nssdns-watch-question

#! /usr/bin/env perl

# Copyright (C) YangBingwu (detailyang)

use 5.006001;
use strict;
use warnings;
use Getopt::Std qw( getopts );

sub usage();

my %opts;

getopts("a:hdl:p:t:T:", \%opts) or die usage();

if ($opts{h}) {
    print usage();
    exit;
}

my $libnss_path = $opts{l} || "";
if (!-f $libnss_path) {
    die "libnss_dns.so path $libnss_path is not exist or ",
    "you do not have enough permissions.\n";
}

my $pid = $opts{p} || 0;
if ($pid !~ /^\d+$/) {
    die "Bad -p option value \"$pid\": not look like a pid\n";
}
my $pid_condition = "";
if ($pid) {
    $pid_condition = <<_EOS_;
    if ($pid > 0) {
        if (pid() != $pid) next
    }
_EOS_
}

my $time = $opts{t} || 20000;
if ($time !~ /^\d+$/) {
    die "Bad -t option value \"$time\": not look like time\n";
}

my $slowtime = $opts{T} || 0;
if ($slowtime !~ /^\d+$/) {
    die "Bad -T option value \"$slowtime\": not look like time\n";
}
my $slowtime_condition = "";
if ($slowtime) {
   $slowtime_condition = <<_EOS_;
   if ($slowtime * 1000 >= elapsed) {
        next
   }
_EOS_
}

my $stap_args = $opts{a} || '';

my $preamble = <<_EOS_;
global c%
global t%

probe begin {
    warn("Tracing libnss_dns($libnss_path) for pid:$pid")
}
_EOS_

my $stap_src = <<_EOS_;
$preamble

probe process("$libnss_path").function("_nss_dns_gethostbyname*") {
    $pid_condition
    c[pid(), execname(), ppfunc()] = \$name
    t[pid(), execname(), ppfunc()] = gettimeofday_us()
}

probe process("$libnss_path").function("_nss_dns_gethostbyname*").return {
    $pid_condition
    name = c[pid(), execname(), ppfunc()]
    begin = t[pid(), execname(), ppfunc()]
    if (name) {
        elapsed = gettimeofday_us() - begin
        $slowtime_condition
        printf("%s(%d): %s %dus\\n", execname(), pid(), user_string(name), elapsed)
    }

    delete c[pid(), execname(), ppfunc()]
    delete t[pid(), execname(), ppfunc()]
}

%(
$time > 0
%?
probe timer.ms($time) {
    warn("Time Ending....")
    exit()
}
%:
probe end {
    exit()
}
%)
_EOS_

if ($opts{d}) {
    print $stap_src;
    exit;
}

open my $in, "|stap --skip-badvars $stap_args -"
    or die "Cannot run stap: $!\n";

print $in $stap_src;

close $in;

sub usage() {

    return <<'_EOC_';
Usage:
    nssdns-watch-question [optoins]
Options:
    -a <args>           Pass extra arguments to the stap utility.
    -d                  Dump out the systemtap script source.
    -h                  Print this usage.
    -l <libnss_dns>     Specify the path of libnss_dns.so to sampling.
    -t <time>ms         Specify the number of mseconds for sampling.
    -T <slow time>ms    Specify the threshold of mseconds for sampling.
Examples:
    nssdns-watch-question -l /usr/lib64/libnss_dns.so.2
_EOC_
}