Examples with RingBuffer org.apache.nifi.util.RingBuffer used on opensource projects

Example 1 with RingBuffer

use of org.apache.nifi.util.RingBuffer in project nifi by apache.

the class PersistentProvenanceRepository method mergeJournals.

/**
 * <p>
 * Merges all of the given Journal Files into a single, merged Provenance
 * Event Log File. As these records are merged, they will be compressed, if
 * the repository is configured to compress records, and will be indexed.
 * </p>
 *
 * <p>
 * If the repository is configured to compress the data, the file written to
 * may not be the same as the <code>suggestedMergeFile</code>, as a filename
 * extension of '.gz' may be appended. If the journals are successfully
 * merged, the file that they were merged into will be returned. If unable
 * to merge the records (for instance, because the repository has been
 * closed or because the list of journal files was empty), this method will
 * return <code>null</code>.
 * </p>
 *
 * @param journalFiles the journal files to merge
 * @param suggestedMergeFile the file to write the merged records to
 * @param eventReporter the event reporter to report any warnings or errors
 * to; may be null.
 *
 * @return the file that the given journals were merged into, or
 * <code>null</code> if no records were merged.
 *
 * @throws IOException if a problem occurs writing to the mergedFile,
 * reading from a journal, or updating the Lucene Index.
 */
File mergeJournals(final List<File> journalFiles, final File suggestedMergeFile, final EventReporter eventReporter) throws IOException {
    logger.debug("Merging {} to {}", journalFiles, suggestedMergeFile);
    if (this.closed.get()) {
        logger.info("Provenance Repository has been closed; will not merge journal files to {}", suggestedMergeFile);
        return null;
    }
    if (journalFiles.isEmpty()) {
        logger.debug("Couldn't merge journals: Journal Files is empty; won't merge journals");
        return null;
    }
    Collections.sort(journalFiles, new Comparator<File>() {

        @Override
        public int compare(final File o1, final File o2) {
            final String suffix1 = LuceneUtil.substringAfterLast(o1.getName(), ".");
            final String suffix2 = LuceneUtil.substringAfterLast(o2.getName(), ".");
            try {
                final int journalIndex1 = Integer.parseInt(suffix1);
                final int journalIndex2 = Integer.parseInt(suffix2);
                return Integer.compare(journalIndex1, journalIndex2);
            } catch (final NumberFormatException nfe) {
                return o1.getName().compareTo(o2.getName());
            }
        }
    });
    // Search for any missing files. At this point they should have been written to disk otherwise cannot continue.
    // Missing files is most likely due to incomplete cleanup of files post merge
    final List<File> availableFiles = filterUnavailableFiles(journalFiles);
    final int numAvailableFiles = availableFiles.size();
    // check if we have all of the "partial" files for the journal.
    if (numAvailableFiles > 0) {
        if (suggestedMergeFile.exists()) {
            // we have all "partial" files and there is already a merged file. Delete the data from the index
            // because the merge file may not be fully merged. We will re-merge.
            logger.warn("Merged Journal File {} already exists; however, all partial journal files also exist " + "so assuming that the merge did not finish. Repeating procedure in order to ensure consistency.");
            final DeleteIndexAction deleteAction = new DeleteIndexAction(this, indexConfig, getIndexManager());
            try {
                deleteAction.execute(suggestedMergeFile);
            } catch (final Exception e) {
                logger.warn("Failed to delete records from Journal File {} from the index; this could potentially result in duplicates. Failure was due to {}", suggestedMergeFile, e.toString());
                if (logger.isDebugEnabled()) {
                    logger.warn("", e);
                }
            }
            // file and the TOC file. Otherwise, we could get the wrong copy and have issues retrieving events.
            if (!suggestedMergeFile.delete()) {
                logger.error("Failed to delete partially written Provenance Journal File {}. This may result in events from this journal " + "file not being able to be displayed. This file should be deleted manually.", suggestedMergeFile);
            }
            final File tocFile = TocUtil.getTocFile(suggestedMergeFile);
            if (tocFile.exists() && !tocFile.delete()) {
                logger.error("Failed to delete .toc file {}; this may result in not being able to read the Provenance Events from the {} Journal File. " + "This can be corrected by manually deleting the {} file", tocFile, suggestedMergeFile, tocFile);
            }
        }
    } else {
        logger.warn("Cannot merge journal files {} because they do not exist on disk", journalFiles);
        return null;
    }
    final long startNanos = System.nanoTime();
    // Map each journal to a RecordReader
    final List<RecordReader> readers = new ArrayList<>();
    int records = 0;
    final boolean isCompress = configuration.isCompressOnRollover();
    final File writerFile = isCompress ? new File(suggestedMergeFile.getParentFile(), suggestedMergeFile.getName() + ".gz") : suggestedMergeFile;
    try {
        for (final File journalFile : availableFiles) {
            try {
                // Use MAX_VALUE for number of chars because we don't want to truncate the value as we write it
                // out. This allows us to later decide that we want more characters and still be able to retrieve
                // the entire event.
                readers.add(RecordReaders.newRecordReader(journalFile, null, Integer.MAX_VALUE));
            } catch (final EOFException eof) {
            // there's nothing here. Skip over it.
            } catch (final IOException ioe) {
                logger.warn("Unable to merge {} with other Journal Files due to {}", journalFile, ioe.toString());
                if (logger.isDebugEnabled()) {
                    logger.warn("", ioe);
                }
                if (eventReporter != null) {
                    eventReporter.reportEvent(Severity.ERROR, EVENT_CATEGORY, "Failed to merge Journal Files due to " + ioe.toString());
                }
            }
        }
        // Create a Map so that the key is the next record available from a reader and the value is the Reader from which
        // the record came. This sorted map is then used so that we are able to always get the first entry, which is the next
        // lowest record id
        final SortedMap<StandardProvenanceEventRecord, RecordReader> recordToReaderMap = new TreeMap<>(new Comparator<StandardProvenanceEventRecord>() {

