Now-proofing your development!

December 12th, 2013

At work today we discussed the concept of future-proofing, which I consider a bad practice. I can elaborate another time but my talented colleague Anders Holmberg invented now-proofing on the spot. That’s what we should be aiming for!

Our bried discussion was inspired by this quote:

If you are not embarrassed by the first version of your product, you’ve launched too late.

- Reid Hoffman

Source: http://startupquote.com/post/855482768

David’s technology radar

November 10th, 2013

Inspired by ThoughtWorks Technology Radar, here is an attempt to write down my current world view:

Adopt

Trial

  • Mozilla Persona - use the same e-mail address and password to login to many web sites (not so many yet though)
  • OpenShift - cloud application platform
  • “Private cloud” – run your own “cloud” server
  • Raspberry Pi - small and cheap computer
  • Server Sent Events
  • WebSockets

Assess

  • Chef or Puppet
  • Docker
  • Gearman
  • Vagrant

formatCurrency bug

October 10th, 2013

Is the formatCurrency method of the NumberFormatter class in PHP working properly for you or does it return things like “NaN” and “¤¤¤”?

This is probably PHP bug #54538 that actually is ICU bug #8561 that might be the same as ICU bug #8214.

I have worked around it by being more careful about what locales are allowed.

Script to update an OpenShift repository with changes made on server

August 22nd, 2013

If you haven’t tried OpenShift yet, you should!

Anyway I have a WordPress installation there. When upgrading WordPress to a new version, files are changed on the server but they would be overwritten if I push the repository. So I created a script to download a snapshot of the OpenShift app, extract the changes in the php directory where WordPress resides, and add them to repository.

It is fully automated except for the crucial git push.

The script is called update-repo-from-snapshot.sh and is meant to be commited to the root of each repository.

PHP Allowed memory size of 134217728 bytes exhausted (tried to allocate 71 bytes)

August 11th, 2013

I’m a very happy user of New Relic for my websites, even if I’m only leeching on the free tier.

One of my WordPress sites, taurin.se has been suffering from this out-of-memory error for quite some time now and I finally tracked it down. New Relic shows the stack trace, with the failing line on top:

in wpdb::get_results called at /usr/share/wordpress/wp-includes/wp-db.php (1413)
in wpdb::get_results called at /usr/share/wordpress/wp-includes/meta.php (295)
in update_meta_cache called at /usr/share/wordpress/wp-includes/post.php (4133)
in update_postmeta_cache called at /usr/share/wordpress/wp-includes/post.php (4113)
in update_post_caches called at /usr/share/wordpress/wp-includes/query.php (2534)
in WP_Query::get_posts called at /usr/share/wordpress/wp-includes/query.php (2695)
in WP_Query::query called at /usr/share/wordpress/wp-includes/query.php (2791)
.
.
.

So, it fails when updating the postmeta cache. What’s that? Well, had a look in the database.

In the database I found the wp_postmeta table. A quick check revealed that it contained thousands of syndication_item_hash entries. These are added by the FeedWordPress plugin.

Unfortunately taurin.se is quite low priority for me, and the blogs I have been syndicating seem quite dead. But the upside is that I could just disable FeedWordPress and delete all syndication_item_hash entries from the wp_postmeta table.

Now my web server should work much better!

Disable some useless stuff in Raspbian

August 9th, 2013

I’m currently running three Raspberry Pi projects, with Raspbian as my choice of distribution. One of the machines will be co-located at FS Data and run ownCloud. The other will be handle switching a central heater between oil and electricyty via SMS. The third is a surveillance camera heavily inspired by Dummy camera made smart with Raspberry Pi by my talented colleague Tomas Bjerre.

While examining the default Raspbian image I noticed there were some things I will never use, so I disabled them to free up some RAM:

  1. Disable the consoles by putting a # in front of all lines containing /sbin/getty in /etc/inittab:

    #1:2345:respawn:/sbin/getty --noclear 38400 tty1
    #2:23:respawn:/sbin/getty 38400 tty2
    #3:23:respawn:/sbin/getty 38400 tty3
    #4:23:respawn:/sbin/getty 38400 tty4
    #5:23:respawn:/sbin/getty 38400 tty5
    #6:23:respawn:/sbin/getty 38400 tty6
    .
    .
    .
    #T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

    If you get into network issues and need the console you can always mount the SD card on another machine and edit the file there!

