Quimateur

Creamos un directorio:

 mkdir -p /db/tmpfs01 && chown mysql:mysql /db/tmpfs01D

Montamos la unidad (en este caso 1Gb):

mount tmpfs /db/tmpfs01 -t tmpfs -o size=1G

Editamos nuestro mysql y añadimos/modificamos:

tmpdir = /db/tmpfs01

Para hacer esto de manera persistente deberemos editar nuestro fichero /etc/fstab

tmpfs /db/tmpfs01 tmpfs rw,uid=105,gid=112,size=1G,nr_inodes=10k,mode=0755 0 0

On the client side:

Increase the ephermal port range, and decrease the fin_timeout To find out the default values:

sysctl net.ipv4.ip_local_port_range

sysctl net.ipv4.tcp_fin_timeout

The ephermal port range defines the maximum number of outbound sockets a host can create from a particular I.P. address. The fin_timeout defines the minimum time these sockets will stay in TIME_WAIT state (unusable after being used once). Usual system defaults are:

net.ipv4.ip_local_port_range = 32768 61000

net.ipv4.tcp_fin_timeout = 60

Setting the range to 15000 61000 is pretty common these days. You could further increase the availability by decreasing the fin_timeout. Suppose you do both, you should see over 1500 outbound connections, more readily.

On the Server Side:

The net.core.somaxconn value has an important role. It limits the maximum number of requests queued to a listen socket. If you are sure of your server application's capability, bump it up from default 128 to something like 128 to 1024. Now you can take advantage of this increase by modifying the listen backlog variable in php-fpm

txqueuelen parameter of your ethernet cards also have a role to play. Default values are 1000, so bump them up to 5000 or even more if your system can handle it.

ifconfig eth0 txqueuelen 5000

Similarly bump up the values for net.core.netdev_max_backlog and net.ipv4.tcp_max_syn_backlog. Their default values are 1000 and 1024 respectively.

Previous to change:

net.ipv4.ip_local_port_range = 32768    61000

net.ipv4.tcp_fin_timeout = 60

Change:

sysctl -w net.ipv4.ip_local_port_range="15000 61000"

sysctl -w net.ipv4.tcp_fin_timeout=30

Previous to change:

net.core.netdev_max_backlog = 1000

net.ipv4.tcp_max_syn_backlog = 1024

net.core.somaxconn = 128

Change:

sysctl -w net.core.netdev_max_backlog=2000

sysctl -w net.core.somaxconn=1024

Listar todas las conexiones TCP a puerto 80

netstat -tunva|grep 80

Y enumerarlas:

netstat -tunva|grep 80|wc -l

Conexiones máximas que acepta nuestro sistema:

ulimit -n

Connections grouped by stat

netstat -an|awk '/tcp/ {print $6}'|sort|uniq -c

Connections in TIME_WAITED

netstat -n | grep TIME_WAIT | wc -l

How long connections will last?

netstat -on | grep TIME_WAIT | less

keep in mind!

tcp_tw_recycle - BOOLEAN Enable fast recycling TIME-WAIT sockets. Default value is 0. It should not be changed without advice/request of technical experts. tcp_tw_reuse - BOOLEAN Allow to reuse TIME-WAIT sockets for new connections when it is safe from protocol viewpoint. Default value is 0. It should not be changed without advice/request of technical experts.

Cuando una aplicación web llega a un cierto numero de usuarios concurrentes, es posible que el método habitual de almacenamiento de sesiones PHP (un directorio en disco) no sea el más eficiente.

PHP soporta de manera nativa el almacenamiento de sesiones en Memcached (o Memcache)

Sólo hay que editar el fichero php.ini

Comentar borrar la línea:

sesion.save_handler = files

Y añadir:

session.save_handler = memcached session.save_path = "localhost:11211"

O si usamos memcache:

session.save_handler = memcache session.save_path = "tcp://localhost:11211"

apt-get install libpcre3 libpcre3-dev

pecl install apc

Algunas notas/ideas a tener en cuenta una vez instalado nginx con soporte php:

- Proteger directorios .svn/htaccess

- Evitar el famoso 502 Bad Gateway, aumentando el numero/tamaño de buffers en:  /etc/nginx/fastcgi_params

fastcgi_buffers 256 16k;

fastcgi_buffer_size 32k;

