聊聊flink的Parallel Execution

序

本文主要研究一下flink的Parallel Execution

实例

Operator Level

final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

DataStream<String> text = [...]
DataStream<Tuple2<String, Integer>> wordCounts = text
    .flatMap(new LineSplitter())
    .keyBy(0)
    .timeWindow(Time.seconds(5))
    .sum(1).setParallelism(5);

wordCounts.print();

env.execute("Word Count Example");

• operators、data sources、data sinks都可以调用setParallelism()方法来设置parallelism

Execution Environment Level

final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
env.setParallelism(3);

DataStream<String> text = [...]
DataStream<Tuple2<String, Integer>> wordCounts = [...]
wordCounts.print();

env.execute("Word Count Example");

• 在ExecutionEnvironment里头可以通过setParallelism来给operators、data sources、data sinks设置默认的parallelism；如果operators、data sources、data sinks自己有设置parallelism则会覆盖ExecutionEnvironment设置的parallelism

Client Level

./bin/flink run -p 10 ../examples/*WordCount-java*.jar

或者

try {
    PackagedProgram program = new PackagedProgram(file, args);
    InetSocketAddress jobManagerAddress = RemoteExecutor.getInetFromHostport("localhost:6123");
    Configuration config = new Configuration();

    Client client = new Client(jobManagerAddress, config, program.getUserCodeClassLoader());

    // set the parallelism to 10 here
    client.run(program, 10, true);

} catch (ProgramInvocationException e) {
    e.printStackTrace();
}

• 使用CLI client，可以在命令行调用是用-p来指定，或者Java/Scala调用时在Client.run的参数中指定parallelism

System Level

# The parallelism used for programs that did not specify and other parallelism.

parallelism.default: 1

• 可以在flink-conf.yaml中通过parallelism.default配置项给所有execution environments指定系统级的默认parallelism

ExecutionEnvironment

flink-java-1.7.1-sources.jar!/org/apache/flink/api/java/ExecutionEnvironment.java

@Public
public abstract class ExecutionEnvironment {
    //......

    private final ExecutionConfig config = new ExecutionConfig();

    /**
     * Sets the parallelism for operations executed through this environment.
     * Setting a parallelism of x here will cause all operators (such as join, map, reduce) to run with
     * x parallel instances.
     *
     * <p>This method overrides the default parallelism for this environment.
     * The {@link LocalEnvironment} uses by default a value equal to the number of hardware
     * contexts (CPU cores / threads). When executing the program via the command line client
     * from a JAR file, the default parallelism is the one configured for that setup.
     *
     * @param parallelism The parallelism
     */
    public void setParallelism(int parallelism) {
        config.setParallelism(parallelism);
    }

    @Internal
    public Plan createProgramPlan(String jobName, boolean clearSinks) {
        if (this.sinks.isEmpty()) {
            if (wasExecuted) {
                throw new RuntimeException("No new data sinks have been defined since the " +
                        "last execution. The last execution refers to the latest call to " +
                        "'execute()', 'count()', 'collect()', or 'print()'.");
            } else {
                throw new RuntimeException("No data sinks have been created yet. " +
                        "A program needs at least one sink that consumes data. " +
                        "Examples are writing the data set or printing it.");
            }
        }

        if (jobName == null) {
            jobName = getDefaultName();
        }

        OperatorTranslation translator = new OperatorTranslation();
        Plan plan = translator.translateToPlan(this.sinks, jobName);

        if (getParallelism() > 0) {
            plan.setDefaultParallelism(getParallelism());
        }
        plan.setExecutionConfig(getConfig());

        // Check plan for GenericTypeInfo's and register the types at the serializers.
        if (!config.isAutoTypeRegistrationDisabled()) {
            plan.accept(new Visitor<org.apache.flink.api.common.operators.Operator<?>>() {

                private final Set<Class<?>> registeredTypes = new HashSet<>();
                private final Set<org.apache.flink.api.common.operators.Operator<?>> visitedOperators = new HashSet<>();

                @Override
                public boolean preVisit(org.apache.flink.api.common.operators.Operator<?> visitable) {
                    if (!visitedOperators.add(visitable)) {
                        return false;
                    }
                    OperatorInformation<?> opInfo = visitable.getOperatorInfo();
                    Serializers.recursivelyRegisterType(opInfo.getOutputType(), config, registeredTypes);
                    return true;
                }