            @Override
            public int compare(final StandardProvenanceEventRecord o1, final StandardProvenanceEventRecord o2) {
                return Long.compare(o1.getEventId(), o2.getEventId());
            }
        });
        long minEventId = 0L;
        long earliestTimestamp = System.currentTimeMillis();
        for (final RecordReader reader : readers) {
            StandardProvenanceEventRecord record = null;
            try {
                record = reader.nextRecord();
            } catch (final EOFException eof) {
            // record will be null and reader can no longer be used
            } catch (final Exception e) {
                logger.warn("Failed to generate Provenance Event Record from Journal due to " + e + "; it's " + "possible that the record wasn't completely written to the file. This journal will be " + "skipped.");
                if (logger.isDebugEnabled()) {
                    logger.warn("", e);
                }
                if (eventReporter != null) {
                    eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to read Provenance Event " + "Record from Journal due to " + e + "; it's possible that the record wasn't " + "completely written to the file. This journal will be skipped.");
                }
            }
            if (record == null) {
                continue;
            }
            if (record.getEventTime() < earliestTimestamp) {
                earliestTimestamp = record.getEventTime();
            }
            if (record.getEventId() < minEventId) {
                minEventId = record.getEventId();
            }
            recordToReaderMap.put(record, reader);
        }
        // We want to keep track of the last 1000 events in the files so that we can add them to 'ringBuffer'.
        // However, we don't want to add them directly to ringBuffer, because once they are added to ringBuffer, they are
        // available in query results. As a result, we can have the issue where we've not finished indexing the file
        // but we try to create the lineage for events in that file. In order to avoid this, we will add the records
        // to a temporary RingBuffer and after we finish merging the records will then copy the data to the
        // ringBuffer provided as a method argument.
        final RingBuffer<ProvenanceEventRecord> latestRecords = new RingBuffer<>(1000);
        // with the next entry from the journal file from which the previous record was written.
        try (final RecordWriter writer = RecordWriters.newSchemaRecordWriter(writerFile, idGenerator, configuration.isCompressOnRollover(), true)) {
            writer.writeHeader(minEventId);
            final IndexingAction indexingAction = createIndexingAction();
            final File indexingDirectory = indexConfig.getWritableIndexDirectory(writerFile, earliestTimestamp);
            long maxId = 0L;
            final BlockingQueue<Tuple<StandardProvenanceEventRecord, Integer>> eventQueue = new LinkedBlockingQueue<>(100);
            final AtomicBoolean finishedAdding = new AtomicBoolean(false);
            final List<Future<?>> futures = new ArrayList<>();
            final EventIndexWriter indexWriter = getIndexManager().borrowIndexWriter(indexingDirectory);
            try {
                final ExecutorService exec = Executors.newFixedThreadPool(configuration.getIndexThreadPoolSize(), new ThreadFactory() {

