Buffer file implementation (#1607)

* Buffer stream.

* Buffer file reader.

apm-commons/apm-util/src/main/java/org/apache/skywalking/apm/util/StringUtil.java

@@ -16,7 +16,6 @@
  *
  */
 
-
 package org.apache.skywalking.apm.util;
 
 public final class StringUtil {

oap-server/pom.xml

@@ -56,6 +56,7 @@
         <h2.version>1.4.196</h2.version>
         <shardingjdbc.version>2.0.3</shardingjdbc.version>
         <commons-dbcp.version>1.4</commons-dbcp.version>
+        <commons-io.version>2.6</commons-io.version>
         <elasticsearch.version>6.3.2</elasticsearch.version>
         <joda-time.version>2.9.9</joda-time.version>
         <kubernetes.version>2.0.0</kubernetes.version>
@@ -250,6 +251,11 @@
                 <artifactId>commons-dbcp</artifactId>
                 <version>${commons-dbcp.version}</version>
             </dependency>
+            <dependency>
+                <groupId>commons-io</groupId>
+                <artifactId>commons-io</artifactId>
+                <version>${commons-io.version}</version>
+            </dependency>
             <dependency>
                 <groupId>io.kubernetes</groupId>
                 <artifactId>client-java</artifactId>

oap-server/server-library/library-buffer/pom.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ 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.
+  ~
+  -->
+
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>server-library</artifactId>
+        <groupId>org.apache.skywalking</groupId>
+        <version>6.0.0-alpha-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>library-buffer</artifactId>
+    <packaging>jar</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.skywalking</groupId>
+            <artifactId>apm-network</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+    </dependencies>
+</project>

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/BufferFileUtils.java

@@ -0,0 +1,52 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import java.text.*;
+import java.util.*;
+
+/**
+ * @author peng-yongsheng
+ */
+class BufferFileUtils {
+
+    private BufferFileUtils() {
+    }
+
+    static final String CHARSET = "UTF-8";
+    static final String DATA_FILE_PREFIX = "data";
+    static final String OFFSET_FILE_PREFIX = "offset";
+    private static final String SEPARATOR = "-";
+    private static final String SUFFIX = ".sw";
+    private static final String DATA_FORMAT_STR = "yyyyMMddHHmmss";
+
+    static void sort(String[] fileList) {
+        Arrays.sort(fileList, (f1, f2) -> {
+            int fileId1 = Integer.parseInt(f1.split("_")[1]);
+            int fileId2 = Integer.parseInt(f2.split("_")[1]);
+
+            return fileId1 - fileId2;
+        });
+    }
+
+    static String buildFileName(String prefix) {
+        DateFormat dateFormat = new SimpleDateFormat(DATA_FORMAT_STR);
+        return prefix + SEPARATOR + dateFormat.format(new Date()) + SUFFIX;
+    }
+}

