2. June 2013

Configure Nginx with uWSGI to serve Pootle

It’s quite easy to set up Pootle. Just follow the manual – Quickstart.

virtualenv /var/www/pootle/env/
 source /var/www/pootle/env/bin/activate
 (env) $ pip install pootle
 (env) $ pootle init
 (env) $ pootle syncdb --noinput
 (env) $ pootle initdb

You can start Pootle with default CherryPy server. In order to boost performance it is necessary to use more powerfull server.

Let’s take intermediate step and serve Pootle by uWSGI.

First of all you’ll need to create wsgi.py file, because this file is missing in default Pootle installation. File: /var/www/pootle/wsgi.py

import os

# this part is only required when running from checkout instead of an install
try:
    import sys
    ROOT_DIR = os.path.abspath(os.path.dirname(__file__))
    sys.path.insert(0, ROOT_DIR) # Top level directory
    import syspath_override
except ImportError:
    # not running from checkout
    pass

# comment the above lines if running from install

os.environ['DJANGO_SETTINGS_MODULE'] = 'pootle.settings'

import django.core.handlers.wsgi

application = django.core.handlers.wsgi.WSGIHandler()

You can start uWSGI server by following command:

uwsgi --socket 127.0.0.1:3031 --chdir /var/www/pootle/lib/python2.7/site-packages/pootle --wsgi-file wsgi.py --master --virtualenv /var/www/pootle/ --http ":9090"

This will create uWSGI server and you can test it by connecting to http://localhost:9090

Let’s take further step and configure Nginx to server Pootle. We can modify previous command, because we do not need to server it as http at port 9090:

uwsgi --socket 127.0.0.1:3031 --chdir /var/www/pootle/lib/python2.7/site-packages/pootle --wsgi-file wsgi.py --master --virtualenv /var/www/pootle/

Create webroot directory where you will put static assets, just to avoid information leackage. Store there symlinks to assets and static files.

mkdir /var/www/pootle/webroot
ln -s /var/www/pootle/lib/python2.7/site-packages/pootle/assets /var/www/pootle/webroot/
ln -s /var/www/pootle/lib/python2.7/site-packages/pootle/static /var/www/pootle/webroot/

Store configuration to /etc/nginx/sites-available and create symlink to /etc/nginx/sites-enabled. Configuration of site:

upstream emperor {
  server 127.0.0.1:3031;
}

server {
  listen 80;
  server_name pootle.sinusgear.com;
  root /var/www/pootle/webroot;

  access_log /var/log/nginx/pootle.sinusgear.com_access.log;
  error_log /var/log/nginx/pootle.sinusgear.com_error.log;

  location / {
    location ~* ^.+\.$ {
      root /var/www/pootle/webroot/static/styles;
      expires 30d;
    }
    try_files $uri @django;
  }

  location @django {
    root /var/www/pootle;
    include uwsgi_params;
    uwsgi_param UWSGI_FASTROUTER_KEY $host;
    uwsgi_pass emperor;
  }

  location = /robots.txt {
    root /var/www/pootle/webroot/static/;
    access_log off;
  }

  location ~* ^.+\.py$ {
    return 404;
  }
}

Reload Nginx and Pootle should be much faster :)

I recommend book Mastering Nginx. You can learn there much more about Nginx configuration.

1. June 2013

GitLab: Could not read from remote repository

When you try to push to GitLab you may end up with following error message:

fatal: Could not read from remote repository.
Please make sure you have the correct access rights
 and the repository exists.

It’s not very clear what’s real cause. You may check the permission, but it might not solve the problem.

One quick solution could be just restart of GitLab service. It still might not help.

Let’s learn some mechanics of GitLab.

You send data via ssh to GitLab server. When authentication by key is succesfull then server will invoke gitlab-shell. This will shell send request to web interface of GitLab. Yes, web interface. Then it will allow you to access git repository.

Schema:

git -> ssh -> sshd -> gitlab-shell -> gitlab web

The problem described in the beginning of this article is between gitlab-shell and gitlab-web. Most likely shell is not able to access gitlab web. URL is broken or host configuration is incorrect or port is not reachable.

Just go to gitlab-shell project and open file config.yml. You’ll see something like this:

gitlab_url: "http://localhost:80/"

Test this URL directly on server e.g. by links:

links http://localhost:80/

You may need to change hostname or port or add base directory to URL. Fix the URL so the gitlab-shell is able to access web interface. Restart gitlab service and try to push again.

Further discussion about this and similar problems is available at github.

1. June 2013

Tomcat installed as Windows service doesn’t create log files

I was chasing one very insidious bug. Tomcat installed as Windows service was not creating logs. The only log produced by Tomcat was stdout and stderr from procrun wrapper.

