Online execution of Java system failures via jstack positioning Case 1

Description of the problem:

In an online implementation of the Java Web System, will be scheduled to perform an FTP upload task, the results one day found that the file is not uploaded after normal generation.

Preliminary analysis of the problem:

1. View Log files

found that this task only prints the log that started to be processed by FTP, but does not print the log that the FTP processing completes.

From the code, the FTP upload processing code exception protection is very good, assuming an exception, it will be printed, and the log file does not have relevant information, it is very strange. Suspicion is an FTP process problem, such as the other side ftpserver what problems, but can not find evidence.

unable to spy on Java execution system internal information, sacrifice the killer- Jstack .

2. Through Jstack analysis

On the execution system, the JPS command (can also be used in other ways, such as PS) to view the process ID of the executing Java program, using Jstack pid > Jstack.log to export the thread stack information to the Jstack.log file, find examples such as the following useful information.

With the code confirmation, the uploadftptask below is indeed the running code for our file upload task.

From the stack information, the thread state is runnable, not the blocked state, and it is not because the lock causes the thread to clog, but rather to plug in the network read.

<span style= "FONT-SIZE:14PX;" > "defaultquartzscheduler_worker-5" prio=10 tid=0x00002aaaf4382801 nid=0x1874 runnable [0x000000004133b000.        0X000000004133BDA0] Java.lang.Thread.State:RUNNABLE at java.net.SocketInputStream.socketRead0 (Native Method) At Java.net.SocketInputStream.read (socketinputstream.java:129) at Sun.nio.cs.StreamDecoder.readBytes (Streamdeco der.java:264) at Sun.nio.cs.StreamDecoder.implRead (streamdecoder.java:306) at Sun.nio.cs.StreamDecoder.read ( streamdecoder.java:158)-Locked <0x00002aaac3cdd061> (a java.io.InputStreamReader) at Sun.nio.cs.Stre  AMDECODER.READ0 (streamdecoder.java:107)-Locked <0x00002aaac3cdd061> (a java.io.InputStreamReader) at Sun.nio.cs.StreamDecoder.read (streamdecoder.java:93) at Java.io.InputStreamReader.read (Inputstreamreader.java : 151) at It.sauronsoftware.ftp4j.NVTASCIIReader.readLine (nvtasciireader.java:105) at it.sauronsoftware.ftp4j . FtpcommuNicationchannel.read (ftpcommunicationchannel.java:142) at It.sauronsoftware.ftp4j.FTPCommunicationChannel.readFTPReply (ftpcommunicationchannel.java:187) at It.sauronsoftware.ftp4j.FTPClient.connect (ftpclient.java:1034)-Locked <0x00002aaac3cdd109> (a JAVA.LANG.OBJ ECT) at Com.xx.FtpClientImpl.connect (ftpclientimpl.java:56) at Com.xx.UploadFtpTask.execute (Uploadftptask.ja va:88) at Org.quartz.core.JobRunShell.run (jobrunshell.java:216) at Org.quartz.simpl.simplethreadpool$workert Hread.run (simplethreadpool.java:549) </span>

confirmed by the referenced jar package, the open source package used by this FTP feature ftp4j to be implemented, using the version number of 1.5.1 .

Write a test program to see the call stack when FTP is connected:

Socket.connect (socketaddress) line:469
Socket.<init> (SocketAddress, SocketAddress, Boolean) line:366
Socket.<init> (String, int) line:180
Directconnector.connect (String, int) line:35
Directconnector.connectforcommunicationchannel (String, int) line:40
Ftpclient.connect (String, int) line:1024
Ftpclient.connect (String) line:991
Test.main (string[]) line:19

And what is the 469 line of the socket?

Connect (endpoint, 0);

This function is defined as: public void Connect (socketaddress endpoint, int timeout), the above call is equivalent to setting a timeout of 0, which means that there is a network packet loss or a problem with the Terminal Services, This connection will wait indefinitely. This is the cup.

and see if this open source project might have changed this issue? Download the 1.7.2 version number and test again to see the call stack:

Socket.connect (socketaddress, int) line:490
Directconnector (Ftpconnector). Tcpconnectforcommunicationchannel (String, int) line:208
Directconnector.connectforcommunicationchannel (String, int) line:39
Ftpclient.connect (String, int) line:1036
Ftpclient.connect (String) line:1003
Test.main (string[]) line:19

When the socket's Connect method is called via Tcpconnectforcommunicationchannel, the timeout time is passed, which is 10 seconds (10*1000). This introduces the time-out mechanism, assuming that there is a problem, it will not be death.

Summarize:

1.jstack tools are a powerful tool for locating online Java systems and are able to view thread stack information, which is important for analyzing problems, especially when log analysis and code analysis cannot determine the problem.

2. When the network is connected, you must set a timeout and cannot wait indefinitely. When developing a system, you must consider various anomalies. To apply that sentence, out of the mix, always have to.

Reprint Please specify source: http://blog.csdn.net/u014569459/article/details/38542949

 

Online execution of Java system failures via jstack positioning Case 1