWarnings("unchecked")
MutableObjectIterator iter =
(MutableObjectIterator) this.localStrategies[index].getIterator();
in = iter;
} else {
throw new RuntimeException(
"Bug: null input iterator, null temp barrier, and null local strategy.");
}
this.inputs[index] = in;
return in;
} catch (InterruptedException iex) {
throw new RuntimeException(
"Interrupted while waiting for input " + index + " to become available.");
} catch (IOException ioex) {
throw new RuntimeException(
"An I/O Exception occurred while obtaining input " + index + ".");
}
}
}
@Override
public TypeSerializerFactory getInputSerializer(int index) {
if (index < 0 || index >= this.driver.getNumberOfInputs()) {
throw new IndexOutOfBoundsException();
}
@SuppressWarnings("unchecked")
final TypeSerializerFactory serializerFactory =
(TypeSerializerFactory) this.inputSerializers[index];
return serializerFactory;
}
@Override
public TypeComparator getDriverComparator(int index) {
if (this.inputComparators == null) {
throw new IllegalStateException("Comparators have not been created!");
} else if (index < 0 || index >= this.driver.getNumberOfDriverComparators()) {
throw new IndexOutOfBoundsException();
}
@SuppressWarnings("unchecked")
final TypeComparator comparator = (TypeComparator) this.inputComparators[index];
return comparator;
}
// ============================================================================================
// Static Utilities
//
// Utilities are consolidated here to ensure a uniform way of running,
// logging, exception handling, and error messages.
// ============================================================================================
// --------------------------------------------------------------------------------------------
// Logging
// --------------------------------------------------------------------------------------------
/**
* Utility function that composes a string for logging purposes. The string includes the given
* message, the given name of the task and the index in its subtask group as well as the number
* of instances that exist in its subtask group.
*
* @param message The main message for the log.
* @param taskName The name of the task.
* @param parent The task that contains the code producing the message.
* @return The string for logging.
*/
public static String constructLogString(
String message, String taskName, AbstractInvokable parent) {
return message
+ ": "
+ taskName
+ " ("
+ (parent.getEnvironment().getTaskInfo().getIndexOfThisSubtask() + 1)
+ '/'
+ parent.getEnvironment().getTaskInfo().getNumberOfParallelSubtasks()
+ ')';
}
/**
* Prints an error message and throws the given exception. If the exception is of the type
* {@link ExceptionInChainedStubException} then the chain of contained exceptions is followed
* until an exception of a different type is found.
*
* @param ex The exception to be thrown.
* @param parent The parent task, whose information is included in the log message.
* @throws Exception Always thrown.
*/
public static void logAndThrowException(Exception ex, AbstractInvokable parent)
throws Exception {
String taskName;
if (ex instanceof ExceptionInChainedStubException) {
do {
ExceptionInChainedStubException cex = (ExceptionInChainedStubException) ex;
taskName = cex.getTaskName();
ex = cex.getWrappedException();
} while (ex instanceof ExceptionInChainedStubException);
} else {
taskName = parent.getEnvironment().getTaskInfo().getTaskName();
}
if (LOG.isErrorEnabled()) {
LOG.error(constructLogString("Error in task code", taskName, parent), ex);
}
throw ex;
}
// --------------------------------------------------------------------------------------------
// Result Shipping and Chained Tasks
// --------------------------------------------------------------------------------------------
/**
* Creates the {@link Collector} for the given task, as described by the given configuration.
* The output collector contains the writers that forward the data to the different tasks that
* the given task is connected to. Each writer applies the partitioning as described in the
* configuration.
*
* @param task The task that the output collector is created for.
* @param config The configuration describing the output shipping strategies.
* @param cl The classloader used to load user defined types.
* @param eventualOutputs The output writers that this task forwards to the next task for each
* output.
* @param outputOffset The offset to start to get the writers for the outputs
* @param numOutputs The number of outputs described in the configuration.
* @return The OutputCollector that data produced in this task is submitted to.
