聊聊Elasticsearch的OsProbe

摘要：序本文主要研究一下的使用代码块反射获取了这几个它们是从获取的方法返回，它由这几部分组成

本文主要研究一下Elasticsearch的OsProbe

elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/monitor/os/OsProbe.java

public class OsProbe {

    private static final OperatingSystemMXBean osMxBean = ManagementFactory.getOperatingSystemMXBean();

    private static final Method getFreePhysicalMemorySize;
    private static final Method getTotalPhysicalMemorySize;
    private static final Method getFreeSwapSpaceSize;
    private static final Method getTotalSwapSpaceSize;
    private static final Method getSystemLoadAverage;
    private static final Method getSystemCpuLoad;

    static {
        getFreePhysicalMemorySize = getMethod("getFreePhysicalMemorySize");
        getTotalPhysicalMemorySize = getMethod("getTotalPhysicalMemorySize");
        getFreeSwapSpaceSize = getMethod("getFreeSwapSpaceSize");
        getTotalSwapSpaceSize = getMethod("getTotalSwapSpaceSize");
        getSystemLoadAverage = getMethod("getSystemLoadAverage");
        getSystemCpuLoad = getMethod("getSystemCpuLoad");
    }

    /**
     * Returns the amount of free physical memory in bytes.
     */
    public long getFreePhysicalMemorySize() {
        if (getFreePhysicalMemorySize == null) {
            return -1;
        }
        try {
            return (long) getFreePhysicalMemorySize.invoke(osMxBean);
        } catch (Exception e) {
            return -1;
        }
    }

    /**
     * Returns the total amount of physical memory in bytes.
     */
    public long getTotalPhysicalMemorySize() {
        if (getTotalPhysicalMemorySize == null) {
            return -1;
        }
        try {
            return (long) getTotalPhysicalMemorySize.invoke(osMxBean);
        } catch (Exception e) {
            return -1;
        }
    }

    /**
     * Returns the amount of free swap space in bytes.
     */
    public long getFreeSwapSpaceSize() {
        if (getFreeSwapSpaceSize == null) {
            return -1;
        }
        try {
            return (long) getFreeSwapSpaceSize.invoke(osMxBean);
        } catch (Exception e) {
            return -1;
        }
    }

    /**
     * Returns the total amount of swap space in bytes.
     */
    public long getTotalSwapSpaceSize() {
        if (getTotalSwapSpaceSize == null) {
            return -1;
        }
        try {
            return (long) getTotalSwapSpaceSize.invoke(osMxBean);
        } catch (Exception e) {
            return -1;
        }
    }

    /**
     * The system load averages as an array.
     *
     * On Windows, this method returns {@code null}.
     *
     * On Linux, this method returns the 1, 5, and 15-minute load averages.
     *
     * On macOS, this method should return the 1-minute load average.
     *
     * @return the available system load averages or {@code null}
     */
    final double[] getSystemLoadAverage() {
        if (Constants.WINDOWS) {
            return null;
        } else if (Constants.LINUX) {
            try {
                final String procLoadAvg = readProcLoadavg();
                assert procLoadAvg.matches("(d+.d+s+){3}d+/d+s+d+");
                final String[] fields = procLoadAvg.split("s+");
                return new double[]{Double.parseDouble(fields[0]), Double.parseDouble(fields[1]), Double.parseDouble(fields[2])};
            } catch (final IOException e) {
                if (logger.isDebugEnabled()) {
                    logger.debug("error reading /proc/loadavg", e);
                }
                return null;
            }
        } else {
            assert Constants.MAC_OS_X;
            if (getSystemLoadAverage == null) {
                return null;
            }
            try {
                final double oneMinuteLoadAverage = (double) getSystemLoadAverage.invoke(osMxBean);
                return new double[]{oneMinuteLoadAverage >= 0 ");if (logger.isDebugEnabled()) {
                    logger.debug("error reading one minute load average from operating system", e);
                }
                return null;
            }
        }
    }

    public short getSystemCpuPercent() {
        return Probes.getLoadAndScaleToPercent(getSystemCpuLoad, osMxBean);
    }

    public OsStats osStats() {
        final OsStats.Cpu cpu = new OsStats.Cpu(getSystemCpuPercent(), getSystemLoadAverage());
        final OsStats.Mem mem = new OsStats.Mem(getTotalPhysicalMemorySize(), getFreePhysicalMemorySize());
        final OsStats.Swap swap = new OsStats.Swap(getTotalSwapSpaceSize(), getFreeSwapSpaceSize());
        final OsStats.Cgroup cgroup = Constants.LINUX ");return new OsStats(System.currentTimeMillis(), cpu, mem, swap, cgroup);
    }