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/BufferStream.java

@@ -0,0 +1,129 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import com.google.protobuf.*;
+import java.io.*;
+import java.nio.channels.FileLock;
+import org.apache.commons.io.FileUtils;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+public class BufferStream<MESSAGE_TYPE extends GeneratedMessageV3> {
+
+    private static final Logger logger = LoggerFactory.getLogger(BufferStream.class);
+
+    private final String absolutePath;
+    private final boolean cleanWhenRestart;
+    private final int dataFileMaxSize;
+    private final int offsetFileMaxSize;
+    private final Parser<MESSAGE_TYPE> parser;
+    private final DataStreamReader.CallBack<MESSAGE_TYPE> callBack;
+    private DataStream<MESSAGE_TYPE> dataStream;
+
+    private BufferStream(String absolutePath, boolean cleanWhenRestart, int dataFileMaxSize, int offsetFileMaxSize,
+        Parser<MESSAGE_TYPE> parser, DataStreamReader.CallBack<MESSAGE_TYPE> callBack) {
+        this.absolutePath = absolutePath;
+        this.cleanWhenRestart = cleanWhenRestart;
+        this.dataFileMaxSize = dataFileMaxSize;
+        this.offsetFileMaxSize = offsetFileMaxSize;
+        this.parser = parser;
+        this.callBack = callBack;
+    }
+
+    public synchronized void initialize() throws IOException {
+        File directory = new File(absolutePath);
+        FileUtils.forceMkdir(directory);
+        tryLock(directory);
+
+        dataStream = new DataStream<>(directory, dataFileMaxSize, offsetFileMaxSize, parser, callBack);
+
+        if (cleanWhenRestart) {
+            dataStream.clean();
+        }
+
+        dataStream.initialize();
+    }
+
+    public synchronized void write(AbstractMessageLite messageLite) {
+        dataStream.getWriter().write(messageLite);
+    }
+
+    private void tryLock(File directory) {
+        logger.info("Try to lock buffer directory, directory is: " + absolutePath);
+        FileLock lock = null;
+
+        try {
+            lock = new FileOutputStream(new File(directory, "lock")).getChannel().tryLock();
+        } catch (IOException e) {
+            logger.error(e.getMessage(), e);
+        }
+
+        if (lock == null) {
+            throw new RuntimeException("The buffer directory is reading or writing by another thread, directory is: " + absolutePath);
+        }
+
+        logger.info("Lock buffer directory successfully, directory is: " + absolutePath);
+    }
+
+    public static class Builder<MESSAGE_TYPE extends GeneratedMessageV3> {
+
+        private final String absolutePath;
+        private boolean cleanWhenRestart;
+        private int dataFileMaxSize;
+        private int offsetFileMaxSize;
+        private Parser<MESSAGE_TYPE> parser;
+        private DataStreamReader.CallBack<MESSAGE_TYPE> callBack;
+
+        public Builder(String absolutePath) {
+            this.absolutePath = absolutePath;
+        }
+
+        public BufferStream<MESSAGE_TYPE> build() {
+            return new BufferStream<>(absolutePath, cleanWhenRestart, dataFileMaxSize, offsetFileMaxSize, parser, callBack);
+        }
+
+        public Builder<MESSAGE_TYPE> cleanWhenRestart(boolean cleanWhenRestart) {
+            this.cleanWhenRestart = cleanWhenRestart;
+            return this;
+        }
+
+        public Builder<MESSAGE_TYPE> offsetFileMaxSize(int offsetFileMaxSize) {
+            this.offsetFileMaxSize = offsetFileMaxSize;
+            return this;
+        }
+
+        public Builder<MESSAGE_TYPE> dataFileMaxSize(int dataFileMaxSize) {
+            this.dataFileMaxSize = dataFileMaxSize;
+            return this;
+        }
+
+        public Builder<MESSAGE_TYPE> parser(Parser<MESSAGE_TYPE> parser) {
+            this.parser = parser;
+            return this;
+        }
+
+        public Builder<MESSAGE_TYPE> callBack(DataStreamReader.CallBack<MESSAGE_TYPE> callBack) {
+            this.callBack = callBack;
+            return this;
+        }
+    }
+}

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/DataStream.java

@@ -0,0 +1,72 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import com.google.protobuf.*;
+import java.io.*;
+import lombok.Getter;
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.filefilter.PrefixFileFilter;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+class DataStream<MESSAGE_TYPE extends GeneratedMessageV3> {
+
+    private static final Logger logger = LoggerFactory.getLogger(DataStream.class);
+
+    private final File directory;
+    private final OffsetStream offsetStream;
+    @Getter private final DataStreamReader<MESSAGE_TYPE> reader;
+    @Getter private final DataStreamWriter<MESSAGE_TYPE> writer;
+    private boolean initialized = false;
+
+    DataStream(File directory, int offsetFileMaxSize, int dataFileMaxSize, Parser<MESSAGE_TYPE> parser,
+        DataStreamReader.CallBack<MESSAGE_TYPE> callBack) {
+        this.directory = directory;
+        this.offsetStream = new OffsetStream(directory, offsetFileMaxSize);
+        this.writer = new DataStreamWriter<>(directory, offsetStream.getOffset().getWriteOffset(), dataFileMaxSize);
+        this.reader = new DataStreamReader<>(directory, offsetStream.getOffset().getReadOffset(), parser, callBack);
+    }
+
+    void clean() throws IOException {
+        String[] fileNames = directory.list(new PrefixFileFilter(BufferFileUtils.DATA_FILE_PREFIX));
+        if (fileNames != null) {
+            for (String fileName : fileNames) {
+                File file = new File(directory, fileName);
+                if (logger.isDebugEnabled()) {
+                    logger.debug("Delete buffer data file: {}", file.getAbsolutePath());
+                }
+                FileUtils.forceDelete(file);
+            }
+        }
+
+        offsetStream.clean();
+    }
+
+    synchronized void initialize() throws IOException {
+        if (!initialized) {
+            offsetStream.initialize();
+            writer.initialize();
+            reader.initialize();
+            initialized = true;
+        }
+    }
+}

