Examples with MessageSet kafka.message.MessageSet used on opensource projects

Example 1 with MessageSet

use of kafka.message.MessageSet in project graylog2-server by Graylog2.

the class KafkaJournal method read.

public List<JournalReadEntry> read(long readOffset, long requestedMaximumCount) {
    // Always read at least one!
    final long maximumCount = Math.max(1, requestedMaximumCount);
    long maxOffset = readOffset + maximumCount;
    if (shuttingDown) {
        return Collections.emptyList();
    }
    final List<JournalReadEntry> messages = new ArrayList<>(Ints.saturatedCast(maximumCount));
    try (Timer.Context ignored = readTime.time()) {
        final long logStartOffset = getLogStartOffset();
        if (readOffset < logStartOffset) {
            LOG.info("Read offset {} before start of log at {}, starting to read from the beginning of the journal.", readOffset, logStartOffset);
            readOffset = logStartOffset;
            maxOffset = readOffset + maximumCount;
        }
        LOG.debug("Requesting to read a maximum of {} messages (or 5MB) from the journal, offset interval [{}, {})", maximumCount, readOffset, maxOffset);
        // TODO benchmark and make read-ahead strategy configurable for performance tuning
        final MessageSet messageSet = kafkaLog.read(readOffset, 5 * 1024 * 1024, Option.<Object>apply(maxOffset)).messageSet();
        final Iterator<MessageAndOffset> iterator = messageSet.iterator();
        long firstOffset = Long.MIN_VALUE;
        long lastOffset = Long.MIN_VALUE;
        long totalBytes = 0;
        while (iterator.hasNext()) {
            final MessageAndOffset messageAndOffset = iterator.next();
            if (firstOffset == Long.MIN_VALUE)
                firstOffset = messageAndOffset.offset();
            // always remember the last seen offset for debug purposes below
            lastOffset = messageAndOffset.offset();
            final byte[] payloadBytes = ByteBufferUtils.readBytes(messageAndOffset.message().payload());
            if (LOG.isTraceEnabled()) {
                final byte[] keyBytes = ByteBufferUtils.readBytes(messageAndOffset.message().key());
                LOG.trace("Read message {} contains {}", bytesToHex(keyBytes), bytesToHex(payloadBytes));
            }
            totalBytes += payloadBytes.length;
            messages.add(new JournalReadEntry(payloadBytes, messageAndOffset.offset()));
            // remember where to read from
            nextReadOffset = messageAndOffset.nextOffset();
        }
        if (messages.isEmpty()) {
            LOG.debug("No messages available to read for offset interval [{}, {}).", readOffset, maxOffset);
        } else {
            LOG.debug("Read {} messages, total payload size {}, from journal, offset interval [{}, {}], requested read at {}", messages.size(), totalBytes, firstOffset, lastOffset, readOffset);
        }
    } catch (OffsetOutOfRangeException e) {
        // This is fine, the reader tries to read faster than the writer committed data. Next read will get the data.
        LOG.debug("Offset out of range, no messages available starting at offset {}", readOffset);
    } catch (Exception e) {
        // sigh.
        if (shuttingDown) {
            LOG.debug("Caught exception during shutdown, ignoring it because we might have been blocked on a read.");
            return Collections.emptyList();
        }
        //noinspection ConstantConditions
        if (e instanceof ClosedByInterruptException) {
            LOG.debug("Interrupted while reading from journal, during shutdown this is harmless and ignored.", e);
        } else {
            throw e;
        }
    }
    readMessages.mark(messages.size());
    return messages;
}