- Setear tamaño máximo de body en /etc/nginx/nginx.conf (de otro modo cascarán todos los uploads mayores de 2M)

client_max_body_size 8m;

- No poner más de 4 workers en /etc/nginx/nginx.conf (1 por core de cpu)

- Esconder la versión de servidor. server_tokens = off

- Customizar errores 404/403

URLS Interesantes:

http://php-fpm.org/wiki/Features

http://www.cyberciti.biz/faq/howto-nginx-customizing-404-403-error-page/

Instalar libreria libaio

apt-get install libaio-dev

Bajamos la última versión de la versión 1.5 de lighttpd (no vale 1.4)

Podemos consultar las versiones en: http://blog.lighttpd.net/articles/tag/1.5.0

wget http://www.lighttpd.net/download/lighttpd-1.5.0-r1992.tar.gz

Instalamos herramientas para descomprimir (si fuera necesario)

apt-get install zip unzip tar

apt-get install libpcre3 libpcre3-dev

Descomprimimos

tar -zxvf lighttpd-1.5.0-r1992.tar.gz

Instalamos libreria glib

apt-get install libglib2.0

Configuramos, activando el soporte para el async I/O

./configure --with-linux-aio

make

make install

Preparamos el fichero de configuración y arranque por defecto al inicio.

sed -e 's/FOO/lighttpd/g' doc/rc.lighttpd > /etc/init.d/lighttpd

chmod a+rx /etc/init.d/lighttpd

update-rc.d lighttpd defaults

Copiamos el fichero de configuración a /etc/lighttpd/lighttpd.conf

Además de todos los parámetros necesarios, es importante activar la directiva de escritura asíncrona.

server.network-backend = "linux-aio-sendfile"

No está de más editar y revisar el fichero /etc/init.d/lighttpd creado, para asegurar que las rutas a los ejecutables/configuraciones son correctas.

Fuentes/Más info:

http://www.cyberciti.biz/tips/rhel-lighttpd-15-installation-configuration-howto.html

http://www.cyberciti.biz/tips/howto-increase-lighttpd-performance-with-linux-aio.html

How To Connect

telnet IP PORT

Supported Commands

Command Description Example get Reads a value get mykey set Set a key unconditionally set mykey 0 60 5 add Add a new key add newkey 0 60 5 replace Overwrite existing key replace key 0 60 5 append Append data to existing key append key 0 60 15 prepend Prepend data to existing key prepend key 0 60 15 incr Increments numerical key value by given number incr mykey 2 decr Decrements numerical key value by given number decr mykey 5 delete Deletes an existing key delete mykey flush_all Invalidate specific items immediately flush_all Invalidate all items in n seconds flush_all 900 stats Prints general statistics stats Prints memory statistics stats slabs Prints memory statistics stats malloc Print higher level allocation statistics stats items stats detail stats sizes Resets statistics stats reset version Prints server version. version verbosity Increases log level verbosity quit Terminate telnet session quit

Traffic Statistics

You can query the current traffic statistics using the command

stats

You will get a listing which serves the number of connections, bytes in/out and much more.

Example Output:

STAT pid 14868 STAT uptime 175931 STAT time 1220540125 STAT version 1.2.2 STAT pointer_size 32 STAT rusage_user 620.299700 STAT rusage_system 1545.703017 STAT curr_items 228 STAT total_items 779 STAT bytes 15525 STAT curr_connections 92 STAT total_connections 1740 STAT connection_structures 165 STAT cmd_get 7411 STAT cmd_set 28445156 STAT get_hits 5183 STAT get_misses 2228 STAT evictions 0 STAT bytes_read 2112768087 STAT bytes_written 1000038245 STAT limit_maxbytes 52428800 STAT threads 1 END

Memory Statistics

You can query the current memory statistics using

stats slabs

Example Output:

STAT 1:chunk_size 80 STAT 1:chunks_per_page 13107 STAT 1:total_pages 1 STAT 1:total_chunks 13107 STAT 1:used_chunks 13106 STAT 1:free_chunks 1 STAT 1:free_chunks_end 12886 STAT 2:chunk_size 100 STAT 2:chunks_per_page 10485 STAT 2:total_pages 1 STAT 2:total_chunks 10485 STAT 2:used_chunks 10484 STAT 2:free_chunks 1 STAT 2:free_chunks_end 10477 [...] STAT active_slabs 3 STAT total_malloced 3145436 END

Which Keys Are Used?

