Category Archives: Drupal

It’s all about drupal coding and whining.

From Drupal to Django: how to migrate contents

In a recent article¬†I explain the motivations for an upgrade from a no longer maintained Drupal 6 installation to¬†Django 1.8. I will now cover more in detail the migration techniques adopted in the upgrade and I’ll deepen the models and the relationships.

Structure

If you’re a drupaler, you’re familiar with the node/NID/edit and the node/add/TYPE pages:

A-New-Page-Drupal-6-Sandbox

Here we have two visible fields: Title and Body. One is an input type text and the other a texarea. The good Form API provided by Drupal calls these two types textfield and textarea. However if you use the Content type creation interface you don’t see any of these, just declare some field types and you’ll see the form populating with new fields after the addition.

It’s similar in Django but you haven’t to pass to a graphical interface to do this: structure is code-driven and the side effect is the ability to put on revision almost anything. You can choose between different field types that will be reflected in database and on the user interface.

Here what the Drupal Body and Title fields looks like in a model called Article:

# models.py
from django.db import models
from tinymce import models as tinymce_models
# Articles
class Article(models.Model):
    title       = models.CharField(max_length=250,null=False, blank=False)
    body        = tinymce_models.HTMLField(blank=True, default='')

The TinyMCE part require TinyMCE app installed and configured.¬†If you’re new to Django read and follow the great Writing your first Django app¬†to understand the basics, e.g the difference between a project and an app or the following sections will sound pretty obscure.

After editing your projectname/appname/models.py file you can now apply the changes in your app via makemigrations (create a migration file for the changes in the database) and migrate (apply the migrations inside the migration files).

In a real world scenario these two fields alone aren’t enough neither in a Drupal 6.¬†These information are all presented by default in any type on Drupal 6:

authoring-info

Drupal 6 treats author as entities you can search through an autocomplete field, and date as a pseudo-ISO 8601 date field. The author field is a link to the User table in Drupal. In Django a similar user model¬†exists but if you want to unchain the access to the admin backend and the authorship it’s simpler to¬†create a custom author model and later associate this with the real user model.

sport3_uml

E-R of our app where migrate the Drupal contents to.

from django.db import models
from tinymce import models as tinymce_models
# Authors
class Author(models.Model):
    alias       = models.CharField(max_length=100)
    name        = models.CharField(max_length=100, null=True, blank=True)
    surname     = models.CharField(max_length=100, null=True, blank=True)
# Articles
class Article(models.Model):
    author      = models.ForeignKey('Author', verbose_name='Authored by')
    title       = models.CharField(max_length=250,null=False, blank=False)
    body        = tinymce_models.HTMLField(blank=True, default='')
    publishing_date = models.DateTimeField(auto_now=False, auto_now_add=False, verbose_name='First published on')

As you can see in the Entity-Relationship diagram one¬†Article must have one and only one Author, but many¬†Articles can have the same Author. This is called Many-to-one relationship¬†and it’s represented in Django as a foreign key from the destination “many” model (e.g. Article) to the “one” model (Author).

The Article.publishing_date field is where publishing date and time are stored and, clicking on the text field, a calendar popup is presented to choose the day and hour, with a useful “now” shortcut to populate the field with the current time.

calendario

How a calendar is represented in a DateTime field.

Now that the basic fields are in the right place you can makemigrations / migrate again to update your app, restarting the webserver to apply the changes.

