Java - 使用 FileWriter 写入同一个文件 - 介绍 multi-threading
Java - write to same file with FileWriter - introduce multi-threading
编辑2：
我很清楚两次票数接近的原因：OP中没有multi-threading。所以我编辑了标题。
线程不在 OP 中，但在我的答案中。
编辑：
好吧，我放弃编辑我的原创 post 而是让我这样问：
此日志模拟器旨在生成用户和设备活动的日志。每行包含多个键和值，以 ;; 分隔，格式为 key=value。键是：User-Name、NAS-Identifier、Acct-Input-Octets、Acct-Output-Octets、date、Acct-Status-Type。
User-Name 应该是随机的，如 user_<random_number>。 NAS-Identifier 一样。
Acct-Input-Octets和Acct-Output-Octets是整数，从0开始，按升序排列；增加的数量是任意的。
date 也应该增加。
Acct-Status-Type是Start、Interim-Update和Stop之一，代表一个用户session的开始、持续状态和结束。应该有一个 Start，然后是多个 Interim-Update，随机数，和一个 Stop。 session.
期间用户和nas相同
因此，它应该生成如下行：
date=lun, 22 ene 2018 18:39:42.052;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Start;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:43.827;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:44.463;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=268;;Acct-Output-Octets=42;;
date=lun, 22 ene 2018 18:39:43.968;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=428;;Acct-Output-Octets=143;;
date=lun, 22 ene 2018 18:39:44.039;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=519;;Acct-Output-Octets=294;;
date=lun, 22 ene 2018 18:39:46.276;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Stop;;Acct-Input-Octets=727;;Acct-Output-Octets=535;;
...
但是，我们这里可以看到，同一个用户的台词都聚集在一起了，不太真实。我想要的是这样的：
User A Start
User B Start
User C Start
User A Interim-Update
User B Stop
User D Start
User C Interim-Update
User A Interim-Update
...
我想创建几个线程，比如4个，相互竞争；一个抓住文件并写一行，然后释放它。然后，另一个线程再次写入文件，一行并退出。
OP
我有这个简单的 Java class 来生成 Radius 日志的模拟：
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.IntStream;
public class RadiusGenerator {
private static final String LOG_PATH = "radius-simulation.log";
private static FileWriter writer;
private static volatile Map<String, String> user_nas; //ensure the newest value read from main heap; use volatile because we read but not write.
private static final SimpleDateFormat fmt_in = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss.SSS");
/* keys in db*/
// private static final String KEY_TIMESTAMP_HOUR = "timestamp_hour";
// private static final String KEY_USERID = "user_id";
// private static final String KEY_NASID = "nas_id";
// private static final String KEY_TYPE = "type";
// private static final String KEY_BALANCES = "balances";
// private static final String KEY_INPUT = "input";
// private static final String KEY_OUTPUT = "output";
/* fields in tuple */
private static final String FIELD_DATE = "date";
private static final String FIELD_USERNAME = "User-Name";
private static final String FIELD_NAS_IDENTIFIER = "NAS-Identifier";
private static final String FIELD_METHOD = "Acct-Status-Type";
private static final String FIELD_BALANCE_INPUT = "Acct-Input-Octets";
private static final String FIELD_BALANCE_OUTPUT = "Acct-Output-Octets";
/* methods */
private static final String METHOD_START = "Start";
private static final String METHOD_UPDATE = "Interim-Update";
private static final String METHOD_STOP = "Stop";
private static String name;
private static String nas;
private static String method;
private static String result;
private static int input;
private static int output;
private static Date now;
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
RadiusGenerator.writer = new FileWriter(new File(LOG_PATH), false);
System.out.println("Initializing with parameters: number of users: " + args[0] + ", number of NAS: " + args[1]);
int numUsers = Integer.parseInt(args[0]);
int numNAS = Integer.parseInt(args[1]);
// List<String> usernames = new ArrayList<String>();
// IntStream.range(1, numUsers).forEach(i -> {
// usernames.add("User_" + i);
