Java:故障排查、JVM性能监控工具单

常用命令

1、jps：JVM进程状态工具

usage: jps [-help]       jps [-q] [-mlvV] [<hostid>]Definitions:    <hostid>:      <hostname>[:<port>]

执行案例：

jps -l1228 sun.tools.jps.Jps

option参数说明：

• -q:输出本地虚拟机进程的ID，省略类名称。
• -m:输出启动时传递给主类main()方法的参数。
• -l:输出全类名，如果执行的是JAR包，会输出JAR包路径。
• -v:输出进程的JVM配置参数。

2、jstat：JVM统计信息监视工具

jstat帮助文档：

invalid argument countUsage: jstat -help|-options       jstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]]Definitions:  <option>      An option reported by the -options option  <vmid>        Virtual Machine Identifier. A vmid takes the following form:                     <lvmid>[@<hostname>[:<port>]]                Where <lvmid> is the local vm identifier for the target                Java virtual machine, typically a process id; <hostname> is                the name of the host running the target Java virtual machine;                and <port> is the port number for the rmiregistry on the                target host. See the jvmstat documentation for a more complete                description of the Virtual Machine Identifier.  <lines>       Number of samples between header lines.  <interval>    Sampling interval. The following forms are allowed:                    <n>["ms"|"s"]                Where <n> is an integer and the suffix specifies the units as                 milliseconds("ms") or seconds("s"). The default units are "ms".  <count>       Number of samples to take before terminating.  -J<flag>      Pass <flag> directly to the runtime system.

执行案例：

//查看垃圾收集等信息jstat -gc 1441 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT   10752.0 10752.0  0.0    0.0   65536.0   9175.5   175104.0     0.0     4480.0 780.7  384.0   76.6       0    0.000   0      0.000    0.000

option参数说明：

• -class：监视类加载、卸载数量、总空间以及类装载的耗时。
• -compiler：即时编译器编译过的方法、耗时等信息。
• -gc：监视Java堆状态，包括Eden区、两个Survivor区、老年代、永久代的容量、已用空间、垃圾收集时间合计等信息。
• -gccapacity：内容与gc基本类似，但输出的主要是关注Java堆各个区域使用的最大、最小空间。
• -gccause：与gcutil功能一样，但是会额外输出上一次导致垃圾收集产生的原因。
• -gcmetacapacity：JDK8下元数据空间统计。
• -gcnew：监视新生代垃圾收集信息。
• -gcnewcapacity：与gcnew类似，输出使用到的最大、最小空间。
• -gcold：监视老年代垃圾收集信息。
• -gcoldcapacity：与gcold类似，输出使用到的最大、最小空间。
• -gcutil：监视内容与gc类似，输出已使用空间占总空间的百分比。
• -printcompilation：输出已经被即时编译的方法。
  

3、jinfo：Java配置信息工具

jinfo帮助文档：

Usage:    jinfo [option] <pid>        (to connect to running process)    jinfo [option] <executable <core>        (to connect to a core file)    jinfo [option] [server_id@]<remote server IP or hostname>        (to connect to remote debug server)where <option> is one of:    -flag <name>         to print the value of the named VM flag    -flag [+|-]<name>    to enable or disable the named VM flag    -flag <name>=<value> to set the named VM flag to the given value    -flags               to print VM flags    -sysprops            to print Java system properties    <no option>          to print both of the above    -h | -help           to print this help message

执行案例：

jinfo -flags 18378Attaching to process ID 18378, please wait...Debugger attached successfully.Server compiler detected.JVM version is 25.261-b12Non-default VM flags: -XX:CICompilerCount=3 -XX:InitialHeapSize=262144000 -XX:MaxHeapSize=4164943872 -XX:MaxNewSize=1388314624 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=87031808 -XX:OldSize=175112192 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC

option参数说明：

• no option 输出全部的参数和系统属性。
• -flag name 输出对应名称的参数。
• -flag [+|-]name 开启或者关闭对应名称的参数。
• -flag name=value 设定对应名称的参数。
• -flags 输出全部的参数。
• -sysprops 输出系统属性。