                @Override
                public void postVisit(org.apache.flink.api.common.operators.Operator<?> visitable) {}
            });
        }

        try {
            registerCachedFilesWithPlan(plan);
        } catch (Exception e) {
            throw new RuntimeException("Error while registering cached files: " + e.getMessage(), e);
        }

        // clear all the sinks such that the next execution does not redo everything
        if (clearSinks) {
            this.sinks.clear();
            wasExecuted = true;
        }

        // All types are registered now. Print information.
        int registeredTypes = config.getRegisteredKryoTypes().size() +
                config.getRegisteredPojoTypes().size() +
                config.getRegisteredTypesWithKryoSerializerClasses().size() +
                config.getRegisteredTypesWithKryoSerializers().size();
        int defaultKryoSerializers = config.getDefaultKryoSerializers().size() +
                config.getDefaultKryoSerializerClasses().size();
        LOG.info("The job has {} registered types and {} default Kryo serializers", registeredTypes, defaultKryoSerializers);

        if (config.isForceKryoEnabled() && config.isForceAvroEnabled()) {
            LOG.warn("In the ExecutionConfig, both Avro and Kryo are enforced. Using Kryo serializer");
        }
        if (config.isForceKryoEnabled()) {
            LOG.info("Using KryoSerializer for serializing POJOs");
        }
        if (config.isForceAvroEnabled()) {
            LOG.info("Using AvroSerializer for serializing POJOs");
        }

        if (LOG.isDebugEnabled()) {
            LOG.debug("Registered Kryo types: {}", config.getRegisteredKryoTypes().toString());
            LOG.debug("Registered Kryo with Serializers types: {}", config.getRegisteredTypesWithKryoSerializers().entrySet().toString());
            LOG.debug("Registered Kryo with Serializer Classes types: {}", config.getRegisteredTypesWithKryoSerializerClasses().entrySet().toString());
            LOG.debug("Registered Kryo default Serializers: {}", config.getDefaultKryoSerializers().entrySet().toString());
            LOG.debug("Registered Kryo default Serializers Classes {}", config.getDefaultKryoSerializerClasses().entrySet().toString());
            LOG.debug("Registered POJO types: {}", config.getRegisteredPojoTypes().toString());

            // print information about static code analysis
            LOG.debug("Static code analysis mode: {}", config.getCodeAnalysisMode());
        }

        return plan;
    }

    //......
}

• ExecutionEnvironment提供了setParallelism方法，给ExecutionConfig指定parallelism；最后createProgramPlan方法创建Plan后会读取ExecutionConfig的parallelism，给Plan设置defaultParallelism

LocalEnvironment

flink-java-1.7.1-sources.jar!/org/apache/flink/api/java/LocalEnvironment.java

@Public
public class LocalEnvironment extends ExecutionEnvironment {

    //......

    public JobExecutionResult execute(String jobName) throws Exception {
        if (executor == null) {
            startNewSession();
        }

        Plan p = createProgramPlan(jobName);

        // Session management is disabled, revert this commit to enable
        //p.setJobId(jobID);
        //p.setSessionTimeout(sessionTimeout);

        JobExecutionResult result = executor.executePlan(p);

        this.lastJobExecutionResult = result;
        return result;
    }

    //......
}

• LocalEnvironment的execute调用的是LocalExecutor的executePlan

LocalExecutor

flink-clients_2.11-1.7.1-sources.jar!/org/apache/flink/client/LocalExecutor.java

public class LocalExecutor extends PlanExecutor {
    
    //......

    @Override
    public JobExecutionResult executePlan(Plan plan) throws Exception {
        if (plan == null) {
            throw new IllegalArgumentException("The plan may not be null.");
        }

        synchronized (this.lock) {

            // check if we start a session dedicated for this execution
            final boolean shutDownAtEnd;

            if (jobExecutorService == null) {
                shutDownAtEnd = true;

                // configure the number of local slots equal to the parallelism of the local plan
                if (this.taskManagerNumSlots == DEFAULT_TASK_MANAGER_NUM_SLOTS) {
                    int maxParallelism = plan.getMaximumParallelism();
                    if (maxParallelism > 0) {
                        this.taskManagerNumSlots = maxParallelism;
                    }
                }

                // start the cluster for us
                start();
            }
            else {
                // we use the existing session
                shutDownAtEnd = false;
            }

            try {
                // TODO: Set job's default parallelism to max number of slots
                final int slotsPerTaskManager = jobExecutorServiceConfiguration.getInteger(TaskManagerOptions.NUM_TASK_SLOTS, taskManagerNumSlots);
                final int numTaskManagers = jobExecutorServiceConfiguration.getInteger(ConfigConstants.LOCAL_NUMBER_TASK_MANAGER, 1);
                plan.setDefaultParallelism(slotsPerTaskManager * numTaskManagers);

