聊聊rocketmq的FileAppender

序

本文主要研究一下rocketmq的FileAppender

WriterAppender

org/apache/rocketmq/logging/inner/LoggingBuilder.java

   public static class WriterAppender extends Appender {        protected boolean immediateFlush = true;        protected String encoding;        protected QuietWriter qw;        public WriterAppender() {

        }        public void setImmediateFlush(boolean value) {
            immediateFlush = value;
        }        public boolean getImmediateFlush() {            return immediateFlush;
        }        public void activateOptions() {
        }        public void append(LoggingEvent event) {            if (!checkEntryConditions()) {                return;
            }
            subAppend(event);
        }        protected boolean checkEntryConditions() {            if (this.closed) {
                SysLogger.warn("Not allowed to write to a closed appender.");                return false;
            }            if (this.qw == null) {
                handleError("No output stream or file set for the appender named [" +
                    name + "].");                return false;
            }            if (this.layout == null) {
                handleError("No layout set for the appender named [" + name + "].");                return false;
            }            return true;
        }        public synchronized void close() {            if (this.closed) {                return;
            }            this.closed = true;
            writeFooter();
            reset();
        }        protected void closeWriter() {            if (qw != null) {                try {
                    qw.close();
                } catch (IOException e) {
                    handleError("Could not close " + qw, e, CODE_CLOSE_FAILURE);
                }
            }
        }        protected OutputStreamWriter createWriter(OutputStream os) {
            OutputStreamWriter retval = null;

            String enc = getEncoding();            if (enc != null) {                try {
                    retval = new OutputStreamWriter(os, enc);
                } catch (IOException e) {
                    SysLogger.warn("Error initializing output writer.");
                    SysLogger.warn("Unsupported encoding?");
                }
            }            if (retval == null) {
                retval = new OutputStreamWriter(os);
            }            return retval;
        }        public String getEncoding() {            return encoding;
        }        public void setEncoding(String value) {
            encoding = value;
        }        public synchronized void setWriter(Writer writer) {
            reset();            this.qw = new QuietWriter(writer, this);
            writeHeader();
        }        protected void subAppend(LoggingEvent event) {            this.qw.write(this.layout.format(event));            if (layout.ignoresThrowable()) {
                String[] s = event.getThrowableStr();                if (s != null) {                    for (String s1 : s) {                        this.qw.write(s1);                        this.qw.write(LINE_SEP);
                    }
                }
            }            if (shouldFlush(event)) {                this.qw.flush();
            }
        }        protected void reset() {
            closeWriter();            this.qw = null;
        }        protected void writeFooter() {            if (layout != null) {
                String f = layout.getFooter();                if (f != null && this.qw != null) {                    this.qw.write(f);                    this.qw.flush();
                }
            }
        }        protected void writeHeader() {            if (layout != null) {
                String h = layout.getHeader();                if (h != null && this.qw != null) {                    this.qw.write(h);
                }
            }
        }        protected boolean shouldFlush(final LoggingEvent event) {            return event != null && immediateFlush;
        }
    }

• 这个接口定义了writeHeader、writeFooter、append等方法

• append方法这里参数是LoggingEvent，内部委托给subAppend

• subAppend方法调用layout进行格式化event，然后如果需要flush，则会直接对qw进行flush

FileAppender

org/apache/rocketmq/logging/inner/LoggingBuilder.java

  public static class FileAppender extends WriterAppender {        protected boolean fileAppend = true;        protected String fileName = null;        protected boolean bufferedIO = false;        protected int bufferSize = 8 * 1024;        public FileAppender() {
        }        public FileAppender(Layout layout, String filename, boolean append)
            throws IOException {            this.layout = layout;            this.setFile(filename, append, false, bufferSize);
        }        public void setFile(String file) {
            fileName = file.trim();
        }        public boolean getAppend() {            return fileAppend;
        }        public String getFile() {            return fileName;
        }        public void activateOptions() {            if (fileName != null) {                try {
                    setFile(fileName, fileAppend, bufferedIO, bufferSize);
                } catch (IOException e) {
                    handleError("setFile(" + fileName + "," + fileAppend + ") call failed.",
                        e, CODE_FILE_OPEN_FAILURE);
                }
            } else {
                SysLogger.warn("File option not set for appender [" + name + "].");
                SysLogger.warn("Are you using FileAppender instead of ConsoleAppender?");
            }
        }        protected void closeFile() {            if (this.qw != null) {                try {                    this.qw.close();
                } catch (IOException e) {                    if (e instanceof InterruptedIOException) {
                        Thread.currentThread().interrupt();
                    }
                    SysLogger.error("Could not close " + qw, e);
                }
            }
        }        public boolean getBufferedIO() {            return this.bufferedIO;
        }        public int getBufferSize() {            return this.bufferSize;
        }        public void setAppend(boolean flag) {
            fileAppend = flag;
        }        public void setBufferedIO(boolean bufferedIO) {            this.bufferedIO = bufferedIO;            if (bufferedIO) {
                immediateFlush = false;
            }
        }        public void setBufferSize(int bufferSize) {            this.bufferSize = bufferSize;
        }        public synchronized void setFile(String fileName, boolean append, boolean bufferedIO, int bufferSize)
            throws IOException {
            SysLogger.debug("setFile called: " + fileName + ", " + append);            if (bufferedIO) {
                setImmediateFlush(false);
            }

            reset();
            FileOutputStream ostream;            try {
                ostream = new FileOutputStream(fileName, append);
            } catch (FileNotFoundException ex) {
                String parentName = new File(fileName).getParent();                if (parentName != null) {
                    File parentDir = new File(parentName);                    if (!parentDir.exists() && parentDir.mkdirs()) {
                        ostream = new FileOutputStream(fileName, append);
                    } else {                        throw ex;
                    }
                } else {                    throw ex;
                }
            }
            Writer fw = createWriter(ostream);            if (bufferedIO) {
                fw = new BufferedWriter(fw, bufferSize);
            }            this.setQWForFiles(fw);            this.fileName = fileName;            this.fileAppend = append;            this.bufferedIO = bufferedIO;            this.bufferSize = bufferSize;
            writeHeader();
            SysLogger.debug("setFile ended");
        }        protected void setQWForFiles(Writer writer) {            this.qw = new QuietWriter(writer, this);
        }        protected void reset() {
            closeFile();            this.fileName = null;            super.reset();
        }
    }

• 写文件，这里定义了bufferSize为8 * 1024，如果开启bufferedIO，则创建的是BufferedWriter

• setQWForFiles方法根据指定的writer创建了QuietWriter

• setFile方法设置了qw之后，就直接writeHeader

QuietWriter

org/apache/rocketmq/logging/inner/LoggingBuilder.java

    private static class QuietWriter extends FilterWriter {

        protected Appender appender;        public QuietWriter(Writer writer, Appender appender) {
            super(writer);            this.appender = appender;
        }        public void write(String string) {            if (string != null) {                try {
                    out.write(string);
                } catch (Exception e) {
                    appender.handleError("Failed to write [" + string + "].", e,
                        Appender.CODE_WRITE_FAILURE);
                }
            }
        }        public void flush() {            try {
                out.flush();
            } catch (Exception e) {
                appender.handleError("Failed to flush writer,", e,
                    Appender.CODE_FLUSH_FAILURE);
            }
        }
    }

• QuietWriter继承自jdk的FilterWriter，实现了write(String)方法，重写了flush方法

• FilterWriter实现了write(int c)，write(char cbuf[], int off, int len)，write(String str, int off, int len)方法，用于对字符串进行过滤

作者：go4it
链接：https://www.jianshu.com/p/ab96bec4f8f6