*/
public static Collector getOutputCollector(
AbstractInvokable task,
TaskConfig config,
ClassLoader cl,
List> eventualOutputs,
int outputOffset,
int numOutputs)
throws Exception {
if (numOutputs == 0) {
return null;
}
// get the factory for the serializer
final TypeSerializerFactory serializerFactory = config.getOutputSerializer(cl);
final List>> writers = new ArrayList<>(numOutputs);
// create a writer for each output
for (int i = 0; i < numOutputs; i++) {
// create the OutputEmitter from output ship strategy
final ShipStrategyType strategy = config.getOutputShipStrategy(i);
final int indexInSubtaskGroup = task.getIndexInSubtaskGroup();
final TypeComparatorFactory compFactory = config.getOutputComparator(i, cl);
final ChannelSelector> oe;
if (compFactory == null) {
oe = new OutputEmitter<>(strategy, indexInSubtaskGroup);
} else {
final DataDistribution dataDist = config.getOutputDataDistribution(i, cl);
final Partitioner partitioner = config.getOutputPartitioner(i, cl);
final TypeComparator comparator = compFactory.createComparator();
oe =
new OutputEmitter<>(
strategy, indexInSubtaskGroup, comparator, partitioner, dataDist);
}
final RecordWriter> recordWriter =
new RecordWriterBuilder()
.setChannelSelector(oe)
.setTaskName(
task.getEnvironment().getTaskInfo().getTaskNameWithSubtasks())
.build(task.getEnvironment().getWriter(outputOffset + i));
recordWriter.setMetricGroup(task.getEnvironment().getMetricGroup().getIOMetricGroup());
writers.add(recordWriter);
}
if (eventualOutputs != null) {
eventualOutputs.addAll(writers);
}
return new OutputCollector<>(writers, serializerFactory.getSerializer());
}
/**
* Creates a writer for each output. Creates an OutputCollector which forwards its input to all
* writers. The output collector applies the configured shipping strategy.
*/
@SuppressWarnings("unchecked")
public static Collector initOutputs(
AbstractInvokable containingTask,
UserCodeClassLoader cl,
TaskConfig config,
List> chainedTasksTarget,
List> eventualOutputs,
ExecutionConfig executionConfig,
Map> accumulatorMap)
throws Exception {
final int numOutputs = config.getNumOutputs();
// check whether we got any chained tasks
final int numChained = config.getNumberOfChainedStubs();
if (numChained > 0) {
// got chained stubs. that means that this one may only have a single forward connection
if (numOutputs != 1 || config.getOutputShipStrategy(0) != ShipStrategyType.FORWARD) {
throw new RuntimeException(
"Plan Generation Bug: Found a chained stub that is not connected via an only forward connection.");
}
// instantiate each task
@SuppressWarnings("rawtypes")
Collector previous = null;
for (int i = numChained - 1; i >= 0; --i) {
// get the task first
final ChainedDriver ct;
try {
Class> ctc = config.getChainedTask(i);
ct = ctc.newInstance();
} catch (Exception ex) {
throw new RuntimeException("Could not instantiate chained task driver.", ex);
}
// get the configuration for the task
final TaskConfig chainedStubConf = config.getChainedStubConfig(i);
final String taskName = config.getChainedTaskName(i);
if (i == numChained - 1) {
// last in chain, instantiate the output collector for this task
previous =
getOutputCollector(
containingTask,
chainedStubConf,
cl.asClassLoader(),
eventualOutputs,
0,
chainedStubConf.getNumOutputs());
}
ct.setup(
chainedStubConf,
taskName,
previous,
containingTask,
cl,
executionConfig,
accumulatorMap);
chainedTasksTarget.add(0, ct);
if (i == numChained - 1) {
ct.getIOMetrics().reuseOutputMetricsForTask();
}
previous = ct;
}
// the collector of the first in the chain is the collector for the task
return (Collector) previous;
}
// else
// instantiate the output collector the default way from this configuration
return getOutputCollector(
containingTask, config, cl.asClassLoader(), eventualOutputs, 0, numOutputs);
}
// --------------------------------------------------------------------------------------------
// User Code LifeCycle
// --------------------------------------------------------------------------------------------
/**
* Opens the given stub using its {@link
* org.apache.flink.api.common.functions.RichFunction#open(OpenContext)} method. If the open
* call produces an exception, a new exception with a standard error message is created, using
* the encountered exception as its cause.
*
* @param stub The user code instance to be opened.
* @param parameters The parameters supplied to the user code.
* @throws Exception Thrown, if the user code's open method produces an exception.