    /**
     * Returns a given method of the OperatingSystemMXBean, or null if the method is not found or unavailable.
     */
    private static Method getMethod(String methodName) {
        try {
            return Class.forName("com.sun.management.OperatingSystemMXBean").getMethod(methodName);
        } catch (Exception e) {
            // not available
            return null;
        }
    }

    //......
}

OsProbe使用static代码块反射获取了getFreePhysicalMemorySize、getTotalPhysicalMemorySize、getFreeSwapSpaceSize、getTotalSwapSpaceSize、getSystemLoadAverage、getSystemCpuLoad这几个method；它们是从com.sun.management.OperatingSystemMXBean获取的；osStats方法返回OsStats，它由OsStats.Cpu、OsStats.Mem、OsStats.Swap、OsStats.Cgroup这几部分组成

elasticsearch-7.0.1/server/src/main/java/org/elasticsearch/monitor/os/OsProbe.java

public class OsProbe {
	//......

    /**
     * Basic cgroup stats.
     *
     * @return basic cgroup stats, or {@code null} if an I/O exception occurred reading the cgroup stats
     */
    private OsStats.Cgroup getCgroup() {
        try {
            if (!areCgroupStatsAvailable()) {
                return null;
            } else {
                final Map controllerMap = getControlGroups();
                assert !controllerMap.isEmpty();

                final String cpuAcctControlGroup = controllerMap.get("cpuacct");
                assert cpuAcctControlGroup != null;
                final long cgroupCpuAcctUsageNanos = getCgroupCpuAcctUsageNanos(cpuAcctControlGroup);

                final String cpuControlGroup = controllerMap.get("cpu");
                assert cpuControlGroup != null;
                final long cgroupCpuAcctCpuCfsPeriodMicros = getCgroupCpuAcctCpuCfsPeriodMicros(cpuControlGroup);
                final long cgroupCpuAcctCpuCfsQuotaMicros = getCgroupCpuAcctCpuCfsQuotaMicros(cpuControlGroup);
                final OsStats.Cgroup.CpuStat cpuStat = getCgroupCpuAcctCpuStat(cpuControlGroup);

                final String memoryControlGroup = controllerMap.get("memory");
                assert memoryControlGroup != null;
                final String cgroupMemoryLimitInBytes = getCgroupMemoryLimitInBytes(memoryControlGroup);
                final String cgroupMemoryUsageInBytes = getCgroupMemoryUsageInBytes(memoryControlGroup);

                return new OsStats.Cgroup(
                    cpuAcctControlGroup,
                    cgroupCpuAcctUsageNanos,
                    cpuControlGroup,
                    cgroupCpuAcctCpuCfsPeriodMicros,
                    cgroupCpuAcctCpuCfsQuotaMicros,
                    cpuStat,
                    memoryControlGroup,
                    cgroupMemoryLimitInBytes,
                    cgroupMemoryUsageInBytes);
            }
        } catch (final IOException e) {
            logger.debug("error reading control group stats", e);
            return null;
        }
    }

    @SuppressForbidden(reason = "access /proc/self/cgroup, /sys/fs/cgroup/cpu, /sys/fs/cgroup/cpuacct and /sys/fs/cgroup/memory")
    boolean areCgroupStatsAvailable() {
        if (!Files.exists(PathUtils.get("/proc/self/cgroup"))) {
            return false;
        }
        if (!Files.exists(PathUtils.get("/sys/fs/cgroup/cpu"))) {
            return false;
        }
        if (!Files.exists(PathUtils.get("/sys/fs/cgroup/cpuacct"))) {
            return false;
        }
        if (!Files.exists(PathUtils.get("/sys/fs/cgroup/memory"))) {
            return false;
        }
        return true;
    }