// });
// List<String> nasNames = new ArrayList<String>();
// IntStream.range(1, numNAS).forEach(i -> {
// nasNames.add("NAS_" + i);
// });
FileWriter writer = new FileWriter(new File(LOG_PATH));
try {
for (int i=0; i < generateRandom(20); i++) {
int indexUser = generateRandom(numUsers-1);
name = "User_" + String.valueOf(indexUser);
int indexNas = generateRandom(numNAS-1);
nas = "NAS_" + String.valueOf(indexNas);
user_nas = new HashMap<String, String>();
method = "";
result = "";
now = new Date();
input = 0;
output = 0;
//first line
method = METHOD_START;
user_nas.put(name, nas);
formLine();
//update
method = METHOD_UPDATE;
do {
if (generateRandom(10) == 9) {
method = "Stop";
}
formLine();
input += generateRandom(300);
output += generateRandom(250);
} while (!method.equals(METHOD_STOP));
//stop
user_nas.remove(name);
input = 0;
output = 0;
}
} catch (Exception e) {
e.printStackTrace();
}
writer.write(result);
writer.flush();
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.println("The paths is not correct. ");
e.printStackTrace();
} catch (NumberFormatException e1) {
System.out.println("The parameters coming in have wrong formats. Double-check them!");
e1.printStackTrace();
}
}
private static String concat(String a, String b) {
return a + "=" + b + ";;";
}
private static int generateRandom(int range) {
return (int) (Math.random() * range);
}
private static void formLine() throws IOException {
result += concat(FIELD_DATE, fmt_in.format(new Date(now.getTime() + (long)generateRandom(5000)))); //randomly add 0-5 seconds
result += concat(FIELD_USERNAME, name);
result += concat(FIELD_NAS_IDENTIFIER, nas);
result += concat(FIELD_METHOD, method);
result += concat(FIELD_BALANCE_INPUT, String.valueOf(input));
result += concat(FIELD_BALANCE_OUTPUT, String.valueOf(output));
result += System.lineSeparator();
}
}
生成如下输出：
date=lun, 22 ene 2018 18:39:42.052;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Start;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:43.827;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:44.463;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=268;;Acct-Output-Octets=42;;
date=lun, 22 ene 2018 18:39:43.968;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=428;;Acct-Output-Octets=143;;
date=lun, 22 ene 2018 18:39:44.039;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=519;;Acct-Output-Octets=294;;
date=lun, 22 ene 2018 18:39:46.276;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=727;;Acct-Output-Octets=535;;
date=lun, 22 ene 2018 18:39:46.126;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=810;;Acct-Output-Octets=694;;
date=lun, 22 ene 2018 18:39:43.908;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=888;;Acct-Output-Octets=848;;
date=lun, 22 ene 2018 18:39:41.839;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1007;;Acct-Output-Octets=1078;;
date=lun, 22 ene 2018 18:39:42.163;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1127;;Acct-Output-Octets=1323;;
date=lun, 22 ene 2018 18:39:43.395;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1367;;Acct-Output-Octets=1543;;
date=lun, 22 ene 2018 18:39:44.430;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1487;;Acct-Output-Octets=1656;;
date=lun, 22 ene 2018 18:39:44.760;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1529;;Acct-Output-Octets=1688;;
date=lun, 22 ene 2018 18:39:43.329;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Stop;;Acct-Input-Octets=1561;;Acct-Output-Octets=1746;;
我们注意到时间戳的顺序不正确；我认为这是因为多个线程同时写入这个文件。我们想要的是这些行严格按照时间戳排序（写入时），但是每个用户的 START 应该排在第一位，然后是 UPDATE，最后是 STOP，就像一个真实的日志。
Java同步的话题一直是个痛点。如果有人擅长这个，请帮忙指出这里应该锁定哪个块或什么object。如果有一些好的参考，更好；同时我会在家里再次研究这个..