Attachments and images

Drupal is shipped with the ability to upload files and images to nodes. Django has two different field for this: FileField and ImageField. Before continuing we have to rethink our E-R model to allow attachments.

sport3_uml

 

The model.py code is:

from django.db import models
from tinymce import models as tinymce_models
# Authors
class Author(models.Model):
    alias       = models.CharField(max_length=100)
    name        = models.CharField(max_length=100, null=True, blank=True)
    surname     = models.CharField(max_length=100, null=True, blank=True)
# Articles
class Article(models.Model):
    author      = models.ForeignKey('Author', verbose_name='Authored by')
    title       = models.CharField(max_length=250,null=False, blank=False)
    body        = tinymce_models.HTMLField(blank=True, default='')
    publishing_date = models.DateTimeField(auto_now=False, auto_now_add=False, verbose_name='First published on')
# Attachments
class Attachments(models.Model):
    description = models.CharField(max_length=255, default='', blank=True)
    list = models.BooleanField(default=True)
    file = models.FileField(upload_to='attachments_directory', max_length=255)

Images are similar: if you want to enrich your model with images you can create another model like Attachments but with an ImageField instead. Remember to use a different upload_to directory in order to keep the attachments and images separated.

We miss the last one field to complete our models: path. Django comes with an useful SlugField that as of Django 1.8 allows only ASCII characters and can be mapped to another field, the title for example.

from django.db import models
from tinymce import models as tinymce_models
# Articles
class Article(models.Model):
    author      = models.ForeignKey('Author', verbose_name='Authored by')
    title       = models.CharField(max_length=250,null=False, blank=False)
    body        = tinymce_models.HTMLField(blank=True, default='')
    publishing_date = models.DateTimeField(auto_now=False, auto_now_add=False, verbose_name='First published on')

Keep in mind that a SlugField differs from a Drupal path field because it doesn’t allow slashes. Consider a path like this:

news/news-title

In Drupal you will have a A) view with the path news and the argument news title or B) a fake path generated by pathauto or similar modules. In years of Drupal development, I can affirm that the B option is the typical easy way that turns into a nightmare of maintainance. Django core as far as I know allows only the A choice, so if you want a news view you have to declare it in urls.py and then in views.py as stated in official documentation.

  • news/: the news root path, coupled with the view
  • news-title: the ¬†argument passed to the view and¬†the SlugField content for an article. It must be unique to be used as key to retreive an article but since it can be empty we cannot force it to has a value or to be unique at first. When all data are imported and fixed we can change this field to unique to improve database retrieval performance.

Categories

And what about categories? If you have a category named Section, and an article can be associated with only one Section, you have to create a Many-to-one relationship. As you see before, you have to put the foreign key in the N side of the relation, in this case Article, so the model Article will have a ForeignKey field referencing a specific section.

On the other hands if you have tags to associate to your article you have to create a Tag model with a Many-to-many relationship to the Article. Django will create an intermediate model storing the Article-Tag relationships.

Do not abuse of M2M relationships because each relation needs a separate table and the number of JOIN on database table will increase with side effects on the performance, not even perceivable on the first since Django ORM is very efficient. The event handling will be more difficult for a beginner since the many to many events occurs only when the parent models are saved and this require some experience if you need to add a custom action to a M2M event. If you design wisely your E-R model you have nothing to be scared of.

Migration techniques

Now that we have the destination models, fields and relationship we can import the content from Drupal. In the previous article I suggested to use Views Datasource module to create a JSON view to export content. Please read the Exporting the data from Drupal section inside the article before continue.

The obtained row is something like:

{
  [
    {
      {nid: '30004',
      domainsourceid: '2',
      nodepath: 'http://example.com/path/here',
      postdate: '2014-09-17T22:18:42+0200',
      nodebody: 'HTML TEXT HERE',
      nodetype: 'drupal type',
      nodetitle: 'Title here',
      nodeauthor: 'monty',
      nodetags: 'Drupal, dragonball, paintball'
      }
    },
    ...
  ]
}

If you haven’t a multi-site Drupal you can ignore domainsourceid field.¬†The nodetags lists some Tag names of a Many-to-many relationship not covered here.

All the other value are useful for the import:

  • nid: the original content id, used for pagination and retrieval
    Destination: parsing
  • nodepath:¬†content path
    Destination: Article.path
  • nodebody: content body
    Destination: Article.body
  • nodetype: type of the node
    Destination: parsing
  • nodetitle: title of the node
    Destination: Article.title
  • nodeauthor:¬†author of the content
    Destination: Article.author -> Author.alias

In the previous article you find how to make the View on Drupal (source) and now you have  rough idea of the field mapping. How to fetch the data from Django?