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/DataStreamReader.java

@@ -0,0 +1,110 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import com.google.protobuf.*;
+import java.io.*;
+import java.util.concurrent.*;
+import org.apache.commons.io.filefilter.PrefixFileFilter;
+import org.apache.skywalking.apm.util.*;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+class DataStreamReader<MESSAGE_TYPE extends GeneratedMessageV3> {
+
+    private static final Logger logger = LoggerFactory.getLogger(DataStreamReader.class);
+
+    private final File directory;
+    private final Offset.ReadOffset readOffset;
+    private final Parser<MESSAGE_TYPE> parser;
+    private final CallBack<MESSAGE_TYPE> callBack;
+    private InputStream inputStream;
+
+    DataStreamReader(File directory, Offset.ReadOffset readOffset, Parser<MESSAGE_TYPE> parser,
+        CallBack<MESSAGE_TYPE> callBack) {
+        this.directory = directory;
+        this.readOffset = readOffset;
+        this.parser = parser;
+        this.callBack = callBack;
+    }
+
+    void initialize() {
+        preRead();
+
+        Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate(
+            new RunnableWithExceptionProtection(this::read,
+                t -> logger.error("Segment buffer pre read failure.", t)), 3, 3, TimeUnit.SECONDS);
+    }
+
+    private void preRead() {
+        String fileName = readOffset.getFileName();
+        if (StringUtil.isEmpty(fileName)) {
+            openInputStream(readEarliestCreateDataFile());
+        } else {
+            File dataFile = new File(directory, fileName);
+            if (dataFile.exists()) {
+                openInputStream(dataFile);
+                read();
+            } else {
+                openInputStream(readEarliestCreateDataFile());
+            }
+        }
+    }
+
+    private void openInputStream(File readFile) {
+        try {
+            inputStream = new FileInputStream(readFile);
+        } catch (FileNotFoundException e) {
+            logger.error(e.getMessage(), e);
+        }
+    }
+
+    private File readEarliestCreateDataFile() {
+        String[] fileNames = directory.list(new PrefixFileFilter(BufferFileUtils.DATA_FILE_PREFIX));
+
+        if (fileNames != null && fileNames.length > 0) {
+            BufferFileUtils.sort(fileNames);
+            readOffset.setFileName(fileNames[0]);
+            readOffset.setOffset(0);
+            return new File(directory, fileNames[0]);
+        } else {
+            return null;
+        }
+    }
+
+    private void read() {
+        try {
+            MESSAGE_TYPE messageType = parser.parseDelimitedFrom(inputStream);
+            if (messageType != null) {
+                callBack.call(messageType);
+                final int serialized = messageType.getSerializedSize();
+                final int offset = CodedOutputStream.computeUInt32SizeNoTag(serialized) + serialized;
+                readOffset.setOffset(readOffset.getOffset() + offset);
+            }
+        } catch (IOException e) {
+            logger.error(e.getMessage(), e);
+        }
+    }
+
+    interface CallBack<MESSAGE_TYPE extends GeneratedMessageV3> {
+        void call(MESSAGE_TYPE message);
+    }
+}

