Month: November 2013

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[Magento] Various tips

Disable log tables usage

If you already have an external “profiling” tool you can trash the content of several magento table like:

  • log_customer
  • log_quote
  • log_summary
  • log_summary_type
  • log_url
  • log_url_info
  • log_visitor
  • log_visitor_info
  • log_visitor_online

and replace the engine for them by ‘blackhole’. This will significantly improves performance.
You can find more info on the subject here.

Directories and NFS

The following directories can be shared inside NFS share:

  • var/cache
  • var/locks
  • var/media
  • var/exports

It recommended to not put var/report and var/logs inside.

SQL request for finding the number of order

mysql> select count(*), date_format(updated_at, '%Y%m%d %H') as datum from sales_flat_order where created_at > '2013-11-20' group by datum ;
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Mosh

I think no body reading this blog need an introduction to SSH, the standard of remote access terminal since the end of the 90’s. We all know and love this protocol, and its main implementation openssh. But sometimes SSH strict and clean design can be a pain in the ass. During my on-call duty i sometime have no other choice than to work using only a poor 3G/EDGE mobile access. High latency and intermittent connectivity don’t play well with SSH. Even with a GNU screen session on the remote server that never an enjoyable moment.

It’s in such situations that a tool like mosh become interesting.

What’s Mosh ?

Mosh stand for Mobile Shell. Like SSH that a remote-terminal protocol, but designed with mobile access in mind. It allows roaming, support intermittent connectivity, predictive echoing and local buffering for line typing/editing/deleting (yep openssh waits for the server’s reply before showing you your own typing, now you understand the typing latency). All of these features make it way more convenient to use on a high latency and/or unreliable links than a standard SSH session.

Installing Mosh

Mosh need to be installed on both the client and the server. For Debian, there is only one package simply call mosh. It’s available in the official repository since Debian Wheezy.

Using Mosh

It’s much simpler than what you think. Just type:

mosh username@server

and the mosh command will take care of everything. First it will log you using the ssh command, then start the mosh-daemon on the remote server. After that it close the ssh session and reconnect you to the mosh one. Note that by default the mosh-daemon chose a random UDP port between 60000 and 61000. If like me, you’re not a fan of subnet opening, you can use the -p parameter to force a specific port of your choice.

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lsof – a more powerful command than you think

lsof is a command used to find out which files are open by which process. But as the Unix way of life is that everything is a file, lsof can be use for a lot more then that:

List processes which opened a specific file

# lsof /var/log/syslog
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME
rsyslogd 13315 root    7w   REG   0,36   246213 15074839 /var/log/syslog

List opened files under a directory

# lsof +D /var/log/
COMMAND    PID          USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME
php5-fpm  1968          root    2w   REG   0,36      434 15074914 /var/log/php5-fpm.log
php5-fpm  1968          root    5w   REG   0,36      434 15074914 /var/log/php5-fpm.log
apache2   7466          root    2w   REG   0,36      279 15076913 /var/log/apache2/error.log
...

List all open files by a specific process

# lsof -p 1968
COMMAND   PID USER   FD   TYPE             DEVICE SIZE/OFF      NODE NAME
php5-fpm 1968 root  cwd    DIR               0,36     4096  15073281 /
php5-fpm 1968 root  rtd    DIR               0,36     4096  15073281 /
php5-fpm 1968 root  txt    REG               0,36  9110296  15081382 /usr/sbin/php5-fpm
php5-fpm 1968 root  mem    REG              253,0           15081382 /usr/sbin/php5-fpm (path dev=0,36)
...

List opened files based on process names

# lsof -c ssh
COMMAND   PID USER   FD   TYPE             DEVICE SIZE/OFF       NODE NAME
sshd     8463 root  cwd    DIR               0,36     4096   15073281 /
sshd     8463 root  rtd    DIR               0,36     4096   15073281 /
sshd     8463 root  txt    REG               0,36   787080   15076801 /usr/sbin/sshd
sshd     8463 root  mem    REG              253,0            15077206 /lib/x86_64-linux-gnu/libnss_files-2.19.so (path dev=0,36)
...

You can use the -c parameter, multiple time.

Show network connections

# lsof -i
COMMAND     PID  USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
ssh         636 daber    3u  IPv4 1381573      0t0  TCP 10.10.32.54:54188->b1.vpn.ti.smile.fr:ssh (ESTABLISHED)
ssh         834 daber    3u  IPv4 1385285      0t0  TCP 10.10.32.54:60902->b3.vpn.ti.smile.fr:ssh (ESTABLISHED)
ssh         892 daber    3u  IPv4 1386338      0t0  TCP 10.10.32.54:39496->b2.vpn.ti.smile.fr:ssh (ESTABLISHED)
chromium   1476 daber   87u  IPv4 1429223      0t0  TCP zapan.dhcp.mpl.intranet:49404->par10s09-in-f35.1e100.net:https (ESTABLISHED)
...

You can also add additional parameters to filter on the port number. For example to only show SSH connections: lsof -i TCP:22
You can also specify a range: lsof -i TCP:1-1024

Show all files opened by a specific user

# lsof -u daber
COMMAND     PID  USER   FD      TYPE             DEVICE  SIZE/OFF       NODE NAME
ssh         636 daber  cwd       DIR               0,35     28672   13238276 /home/daber
ssh         636 daber  rtd       DIR                8,1      4096          2 /
ssh         636 daber  txt       REG                8,1    666088     659561 /usr/bin/ssh
ssh         636 daber  mem       REG                8,1     22952     524315 /lib/x86_64-linux-gnu/libnss_dns-2.19.so
...

Note that you can use ^ to inverse the command (exclude only a particular user).

Kill all process of particular user

# kill `lsof -t -u daber`