Java tutorial
/* * 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.gobblin.instrumented.extractor; import java.io.Closeable; import java.io.IOException; import java.util.List; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicBoolean; import com.codahale.metrics.Meter; import com.codahale.metrics.Timer; import com.google.common.base.Optional; import com.google.common.collect.Lists; import com.google.common.io.Closer; import org.apache.gobblin.configuration.State; import org.apache.gobblin.configuration.WorkUnitState; import org.apache.gobblin.instrumented.Instrumentable; import org.apache.gobblin.instrumented.Instrumented; import org.apache.gobblin.metadata.GlobalMetadata; import org.apache.gobblin.metrics.GobblinMetrics; import org.apache.gobblin.metrics.MetricContext; import org.apache.gobblin.metrics.MetricNames; import org.apache.gobblin.metrics.Tag; import org.apache.gobblin.records.RecordStreamWithMetadata; import org.apache.gobblin.source.extractor.DataRecordException; import org.apache.gobblin.source.extractor.Extractor; import org.apache.gobblin.stream.RecordEnvelope; import org.apache.gobblin.stream.StreamEntity; import org.apache.gobblin.util.FinalState; import edu.umd.cs.findbugs.annotations.SuppressWarnings; import io.reactivex.Emitter; import io.reactivex.Flowable; import io.reactivex.functions.BiConsumer; import javax.annotation.Nullable; /** * package-private implementation of instrumentation for {@link org.apache.gobblin.source.extractor.Extractor}. * See {@link org.apache.gobblin.instrumented.extractor.InstrumentedExtractor} for extensible class. */ public abstract class InstrumentedExtractorBase<S, D> implements Extractor<S, D>, Instrumentable, Closeable, FinalState { private final boolean instrumentationEnabled; private MetricContext metricContext; private Optional<Meter> readRecordsMeter; private Optional<Meter> dataRecordExceptionsMeter; private Optional<Timer> extractorTimer; protected final Closer closer; public InstrumentedExtractorBase(WorkUnitState workUnitState) { this(workUnitState, Optional.<Class<?>>absent()); } protected InstrumentedExtractorBase(WorkUnitState workUnitState, Optional<Class<?>> classTag) { super(); this.closer = Closer.create(); this.instrumentationEnabled = GobblinMetrics.isEnabled(workUnitState); this.metricContext = this.closer.register(Instrumented.getMetricContext(workUnitState, classTag.or(this.getClass()), generateTags(workUnitState))); regenerateMetrics(); } @Override public void switchMetricContext(List<Tag<?>> tags) { this.metricContext = this.closer.register( Instrumented.newContextFromReferenceContext(this.metricContext, tags, Optional.<String>absent())); regenerateMetrics(); } @Override public void switchMetricContext(MetricContext context) { this.metricContext = context; regenerateMetrics(); } /** * Generates metrics for the instrumentation of this class. */ protected void regenerateMetrics() { if (isInstrumentationEnabled()) { this.readRecordsMeter = Optional .of(this.metricContext.meter(MetricNames.ExtractorMetrics.RECORDS_READ_METER)); this.dataRecordExceptionsMeter = Optional .of(this.metricContext.meter(MetricNames.ExtractorMetrics.RECORDS_FAILED_METER)); this.extractorTimer = Optional .<Timer>of(this.metricContext.timer(MetricNames.ExtractorMetrics.EXTRACT_TIMER)); } else { this.readRecordsMeter = Optional.absent(); this.dataRecordExceptionsMeter = Optional.absent(); this.extractorTimer = Optional.absent(); } } @Override public boolean isInstrumentationEnabled() { return this.instrumentationEnabled; } /** Default with no additional tags */ @Override public List<Tag<?