                    @Override
                    public Thread newThread(final Runnable r) {
                        final Thread t = Executors.defaultThreadFactory().newThread(r);
                        t.setName("Index Provenance Events");
                        return t;
                    }
                });
                final AtomicInteger indexingFailureCount = new AtomicInteger(0);
                try {
                    for (int i = 0; i < configuration.getIndexThreadPoolSize(); i++) {
                        final Callable<Object> callable = new Callable<Object>() {

                            @Override
                            public Object call() throws IOException {
                                while (!eventQueue.isEmpty() || !finishedAdding.get()) {
                                    try {
                                        final Tuple<StandardProvenanceEventRecord, Integer> tuple;
                                        try {
                                            tuple = eventQueue.poll(10, TimeUnit.MILLISECONDS);
                                        } catch (final InterruptedException ie) {
                                            Thread.currentThread().interrupt();
                                            continue;
                                        }
                                        if (tuple == null) {
                                            continue;
                                        }
                                        indexingAction.index(tuple.getKey(), indexWriter.getIndexWriter(), tuple.getValue());
                                    } catch (final Throwable t) {
                                        logger.error("Failed to index Provenance Event for " + writerFile + " to " + indexingDirectory, t);
                                        if (indexingFailureCount.incrementAndGet() >= MAX_INDEXING_FAILURE_COUNT) {
                                            return null;
                                        }
                                    }
                                }
                                return null;
                            }
                        };
                        final Future<?> future = exec.submit(callable);
                        futures.add(future);
                    }
                    boolean indexEvents = true;
                    while (!recordToReaderMap.isEmpty()) {
                        final StandardProvenanceEventRecord record = recordToReaderMap.firstKey();
                        final RecordReader reader = recordToReaderMap.get(record);
                        writer.writeRecord(record);
                        final int blockIndex = writer.getTocWriter().getCurrentBlockIndex();
                        boolean accepted = false;
                        while (!accepted && indexEvents) {
                            try {
                                accepted = eventQueue.offer(new Tuple<>(record, blockIndex), 10, TimeUnit.MILLISECONDS);
                            } catch (final InterruptedException ie) {
                                Thread.currentThread().interrupt();
                            }
                            // So, if the queue is filled, we will check if this is the case.
                            if (!accepted && indexingFailureCount.get() >= MAX_INDEXING_FAILURE_COUNT) {
                                // don't add anything else to the queue.
                                indexEvents = false;
                                eventQueue.clear();
                                final String warning = String.format("Indexing Provenance Events for %s has failed %s times. This exceeds the maximum threshold of %s failures, " + "so no more Provenance Events will be indexed for this Provenance file.", writerFile, indexingFailureCount.get(), MAX_INDEXING_FAILURE_COUNT);
                                logger.warn(warning);
                                if (eventReporter != null) {
                                    eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, warning);
                                }
                            }
                        }
                        maxId = record.getEventId();
                        latestRecords.add(truncateAttributes(record));
                        records++;
                        // Remove this entry from the map
                        recordToReaderMap.remove(record);
                        // Get the next entry from this reader and add it to the map
                        StandardProvenanceEventRecord nextRecord = null;
                        try {
                            nextRecord = reader.nextRecord();
                        } catch (final EOFException eof) {
                        // record will be null and reader can no longer be used
                        } catch (final Exception e) {
                            logger.warn("Failed to generate Provenance Event Record from Journal due to " + e + "; it's possible that the record wasn't completely written to the file. " + "The remainder of this journal will be skipped.");
                            if (logger.isDebugEnabled()) {
                                logger.warn("", e);
                            }
                            if (eventReporter != null) {
                                eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to read " + "Provenance Event Record from Journal due to " + e + "; it's possible " + "that the record wasn't completely written to the file. The remainder " + "of this journal will be skipped.");
                            }
                        }
                        if (nextRecord != null) {
                            recordToReaderMap.put(nextRecord, reader);
                        }
                    }
                } finally {
                    finishedAdding.set(true);
                    exec.shutdown();
                }
                for (final Future<?> future : futures) {
                    try {
                        future.get();
                    } catch (final ExecutionException ee) {
                        final Throwable t = ee.getCause();
                        if (t instanceof RuntimeException) {
                            throw (RuntimeException) t;
                        }
                        throw new RuntimeException(t);
                    } catch (final InterruptedException e) {
                        Thread.currentThread().interrupt();
                        throw new RuntimeException("Thread interrupted");
                    }
                }
            } finally {
                getIndexManager().returnIndexWriter(indexWriter);
            }
            indexConfig.setMaxIdIndexed(maxId);
        }
        // record should now be available in the repository. We can copy the values from latestRecords to ringBuffer.
        final RingBuffer<ProvenanceEventRecord> latestRecordBuffer = this.latestRecords;
        latestRecords.forEach(new ForEachEvaluator<ProvenanceEventRecord>() {