感谢所有评论，由于您的帮助，我在我的代码中发现了一些问题并修复了它们。 线程不在 OP 中，但在这个答案中我有。
从结果来看，我认为：
- 当访问同一个文件时，写入行是原子性的：一旦某个线程占用了文件，其他线程不能干涉，直到所有者完成他的行写入，因为none 的行由来自两个线程的内容组成。
- 当一个线程完成一行时，它会释放文件，其他等待的线程可以立即获取文件并写入他的行。 这里是比赛，但是没有条件比赛，导致不一致。
所以我猜 FileWriter 是线程安全的？
最终的工作代码如下：
- 创建多个
Runnable写入同一个文件
- 每次
Runnable打开文件写一行，立即做一个flush()，没有close()。要写入的日期是当前时间。在每次写作之间我添加了一些间隔 Thread.sleep(xxx).
现在我使用4个launch参数：
100
10
30
D:\temp\radius-simulator.log
class 现在变成：
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ThreadLocalRandom;
/**
* A generator simulative of Radius log. Generate lines of log and save to a file.
* The parameters expected, in order, are:
* - Number of users, integer(will be number of threads running simultaneously)
* - Number of NAS, integer
* - Number of seconds to sleep between the previous Stop and the next Start of each thread, integer
* - The full path of log file, string (the app in Windows has right to create file, but not the parent folder,
* so be sure to create the parent folder first)
*
*
*/
public class RadiusSimulator implements Runnable {
private static File log;
private static volatile Map<String, String> user_nas; //ensure the newest value read from main heap; use volatile because we read but not write.
private static final SimpleDateFormat fmt_in = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss.SSS");
/* fields in tuple */
private static final String FIELD_DATE = "date";
private static final String FIELD_USERNAME = "User-Name";
private static final String FIELD_NAS_IDENTIFIER = "NAS-Identifier";
private static final String FIELD_METHOD = "Acct-Status-Type";
private static final String FIELD_BALANCE_INPUT = "Acct-Input-Octets";
private static final String FIELD_BALANCE_OUTPUT = "Acct-Output-Octets";
/* methods */
private static final String METHOD_START = "Start";
private static final String METHOD_UPDATE = "Interim-Update";
private static final String METHOD_STOP = "Stop";
/* parameters */
private static int numUsers;
private static int numNAS;
private static int sleepTime;
private String username;
private String nas;
private String method;
private String result;
private int input;
private int output;
private FileWriter writer;
private int status;
private boolean stop;
private String name;
public RadiusSimulator(String name) {
this.name = name;
this.method = METHOD_START;
status = 0;
stop = false;
// just open the file without appending, to clear content
try {
writer = new FileWriter(log, false);
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
try {
System.out.println("/**\r\n" +
" * A simulated generator of Radius log. Generate lines of log and save to a file. \r\n" +
" * The parameters expected, in order, are: \r\n" +
" * - Number of users, integer(will be number of threads running simultaneously)\r\n" +
" * - Number of NAS, integer\r\n" +
" * - Number of maximum of seconds to sleep between the previous Stop and the next Start of each thread, integer(>60)\r\n" +
" * - The full path of log file, string (be sure to create the parent folder first)\r\n" +
" * \r\n" +
" * (require Java 1.7 or above) \r\n\"" +
" * \r\n" +
" *\r\n" +
" */");
System.out.println("Initializing with parameters: number of users: " + args[0] + ", number of NAS: " + args[1]);
numUsers = Integer.parseInt(args[0]);
numNAS = Integer.parseInt(args[1]);
sleepTime = Integer.parseInt(args[2]);
log = new File(args[3]);
for (int i=0; i<numUsers; i++) {
new Thread(new RadiusSimulator("User_" + i)).start();
}
} catch (Exception e) {