4、jmap：Java内存映像工具

jmap帮助文档：

Usage:    jmap [option] <pid>        (to connect to running process)    jmap [option] <executable <core>        (to connect to a core file)    jmap [option] [server_id@]<remote server IP or hostname>        (to connect to remote debug server)where <option> is one of:    <none>               to print same info as Solaris pmap    -heap                to print java heap summary    -histo[:live]        to print histogram of java object heap; if the "live"                         suboption is specified, only count live objects    -clstats             to print class loader statistics    -finalizerinfo       to print information on objects awaiting finalization    -dump:<dump-options> to dump java heap in hprof binary format                         dump-options:                           live         dump only live objects; if not specified,                                        all objects in the heap are dumped.                           format=b     binary format                           file=<file>  dump heap to <file>                         Example: jmap -dump:live,format=b,file=heap.bin <pid>    -F                   force. Use with -dump:<dump-options> <pid> or -histo                         to force a heap dump or histogram when <pid> does not                         respond. The "live" suboption is not supported                         in this mode.    -h | -help           to print this help message    -J<flag>             to pass <flag> directly to the runtime system

执行案例：

jmap -dump:format=b,file=test.bin 1713Dumping heap to /Users/handexing/test.bin ...Heap dump file created

option参数说明：

• -dump:生成Java堆转储快照。格式为-dump:[live,]format=b,file=<filename>,其中live参数说明是否只dump出存活对象。
• -finalization：显示在F-queue中等待Finalizer线程执行finalize方法的对象。
• -heap：显示Java堆详细信息。例如哪种回收器、参数配置、分代情况等。linux平台下有效。
• -histo：显示堆中对象统计信息，包括类、实例数量等。
• -permstat：以classloader为统计口径显示永久代内存状态。linux平台下有效。
• -F：当JVM对-dump没有响应时，可以使用-F强制生成dump快照，linux平台下有效。

5、jhat：JVM堆转储快照分析工具

jhat帮助文档：

Usage:  jhat [-stack <bool>] [-refs <bool>] [-port <port>] [-baseline <file>] [-debug <int>] [-version] [-h|-help] <file>-J<flag>          Pass <flag> directly to the runtime system. For example, -J-mx512m to use a maximum heap size of 512MB-stack false:     Turn off tracking object allocation call stack.-refs false:      Turn off tracking of references to objects-port <port>:     Set the port for the HTTP server.  Defaults to 7000-exclude <file>:  Specify a file that lists data members that should be excluded from the reachableFrom query.-baseline <file>: Specify a baseline object dump.  Objects in both heap dumps with the same ID and same class will be marked as not being "new".-debug <int>:     Set debug level.   0:  No debug output   1:  Debug hprof file parsing   2:  Debug hprof file parsing, no server-version          Report version number-h|-help          Print this help and exit<file>            The file to readFor a dump file that contains multiple heap dumps,you may specify which dump in the fileby appending "#<number>" to the file name, i.e. "foo.hprof#3".All boolean options default to "true"

执行案例：

jhat test.bin  Reading from dump.bin...Dump file created Sat Feb 8 21:54:58 CST 2021Snapshot read, resolving...Resolving 271309 objects...Chasing references, expect 54 dots......................................................Eliminating duplicate references......................................................Snapshot resolved.Started HTTP server on port 7000Server is ready.

访问localhost:7000可以查看分析结果。

6、jstack：Java堆栈跟踪工具

Usage:    jstack [-l] <pid>        (to connect to running process)    jstack -F [-m] [-l] <pid>        (to connect to a hung process)    jstack [-m] [-l] <executable> <core>        (to connect to a core file)    jstack [-m] [-l] [server_id@]<remote server IP or hostname>        (to connect to a remote debug server)Options:    -F  to force a thread dump. Use when jstack <pid> does not respond (process is hung)    -m  to print both java and native frames (mixed mode)    -l  long listing. Prints additional information about locks    -h or -help to print this help message

执行案例：

jstack -l 17132021-02-08 20:16:16Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.261-b12 mixed mode):"DestroyJavaVM" #53 prio=5 os_prio=31 tid=0x00007fa898808800 nid=0x1103 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE   Locked ownable synchronizers:- None"http-nio-8080-AsyncTimeout" #51 daemon prio=5 os_prio=31 tid=0x00007fa898a4a000 nid=0x7903 waiting on condition [0x0000700007b0b000]   java.lang.Thread.State: TIMED_WAITING (sleeping)at java.lang.Thread.sleep(Native Method)at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1133)at java.lang.Thread.run(Thread.java:748)   Locked ownable synchronizers:- None

option参数说明：

• -F：正常输入不被响应时，强制输出堆栈。
• -m：如果调用本地方法的话，显示C/C++的堆栈。
• -l：除堆栈外，显示关于锁的附加信息。
  

Java调试进阶工具单

• btrace：https://github.com/btraceio/btrace
• arthas：https://arthas.aliyun.com/doc/
• JProfiler：https://www.ej-technologies.com/products/jprofiler/overview.html