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/DataStreamWriter.java

@@ -0,0 +1,97 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import com.google.protobuf.*;
+import java.io.*;
+import org.apache.commons.io.FileUtils;
+import org.apache.skywalking.apm.util.StringUtil;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+class DataStreamWriter<MESSAGE_TYPE extends GeneratedMessageV3> {
+
+    private static final Logger logger = LoggerFactory.getLogger(DataStreamWriter.class);
+
+    private final File directory;
+    private final Offset.WriteOffset writeOffset;
+
+    private final int dataFileMaxSize;
+
+    private boolean initialized = false;
+    private FileOutputStream outputStream;
+
+    DataStreamWriter(File directory, Offset.WriteOffset writeOffset, int dataFileMaxSize) {
+        this.directory = directory;
+        this.dataFileMaxSize = dataFileMaxSize;
+        this.writeOffset = writeOffset;
+    }
+
+    synchronized void initialize() throws IOException {
+        if (!initialized) {
+            String writeFileName = writeOffset.getFileName();
+
+            File dataFile;
+            if (StringUtil.isEmpty(writeFileName)) {
+                dataFile = createNewFile();
+            } else {
+                dataFile = new File(directory, writeFileName);
+                if (!dataFile.exists()) {
+                    dataFile = createNewFile();
+                }
+            }
+
+            outputStream = FileUtils.openOutputStream(dataFile, true);
+            initialized = true;
+        }
+    }
+
+    private File createNewFile() throws IOException {
+        String fileName = BufferFileUtils.buildFileName(BufferFileUtils.DATA_FILE_PREFIX);
+        File dataFile = new File(directory, fileName);
+
+        boolean created = dataFile.createNewFile();
+        if (!created) {
+            logger.info("The file named {} already exists.", dataFile.getAbsolutePath());
+        } else {
+            logger.info("Create a new buffer data file: {}", dataFile.getAbsolutePath());
+        }
+
+        writeOffset.setOffset(0);
+        writeOffset.setFileName(dataFile.getName());
+
+        return dataFile;
+    }
+
+    void write(AbstractMessageLite messageLite) {
+        try {
+            messageLite.writeDelimitedTo(outputStream);
+            long position = outputStream.getChannel().position();
+            writeOffset.setOffset(position);
+            if (position > (FileUtils.ONE_MB * dataFileMaxSize)) {
+                File dataFile = createNewFile();
+                outputStream = FileUtils.openOutputStream(dataFile, true);
+            }
+        } catch (IOException e) {
+            logger.error(e.getMessage(), e);
+        }
+    }
+}

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/Offset.java

@@ -0,0 +1,64 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import lombok.*;
+import org.apache.skywalking.apm.util.StringUtil;
+
+/**
+ * @author peng-yongsheng
+ */
+class Offset {
+
+    private static final String SPLIT_CHARACTER = ",";
+    @Getter private final ReadOffset readOffset;
+    @Getter private final WriteOffset writeOffset;
+
+    Offset() {
+        readOffset = new ReadOffset();
+        writeOffset = new WriteOffset();
+    }
+
+    String serialize() {
+        return readOffset.getFileName() + SPLIT_CHARACTER + String.valueOf(readOffset.getOffset())
+            + SPLIT_CHARACTER + writeOffset.getFileName() + SPLIT_CHARACTER + String.valueOf(writeOffset.getOffset());
+    }
+
+    void deserialize(String value) {
+        if (!StringUtil.isEmpty(value)) {
+            String[] values = value.split(SPLIT_CHARACTER);
+            if (values.length == 4) {
+                readOffset.setFileName(values[0]);
+                readOffset.setOffset(Long.parseLong(values[1]));
+                writeOffset.setFileName(values[2]);
+                writeOffset.setOffset(Long.parseLong(values[3]));
+            }
+        }
+    }
+
+    static class ReadOffset {
+        @Getter @Setter private String fileName;
+        @Getter @Setter private long offset = 0;
+    }
+
+    static class WriteOffset {
+        @Getter @Setter private String fileName;
+        @Getter @Setter private long offset = 0;
+    }
+}

oap-server/server-library/library-buffer/src/main/java/org/apache/skywalking/oap/server/library/buffer/OffsetStream.java