Management command and paged view

To start a one-time import you can write a custom management command for your Django application named project/app/management/commands/myimport.py.

from __future__ import unicode_literals
from django.core.management.base import BaseCommand, CommandError
from django.core.exceptions import ValidationError, MultipleObjectsReturned, ObjectDoesNotExist
import json, urllib
import urlparse
from shutil import copyfile
from django.conf import settings
from os import sep
from django.core.files.storage import default_storage
from django.utils.text import slugify
import requests
import grequests
import time
from md5 import md5

class Command(BaseCommand):
    help = 'Import data from Drupal 6 Json view'
    def add_arguments(self, parser):
        parser.add_argument('start', nargs=1, type=int)
        parser.add_argument('importtype', nargs=1)
        # Named (optional) arguments
        # Crawl
        parser.add_argument('--crawl',
            action='store_true',
            dest='crawl',
            default=False,
            help='Crawl data.')
    def handle(self, *args, **options):
        # process data
        pass

This management command can be launched with

python manage.py myimport 0 article --crawl

Where 0 is the item to start + 1, “article” is the type of content to import (e.g. the destination model) and –crawl is the import option. Let’s add the import logic to the Command.handle method:

def handle(self, *args, **options):
    try:
        assert options['crawl'] and options['importtype']
        # start to import or store data
        sid = int(options['start'].pop())
        reading = True
        while reading:
            importazioni = []
            articoli = []
            url = 'http://www.example.com/json-path-verylongkey?nid=%d' % (sid,)
            print url
            response = urllib.urlopen(url)
            data = json.loads(response.read())
            data = data['']
            # no data received, quit
            if not data:
                reading = False
                break
            for n, record in enumerate(data):
                sid = int(record['']['nid'])
                title = record['']['nodetitle']
                # continue to process data, row after row
                # ...

    except AssertionError:
        raise CommandError('Invalid import command')

This example will fetch /json-path-verylongkey starting from nid passed from the command + 1. Then, it will process the json row after row and keep in memory the id of the last item. When no content is available, the cycle will stop. It’s a common method and it’s lightweight on the source server because only one request at time are sent and then the response is processed. Anyway, this method can be also slow because we have to sum waiting time: (request 1 + response 1 + parse 1) + (request 2 + response 2 + parse 2) etc.

Multiple, asyncronous requests

We can speed up the retrieval by using grequests. You have to check what is the last element first by cloning the Drupal data source json view and showing only the last item, then fetching the id.

def handle(self, *args, **options):
    try:
        assert options['crawl'] and options['importtype']
        # start to import or store data
        sid = int(options['start'].pop())
        # find last node id to create an url list
        url = 'http://www.example.com/json-path-verylongkey-last-nid'
        response = requests.get(url, timeout = 50)
        r = response.json()
        last_nid = int(r[''].pop()['']['nid'])

You can then create a from-to range starting from the first element passed by command line to the last.

url_pattern = "http://www.example.com/json-path-verylongkey-last-nid?fromnid=%d&tonid=%d";
urls = []
per_page = 20
# e.g. [0, 20, 40, 60]
relements       = range(0, last_nid, per_page)
if relements[-1] < last_nid:
    relements.append(last_nid + 1)
for fromx, toy in zip(relements, relements[1:]):
    u = url_pattern % (fromx, toy)
    urls.append(u)

rs = (grequests.get(u) for u in self.urls)
# blocking request: stay here until the last response is received
async_responses = grequests.map(rs)
# all responses fetched

The per_page is the number of element per page specified on Drupal json view. Instead of a single nid parameter, fromnid and tonid are the parameter “greater than” and “less or equal than” specified in the Drupal view.

The core of the asyncronous, multiple requests is grequests.map(). It take a list of urls and then request them. The response will arrive in random order but the async_responses will be populated by all of them.