There seems to be no builtin function to determine the currently set keys. However you can use the

stats items

command to determine how many keys do exist.

stats items STAT items:1:number 220 STAT items:1:age 83095 STAT items:2:number 7 STAT items:2:age 1405 [...] END

Never Set a Timeout > 30 Days!

While this has nothing to do with the telnet access this is a problem you might run into. If you try to "set" or "add" a key with a timeout bigger than the allowed maximum you might not get what you expect because memcached then treats the value as a Unix timestamp. Also if the timestamp is in the past it will do nothing at all. Your command will silently fail.

So if you want to use the maximum lifetime specify 2592000. Example:

set my_key 0 2592000 1 1

Disappearing Keys on Overflow

varnishtop The varnishtop utility reads the shared memory logs and presents a continuously updated list of the most commonly occurring log entries. With suitable filtering using the -I, -i, -X and -x options, it can be used to display a ranking of requested documents, clients, user agents, or any other information which is recorded in the log. varnishtop -i rxurl will show you what URLs are beeing asked for by the client. varnishtop -i txurl will show you what your backend is beeing asked the most. varnishtop -i RxHeader -I Accept-Encoding will show the most popular Accept-Encoding header the client are sendning you.

varnishhist The varnishhist utility reads varnishd(1) shared memory logs and presents a continuously updated histogram showing the distribution of the last N requests by their processing. The value of N and the vertical scale are displayed in the top left corner. The horizontal scale is logarithmic. Hits are marked with a pipe character (“|”), and misses are marked with a hash character (“#”).

varnishsizes Varnishsizes does the same as varnishhist, except it shows the size of the objects and not the time take to complete the request. This gives you a good overview of how big the objects you are serving are.

A veces, grub deja de funcionar: intenta arrancar desde un dispositivo que no existe o que no está configurado para ello.

En esos casos nos deja en un prompt de la consola de rescate de grub.

grub rescue>

Cada vez tengo más claro que la persona que hizo esta consola, es un jodido sádico hijodeputa: no le dió la gana de poner un comando de ayuda para saber la lista de comandos disponibles.

Venga, vamos a hacer que esto arranque:

Necesitamos ver la lista de particiones que tenemos disponibles

ls

Este comando nos mostrará todas las particiones que ha podido encontrar.

En mi caso: 

(hd0) (hd0,1) (hd1) (hd1,1) (hd1,5) (hd2) (hd2,1) (hd3) (hd3,1)

Ahora debemos saber cual de esas particiones contiene la carpeta /boot/grub, con todos los datos necesarios para arrancar, para ello, bastará con ir haciendo un "ls" para cada una de las particiones, tal que:

ls (hd1,1)/

* Ojo con la barra del final, dió por culo cosa mala, oiga

Una vez encontremos la partición correcta el "ls" nos devolverá un listado caracterísitico de carpetas, entre ellas la necesitada boot

Ahora hemos de añadir el prefijo:

set prefix=(hd1,1)/boot/grub

* Obviamente cambia el hd1,1 por hdX,Y según toque en tu caso, la carpeta grub no tiene porque estár debajo de boot.

Vale, ahora vamos a ampliar un poco los comandos que disponemos en la consola:

insmod (hd1,1)/boot/grub/linux.mod

Ahora sólo quedará:

Setear como root la partición

set root=(hd1,1)

Cargamos la imagen de linux

linux /boot/vmlinuz-2.6.32-23-generic root=/dev/sdb1

* Si no estamos seguros de que imagen cargar lo podemos comprobar con un "ls" del directorio boot

** La nomenclatura del punto de montaje: sdb1, viene dada por el nombre de la partición: (hd1,1) es sdb1, del mismo modo que (hd0,2) sería: sda2

Ahora falta cargar el kernel:

initrd /initrd.img

Y,finally, podemos arrancar

boot

Una vez dentro del sistema, podremos reinstalar grub para evitar este error en la próxima carga

¿Un claro ejemplo de fallo en publicidad contextual? ¿O simplemente mala leche?