  2. If you don’t have a keyboard connected or otherwise don’t want global hotkeys, disable the triggerhappy global hotkey daemon:

    sudo update-rc.d triggerhappy disable

  3. If you have Transmission installed but is not using UPnP, disable the minissdpd daemon for keeping track of UPnP devices:

    sudo update-rc.d minissdpd disable

  4. If you run Apache, disable modules you don’t use. Maybe:

    sudo a2dismod dir
    sudo a2dismod cgi
    sudo a2dismod negotiation
    sudo a2dismod autoindex
    sudo a2dismod setenvif

Using mod_spamhaus to block TOR in Apache

November 18th, 2012
Some web spammers use the Tor Project to hide their wrongdoings. Because of this, I want to block Tor exit nodes from submitting forms on my web sites. However, there are many legitmate uses of the Tor Project, so I don’t want to block GET requests but primarily POST requests.
  1. Run sudo apt-get install libapache2-mod-spamhaus
  2. Open /etc/apache2/mods-enabled/mod-spamhaus.conf for editing (as root)
  3. Edit the MS_METHODS configuration setting. Make sure that POST is included and GET is not. Example:
    MS_METHODS  POST,PUT,OPTIONS,CONNECT
  4. Edit the MS_Dns configuration setting. If the IP address of your server is 198.51.100.222, and the port of your web server is 80 as usual, you start with the port number, reverse the numbers in the IP address and the setting becomes:
    MS_Dns 80.222.100.51.198.ip-port.exitlist.torproject.org
    So, for IP address A.B.C.D and port E, the value becomes E.D.C.B.A.ip-port.exitlist.torproject.org
  5. You may also want to edit the MS_CustomError setting. In my case it looks like this:
    MS_CustomError “Limited access for certain clients. Please contact abuse at 2good.net to get full access to our services.”
  6. Enable the apache module with sudo a2enmod mod-spamhaus
  7. Restart apache with sudo service apache2 restart
Your will get log entries like this:

[Fri Nov 16 04:28:05 2012] [crit] [client 37.59.162.218] mod_spamhaus: address 218.162.59.37.80.222.10.74.109.ip-port.exitlist.torproject.org is blacklisted. Deny connection to forum.taurin.se/index.php, referer: http://forum.taurin.se/index.php?topic=1731.0

Customizing Zend\View\Helper\Navigation\Menu in ZF2

November 9th, 2012

I have created gist: 4045344 with example code for replacing the navigation menu helper in Zend Framework 2.

Unable to use Mosh to connect to one of my servers

August 10th, 2012

I’ve only used Mosh: the mobile shell for a  couple of weeks, but I am definitely a convert! However, I couldn’t get mosh to connect to one of my servers (an OpenVZ instance).

The error manifested itself as the client trying to connect to the server but not getting any response:

mosh: Connecting... [To quit: Ctrl-^ .]

Today I decided to debug the issue. As the client actually was trying to connect, I tried to simply start the server:

$ mosh-server new

MOSH CONNECT 60001 rSbp4ENDdzd/TKBOrrEeVg

mosh-server (mosh 1.2.2)
Copyright 2012 Keith Winstein
License GPLv3+: GNU GPL version 3 or later .
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

[mosh-server detached, pid = 32582]

But when I checked the process list, it wasn’t running anymore:

$ pgrep mosh-server
$

Time to add some verbose output:

$ mosh-server new -v 

MOSH CONNECT 60001 hQ5ab1JjgUytXRZmy5ti6A

mosh-server (mosh 1.2.2)
Copyright 2012 Keith Winstein
License GPLv3+: GNU GPL version 3 or later .
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

[mosh-server detached, pid = 14208]
forkpty: No such file or directory

This must be important: forkpty: No such file or directory, but what does it mean?

Some googling showed that it meant that /dev/pts was not mounted on my system, and it was indeed not mounted:

$ mount
 /dev/simfs on / type reiserfs (rw,usrquota,grpquota)

(Yes, I’ve also wondered why my host is running ReiserFS.)

So I checked my /etc/fsab:

$ cat /etc/fstab
proc  /proc       proc    defaults    0    0
none  /dev/pts    devpts  rw          0    0

It’s there, but still not mounted? Oh well, easy fix:

sudo mount /dev/pts

After that fix, I could successfully connect to my server with mosh!

Injecting context into controller?

July 8th, 2012

I’m toying with my own PHP micro-framework. I’m trying to make it both simple and easy; explicit but not verbose. (Good luck to me!)

For testability I have abstracted the Superglobals so that I have full control of them in my tests. Currently they are passed as a parameter to the controller action. Would it make sense to have them injected into the controller instead? It might be simpler, but it is less explicit.