            @Override
            public boolean evaluate(final ProvenanceEventRecord event) {
                latestRecordBuffer.add(event);
                return true;
            }
        });
    } finally {
        for (final RecordReader reader : readers) {
            try {
                reader.close();
            } catch (final IOException ioe) {
            }
        }
    }
    // Success. Remove all of the journal files, as they're no longer needed, now that they've been merged.
    for (final File journalFile : availableFiles) {
        if (!journalFile.delete() && journalFile.exists()) {
            logger.warn("Failed to remove temporary journal file {}; this file should be cleaned up manually", journalFile.getAbsolutePath());
            if (eventReporter != null) {
                eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to remove temporary journal file " + journalFile.getAbsolutePath() + "; this file should be cleaned up manually");
            }
        }
        final File tocFile = TocUtil.getTocFile(journalFile);
        if (!tocFile.delete() && tocFile.exists()) {
            logger.warn("Failed to remove temporary journal TOC file {}; this file should be cleaned up manually", tocFile.getAbsolutePath());
            if (eventReporter != null) {
                eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to remove temporary journal TOC file " + tocFile.getAbsolutePath() + "; this file should be cleaned up manually");
            }
        }
    }
    if (records == 0) {
        writerFile.delete();
        logger.debug("Couldn't merge journals: No Records to merge");
        return null;
    } else {
        final long nanos = System.nanoTime() - startNanos;
        final long millis = TimeUnit.MILLISECONDS.convert(nanos, TimeUnit.NANOSECONDS);
        logger.info("Successfully merged {} journal files ({} records) into single Provenance Log File {} in {} milliseconds", numAvailableFiles, records, suggestedMergeFile, millis);
    }
    return writerFile;
}

Example 2 with RingBuffer

use of org.apache.nifi.util.RingBuffer in project nifi by apache.

the class TestRingBuffer method testIterateBackwards.

@Test
public void testIterateBackwards() {
    final RingBuffer<Integer> ringBuffer = new RingBuffer<>(10);
    final int[] values = new int[] { 3, 5, 20, 7 };
    for (final int v : values) {
        ringBuffer.add(v);
    }
    final AtomicInteger countHolder = new AtomicInteger(0);
    ringBuffer.forEach(new ForEachEvaluator<Integer>() {

        int counter = 0;

        @Override
        public boolean evaluate(final Integer value) {
            final int index = values.length - 1 - counter;
            final int expected = values[index];
            countHolder.incrementAndGet();
            assertEquals(expected, value.intValue());
            counter++;
            return true;
        }
    }, IterationDirection.BACKWARD);
    assertEquals(4, countHolder.get());
}

Example 3 with RingBuffer

use of org.apache.nifi.util.RingBuffer in project nifi by apache.

the class TestRingBuffer method testIterateForwards.