It was very weird. Tomcat downloaded from Apache’s website was creating logs without problem. There was no difference between directories of problematic Tomcat and working Tomcat.

Ok, let’s cut long story short. After several attempts to locate the bug I realized that Tomcat started by startup.bat was working correctly.

The only difference was in the Tomcat’s start method.

It was necessary to open Tomcat service properties (ES stands for Edit Service):

tomcat7w.exe \\ES\\tomcatweb

The tricky part here was not to check the Logging tab. This issue had nothing to do with stuff displayed in Logging tab. It was necessary to open Java tab.

When I compared working service and Tomcat service without logging I found that following lines were missing:

-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
-Djava.util.logging.config.file=C:\projects\apache-tomcat-7.0.40\conf\logging.properties

tomcat-edit-windows-service

Somebody who was registering the service just omitted those lines when overriding –JvmOptions. It was sufficient to add java.util.logging.manager and config.file. Restart service and Tomcat was logging without problem.

29. May 2013

Solution: KVM guest IO very slow

One problem of virtual server based on qemu KVM is that IO operations are slow in some cases.

The most common reason is that virtual disks are stored on RAID and virtual is using default HDD configuration.

It is recommended to turn off cache and set io operations to native:

<driver name='qemu' type='raw' cache='none' io='native'/>

There is very good article at serverfault. You can find there further explanations.

26. May 2013

Python virtualenv and PowerShell

It’s quite easy to set up virtual environment with isolated packages for Python in PowerShell.

Creating virtual environment is the same like in any other shell. Let’s call this environment pyenv:

pip install virtualenv
virtualenv pyenv

The last step is to activate this environment in PowerShell (watch dots and spaces):

. .\pyenv\Scripts\activate.ps1

You should see name of your virtual environment in command line. Virtual environment is active.

26. May 2013

Useful tips for PowerShell users

You can find my new powershell-examples project at GitHub.

I store there small code snippets and support tool which could be useful for day to day life with PowerShell ;)

12. May 2013

How to fix broken style in Plone

Some Products for Plone are little bit broken and uninstallation procedure does not work very well. When you install and then uninstall crappy product you might end up with messed layout of Plone portal.

That’s the time to pay a visit to plone_css folder in ZMI.

Remove any reference to broken style (whole box with style has yellow color) and click Save to reset Plone CSS caching system.

12. May 2013

Unicode Python plugin for Unicode NSIS

NSIS is very common project for building installer packages. It requires less time to work with NSIS than using WiX or MSI.

It has also certain drawbacks like very weird programming language which resembles assembler mixed with Postscript. Quite scary at first glance. There is remedy for this glitch.

NSIS is good for building installer “container” and it could hand over more complex logic to its plugins like Python plugin.

Original NSIS has another one glitch: no support for unicode. Luckily guys took NSIS and they fixed the issue by creating Unicode NSIS.

Unfortunately unicode version was not able to work with former Python plugin.

It required some effort to fix Python calls from NSIS and voilà Unicode Python plugin is available at github – nsPythonUnicode. :-)

11. May 2013

Plone Error: There is a version conflict. We already have: distribute 0.6.38

I was trying to update one very old instance of Plone configured by buildout. Result of running ./bin/buildout was this error message:

While:
  Installing.
  Loading extensions.
Error: There is a version conflict.
We already have: distribute 0.6.38

There was distribute package installed on system which caused conflict. The solution was to remove the package:

apt-get remove --purge python-zc.buildout

That leads to another error message that buildout script is outdated. Correction:

curl -O http://downloads.buildout.org/2/bootstrap.py
python bootstrap.py

There was another error after using latest version of buildout:

While:
  Installing.
  Getting section instance.
  Initializing section instance.
  Installing recipe plone.recipe.zope2instance.
Error: There is a version conflict.
We already have: zope.interface 3.6.1

Solution was same as before. Just remove zope.interface package from system:

apt-get remove --purge python-zope.interface

After this small fix it was possible to run buildout without any problem.

11. May 2013

Edge – invoke PowerShell from NodeJS

Project Edge allows seamless integration of NodeJS and PowrShell.

Just install packages:

npm install edge
npm install edge-ps

Create NodeJS application which contains PowerShell code:

var edge = require('edge');

var hello = edge.func('ps', function () {/*
"PowerShell welcomes $inputFromJS on $(Get-Date)"
*/});

hello('Node.js', function (error, result) {
 if (error) throw error;
 console.log(result[0]);
});

Start application and you’ll get output

PowerShell welcomes Node.js on 05/11/2013 07:14:38

Project Edge also allows integration of NodeJS with other technologies (e.g. Python)

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