@@ -0,0 +1,126 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import java.io.*;
+import java.nio.charset.Charset;
+import java.util.concurrent.*;
+import lombok.Getter;
+import org.apache.commons.io.*;
+import org.apache.commons.io.filefilter.PrefixFileFilter;
+import org.apache.commons.io.input.ReversedLinesFileReader;
+import org.apache.skywalking.apm.util.RunnableWithExceptionProtection;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+class OffsetStream {
+
+    private static final Logger logger = LoggerFactory.getLogger(OffsetStream.class);
+
+    private final File directory;
+    private final int offsetFileMaxSize;
+
+    @Getter private final Offset offset;
+    private File offsetFile;
+    private boolean initialized = false;
+    private String lastOffsetRecord = "";
+
+    OffsetStream(File directory, int offsetFileMaxSize) {
+        this.directory = directory;
+        this.offsetFileMaxSize = offsetFileMaxSize;
+        this.offset = new Offset();
+    }
+
+    void clean() throws IOException {
+        String[] fileNames = directory.list(new PrefixFileFilter(BufferFileUtils.OFFSET_FILE_PREFIX));
+        if (fileNames != null) {
+            for (String fileName : fileNames) {
+                File file = new File(directory, fileName);
+                if (logger.isDebugEnabled()) {
+                    logger.debug("Delete buffer offset file: {}", file.getAbsolutePath());
+                }
+                FileUtils.forceDelete(new File(directory, fileName));
+            }
+        }
+    }
+
+    synchronized void initialize() throws IOException {
+        if (!initialized) {
+            String[] fileNames = directory.list(new PrefixFileFilter(BufferFileUtils.OFFSET_FILE_PREFIX));
+            if (fileNames != null && fileNames.length > 0) {
+                for (int i = 0; i < fileNames.length; i++) {
+                }
+            } else {
+                offsetFile = newFile();
+            }
+            offset.deserialize(readLastLine());
+            initialized = true;
+
+            Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate(
+                new RunnableWithExceptionProtection(this::flush,
+                    t -> logger.error("Flush offset file in background failure.", t)
+                ), 2, 1, TimeUnit.SECONDS);
+        }
+    }
+
+    void flush() {
+        try {
+            String offsetRecord = offset.serialize();
+            logger.debug("flush offset, record: {}", offsetRecord);
+            if (!lastOffsetRecord.equals(offsetRecord)) {
+                if (offsetFile.length() >= FileUtils.ONE_MB * offsetFileMaxSize) {
+                    nextFile();
+                }
+
+                try (OutputStream out = new BufferedOutputStream(FileUtils.openOutputStream(offsetFile, true))) {
+                    IOUtils.write(offsetRecord, out, Charset.forName(BufferFileUtils.CHARSET));
+                    IOUtils.write(System.lineSeparator(), out, Charset.forName(BufferFileUtils.CHARSET));
+                }
+                lastOffsetRecord = offsetRecord;
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e.getMessage(), e);
+        }
+    }
+
+    private void nextFile() throws IOException {
+        File newOffsetFile = newFile();
+        if (!offsetFile.delete()) {
+            logger.warn("Offset file {} delete failure.", newOffsetFile.getAbsolutePath());
+        }
+        offsetFile = newOffsetFile;
+        this.flush();
+    }
+
+    private File newFile() throws IOException {
+        String fileName = BufferFileUtils.buildFileName(BufferFileUtils.OFFSET_FILE_PREFIX);
+        File file = new File(directory, fileName);
+        if (file.createNewFile()) {
+            logger.info("Create a new offset file {}", fileName);
+        }
+        return file;
+    }
+
+    private String readLastLine() throws IOException {
+        ReversedLinesFileReader reader = new ReversedLinesFileReader(offsetFile, Charset.forName(BufferFileUtils.CHARSET));
+        return reader.readLine();
+    }
+}

oap-server/server-library/library-buffer/src/test/java/org/apache/skywalking/oap/server/library/buffer/BufferStreamTestCase.java

@@ -0,0 +1,69 @@
+/*
+ * 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.skywalking.oap.server.library.buffer;
+
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+import org.apache.skywalking.apm.network.language.agent.*;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+public class BufferStreamTestCase {
+
+    private static final Logger logger = LoggerFactory.getLogger(BufferStreamTestCase.class);
+
+    public static void main(String[] args) throws IOException, InterruptedException {
+        String directory = "/Users/pengys5/code/sky-walking/buffer-test";
+        BufferStream.Builder<TraceSegmentObject> builder = new BufferStream.Builder<>(directory);
+        builder.cleanWhenRestart(true);
+        builder.dataFileMaxSize(1);
+        builder.offsetFileMaxSize(1);
+        builder.parser(TraceSegmentObject.parser());
+        builder.callBack(new SegmentParse());
+
+        BufferStream<TraceSegmentObject> stream = builder.build();
+        stream.initialize();
+
+        TimeUnit.SECONDS.sleep(5);
+
+        String str = "2018-08-27 11:59:45,261 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28" +
+            "main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28" +
+            "main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28" +
+            "main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28 main DEBUG Registering MBean org.apache.logging.log4j2:type=6d6f6e28";
+
+        for (int i = 0; i < 100; i++) {
+            TraceSegmentObject.Builder segment = TraceSegmentObject.newBuilder();
+            SpanObject.Builder span = SpanObject.newBuilder();
+
+            span.setOperationName(String.valueOf(i) + "  " + str);
+            segment.addSpans(span);
+            stream.write(segment.build());
+        }
+
+    }
+
+    private static class SegmentParse implements DataStreamReader.CallBack<TraceSegmentObject> {
+
+        @Override public void call(TraceSegmentObject message) {
+            logger.info("segment parse: {}", message.getSpans(0).getOperationName());
+        }
+    }
+}