@Test
public void testIterateForwards() {
    final RingBuffer<Integer> ringBuffer = new RingBuffer<>(10);
    final int[] values = new int[] { 3, 5, 20, 7 };
    for (final int v : values) {
        ringBuffer.add(v);
    }
    final AtomicInteger countHolder = new AtomicInteger(0);
    ringBuffer.forEach(new ForEachEvaluator<Integer>() {

        int counter = 0;

        @Override
        public boolean evaluate(final Integer value) {
            final int expected = values[counter++];
            countHolder.incrementAndGet();
            assertEquals(expected, value.intValue());
            return true;
        }
    }, IterationDirection.FORWARD);
    assertEquals(4, countHolder.get());
}

Example 4 with RingBuffer

use of org.apache.nifi.util.RingBuffer in project nifi-minifi by apache.

the class MiNiFiPersistentProvenanceRepository method mergeJournals.

/**
 * <p>
 * Merges all of the given Journal Files into a single, merged Provenance
 * Event Log File. As these records are merged, they will be compressed, if
 * the repository is configured to compress records, and will be indexed.
 * </p>
 *
 * <p>
 * If the repository is configured to compress the data, the file written to
 * may not be the same as the <code>suggestedMergeFile</code>, as a filename
 * extension of '.gz' may be appended. If the journals are successfully
 * merged, the file that they were merged into will be returned. If unable
 * to merge the records (for instance, because the repository has been
 * closed or because the list of journal files was empty), this method will
 * return <code>null</code>.
 * </p>
 *
 * @param journalFiles the journal files to merge
 * @param suggestedMergeFile the file to write the merged records to
 * @param eventReporter the event reporter to report any warnings or errors
 * to; may be null.
 *
 * @return the file that the given journals were merged into, or
 * <code>null</code> if no records were merged.
 *
 * @throws IOException if a problem occurs writing to the mergedFile,
 * reading from a journal, or updating the Lucene Index.
 */
File mergeJournals(final List<File> journalFiles, final File suggestedMergeFile, final EventReporter eventReporter) throws IOException {
    logger.debug("Merging {} to {}", journalFiles, suggestedMergeFile);
    if (this.closed.get()) {
        logger.info("Provenance Repository has been closed; will not merge journal files to {}", suggestedMergeFile);
        return null;
    }
    if (journalFiles.isEmpty()) {
        logger.debug("Couldn't merge journals: Journal Files is empty; won't merge journals");
        return null;
    }
    Collections.sort(journalFiles, new Comparator<File>() {