At that point you can treat the response list like before, parsing the response.json() of each element of the list.

With these hints you can now create JSON views within Drupal ready to be fetched and parsed in Django. In a next article I will cover the conversion between the data and Django using the Django ORM.

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Guide to migrate a Drupal website to Django after the release of Drupal 8

I maintain a news website written in Drupal since 2007. It is a Drupal 6, before was a 5. I made many Drupal 7 installations in these years and I went to three Drupal local conventions. This is a guide on how to abandon Drupal if you already knows some basics of Django and Python.

Drupal on LAMP: lessons learned

  • PHP is for (not so) fast development¬†but¬†maintainability can be a pain.
  • Drupal try to overcome PHP limits, with mixed results.
  • Apache cannot stands heavy¬†traffic without an accelerator like Varnish and time-consuming ad-hoc configurations. If traffic increases, Apache cannot stand it at all.
  • Drupal¬†contrib modules are¬†a mix of high quality tools (like Webform or Views Datasource) and bad written¬†projects. The more module are enabled, the more the project¬†lose in maintainability. It is not so evident if you don’t see any other open source project.

This is not the only real truth, this is my experience in these 8 years. I feel a more confident Python programmer than PHP programmer having spent less than one-third of the years working on it. At the end of the article I cite a list of article written for programmers feeling the same uneasiness of mine working on PHP and Drupal after trying other tools.

Django experiences

In the last years with Drupal still paying most of my bills I used the Django MVC framework written in Python for three project: an e-mail application, a real estate catalog  and a custom-made CRM. One of this is a porting of something written in PHP on Drupal 5. In all of these three project I was very happy with the maintainability, clearness of the code and high-level, well written packages I found while exploring it like Tastypie and many python packages found on cake shop.

Even considering I’m the only developer of these, I haven’t experienced the frustration I feel on Drupal when trying to make something work as I design or trying to fix some code I write time ago. I know that a CMS is at higher level than a framework, simply some projects are not suited for Drupal and I found more comfortable with Python than PHP in these days.

At the time I write¬†Drupal 8 is out as Release Candidate. I made migrations from 5 to 6 and from 6 to 7 on some websites in the past. Migrating to a new major¬†it’s not a science, it’s a sort of mystical art. When the Drupal 8 will be out, Drupal 6 will be automatically unsupported after 3 months Drupal 8 is out as of Drupal announcement since only the current and previous version are supported, 8.x and 7.x when 8 is out. Keeping a Drupal 6 running after that term will be risky.

Choosing the stack

Back to the news website I maintain, the choice is between a platform I already know well and it proves stable and maintainable for small/one-person team and another I have to learn. Plus,¬†Django will be the natural choice to avoid the problems I’ve listed above and use the¬†solutions I used on past django projects exploring new tools in the meanwhile.

Here the choices I made:

I decided to use gunicorn because it’s very easy to run and maintain¬†for a django project and you haven’t to make wsgi run on nginx. Nginx is in front of gunicorn, serving static files and sending right requests to it. Memcached is used inside Django and it will store cached pages from views¬†on volatile memory avoiding to read from the database any time a page is requested. I try to avoid using Varnish even if is a very good tool because I want to keep the stack¬†as simple as I can and I’m confident Varnish and Memcache will speed up the website enough. Now is the time to rewrite the Drupal-hosted website into a Django application.

Write the E-R model

If you are here probably you have a running Drupal website you want to port to Django. Browse it like an user, and then open your Content types list to identify the Entities and the Relationships as of the E-R model suggests. If your website is running for a long time you probably want to redesign some parts, adding, removing or fusing entities into another.

Take my news website¬†for example. I have 15 content types + 12 vocabularies (27 entities) on Drupal. After rewriting the E-R I’ve 14 models (entities), including the core ones. On the database side it translates into a 199 tables for Drupal and 25 for Django¬†since it¬†usually make an entity property into a database column. I trash some entities and fuse 4 entities into one.