oap-server/server-library/library-buffer/src/test/resources/log4j2.xml

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ 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.
+  ~
+  -->
+
+<Configuration status="DEBUG">
+    <Appenders>
+        <Console name="Console" target="SYSTEM_OUT">
+            <PatternLayout charset="UTF-8" pattern="%d - %c -%-4r [%t] %-5p %x - %m%n"/>
+        </Console>
+    </Appenders>
+    <Loggers>
+        <Root level="DEBUG">
+            <AppenderRef ref="Console"/>
+        </Root>
+    </Loggers>
+</Configuration>

oap-server/server-library/library-util/src/main/java/org/apache/skywalking/oap/server/library/util/FileUtils.java

@@ -0,0 +1,84 @@
+/*
+ * 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.skywalking.oap.server.library.util;
+
+import java.io.*;
+import org.slf4j.*;
+
+/**
+ * @author peng-yongsheng
+ */
+public enum FileUtils {
+    INSTANCE;
+
+    private static final Logger logger = LoggerFactory.getLogger(FileUtils.class);
+
+    public String readLastLine(File file) {
+        RandomAccessFile randomAccessFile = null;
+        try {
+            randomAccessFile = new RandomAccessFile(file, "r");
+            long length = randomAccessFile.length();
+            if (length == 0) {
+                return "";
+            } else {
+                long position = length - 1;
+                randomAccessFile.seek(position);
+                while (position >= 0) {
+                    if (randomAccessFile.read() == '\n') {
+                        return randomAccessFile.readLine();
+                    }
+                    randomAccessFile.seek(position);
+                    if (position == 0) {
+                        return randomAccessFile.readLine();
+                    }
+                    position--;
+                }
+            }
+        } catch (IOException e) {
+            logger.error(e.getMessage(), e);
+        } finally {
+            if (randomAccessFile != null) {
+                try {
+                    randomAccessFile.close();
+                } catch (IOException e) {
+                    logger.error(e.getMessage(), e);
+                }
+            }
+        }
+        return "";
+    }
+
+    public void writeAppendToLast(File file, RandomAccessFile randomAccessFile, String value) {
+        if (randomAccessFile == null) {
+            try {
+                randomAccessFile = new RandomAccessFile(file, "rwd");
+            } catch (FileNotFoundException e) {
+                logger.error(e.getMessage(), e);
+            }
+        }
+        try {
+            long length = randomAccessFile.length();
+            randomAccessFile.seek(length);
+            randomAccessFile.writeBytes(System.lineSeparator());
+            randomAccessFile.writeBytes(value);
+        } catch (IOException e) {
+            logger.error(e.getMessage(), e);
+        }
+    }
+}

oap-server/server-library/pom.xml

@@ -34,5 +34,13 @@
         <module>library-server</module>
         <module>library-util</module>
         <module>library-client</module>
+        <module>library-buffer</module>
     </modules>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.skywalking</groupId>
+            <artifactId>apm-util</artifactId>
+        </dependency>
+    </dependencies>
 </project>

oap-server/server-starter/pom.xml

@@ -75,6 +75,11 @@
             <artifactId>skywalking-jvm-receiver-plugin</artifactId>
             <version>${project.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.skywalking</groupId>
+            <artifactId>skywalking-trace-receiver-plugin</artifactId>
+            <version>${project.version}</version>
+        </dependency>
         <!-- receiver module -->
 
         <!-- storage module -->