        @Override
        public int compare(final File o1, final File o2) {
            final String suffix1 = LuceneUtil.substringAfterLast(o1.getName(), ".");
            final String suffix2 = LuceneUtil.substringAfterLast(o2.getName(), ".");
            try {
                final int journalIndex1 = Integer.parseInt(suffix1);
                final int journalIndex2 = Integer.parseInt(suffix2);
                return Integer.compare(journalIndex1, journalIndex2);
            } catch (final NumberFormatException nfe) {
                return o1.getName().compareTo(o2.getName());
            }
        }
    });
    // Search for any missing files. At this point they should have been written to disk otherwise cannot continue.
    // Missing files is most likely due to incomplete cleanup of files post merge
    final List<File> availableFiles = filterUnavailableFiles(journalFiles);
    final int numAvailableFiles = availableFiles.size();
    // check if we have all of the "partial" files for the journal.
    if (numAvailableFiles > 0) {
        if (suggestedMergeFile.exists()) {
            // we have all "partial" files and there is already a merged file. Delete the data from the index
            // because the merge file may not be fully merged. We will re-merge.
            logger.warn("Merged Journal File {} already exists; however, all partial journal files also exist " + "so assuming that the merge did not finish. Repeating procedure in order to ensure consistency.");
            // file and the TOC file. Otherwise, we could get the wrong copy and have issues retrieving events.
            if (!suggestedMergeFile.delete()) {
                logger.error("Failed to delete partially written Provenance Journal File {}. This may result in events from this journal " + "file not being able to be displayed. This file should be deleted manually.", suggestedMergeFile);
            }
            final File tocFile = TocUtil.getTocFile(suggestedMergeFile);
            if (tocFile.exists() && !tocFile.delete()) {
                logger.error("Failed to delete .toc file {}; this may result in not being able to read the Provenance Events from the {} Journal File. " + "This can be corrected by manually deleting the {} file", tocFile, suggestedMergeFile, tocFile);
            }
        }
    } else {
        logger.warn("Cannot merge journal files {} because they do not exist on disk", journalFiles);
        return null;
    }
    final long startNanos = System.nanoTime();
    // Map each journal to a RecordReader
    final List<RecordReader> readers = new ArrayList<>();
    int records = 0;
    final boolean isCompress = configuration.isCompressOnRollover();
    final File writerFile = isCompress ? new File(suggestedMergeFile.getParentFile(), suggestedMergeFile.getName() + ".gz") : suggestedMergeFile;
    try {
        for (final File journalFile : availableFiles) {
            try {
                // Use MAX_VALUE for number of chars because we don't want to truncate the value as we write it
                // out. This allows us to later decide that we want more characters and still be able to retrieve
                // the entire event.
                readers.add(RecordReaders.newRecordReader(journalFile, null, Integer.MAX_VALUE));
            } catch (final EOFException eof) {
            // there's nothing here. Skip over it.
            } catch (final IOException ioe) {
                logger.warn("Unable to merge {} with other Journal Files due to {}", journalFile, ioe.toString());
                if (logger.isDebugEnabled()) {
                    logger.warn("", ioe);
                }
                if (eventReporter != null) {
                    eventReporter.reportEvent(Severity.ERROR, EVENT_CATEGORY, "Failed to merge Journal Files due to " + ioe.toString());
                }
            }
        }
        // Create a Map so that the key is the next record available from a reader and the value is the Reader from which
        // the record came. This sorted map is then used so that we are able to always get the first entry, which is the next
        // lowest record id
        final SortedMap<StandardProvenanceEventRecord, RecordReader> recordToReaderMap = new TreeMap<>(new Comparator<StandardProvenanceEventRecord>() {

            @Override
            public int compare(final StandardProvenanceEventRecord o1, final StandardProvenanceEventRecord o2) {
                return Long.compare(o1.getEventId(), o2.getEventId());
            }
        });
        long minEventId = 0L;
        long earliestTimestamp = System.currentTimeMillis();
        for (final RecordReader reader : readers) {
            StandardProvenanceEventRecord record = null;
            try {
                record = reader.nextRecord();
            } catch (final EOFException eof) {
            // record will be null and reader can no longer be used
            } catch (final Exception e) {
                logger.warn("Failed to generate Provenance Event Record from Journal due to " + e + "; it's " + "possible that the record wasn't completely written to the file. This journal will be " + "skipped.");
                if (logger.isDebugEnabled()) {
                    logger.warn("", e);
                }
                if (eventReporter != null) {
                    eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to read Provenance Event " + "Record from Journal due to " + e + "; it's possible that the record wasn't " + "completely written to the file. This journal will be skipped.");
                }
            }
            if (record == null) {
                continue;
            }
            if (record.getEventTime() < earliestTimestamp) {
                earliestTimestamp = record.getEventTime();
            }
            if (record.getEventId() < minEventId) {
                minEventId = record.getEventId();
            }
            recordToReaderMap.put(record, reader);
        }
        // We want to keep track of the last 1000 events in the files so that we can add them to 'ringBuffer'.
        // However, we don't want to add them directly to ringBuffer, because once they are added to ringBuffer, they are
        // available in query results. As a result, we can have the issue where we've not finished indexing the file
        // but we try to create the lineage for events in that file. In order to avoid this, we will add the records
        // to a temporary RingBuffer and after we finish merging the records will then copy the data to the
        // ringBuffer provided as a method argument.
        final RingBuffer<ProvenanceEventRecord> latestRecords = new RingBuffer<>(1000);
        // with the next entry from the journal file from which the previous record was written.
        try (final RecordWriter writer = RecordWriters.newSchemaRecordWriter(writerFile, idGenerator, configuration.isCompressOnRollover(), true)) {
            writer.writeHeader(minEventId);
            final IndexingAction indexingAction = createIndexingAction();
            final File indexingDirectory = indexConfig.getWritableIndexDirectory(writerFile, earliestTimestamp);
            long maxId = 0L;
            final BlockingQueue<Tuple<StandardProvenanceEventRecord, Integer>> eventQueue = new LinkedBlockingQueue<>(100);
            final AtomicBoolean finishedAdding = new AtomicBoolean(false);
            final List<Future<?>> futures = new ArrayList<>();
            final EventIndexWriter indexWriter = getIndexManager().borrowIndexWriter(indexingDirectory);
            try {
                final ExecutorService exec = Executors.newFixedThreadPool(configuration.getIndexThreadPoolSize(), new ThreadFactory() {