e.printStackTrace();
}
}
private int generateRandom(int min, int max) {
if (max < min) max = min;
int randomNum = ThreadLocalRandom.current().nextInt(min, max + 1);
return randomNum;
}
private static String concat(String a, String b) {
return a + "=" + b + ";;";
}
private void formLine() throws IOException {
result += concat(FIELD_DATE, fmt_in.format(new Date())); //print always the date of now
result += concat(FIELD_USERNAME, name);
result += concat(FIELD_NAS_IDENTIFIER, nas);
result += concat(FIELD_METHOD, method);
result += concat(FIELD_BALANCE_INPUT, String.valueOf(input));
result += concat(FIELD_BALANCE_OUTPUT, String.valueOf(output));
result += System.lineSeparator();
}
@Override
public void run() {
try {
writer = new FileWriter(log, true);
} catch (IOException e1) {
e1.printStackTrace();
}
// while (!stop) {
while (true) {
try {
Thread.sleep(generateRandom(0, 3000));
if (status == 0) {
// stage 1
int indexUser = generateRandom(0, numUsers-1);
username = "User_" + String.valueOf(indexUser);
int indexNas = generateRandom(0, numNAS-1);
nas = "NAS_" + String.valueOf(indexNas);
user_nas = new HashMap<String, String>();
result = "";
input = 0;
output = 0;
//first line
user_nas.put(username, nas);
formLine();
System.out.println(result);
writer.write(result);
writer.flush();
status ++; //next stage
result = "";
} else if (status == 1) {
method = METHOD_UPDATE;
input += generateRandom(0, 400);
output += generateRandom(0, 500);
formLine();
System.out.println(result);
writer.write(result);
writer.flush();
// 1 out of 10 of probability to enter stage 3
if (generateRandom(0, 10) == 9) {
status = 2;
}
result = "";
} else if (status == 2) {
method = METHOD_STOP;
input += generateRandom(0, 400);
output += generateRandom(0, 500);
formLine();
System.out.println(result);
/* write inmediately after constructing the line */
writer.write(result);
writer.flush();
user_nas.remove(username);
input = 0;
output = 0;
// stop = true;
result = "";
status = 0; //go back to stage 1
Thread.sleep(generateRandom(60*1000, sleepTime*1000));
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
编辑2： 我很清楚两次票数接近的原因：OP中没有multi-threading。所以我编辑了标题。
线程不在 OP 中，但在我的答案中。
编辑：
好吧，我放弃编辑我的原创 post 而是让我这样问：
此日志模拟器旨在生成用户和设备活动的日志。每行包含多个键和值，以 ;; 分隔，格式为 key=value。键是：User-Name、NAS-Identifier、Acct-Input-Octets、Acct-Output-Octets、date、Acct-Status-Type。
User-Name 应该是随机的，如 user_<random_number>。 NAS-Identifier 一样。
Acct-Input-Octets和Acct-Output-Octets是整数，从0开始，按升序排列；增加的数量是任意的。
date 也应该增加。
Acct-Status-Type是Start、Interim-Update和Stop之一，代表一个用户session的开始、持续状态和结束。应该有一个 Start，然后是多个 Interim-Update，随机数，和一个 Stop。 session.
因此，它应该生成如下行：
date=lun, 22 ene 2018 18:39:42.052;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Start;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:43.827;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:44.463;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=268;;Acct-Output-Octets=42;;
date=lun, 22 ene 2018 18:39:43.968;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=428;;Acct-Output-Octets=143;;
date=lun, 22 ene 2018 18:39:44.039;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=519;;Acct-Output-Octets=294;;
date=lun, 22 ene 2018 18:39:46.276;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Stop;;Acct-Input-Octets=727;;Acct-Output-Octets=535;;
...
但是，我们这里可以看到，同一个用户的台词都聚集在一起了，不太真实。我想要的是这样的：
User A Start
User B Start
User C Start
User A Interim-Update
User B Stop
User D Start
User C Interim-Update
User A Interim-Update
...