From entities to models: understanding relationships

When you establish a relation between your re-designed entities you can have N:1¬†relations, N:N relations and 1:1 relations. A Drupal node “Article” that accepts a single term for a vocabulary named “Cheese type” translates into a N:1 relationship between the model Article¬†(N)¬†and the¬†model¬†CheeseType (1).¬†It is a simple case since you can translate it into a ForeignKey¬†field on your model since Article will get a ForeignKey field named author referencing to the Author model.

from django.db import models
from tinymce import models as tinymce_models
# Authors
class Author(models.Model):
    alias       = models.CharField(max_length=100)
    name        = models.CharField(max_length=100, null=True, blank=True)
    surname     = models.CharField(max_length=100, null=True, blank=True)
# Articles
class Article(models.Model):
    author      = models.ForeignKey('Author')
    title       = models.CharField(max_length=250,null=False, blank=False)
    body        = tinymce_models.HTMLField(blank=True, default='')
# Attachments to an Article
class Attachment(models.Model):
    article       = models.ForeignKey('Article', blank=True, null=True)
    file          = models.FileField(upload_to='attachment_dir', max_length=255, blank=True, null=True)
    description   = models.TextField(null=True, blank=True)
    weight        = models.PositiveSmallIntegerField()

In the case of a list of attachments to Article, you have a 1:N relationship between the Article model (1) and the Attachment model (N). Since the relationship is reversed, in the usual Django admin interface you cannot see the attachments in the article as is since you have to create an Attachment and then choose an article from a dropdown where attach it to.

For this case, Django provides an handy administration interface called inline to include entities in reversed relationship. This approach fix by design something that in Drupal world costs a lot of effort, with dozen of modules like Field Collection or workaround like this I write of in the past and it keep aligned your E-R design with your models. Plus, a list of all Attachment are available for free.

Exporting the data from Drupal

JSON is a pretty good interchange format: very fast to encode and decode, very well supported. I’m fascinated with YAML format but since I’ve to export thousands of articles I need pure speed and solid import/export modules on both Django and Drupal side.

There are many export module in the Drupal world. I’m very fond of Views Datasource and here how I used it:

  1. Install Views Json (part of Views Datasource): it is available for Drupal 6 and 7 and very solid
  2. Create a new view with your published nodes with the JSON Data style
    1. Field output: Normal
    2. Without Plain text (you need HTML)
    3. Json data format: Simple
    4. Without Views API mode
    5. application/json as Mime type
    6. Remove all parent / children tag name so you will have only arrays and objects
  3. Choose a path for your view
  4. Limit the view to a large number of elements, e.g. 1000
  5. Sort by node id, ascendent
  6. Add an exposed filter “greater than” Nid with a custom Filter identifier (e.g. nid)
  7. Add any field you need to import and any filter you need to limit the results
  8. Avoid caching the view
  9. Limit the access to the view if you don’t want to expose sensible contents¬†(optional)
  10. Install a plugin like JsonView (chrome) or JsonView (firefox) to look at the data on your browser

You will get something like that:

{
  [
    {
      {nid: "30004",
      domainsourceid: "1",
      nodepath: "http://example.com/path/here",
      postdate: "2014-09-17T22:18:42+0200",
      nodebody: "HTML TEXT HERE",
      nodetype: "drupal type",
      nodetitle: "Title here",
      nodeauthor: "monty",
      nodetags: "Drupal, basketball, paintball"
      }
    },
    ...
  ]
}

Now you can reach the view appending ?nid=0 to your path. It means that any node with id greater than 0 will be listed. With nid=0 a max of 1000 elements are listed. To get other nodes you have simply to get the nid from the last record (e.g. 2478) and use it as value for the nid parameter obtaining something like http://example.com/myview?nid=2478.

Try it on your browser simulating what a procedure will do for you: check the response size and adapt the number of elements (#4) accordingly to avoid to overload your server, hit the timeout or simply storing too much data into the memory when parsing. When the view response is¬†empty you’ve listed all nodes matching your filters and the parsing is complete.