                    @Override
                    public Thread newThread(final Runnable r) {
                        final Thread t = Executors.defaultThreadFactory().newThread(r);
                        t.setName("Index Provenance Events");
                        return t;
                    }
                });
                final AtomicInteger indexingFailureCount = new AtomicInteger(0);
                try {
                    for (int i = 0; i < configuration.getIndexThreadPoolSize(); i++) {
                        final Callable<Object> callable = new Callable<Object>() {

                            @Override
                            public Object call() throws IOException {
                                while (!eventQueue.isEmpty() || !finishedAdding.get()) {
                                    try {
                                        final Tuple<StandardProvenanceEventRecord, Integer> tuple;
                                        try {
                                            tuple = eventQueue.poll(10, TimeUnit.MILLISECONDS);
                                        } catch (final InterruptedException ie) {
                                            Thread.currentThread().interrupt();
                                            continue;
                                        }
                                        if (tuple == null) {
                                            continue;
                                        }
                                        indexingAction.index(tuple.getKey(), indexWriter.getIndexWriter(), tuple.getValue());
                                    } catch (final Throwable t) {
                                        logger.error("Failed to index Provenance Event for " + writerFile + " to " + indexingDirectory, t);
                                        if (indexingFailureCount.incrementAndGet() >= MAX_INDEXING_FAILURE_COUNT) {
                                            return null;
                                        }
                                    }
                                }
                                return null;
                            }
                        };
                        final Future<?> future = exec.submit(callable);
                        futures.add(future);
                    }
                    boolean indexEvents = true;
                    while (!recordToReaderMap.isEmpty()) {
                        final Map.Entry<StandardProvenanceEventRecord, RecordReader> entry = recordToReaderMap.entrySet().iterator().next();
                        final StandardProvenanceEventRecord record = entry.getKey();
                        final RecordReader reader = entry.getValue();
                        writer.writeRecord(record);
                        final int blockIndex = writer.getTocWriter().getCurrentBlockIndex();
                        boolean accepted = false;
                        while (!accepted && indexEvents) {
                            try {
                                accepted = eventQueue.offer(new Tuple<>(record, blockIndex), 10, TimeUnit.MILLISECONDS);
                            } catch (final InterruptedException ie) {
                                Thread.currentThread().interrupt();
                            }
                            // So, if the queue is filled, we will check if this is the case.
                            if (!accepted && indexingFailureCount.get() >= MAX_INDEXING_FAILURE_COUNT) {
                                // don't add anything else to the queue.
                                indexEvents = false;
                                eventQueue.clear();
                                final String warning = String.format("Indexing Provenance Events for %s has failed %s times. This exceeds the maximum threshold of %s failures, " + "so no more Provenance Events will be indexed for this Provenance file.", writerFile, indexingFailureCount.get(), MAX_INDEXING_FAILURE_COUNT);
                                logger.warn(warning);
                                if (eventReporter != null) {
                                    eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, warning);
                                }
                            }
                        }
                        maxId = record.getEventId();
                        latestRecords.add(truncateAttributes(record));
                        records++;
                        // Remove this entry from the map
                        recordToReaderMap.remove(record);
                        // Get the next entry from this reader and add it to the map
                        StandardProvenanceEventRecord nextRecord = null;
                        try {
                            nextRecord = reader.nextRecord();
                        } catch (final EOFException eof) {
                        // record will be null and reader can no longer be used
                        } catch (final Exception e) {
                            logger.warn("Failed to generate Provenance Event Record from Journal due to " + e + "; it's possible that the record wasn't completely written to the file. " + "The remainder of this journal will be skipped.");
                            if (logger.isDebugEnabled()) {
                                logger.warn("", e);
                            }
                            if (eventReporter != null) {
                                eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to read " + "Provenance Event Record from Journal due to " + e + "; it's possible " + "that the record wasn't completely written to the file. The remainder " + "of this journal will be skipped.");
                            }
                        }
                        if (nextRecord != null) {
                            recordToReaderMap.put(nextRecord, reader);
                        }
                    }
                } finally {
                    finishedAdding.set(true);
                    exec.shutdown();
                }
                for (final Future<?> future : futures) {
                    try {
                        future.get();
                    } catch (final ExecutionException ee) {
                        final Throwable t = ee.getCause();
                        if (t instanceof RuntimeException) {
                            throw (RuntimeException) t;
                        }
                        throw new RuntimeException(t);
                    } catch (final InterruptedException e) {
                        Thread.currentThread().interrupt();
                        throw new RuntimeException("Thread interrupted");
                    }
                }
            } finally {
                getIndexManager().returnIndexWriter(indexWriter);
            }
            indexConfig.setMaxIdIndexed(maxId);
        }
        // record should now be available in the repository. We can copy the values from latestRecords to ringBuffer.
        final RingBuffer<ProvenanceEventRecord> latestRecordBuffer = this.latestRecords;
        latestRecords.forEach(new ForEachEvaluator<ProvenanceEventRecord>() {