我想创建几个线程，比如4个，相互竞争；一个抓住文件并写一行，然后释放它。然后，另一个线程再次写入文件，一行并退出。
OP
我有这个简单的 Java class 来生成 Radius 日志的模拟：
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.IntStream;
public class RadiusGenerator {
private static final String LOG_PATH = "radius-simulation.log";
private static FileWriter writer;
private static volatile Map<String, String> user_nas; //ensure the newest value read from main heap; use volatile because we read but not write.
private static final SimpleDateFormat fmt_in = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss.SSS");
/* keys in db*/
// private static final String KEY_TIMESTAMP_HOUR = "timestamp_hour";
// private static final String KEY_USERID = "user_id";
// private static final String KEY_NASID = "nas_id";
// private static final String KEY_TYPE = "type";
// private static final String KEY_BALANCES = "balances";
// private static final String KEY_INPUT = "input";
// private static final String KEY_OUTPUT = "output";
/* fields in tuple */
private static final String FIELD_DATE = "date";
private static final String FIELD_USERNAME = "User-Name";
private static final String FIELD_NAS_IDENTIFIER = "NAS-Identifier";
private static final String FIELD_METHOD = "Acct-Status-Type";
private static final String FIELD_BALANCE_INPUT = "Acct-Input-Octets";
private static final String FIELD_BALANCE_OUTPUT = "Acct-Output-Octets";
/* methods */
private static final String METHOD_START = "Start";
private static final String METHOD_UPDATE = "Interim-Update";
private static final String METHOD_STOP = "Stop";
private static String name;
private static String nas;
private static String method;
private static String result;
private static int input;
private static int output;
private static Date now;
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
RadiusGenerator.writer = new FileWriter(new File(LOG_PATH), false);
System.out.println("Initializing with parameters: number of users: " + args[0] + ", number of NAS: " + args[1]);
int numUsers = Integer.parseInt(args[0]);
int numNAS = Integer.parseInt(args[1]);
// List<String> usernames = new ArrayList<String>();
// IntStream.range(1, numUsers).forEach(i -> {
// usernames.add("User_" + i);
// });
// List<String> nasNames = new ArrayList<String>();
// IntStream.range(1, numNAS).forEach(i -> {
// nasNames.add("NAS_" + i);
// });
FileWriter writer = new FileWriter(new File(LOG_PATH));
try {
for (int i=0; i < generateRandom(20); i++) {
int indexUser = generateRandom(numUsers-1);
name = "User_" + String.valueOf(indexUser);
int indexNas = generateRandom(numNAS-1);
nas = "NAS_" + String.valueOf(indexNas);
user_nas = new HashMap<String, String>();
method = "";
result = "";
now = new Date();
input = 0;
output = 0;
//first line
method = METHOD_START;
user_nas.put(name, nas);
formLine();
//update
method = METHOD_UPDATE;
do {
if (generateRandom(10) == 9) {
method = "Stop";
}
formLine();
input += generateRandom(300);
output += generateRandom(250);
} while (!method.equals(METHOD_STOP));
//stop
user_nas.remove(name);
input = 0;
output = 0;
}
} catch (Exception e) {
e.printStackTrace();
}
writer.write(result);
writer.flush();
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.println("The paths is not correct. ");
e.printStackTrace();
} catch (NumberFormatException e1) {
System.out.println("The parameters coming in have wrong formats. Double-check them!");
e1.printStackTrace();
}
}
private static String concat(String a, String b) {
return a + "=" + b + ";;";
}
private static int generateRandom(int range) {
return (int) (Math.random() * range);
}
private static void formLine() throws IOException {
