memcached tool. Herramienta para visualizar el uso de la cache en ram con memcached

Como he comentado en otro post Memcache es una cache en memoria ram, al contrario que la mayoria de los tipos de cache que son mediante ficheros físicos en disco duro. Se puede almacenar fragmentos arbitrarios de datos, ya sean un cadena, un array, un objeto un trozo de html o una página entera.

Tengo un código que he encontrado buscando memcached tool y está muy bien para visualizar las diferentes secciones de espacio que asigna el servicio de memcache y la cantidad de elementos que hay cacheados en ram.

vi /home/mi_usuario/memcached-tool

Pegar el siguiente código

#!/usr/bin/perl
#
# memcached-tool:
#   stats/management tool for memcached.
#
# Author:
#   Brad Fitzpatrick <brad@danga.com>
#
# License:
#   public domain.  I give up all rights to this
#   tool.  modify and copy at will.
#

use strict;
use IO::Socket::INET;

my $host = shift;
my $mode = shift || "display";
my ($from, $to);

if ($mode eq "display") {
    undef $mode if @ARGV;
} elsif ($mode eq "move") {
    $from = shift;
    $to = shift;
    undef $mode if $from < 6 || $from > 17;
    undef $mode if $to   < 6 || $to   > 17;
    print STDERR "ERROR: parameters out of rangenn" unless $mode;
} elsif ($mode eq 'dump') {
    ;
} elsif ($mode eq 'stats') {
    ;
} else {
    undef $mode;
}

undef $mode if @ARGV;

die
"Usage: memcached-tool <host[:port]> [mode]n
       memcached-tool 10.0.0.5:11211 display    # shows slabs
       memcached-tool 10.0.0.5:11211            # same.  (default is display)
       memcached-tool 10.0.0.5:11211 stats      # shows general stats
       memcached-tool 10.0.0.5:11211 move 7 9   # takes 1MB slab from class #7
                                                # to class #9.

You can only move slabs around once memory is totally allocated, and only
once the target class is full.  (So you can't move from #6 to #9 and #7
to #9 at the same itme, since you'd have to wait for #9 to fill from
the first reassigned page)
" unless $host && $mode;

$host .= ":11211" unless $host =~ /:d+/;

my $sock = IO::Socket::INET->new(PeerAddr => $host,
				 Proto    => 'tcp');
die "Couldn't connect to $hostn" unless $sock;

if ($mode eq "move") {
    my $tries = 0;
    while (1) {
	print $sock "slabs reassign $from $torn";
	my $res = <$sock>;
	$res =~ s/s+//;
	if ($res eq "DONE") {
	    print "Success.n";
	    exit 0;
	} elsif ($res eq "CANT") {
	    print "Error: can't move from $from to $to.  Destination not yet full?  See usage docs.n";
	    exit;
	} elsif ($res eq "BUSY") {
	    if (++$tries == 3) {
		print "Failed to move after 3 tries.  Try again later.n";
		exit;
	    }

	    print "Page busy, retrying...n";
	    sleep 1;
	}
    }

    exit;
}

if ($mode eq 'dump') {
    my %items;
    my $totalitems;

    print $sock "stats itemsrn";

    while (<$sock>) {
        last if /^END/;
        if (/^STAT items:(d*):number (d*)/) {
            $items{$1} = $2;
            $totalitems += $2;
        }
    }
    print STDERR "Dumping memcache contentsn";
    print STDERR "  Number of buckets: " . scalar(keys(%items)) . "n";
    print STDERR "  Number of items  : $totalitemsn";

    foreach my $bucket (sort(keys(%items))) {
        print STDERR "Dumping bucket $bucket - " . $items{$bucket} . " total itemsn";
        print $sock "stats cachedump $bucket $items{$bucket} 1rn";
        my %keyexp;
        while (<$sock>) {
            last if /^END/;
            # return format looks like this
            # ITEM foo [6 b; 1176415152 s]
            if (/^ITEM (S+) [.* (d+) s]/) {
                $keyexp{$1} = $2;
            }
        }

        foreach my $k (keys(%keyexp)) {
            my $val;
            print $sock "get $krn";
            my $response = <$sock>;
            $response =~ /VALUE (S+) (d+) (d+)/;
            my $flags = $2;
            my $len = $3;
            read $sock, $val , $len;
            # get the END
            $_ = <$sock>;
            $_ = <$sock>;
            print "add $k $flags $keyexp{$k} $lenrn$valrn";
        }
    }
    exit;
}

if ($mode eq 'stats') {
    my %items;

    print $sock "statsrn";

    while (<$sock>) {
        last if /^END/;
        chomp;
        if (/^STATs+(S*)s+(.*)/) {
            $items{$1} = $2;
        }
    }
    printf ("#%-17s %5s %11sn", $host, "Field", "Value");
    foreach my $name (sort(keys(%items))) {
      printf ("%24s %12sn", $name, $items{$name});

    }
    exit;
}

# display mode:

my %items;  # class -> { number, age, chunk_size, chunks_per_page,
            #            total_pages, total_chunks, used_chunks,
            #            free_chunks, free_chunks_end }

print $sock "stats itemsrn";
while (<$sock>) {
    last if /^END/;
    if (/^STAT items:(d+):(w+) (d+)/) {
	$items{$1}{$2} = $3;
    }
}

print $sock "stats slabsrn";
while (<$sock>) {
    last if /^END/;
    if (/^STAT (d+):(w+) (d+)/) {
	$items{$1}{$2} = $3;
    }
}

print "  #  Item_Size   Max_age  1MB_pages Count   Full?n";
foreach my $n (1..40) {
    my $it = $items{$n};
    next if (0 == $it->{total_pages});
    my $size = $it->{chunk_size} < 1024 ? "$it->{chunk_size} B " :
	sprintf("%.1f kB", $it->{chunk_size} / 1024.0);
    my $full = $it->{free_chunks_end} == 0 ? "yes" : " no";
    printf "%3d   %8s %7d s %7d %7d %7sn",
                        $n, $size, $it->{age}, $it->{total_pages},
                        $it->{number}, $full;
}

Comprobar cuanta memoria se está usando y la distribución de la misma. En el siguiente ejemplo voy a estimar que se ha instalado memcached con la configuracion por defecto, en localhost y escuchando las peticiones del puerto 11211

cd /home/mi_usuario
./memcached-tool 127.0.0.1:11211 display

Tendrá que aparecer por consola un tabla parecida a la siguiente.

En la columna “count” aparecen el numero de elementos que hay cacheados para los diferentes tipos de espacios asignados.