co.cask.cdap.logging.gateway.handlers.AbstractChunkedCallback.java Source code

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Here is the source code for co.cask.cdap.logging.gateway.handlers.AbstractChunkedCallback.java

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/*
 * Copyright  2016 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.logging.gateway.handlers;

import co.cask.cdap.logging.read.Callback;
import co.cask.cdap.logging.read.LogEvent;
import co.cask.http.ChunkResponder;
import co.cask.http.HttpResponder;
import com.google.common.collect.Multimap;
import com.google.common.io.Closeables;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.handler.codec.http.HttpResponseStatus;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * LogReader Callback class that uses {@link ChunkResponder} to send logs back in chunks.
 */
public abstract class AbstractChunkedCallback implements Callback {
    private static final Logger LOG = LoggerFactory.getLogger(AbstractChunkedCallback.class);

    private final AtomicBoolean initialized = new AtomicBoolean();
    private final AtomicBoolean closed = new AtomicBoolean();
    private final HttpResponder responder;
    private final ByteBuffer chunkBuffer = ByteBuffer.allocate(8 * 1024);
    private final CharsetEncoder charsetEncoder = Charset.forName("UTF-8").newEncoder();
    private final AtomicInteger count = new AtomicInteger();
    private ChunkResponder chunkResponder;

    AbstractChunkedCallback(HttpResponder responder) {
        this.responder = responder;
    }

    @Override
    public void init() {
        // if initialized already, then return
        if (!initialized.compareAndSet(false, true)) {
            return;
        }
        chunkResponder = responder.sendChunkStart(HttpResponseStatus.OK, getResponseHeaders());
    }

    @Override
    public int getCount() {
        return count.get();
    }

    /**
     * Return {@link Multimap} of HTTP response headers
     */
    protected abstract Multimap<String, String> getResponseHeaders();

    /**
     * Handle each {@link LogEvent}
     */
    protected abstract void handleEvent(LogEvent event);

    protected void writeFinal() throws IOException {
        encodeSend(CharBuffer.allocate(0), true);
    }

    @Override
    public final void handle(LogEvent event) {
        handleEvent(event);
        count.incrementAndGet();
    }

    @Override
    public void close() {
        // If closed already, then return
        if (!closed.compareAndSet(false, true)) {
            return;
        }

        try {
            // Write the last chunk
            writeFinal();
            // Flush the encoder
            CoderResult coderResult;
            do {
                coderResult = charsetEncoder.flush(chunkBuffer);
                chunkBuffer.flip();
                chunkResponder.sendChunk(ChannelBuffers.copiedBuffer(chunkBuffer));
                chunkBuffer.clear();
            } while (coderResult.isOverflow());
        } catch (IOException e) {
            // If cannot send chunks, nothing can be done (since the client closed connection).
            // Just log the error as debug.
            LOG.debug("Failed to send chunk", e);
        } finally {
            Closeables.closeQuietly(chunkResponder);
        }
    }

    protected void encodeSend(CharBuffer inBuffer, boolean endOfInput) throws IOException {
        while (true) {
            CoderResult coderResult = charsetEncoder.encode(inBuffer, chunkBuffer, endOfInput);
            if (coderResult.isOverflow()) {
                // if reached buffer capacity then flush chunk
                chunkBuffer.flip();
                chunkResponder.sendChunk(ChannelBuffers.copiedBuffer(chunkBuffer));
                chunkBuffer.clear();
            } else if (coderResult.isError()) {
                // skip characters causing error, and retry
                inBuffer.position(inBuffer.position() + coderResult.length());
            } else {
                // log line was completely written
                break;
            }
        }
    }
}