    private Map getControlGroups() throws IOException {
        final List lines = readProcSelfCgroup();
        final Map controllerMap = new HashMap<>();
        for (final String line : lines) {
            /*
             * The virtual file /proc/self/cgroup lists the control groups that the Elasticsearch process is a member of. Each line contains
             * three colon-separated fields of the form hierarchy-ID:subsystem-list:cgroup-path. For cgroups version 1 hierarchies, the
             * subsystem-list is a comma-separated list of subsystems. The subsystem-list can be empty if the hierarchy represents a cgroups
             * version 2 hierarchy. For cgroups version 1
             */
            final String[] fields = line.split(":");
            assert fields.length == 3;
            final String[] controllers = fields[1].split(",");
            for (final String controller : controllers) {
                final String controlGroupPath;
                if (CONTROL_GROUPS_HIERARCHY_OVERRIDE != null) {
                    /*
                     * Docker violates the relationship between /proc/self/cgroup and the /sys/fs/cgroup hierarchy. It"s possible that this
                     * will be fixed in future versions of Docker with cgroup namespaces, but this requires modern kernels. Thus, we provide
                     * an undocumented hack for overriding the control group path. Do not rely on this hack, it will be removed.
                     */
                    controlGroupPath = CONTROL_GROUPS_HIERARCHY_OVERRIDE;
                } else {
                    controlGroupPath = fields[2];
                }
                final String previous = controllerMap.put(controller, controlGroupPath);
                assert previous == null;
            }
        }
        return controllerMap;
    }

    private long getCgroupCpuAcctUsageNanos(final String controlGroup) throws IOException {
        return Long.parseLong(readSysFsCgroupCpuAcctCpuAcctUsage(controlGroup));
    }

    @SuppressForbidden(reason = "access /sys/fs/cgroup/cpuacct")
    String readSysFsCgroupCpuAcctCpuAcctUsage(final String controlGroup) throws IOException {
        return readSingleLine(PathUtils.get("/sys/fs/cgroup/cpuacct", controlGroup, "cpuacct.usage"));
    }

    private long getCgroupCpuAcctCpuCfsPeriodMicros(final String controlGroup) throws IOException {
        return Long.parseLong(readSysFsCgroupCpuAcctCpuCfsPeriod(controlGroup));
    }

    @SuppressForbidden(reason = "access /sys/fs/cgroup/cpu")
    String readSysFsCgroupCpuAcctCpuCfsPeriod(final String controlGroup) throws IOException {
        return readSingleLine(PathUtils.get("/sys/fs/cgroup/cpu", controlGroup, "cpu.cfs_period_us"));
    }

    private long getCgroupCpuAcctCpuCfsQuotaMicros(final String controlGroup) throws IOException {
        return Long.parseLong(readSysFsCgroupCpuAcctCpuAcctCfsQuota(controlGroup));
    }

    @SuppressForbidden(reason = "access /sys/fs/cgroup/cpu")
    String readSysFsCgroupCpuAcctCpuAcctCfsQuota(final String controlGroup) throws IOException {
        return readSingleLine(PathUtils.get("/sys/fs/cgroup/cpu", controlGroup, "cpu.cfs_quota_us"));
    }    

    private OsStats.Cgroup.CpuStat getCgroupCpuAcctCpuStat(final String controlGroup) throws IOException {
        final List lines = readSysFsCgroupCpuAcctCpuStat(controlGroup);
        long numberOfPeriods = -1;
        long numberOfTimesThrottled = -1;
        long timeThrottledNanos = -1;
        for (final String line : lines) {
            final String[] fields = line.split("s+");
            switch (fields[0]) {
                case "nr_periods":
                    numberOfPeriods = Long.parseLong(fields[1]);
                    break;
                case "nr_throttled":
                    numberOfTimesThrottled = Long.parseLong(fields[1]);
                    break;
                case "throttled_time":
                    timeThrottledNanos = Long.parseLong(fields[1]);
                    break;
            }
        }
        assert numberOfPeriods != -1;
        assert numberOfTimesThrottled != -1;
        assert timeThrottledNanos != -1;
        return new OsStats.Cgroup.CpuStat(numberOfPeriods, numberOfTimesThrottled, timeThrottledNanos);
    }

    private String getCgroupMemoryLimitInBytes(final String controlGroup) throws IOException {
        return readSysFsCgroupMemoryLimitInBytes(controlGroup);
    }

    @SuppressForbidden(reason = "access /sys/fs/cgroup/memory")
    String readSysFsCgroupMemoryLimitInBytes(final String controlGroup) throws IOException {
        return readSingleLine(PathUtils.get("/sys/fs/cgroup/memory", controlGroup, "memory.limit_in_bytes"));
    }

    private String getCgroupMemoryUsageInBytes(final String controlGroup) throws IOException {
        return readSysFsCgroupMemoryUsageInBytes(controlGroup);
    }