                Optimizer pc = new Optimizer(new DataStatistics(), jobExecutorServiceConfiguration);
                OptimizedPlan op = pc.compile(plan);

                JobGraphGenerator jgg = new JobGraphGenerator(jobExecutorServiceConfiguration);
                JobGraph jobGraph = jgg.compileJobGraph(op, plan.getJobId());

                return jobExecutorService.executeJobBlocking(jobGraph);
            }
            finally {
                if (shutDownAtEnd) {
                    stop();
                }
            }
        }
    }

    //......
}

• LocalExecutor的executePlan方法还会根据slotsPerTaskManager及numTaskManagers对plan设置defaultParallelism

RemoteEnvironment

flink-java-1.7.1-sources.jar!/org/apache/flink/api/java/RemoteEnvironment.java

@Public
public class RemoteEnvironment extends ExecutionEnvironment {

    //......

    public JobExecutionResult execute(String jobName) throws Exception {
        PlanExecutor executor = getExecutor();

        Plan p = createProgramPlan(jobName);

        // Session management is disabled, revert this commit to enable
        //p.setJobId(jobID);
        //p.setSessionTimeout(sessionTimeout);

        JobExecutionResult result = executor.executePlan(p);

        this.lastJobExecutionResult = result;
        return result;
    }

    //......
}

• RemoteEnvironment的execute调用的是RemoteExecutor的executePlan

RemoteExecutor

flink-clients_2.11-1.7.1-sources.jar!/org/apache/flink/client/RemoteExecutor.java

public class RemoteExecutor extends PlanExecutor {

    private final Object lock = new Object();

    private final List<URL> jarFiles;

    private final List<URL> globalClasspaths;

    private final Configuration clientConfiguration;

    private ClusterClient<?> client;

    //......

    @Override
    public JobExecutionResult executePlan(Plan plan) throws Exception {
        if (plan == null) {
            throw new IllegalArgumentException("The plan may not be null.");
        }

        JobWithJars p = new JobWithJars(plan, this.jarFiles, this.globalClasspaths);
        return executePlanWithJars(p);
    }

    public JobExecutionResult executePlanWithJars(JobWithJars program) throws Exception {
        if (program == null) {
            throw new IllegalArgumentException("The job may not be null.");
        }

        synchronized (this.lock) {
            // check if we start a session dedicated for this execution
            final boolean shutDownAtEnd;

            if (client == null) {
                shutDownAtEnd = true;
                // start the executor for us
                start();
            }
            else {
                // we use the existing session
                shutDownAtEnd = false;
            }

            try {
                return client.run(program, defaultParallelism).getJobExecutionResult();
            }
            finally {
                if (shutDownAtEnd) {
                    stop();
                }
            }
        }
    }

    //......
}

• RemoteExecutor的executePlan调用了executePlanWithJars方法，而后者则调用了ClusterClient的run，并在参数中指定了defaultParallelism

ClusterClient

flink-clients_2.11-1.7.1-sources.jar!/org/apache/flink/client/program/ClusterClient.java

public abstract class ClusterClient<T> {
    //......

    public JobSubmissionResult run(JobWithJars program, int parallelism) throws ProgramInvocationException {
        return run(program, parallelism, SavepointRestoreSettings.none());
    }

    public JobSubmissionResult run(JobWithJars jobWithJars, int parallelism, SavepointRestoreSettings savepointSettings)
            throws CompilerException, ProgramInvocationException {
        ClassLoader classLoader = jobWithJars.getUserCodeClassLoader();
        if (classLoader == null) {
            throw new IllegalArgumentException("The given JobWithJars does not provide a usercode class loader.");
        }

        OptimizedPlan optPlan = getOptimizedPlan(compiler, jobWithJars, parallelism);
        return run(optPlan, jobWithJars.getJarFiles(), jobWithJars.getClasspaths(), classLoader, savepointSettings);
    }

    private static OptimizedPlan getOptimizedPlan(Optimizer compiler, JobWithJars prog, int parallelism)
            throws CompilerException, ProgramInvocationException {
        return getOptimizedPlan(compiler, prog.getPlan(), parallelism);
    }

    public static OptimizedPlan getOptimizedPlan(Optimizer compiler, Plan p, int parallelism) throws CompilerException {
        Logger log = LoggerFactory.getLogger(ClusterClient.class);

        if (parallelism > 0 && p.getDefaultParallelism() <= 0) {
            log.debug("Changing plan default parallelism from {} to {}", p.getDefaultParallelism(), parallelism);
            p.setDefaultParallelism(parallelism);
        }
        log.debug("Set parallelism {}, plan default parallelism {}", parallelism, p.getDefaultParallelism());

        return compiler.compile(p);
    }

    //......
}

• ClusterClient的run方法中的parallelism在parallelism > 0以及p.getDefaultParallelism() <= 0的时候会作用到Plan中