result += concat(FIELD_DATE, fmt_in.format(new Date(now.getTime() + (long)generateRandom(5000)))); //randomly add 0-5 seconds
result += concat(FIELD_USERNAME, name);
result += concat(FIELD_NAS_IDENTIFIER, nas);
result += concat(FIELD_METHOD, method);
result += concat(FIELD_BALANCE_INPUT, String.valueOf(input));
result += concat(FIELD_BALANCE_OUTPUT, String.valueOf(output));
result += System.lineSeparator();
}
}
生成如下输出：
date=lun, 22 ene 2018 18:39:42.052;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Start;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:43.827;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=0;;Acct-Output-Octets=0;;
date=lun, 22 ene 2018 18:39:44.463;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=268;;Acct-Output-Octets=42;;
date=lun, 22 ene 2018 18:39:43.968;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=428;;Acct-Output-Octets=143;;
date=lun, 22 ene 2018 18:39:44.039;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=519;;Acct-Output-Octets=294;;
date=lun, 22 ene 2018 18:39:46.276;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=727;;Acct-Output-Octets=535;;
date=lun, 22 ene 2018 18:39:46.126;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=810;;Acct-Output-Octets=694;;
date=lun, 22 ene 2018 18:39:43.908;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=888;;Acct-Output-Octets=848;;
date=lun, 22 ene 2018 18:39:41.839;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1007;;Acct-Output-Octets=1078;;
date=lun, 22 ene 2018 18:39:42.163;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1127;;Acct-Output-Octets=1323;;
date=lun, 22 ene 2018 18:39:43.395;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1367;;Acct-Output-Octets=1543;;
date=lun, 22 ene 2018 18:39:44.430;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1487;;Acct-Output-Octets=1656;;
date=lun, 22 ene 2018 18:39:44.760;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Interim-Update;;Acct-Input-Octets=1529;;Acct-Output-Octets=1688;;
date=lun, 22 ene 2018 18:39:43.329;;User-Name=User_703;;NAS-Identifier=NAS_0;;Acct-Status-Type=Stop;;Acct-Input-Octets=1561;;Acct-Output-Octets=1746;;
我们注意到时间戳的顺序不正确；我认为这是因为多个线程同时写入这个文件。我们想要的是这些行严格按照时间戳排序（写入时），但是每个用户的 START 应该排在第一位，然后是 UPDATE，最后是 STOP，就像一个真实的日志。
Java同步的话题一直是个痛点。如果有人擅长这个，请帮忙指出这里应该锁定哪个块或什么object。如果有一些好的参考，更好；同时我会在家里再次研究这个..
感谢所有评论，由于您的帮助，我在我的代码中发现了一些问题并修复了它们。 线程不在 OP 中，但在这个答案中我有。
从结果来看，我认为：
- 当访问同一个文件时，写入行是原子性的：一旦某个线程占用了文件，其他线程不能干涉，直到所有者完成他的行写入，因为none 的行由来自两个线程的内容组成。
- 当一个线程完成一行时，它会释放文件，其他等待的线程可以立即获取文件并写入他的行。 这里是比赛，但是没有条件比赛，导致不一致。
所以我猜 FileWriter 是线程安全的？
最终的工作代码如下：
- 创建多个
Runnable写入同一个文件 - 每次
Runnable打开文件写一行，立即做一个flush()，没有close()。要写入的日期是当前时间。在每次写作之间我添加了一些间隔Thread.sleep(xxx).
现在我使用4个launch参数：
100
10
30
D:\temp\radius-simulator.log
class 现在变成：
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ThreadLocalRandom;
/**
* A generator simulative of Radius log. Generate lines of log and save to a file.
* The parameters expected, in order, are:
* - Number of users, integer(will be number of threads running simultaneously)
* - Number of NAS, integer
* - Number of seconds to sleep between the previous Stop and the next Start of each thread, integer
* - The full path of log file, string (the app in Windows has right to create file, but not the parent folder,
* so be sure to create the parent folder first)
*
*
*/
public class RadiusSimulator implements Runnable {
private static File log;
private static volatile Map<String, String> user_nas; //ensure the newest value read from main heap; use volatile because we read but not write.