            @Override
            public boolean evaluate(final ProvenanceEventRecord event) {
                latestRecordBuffer.add(event);
                return true;
            }
        });
    } finally {
        for (final RecordReader reader : readers) {
            try {
                reader.close();
            } catch (final IOException ioe) {
            }
        }
    }
    // Success. Remove all of the journal files, as they're no longer needed, now that they've been merged.
    for (final File journalFile : availableFiles) {
        if (!journalFile.delete() && journalFile.exists()) {
            logger.warn("Failed to remove temporary journal file {}; this file should be cleaned up manually", journalFile.getAbsolutePath());
            if (eventReporter != null) {
                eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to remove temporary journal file " + journalFile.getAbsolutePath() + "; this file should be cleaned up manually");
            }
        }
        final File tocFile = TocUtil.getTocFile(journalFile);
        if (!tocFile.delete() && tocFile.exists()) {
            logger.warn("Failed to remove temporary journal TOC file {}; this file should be cleaned up manually", tocFile.getAbsolutePath());
            if (eventReporter != null) {
                eventReporter.reportEvent(Severity.WARNING, EVENT_CATEGORY, "Failed to remove temporary journal TOC file " + tocFile.getAbsolutePath() + "; this file should be cleaned up manually");
            }
        }
    }
    if (records == 0) {
        writerFile.delete();
        logger.debug("Couldn't merge journals: No Records to merge");
        return null;
    } else {
        final long nanos = System.nanoTime() - startNanos;
        final long millis = TimeUnit.MILLISECONDS.convert(nanos, TimeUnit.NANOSECONDS);
        logger.info("Successfully merged {} journal files ({} records) into single Provenance Log File {} in {} milliseconds", numAvailableFiles, records, suggestedMergeFile, millis);
    }
    return writerFile;
}