            
	//......
}

OsProbe.getCgroup方法首先通过areCgroupStatsAvailable方法确定是否有cgroup的统计信息，不存在则直接返回null；存在则通过getControlGroups读取相关信息构建OsStats.Cgroup

areCgroupStatsAvailable方法判断/proc/self/cgroup、/sys/fs/cgroup/cpu、/sys/fs/cgroup/cpuacct、/sys/fs/cgroup/memory这几个文件是否存在，不存在则返回false，都存在则返回true

getControlGroups()方法从/proc/self/cgroup读取信息，它包括cpu、cpuacct、memory三部分；其中cpu信息从/sys/fs/cgroup/cpu读取；cpuacct信息从/sys/fs/cgroup/cpuacct读取；memory信息从/sys/fs/cgroup/memory读取

cat /proc/self/cgroup
12:pids:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
11:hugetlb:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
10:net_prio:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
9:perf_event:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
8:net_cls:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
7:freezer:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
6:devices:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
5:memory:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
4:blkio:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
3:cpuacct:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
2:cpu:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845
1:cpuset:/docker/d8942cd630dbfddeb5696bd2dc134405c11433458d2aaa1845218086a2015845

/sys/fs/cgroup/cpu # ls
cgroup.clone_children  cpu.rt_period_us       notify_on_release
cgroup.procs           cpu.rt_runtime_us      tasks
cpu.cfs_period_us      cpu.shares
cpu.cfs_quota_us       cpu.stat

cat /sys/fs/cgroup/cpu/cpu.cfs_period_us
100000

cat /sys/fs/cgroup/cpu/cpu.cfs_quota_us
-1

/sys/fs/cgroup/cpuacct # ls
cgroup.clone_children      cpuacct.usage_percpu_sys
cgroup.procs               cpuacct.usage_percpu_user
cpuacct.stat               cpuacct.usage_sys
cpuacct.usage              cpuacct.usage_user
cpuacct.usage_all          notify_on_release
cpuacct.usage_percpu       tasks

cat /sys/fs/cgroup/cpuacct/cpuacct.usage
31322196847

cat /sys/fs/cgroup/cpuacct/cpuacct.stat
user 2759
system 179

/sys/fs/cgroup/memory # ls
cgroup.clone_children               memory.memsw.failcnt
cgroup.event_control                memory.memsw.limit_in_bytes
cgroup.procs                        memory.memsw.max_usage_in_bytes
memory.failcnt                      memory.memsw.usage_in_bytes
memory.force_empty                  memory.move_charge_at_immigrate
memory.kmem.failcnt                 memory.numa_stat
memory.kmem.limit_in_bytes          memory.oom_control
memory.kmem.max_usage_in_bytes      memory.pressure_level
memory.kmem.slabinfo                memory.soft_limit_in_bytes
memory.kmem.tcp.failcnt             memory.stat
memory.kmem.tcp.limit_in_bytes      memory.swappiness
memory.kmem.tcp.max_usage_in_bytes  memory.usage_in_bytes
memory.kmem.tcp.usage_in_bytes      memory.use_hierarchy
memory.kmem.usage_in_bytes          notify_on_release
memory.limit_in_bytes               tasks
memory.max_usage_in_bytes

cat /sys/fs/cgroup/memory/memory.limit_in_bytes
9223372036854771712

cat /sys/fs/cgroup/memory/memory.usage_in_bytes
198819840

OsProbe使用static代码块反射获取了getFreePhysicalMemorySize、getTotalPhysicalMemorySize、getFreeSwapSpaceSize、getTotalSwapSpaceSize、getSystemLoadAverage、getSystemCpuLoad这几个method；它们是从com.sun.management.OperatingSystemMXBean获取的；osStats方法返回OsStats，它由OsStats.Cpu、OsStats.Mem、OsStats.Swap、OsStats.Cgroup这几部分组成

OsProbe.getCgroup方法首先通过areCgroupStatsAvailable方法确定是否有cgroup的统计信息，不存在则直接返回null；存在则通过getControlGroups读取相关信息构建OsStats.Cgroup

areCgroupStatsAvailable方法判断/proc/self/cgroup、/sys/fs/cgroup/cpu、/sys/fs/cgroup/cpuacct、/sys/fs/cgroup/memory这几个文件/目录是否存在，不存在则返回false，都存在则返回true；getControlGroups()方法从/proc/self/cgroup读取信息，它包括cpu、cpuacct、memory三部分；其中cpu信息从/sys/fs/cgroup/cpu读取；cpuacct信息从/sys/fs/cgroup/cpuacct读取；memory信息从/sys/fs/cgroup/memory读取

OsProbe