DataStreamSource

flink-streaming-java_2.11-1.7.1-sources.jar!/org/apache/flink/streaming/api/datastream/DataStreamSource.java

@Public
public class DataStreamSource<T> extends SingleOutputStreamOperator<T> {

    boolean isParallel;

    public DataStreamSource(StreamExecutionEnvironment environment,
            TypeInformation<T> outTypeInfo, StreamSource<T, ?> operator,
            boolean isParallel, String sourceName) {
        super(environment, new SourceTransformation<>(sourceName, operator, outTypeInfo, environment.getParallelism()));

        this.isParallel = isParallel;
        if (!isParallel) {
            setParallelism(1);
        }
    }

    public DataStreamSource(SingleOutputStreamOperator<T> operator) {
        super(operator.environment, operator.getTransformation());
        this.isParallel = true;
    }

    @Override
    public DataStreamSource<T> setParallelism(int parallelism) {
        if (parallelism != 1 && !isParallel) {
            throw new IllegalArgumentException("Source: " + transformation.getId() + " is not a parallel source");
        } else {
            super.setParallelism(parallelism);
            return this;
        }
    }
}

• DataStreamSource继承了SingleOutputStreamOperator，它提供了setParallelism方法，最终调用的是父类SingleOutputStreamOperator的setParallelism

SingleOutputStreamOperator

flink-streaming-java_2.11-1.7.1-sources.jar!/org/apache/flink/streaming/api/datastream/SingleOutputStreamOperator.java

@Public
public class SingleOutputStreamOperator<T> extends DataStream<T> {
    //......

    /**
     * Sets the parallelism for this operator.
     *
     * @param parallelism
     *            The parallelism for this operator.
     * @return The operator with set parallelism.
     */
    public SingleOutputStreamOperator<T> setParallelism(int parallelism) {
        Preconditions.checkArgument(canBeParallel() || parallelism == 1,
                "The parallelism of non parallel operator must be 1.");

        transformation.setParallelism(parallelism);

        return this;
    }

    //......
}

• SingleOutputStreamOperator的setParallelism最后是作用到StreamTransformation

DataStreamSink

flink-streaming-java_2.11-1.7.1-sources.jar!/org/apache/flink/streaming/api/datastream/DataStreamSink.java

@Public
public class DataStreamSink<T> {

    private final SinkTransformation<T> transformation;

    //......

    /**
     * Sets the parallelism for this sink. The degree must be higher than zero.
     *
     * @param parallelism The parallelism for this sink.
     * @return The sink with set parallelism.
     */
    public DataStreamSink<T> setParallelism(int parallelism) {
        transformation.setParallelism(parallelism);
        return this;
    }

    //......
}

• DataStreamSink提供了setParallelism方法，最后是作用于SinkTransformation

小结

• flink可以设置好几个level的parallelism，其中包括Operator Level、Execution Environment Level、Client Level、System Level
• 在flink-conf.yaml中通过parallelism.default配置项给所有execution environments指定系统级的默认parallelism；在ExecutionEnvironment里头可以通过setParallelism来给operators、data sources、data sinks设置默认的parallelism；如果operators、data sources、data sinks自己有设置parallelism则会覆盖ExecutionEnvironment设置的parallelism
• ExecutionEnvironment提供的setParallelism方法用于给ExecutionConfig指定parallelism(如果使用CLI client，可以在命令行调用是用-p来指定，或者Java/Scala调用时在Client.run的参数中指定parallelism；LocalEnvironment及RemoteEnvironment设置的parallelism最后都是设置到Plan中)；DataStreamSource继承了SingleOutputStreamOperator，它提供了setParallelism方法，最终调用的是父类SingleOutputStreamOperator的setParallelism；SingleOutputStreamOperator的setParallelism最后是作用到StreamTransformation；DataStreamSink提供了setParallelism方法，最后是作用于SinkTransformation

doc

• Parallel Execution