>> generateTags(State state) { return Lists.newArrayList(); } @Override public RecordEnvelope<D> readRecordEnvelope() throws DataRecordException, IOException { if (!isInstrumentationEnabled()) { return readRecordEnvelopeImpl(); } try { long startTimeNanos = System.nanoTime(); beforeRead(); RecordEnvelope<D> record = readRecordEnvelopeImpl(); afterRead(record == null ? null : record.getRecord(), startTimeNanos); return record; } catch (DataRecordException exception) { onException(exception); throw exception; } catch (IOException exception) { onException(exception); throw exception; } } /** * @param shutdownRequest an {@link AtomicBoolean} that becomes true when a shutdown has been requested. * @return a {@link Flowable} with the records from this source. Note the flowable should honor downstream backpressure. */ @Override public RecordStreamWithMetadata<D, S> recordStream(AtomicBoolean shutdownRequest) throws IOException { S schema = getSchema(); Flowable<StreamEntity<D>> recordStream = Flowable.generate(() -> shutdownRequest, (BiConsumer<AtomicBoolean, Emitter<StreamEntity<D>>>) (state, emitter) -> { if (state.get()) { emitter.onComplete(); } try { long startTimeNanos = 0; if (isInstrumentationEnabled()) { startTimeNanos = System.nanoTime(); beforeRead(); } StreamEntity<D> record = readStreamEntityImpl(); if (isInstrumentationEnabled()) { D unwrappedRecord = null; if (record instanceof RecordEnvelope) { unwrappedRecord = ((RecordEnvelope<D>) record).getRecord(); } afterRead(unwrappedRecord, startTimeNanos); } if (record != null) { emitter.onNext(record); } else { emitter.onComplete(); } } catch (DataRecordException | IOException exc) { if (isInstrumentationEnabled()) { onException(exc); } emitter.onError(exc); } }); recordStream = recordStream.doFinally(this::close); return new RecordStreamWithMetadata<>(recordStream, GlobalMetadata.<S>builder().schema(schema).build()); } /** * Called before each record is read. */ public void beforeRead() { } /** * Called after each record is read. * @param record record read. * @param startTime reading start time. */ public void afterRead(D record, long startTime) { Instrumented.updateTimer(this.extractorTimer, System.nanoTime() - startTime, TimeUnit.NANOSECONDS); if (record != null) { Instrumented.markMeter(this.readRecordsMeter); } } /** * Called on exception when trying to read. * @param exception exception thrown. */ public void onException(Exception exception) { if (DataRecordException.class.isInstance(exception)) { Instrumented.markMeter(this.dataRecordExceptionsMeter); } } /** * Subclasses should implement this or {@link #readRecordEnvelopeImpl()} * instead of {@link org.apache.gobblin.source.extractor.Extractor#readRecord} */ protected StreamEntity<D> readStreamEntityImpl() throws DataRecordException, IOException { return readRecordEnvelopeImpl(); } /** * Subclasses should implement this or {@link #readRecordImpl(Object)} * instead of {@link org.apache.gobblin.source.extractor.Extractor#readRecord} */ @SuppressWarnings(value = "RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE", justification = "Findbugs believes readRecord(null) is non-null. This is not true.") protected RecordEnvelope<D> readRecordEnvelopeImpl() throws DataRecordException, IOException { D record = readRecordImpl(null); return record == null ? null : new RecordEnvelope<>(record); } /** * Subclasses should implement this or {@link #readRecordEnvelopeImpl()} * instead of {@link org.apache.gobblin.source.extractor.Extractor#readRecord} */ @Nullable protected D readRecordImpl(D reuse) throws DataRecordException, IOException { throw new UnsupportedOperationException(); } /** * Get final state for this object. By default this returns an empty {@link org.apache.gobblin.configuration.State}, but * concrete subclasses can add information that will be added to the task state. * @return Empty {@link org.apache.gobblin.configuration.State}. */ @Override public State getFinalState() { return new State(); } @Override public void close() throws IOException { this.closer.close(); } @Override public MetricContext getMetricContext() { return this.metricContext; } }