libcjstat

A C library to get jstat-like metrics for running jvms.

The jstat tool displays performance statistics for an instrumented HotSpot Java virtual machine (JVM). Java developers concern performance statistics when performance tuning or tracking memory leak problem. Tool jstat from JDK is easy-to-use and useful when coping with a single JVM. But jstat is a java program itself, cost highly when raising a jstat, it is hard to track lots of JVMs in the cluster.

With libcjstat, you can build a JVM cluster monitor easily, collecting the statistics without high cost, storing them in InfluxDB, visualizing them by Grafana.

Version: 0.1

Features

• Get all jstat metrics via a simple function call.
• Get started with including some headers simply.
• No external dependencies.
• Tested.

Requirements

• GNU99 C Compiler
• Java 7
• Linux or OS X (No support for Windows)

How to start

1. Copy folder cjstat/ to your project.
2. Include headers in your code.
3. Done.

Typical usages

Suppose a java program is running (pid=14548) for demonstrations.

Get jstat metrics

#include <stdio.h>
#include "cjstat/hsperfdata.h"
#include "cjstat/jstat_metrics.h"

int main() {

    hsperfdata * hs = get_hsperfdata_by_pid(14548);
    hsperfdata_hashmap * hm = convert_hsperfdata_to_hashmap(hs);
    jstat_metrics jm = get_jstat_metrics(hm);

    printf("S0C = %.4lf\n", jm.S0C);
    printf("S1C = %.4lf\n", jm.S1C);
    printf("S0U = %.4lf\n", jm.S0U);
    printf("S1U = %.4lf\n", jm.S1U);
    printf("EC = %.4lf\n", jm.EC);
    printf("EU = %.4lf\n", jm.EU);
    printf("OC = %.4lf\n", jm.OC);
    printf("OU = %.4lf\n", jm.OU);
    printf("PC = %.4lf\n", jm.PC);
    printf("PU = %.4lf\n", jm.PU);
    printf("YGC = %lld\n", jm.YGC);
    printf("YGCT = %.4lf\n", jm.YGCT);
    printf("FGC = %lld\n", jm.FGC);
    printf("FGCT = %.4lf\n", jm.FGCT);
    printf("GCT = %.4lf\n", jm.GCT);

    _hashmap_destroy(hm);
    destroy_hsperfdata(hs);

    return 0;
}

Output

S0C = 6528.0000
S1C = 6528.0000
S0U = 0.0000
S1U = 0.0000
EC = 52480.0000
EU = 3148.9531
OC = 5312.0000
OU = 0.0000
PC = 21248.0000
PU = 4954.5078
YGC = 0
YGCT = 0.0000
FGC = 0
FGCT = 0.0000
GCT = 0.0000

Get pids of all running JVMs

#include <stdio.h>
#include "cjstat/util.h"

int main() {

    cjstat_jvm_pid * pids = get_all_jvm_pid();
    while (NULL != pids) {
        printf("%d %s\n", pids->pid, pids->path);
        get_next_jvm_pid(&pids);
    }

    return 0;
}

Output

14548 /var/folders/xx/pxh4yd_56yn8lsx944bvv_s80000gn/T/hsperfdata_weiyulan/14548

To-do

• Write docs
• Make it compatible with standard C99 compiler (small changes)
• Make it compatible with Java 8
• Write a essay to explain how hsperfdata works

Contributor

aheadlead email: aheadlead@dlifep.com

A junior student in NUAA, China.

License

MIT

What's more?

This project originates from my intern work, with my rewriting in C for a month, at the end of my sophomore year.

I know the importance of codes quailty, and did write codes with heart and soul. Because it is the FIRST open source project since I wrote codes. It is inevitable that making mistakes when coding. If you have any problem or question, please send mails or issue to me so that let me know.

Thank you very much.