diff --git a/README.md b/README.md
index 818eb32..2bc1f15 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# ja-netfilter v2.3.0
+# ja-netfilter v2.3.1
 
 ### A javaagent framework
 
@@ -51,6 +51,13 @@ EQUAL,somedomain
 * or add system property `-Djanf.debug=1` (log level) to enable it
 * log level: `NONE=0`, `DEBUG=1`, `INFO=2`, `WARN=3`, `ERROR=4`
 
+## Debug output
+
+* the `ja-netfilter` will output debugging information to the `console` by default
+* add environment variable `JANF_OUTPUT=value` and start to change output medium
+* or add system property `-Djanf.output=value` to change output medium
+* output medium value: [`NONE=0`, `CONSOLE=1`, `FILE=2`, `CONSOLE+FILE=3`]
+
 ## Plugin system
 
 * for developer:
diff --git a/pom.xml b/pom.xml
index 7dde3b4..bb0942b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 
     <groupId>com.ja-netfilter</groupId>
     <artifactId>ja-netfilter</artifactId>
-    <version>2.3.0</version>
+    <version>2.3.1</version>
 
     <name>ja-netfilter</name>
     <description>A javaagent framework</description>
diff --git a/src/main/java/com/janetfilter/core/Launcher.java b/src/main/java/com/janetfilter/core/Launcher.java
index fae7ad6..d6e013d 100644
--- a/src/main/java/com/janetfilter/core/Launcher.java
+++ b/src/main/java/com/janetfilter/core/Launcher.java
@@ -12,7 +12,7 @@ import java.util.jar.JarFile;
 
 public class Launcher {
     public static final String ATTACH_ARG = "--attach";
-    public static final String VERSION = "v2.3.0";
+    public static final String VERSION = "v2.3.1";
 
     private static boolean loaded = false;
 
@@ -50,6 +50,10 @@ public class Launcher {
             System.setProperty("janf.debug", "1");
         }
 
+        if (null == System.getProperty("janf.output")) {
+            System.setProperty("janf.output", "3");
+        }
+
         premain(args, inst, true);
     }
 
diff --git a/src/main/java/com/janetfilter/core/commons/DebugInfo.java b/src/main/java/com/janetfilter/core/commons/DebugInfo.java
index 00cbaac..c7c9ea9 100644
--- a/src/main/java/com/janetfilter/core/commons/DebugInfo.java
+++ b/src/main/java/com/janetfilter/core/commons/DebugInfo.java
@@ -2,28 +2,42 @@ package com.janetfilter.core.commons;
 
 import com.janetfilter.core.utils.DateUtils;
 import com.janetfilter.core.utils.ProcessUtils;
+import com.janetfilter.core.utils.StringUtils;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
-import java.io.IOException;
 import java.io.PrintStream;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
 public class DebugInfo {
-    private static final ExecutorService EXECUTOR = Executors.newCachedThreadPool();
+    private static final long OUTPUT_CONSOLE = 0x1L;
+    private static final long OUTPUT_FILE = 0x2L;
+
+    private static final ExecutorService CONSOLE_EXECUTOR = Executors.newSingleThreadExecutor();
+    private static final ExecutorService FILE_EXECUTOR = Executors.newSingleThreadExecutor();
     private static final String CLASS_NAME = DebugInfo.class.getName();
-    private static final String LOG_TEMPLATE = "%s %-5s [%s] %s-%d : %s%n";
+    private static final String LOG_TEMPLATE = "%s %-5s [%s@%-5s] %s-%d : %s%n";
+    private static final String PID = ProcessUtils.currentId();
     private static final Level LOG_LEVEL;
-    private static File logFile;
+    private static final Long LOG_OUTPUT;
+
+    private static File logDir;
 
     static {
         Level level = Level.of(System.getProperty("janf.debug"));
         LOG_LEVEL = Level.NONE == level ? Level.of(System.getenv("JANF_DEBUG")) : level;
+
+        Long output = StringUtils.toLong(System.getProperty("janf.output"));
+        if (null == output) {
+            output = StringUtils.toLong(System.getenv("JANF_OUTPUT"));
+        }
+        LOG_OUTPUT = null == output ? OUTPUT_CONSOLE : output;
     }
 
     public static void useFile(File dir) {
-        if (LOG_LEVEL == Level.NONE || null == dir) {
+        if (Level.NONE == LOG_LEVEL || 0 == (LOG_OUTPUT & OUTPUT_FILE) || null == dir) {
             return;
         }
 
@@ -42,13 +56,7 @@ public class DebugInfo {
             return;
         }
 
-        File file = new File(dir, String.format("%s-%s.log", DateUtils.formatDate(), ProcessUtils.currentId()));
-        if (file.exists()) {
-            error("Log file exists: " + file);
-            return;
-        }
-
-        logFile = file;
+        logDir = dir;
     }
 
     public static void debug(String content, Throwable e) {
@@ -96,40 +104,12 @@ public class DebugInfo {
             return;
         }
 
-        EXECUTOR.execute(new WriteTask(level, content, e));
-    }
-
-    private static void writeContent(String content) {
-        writeContent(content, System.out);
-    }
-
-    private static void writeContent(String content, PrintStream fallback) {
-        if (null == logFile) {
-            fallback.print(content);
-            return;
+        if (0 != (LOG_OUTPUT & OUTPUT_CONSOLE)) {
+            CONSOLE_EXECUTOR.execute(new ConsoleWriteTask(PID, level, content, e));
         }
 