private static final SimpleDateFormat fmt_in = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss.SSS");
/* fields in tuple */
private static final String FIELD_DATE = "date";
private static final String FIELD_USERNAME = "User-Name";
private static final String FIELD_NAS_IDENTIFIER = "NAS-Identifier";
private static final String FIELD_METHOD = "Acct-Status-Type";
private static final String FIELD_BALANCE_INPUT = "Acct-Input-Octets";
private static final String FIELD_BALANCE_OUTPUT = "Acct-Output-Octets";
/* methods */
private static final String METHOD_START = "Start";
private static final String METHOD_UPDATE = "Interim-Update";
private static final String METHOD_STOP = "Stop";
/* parameters */
private static int numUsers;
private static int numNAS;
private static int sleepTime;
private String username;
private String nas;
private String method;
private String result;
private int input;
private int output;
private FileWriter writer;
private int status;
private boolean stop;
private String name;
public RadiusSimulator(String name) {
this.name = name;
this.method = METHOD_START;
status = 0;
stop = false;
// just open the file without appending, to clear content
try {
writer = new FileWriter(log, false);
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
try {
System.out.println("/**\r\n" +
" * A simulated generator of Radius log. Generate lines of log and save to a file. \r\n" +
" * The parameters expected, in order, are: \r\n" +
" * - Number of users, integer(will be number of threads running simultaneously)\r\n" +
" * - Number of NAS, integer\r\n" +
" * - Number of maximum of seconds to sleep between the previous Stop and the next Start of each thread, integer(>60)\r\n" +
" * - The full path of log file, string (be sure to create the parent folder first)\r\n" +
" * \r\n" +
" * (require Java 1.7 or above) \r\n\"" +
" * \r\n" +
" *\r\n" +
" */");
System.out.println("Initializing with parameters: number of users: " + args[0] + ", number of NAS: " + args[1]);
numUsers = Integer.parseInt(args[0]);
numNAS = Integer.parseInt(args[1]);
sleepTime = Integer.parseInt(args[2]);
log = new File(args[3]);
for (int i=0; i<numUsers; i++) {
new Thread(new RadiusSimulator("User_" + i)).start();
}
} catch (Exception e) {
e.printStackTrace();
}
}
private int generateRandom(int min, int max) {
if (max < min) max = min;
int randomNum = ThreadLocalRandom.current().nextInt(min, max + 1);
return randomNum;
}
private static String concat(String a, String b) {
return a + "=" + b + ";;";
}
private void formLine() throws IOException {
result += concat(FIELD_DATE, fmt_in.format(new Date())); //print always the date of now
result += concat(FIELD_USERNAME, name);
result += concat(FIELD_NAS_IDENTIFIER, nas);
result += concat(FIELD_METHOD, method);
result += concat(FIELD_BALANCE_INPUT, String.valueOf(input));
result += concat(FIELD_BALANCE_OUTPUT, String.valueOf(output));
result += System.lineSeparator();
}
@Override
public void run() {
try {
writer = new FileWriter(log, true);
} catch (IOException e1) {
e1.printStackTrace();
}
// while (!stop) {
while (true) {
try {
Thread.sleep(generateRandom(0, 3000));
if (status == 0) {
// stage 1
int indexUser = generateRandom(0, numUsers-1);
username = "User_" + String.valueOf(indexUser);
int indexNas = generateRandom(0, numNAS-1);
nas = "NAS_" + String.valueOf(indexNas);
user_nas = new HashMap<String, String>();
result = "";
input = 0;
output = 0;
//first line
user_nas.put(username, nas);
formLine();
System.out.println(result);
writer.write(result);
writer.flush();
status ++; //next stage
result = "";
} else if (status == 1) {
method = METHOD_UPDATE;
input += generateRandom(0, 400);
output += generateRandom(0, 500);
formLine();
System.out.println(result);
writer.write(result);
writer.flush();
// 1 out of 10 of probability to enter stage 3
if (generateRandom(0, 10) == 9) {
status = 2;
}
result = "";
} else if (status == 2) {
method = METHOD_STOP;
input += generateRandom(0, 400);
output += generateRandom(0, 500);
formLine();
System.out.println(result);
/* write inmediately after constructing the line */
writer.write(result);
writer.flush();
user_nas.remove(username);
input = 0;
output = 0;
// stop = true;
result = "";
status = 0; //go back to stage 1
Thread.sleep(generateRandom(60*1000, sleepTime*1000));
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}