*/
public static void openUserCode(Function stub, Configuration parameters) throws Exception {
try {
FunctionUtils.openFunction(stub, DefaultOpenContext.INSTANCE);
} catch (Throwable t) {
throw new Exception(
"The user defined 'open(OpenContext)' method in "
+ stub.getClass().toString()
+ " caused an exception: "
+ t.getMessage(),
t);
}
}
/**
* Closes the given stub using its {@link
* org.apache.flink.api.common.functions.RichFunction#close()} method. If the close call
* produces an exception, a new exception with a standard error message is created, using the
* encountered exception as its cause.
*
* @param stub The user code instance to be closed.
* @throws Exception Thrown, if the user code's close method produces an exception.
*/
public static void closeUserCode(Function stub) throws Exception {
try {
FunctionUtils.closeFunction(stub);
} catch (Throwable t) {
throw new Exception(
"The user defined 'close()' method caused an exception: " + t.getMessage(), t);
}
}
// --------------------------------------------------------------------------------------------
// Chained Task LifeCycle
// --------------------------------------------------------------------------------------------
/**
* Opens all chained tasks, in the order as they are stored in the array. The opening process
* creates a standardized log info message.
*
* @param tasks The tasks to be opened.
* @param parent The parent task, used to obtain parameters to include in the log message.
* @throws Exception Thrown, if the opening encounters an exception.
*/
public static void openChainedTasks(List> tasks, AbstractInvokable parent)
throws Exception {
// start all chained tasks
for (ChainedDriver task : tasks) {
if (LOG.isDebugEnabled()) {
LOG.debug(constructLogString("Start task code", task.getTaskName(), parent));
}
task.openTask();
}
}
/**
* Closes all chained tasks, in the order as they are stored in the array. The closing process
* creates a standardized log info message.
*
* @param tasks The tasks to be closed.
* @param parent The parent task, used to obtain parameters to include in the log message.
* @throws Exception Thrown, if the closing encounters an exception.
*/
public static void closeChainedTasks(List> tasks, AbstractInvokable parent)
throws Exception {
for (ChainedDriver task : tasks) {
task.closeTask();
if (LOG.isDebugEnabled()) {
LOG.debug(constructLogString("Finished task code", task.getTaskName(), parent));
}
}
}
/**
* Cancels all tasks via their {@link ChainedDriver#cancelTask()} method. Any occurring
* exception and error is suppressed, such that the canceling method of every task is invoked in
* all cases.
*
* @param tasks The tasks to be canceled.
*/
public static void cancelChainedTasks(List> tasks) {
for (ChainedDriver task : tasks) {
try {
task.cancelTask();
} catch (Throwable t) {
// do nothing
}
}
}
// --------------------------------------------------------------------------------------------
// Miscellaneous Utilities
// --------------------------------------------------------------------------------------------
/**
* Instantiates a user code class from is definition in the task configuration. The class is
* instantiated without arguments using the null-ary constructor. Instantiation will fail if
* this constructor does not exist or is not public.
*
* @param The generic type of the user code class.
* @param config The task configuration containing the class description.
* @param cl The class loader to be used to load the class.
* @param superClass The super class that the user code class extends or implements, for type
* checking.
* @return An instance of the user code class.
*/
public static T instantiateUserCode(
TaskConfig config, ClassLoader cl, Class superClass) {
try {
T stub = config.getStubWrapper(cl).getUserCodeObject(superClass, cl);
// check if the class is a subclass, if the check is required
if (superClass != null && !superClass.isAssignableFrom(stub.getClass())) {
throw new RuntimeException(
"The class '"
+ stub.getClass().getName()
+ "' is not a subclass of '"
+ superClass.getName()
+ "' as is required.");
}
return stub;
} catch (ClassCastException ccex) {
throw new RuntimeException(
"The UDF class is not a proper subclass of " + superClass.getName(), ccex);
}
}
private static int[] asArray(List list) {
int[] a = new int[list.size()];
int i = 0;
for (int val : list) {
a[i++] = val;
}
return a;
}
public static void clearWriters(List> writers) {
for (RecordWriter writer : writers) {
writer.close();
}
}
public static void clearReaders(MutableReader[] readers) {
for (MutableReader reader : readers) {
reader.clearBuffers();
}
}
}