-        try (PrintStream ps = new PrintStream(new FileOutputStream(logFile, true))) {
-            ps.print(content);
-        } catch (IOException e) {
-            fallback.println(content);
-        }
-    }
-
-    private static void writeException(Throwable e) {
-        writeException(e, System.err);
-    }
-
-    private static void writeException(Throwable e, PrintStream fallback) {
-        if (null == logFile) {
-            e.printStackTrace(fallback);
-            return;
-        }
-
-        try (PrintStream ps = new PrintStream(new FileOutputStream(logFile, true))) {
-            e.printStackTrace(ps);
-        } catch (IOException ex) {
-            e.printStackTrace(fallback);
+        if (null != logDir) {
+            FILE_EXECUTOR.execute(new FileWriteTask(logDir, PID, level, content, e));
         }
     }
 
@@ -158,20 +138,59 @@ public class DebugInfo {
         }
     }
 
-    private static class WriteTask implements Runnable {
+    private static class ConsoleWriteTask implements Runnable {
+        private final String pid;
         private final Level level;
         private final String content;
         private final Throwable exception;
         private final Throwable stackException;
-
         private final String threadName;
 
-        WriteTask(Level level, String content, Throwable exception) {
+        private PrintStream ps;
+
+        ConsoleWriteTask(String pid, Level level, String content, Throwable exception) {
+            this.pid = pid;
             this.level = level;
             this.content = content;
             this.exception = exception;
             this.stackException = new Throwable();
             this.threadName = Thread.currentThread().getName();
+
+            setPrintStream(null == exception ? System.out : System.err);
+        }
+
+        protected static void writeContent(String content, PrintStream ps) {
+            if (null == ps) {
+                return;
+            }
+
+            ps.print(content);
+        }
+
+        protected static void writeException(String content, Throwable e, PrintStream ps) {
+            if (null == ps) {
+                return;
+            }
+
+            ps.print(content);
+            e.printStackTrace(ps);
+        }
+
+        protected static void write(String content, Throwable e, PrintStream stream) {
+            if (null == e) {
+                writeContent(content, stream);
+                return;
+            }
+
+            writeException(content, e, stream);
+        }
+
+        protected PrintStream getPrintStream() {
+            return ps;
+        }
+
+        protected void setPrintStream(PrintStream ps) {
+            this.ps = ps;
         }
 
         @Override
@@ -188,15 +207,30 @@ public class DebugInfo {
                 }
             }
 
-            String outContent = String.format(LOG_TEMPLATE, DateUtils.formatDateTimeMicro(), level, threadName, caller, line, content);
-            if (null == exception) {
-                writeContent(outContent);
-                return;
-            }
+            String outContent = String.format(LOG_TEMPLATE, DateUtils.formatDateTimeMicro(), level, threadName, pid, caller, line, content);
+            write(outContent, exception, getPrintStream());
+        }
+    }
 
-            synchronized (DebugInfo.class) {
-                writeContent(outContent, System.err);
-                writeException(exception);
+    private static class FileWriteTask extends ConsoleWriteTask {
+        private final File logDir;
+
+        FileWriteTask(File logDir, String pid, Level level, String content, Throwable exception) {
+            super(pid, level, content, exception);
+
+            this.logDir = logDir;
+        }
+
+        @Override
+        public void run() {
+            File logFile = new File(logDir, String.format("%s.log", DateUtils.formatDate()));
+
+            try (PrintStream ps = new PrintStream(new FileOutputStream(logFile, true))) {
+                setPrintStream(ps);
+
+                super.run();
+            } catch (FileNotFoundException e) {
+                writeException("log file not found!", e, System.err);
             }
         }
     }
diff --git a/src/main/java/com/janetfilter/core/utils/StringUtils.java b/src/main/java/com/janetfilter/core/utils/StringUtils.java
index feab05a..0832b51 100644
--- a/src/main/java/com/janetfilter/core/utils/StringUtils.java
+++ b/src/main/java/com/janetfilter/core/utils/StringUtils.java
@@ -25,4 +25,16 @@ public class StringUtils {
 
         return new String(buffer);
     }
+
+    public static Long toLong(String val) {
+        if (null == val) {
+            return null;
+        }
+
+        try {
+            return Long.parseLong(val);
+        } catch (NumberFormatException e) {
+            return null;
+        }
+    }
 }
diff --git a/src/main/java/com/janetfilter/core/utils/WhereIsUtils.java b/src/main/java/com/janetfilter/core/utils/WhereIsUtils.java
index 6f45e82..4296c43 100644
--- a/src/main/java/com/janetfilter/core/utils/WhereIsUtils.java
+++ b/src/main/java/com/janetfilter/core/utils/WhereIsUtils.java
@@ -55,7 +55,7 @@ public class WhereIsUtils {
             return url.toURI();
         }
 
-        String resourcePath = "/288daf08f4ba46dfde71b7f0624b0ad7f234a67a.txt";
+        String resourcePath = "/6c81ec87e55d331c267262e892427a3d93d76683.txt";
         url = Launcher.class.getResource(resourcePath);
         if (null == url) {
             throw new Exception("Can not locate resource file.");
diff --git a/src/main/resources/288daf08f4ba46dfde71b7f0624b0ad7f234a67a.txt b/src/main/resources/6c81ec87e55d331c267262e892427a3d93d76683.txt
similarity index 100%
rename from src/main/resources/288daf08f4ba46dfde71b7f0624b0ad7f234a67a.txt
rename to src/main/resources/6c81ec87e55d331c267262e892427a3d93d76683.txt