In this example I’ve talked about nodes but you can do the same with files, using fid as id to pass as parameter and to sort your rows. In the case of files you have to move the files as well but it’s pretty simple to import these on a custom model on Django as you will see.

Importing data to Django

Django comes with some nice export (dumpdata)¬†¬†and import¬†(loaddata) commands. I’ve used a lot the YAML format to migrate and backup data from models but Json and SQL are other supported formats you can try. However in this migration I choose¬†custom admin command to do the job. It’s fast: in less than 10 minutes the procedure¬†imported 15k+ articles writing on a custom model some logging information on both error and¬†success.

All the import code in my case, comments and import included, is about 300 lines of python code. The core of the import function for nodes willing to become Articles is that:

import json, urllib
# ...
sid = int(options['start'].pop())
reading = True
while reading:
    url = "http://mydrupalwebsite.example.com/myview?nid=%d" % (sid,)
    print url
    response = urllib.urlopen(url)
    data = json.loads(response.read())
    data = data['']
    # no data received, empty view result, quit
    if not data:
        reading = False
        break
    for n, record in enumerate(data):
        sid = int(record['']['nid'])
        # ... do something with data ...

In this cycle, sid is the start argument passed to the admin command via command line. Next, sid will be set to the last read record so, when record finishes, a new request to myview starting from the last read element will be made.

All input and output is UTF-8 in my case. JSON View quotes strings and you have to decode them before saving in Django:

from myapp.models import Article
import HTMLParser
hp = HTMLParser.HTMLParser()
authors = Author.objects.all()
...
for n, record in enumerate(data):
    try:
        art = Article(
            title = hp.unescape(record['']['nodetitle']),
            body = record['']['nodebody'],
            author = authors.get(alias=record['']['nodeauthor'])
        )
        # run the same validation of an admin interface submit
        art.full_clean()
        art.save()
    except ValidationError as e:
      # cannot save the element
      # inside e all the error data you can save into
      # a custom log model or print to screen
    except:
      # any other exception
      pass

On line 9 a new article is declared. The title in Json source is named nodetitle. On line 10 the title from json is unescaped and assigned to title CharField of Article. The nodebody  is set as it is since the destination field is a TextField with HTML. On line 11 username nodeauthor from Json is used as key to associate the already imported user to the ForeignKey field author, where username is saved as Author.alias.

Conclusion

Here the very basics on how to prepare a migration from Django to Drupal using Views Datasource module and a custom admin command. I described why I choose Django after years of Drupal development for this migration suggesting some tools to do the job and introducing some basic concepts for Drupal developer who wants to try Django.

Before leaving here a list of good contributions I’ve read about Drupal enthusiasts that suffers the same uneasiness of mine after long-time Drupal / PHP development. In their words I found some confort in my day programming job and a lot of inspiration. As an half-joke, I put on parenthesis the time that specific developer have spent on Drupal.

Epilogue

Here the download time graph from Google Search Console after some months:
downloadtime

You can clearly see the results in speed, expressed in milliseconds, between 2015 (old Drupal 6 platform) and 2016 (new Django platform).

Finally I quit my Drupal job and now I’m programming mostly with Python.

Clear Varnish cache via PHP: a Drupal 7 proof of concept

Using Varnish as reverse proxy or proxy is an useful approach to reduce the load of webservers like Apache.

In Drupal 7 I’ve to clear the varnish cache of a specific domain when Drupal caches are globally cleared. Drupal has the right hook invoked when cache are cleared:

function clearcachevarnish_flush_caches() {
  $filename = '/var/www/varnishdomains2cleardir/varnishdomains2clear';
  // each domain on a separate line: append to the end of the file
  $myfile = fopen($filename, "a");
  $h = $_SERVER['HTTP_HOST'];
  $txt = $h . "\n";
  fwrite($myfile, $txt);
  fclose($myfile);
  drupal_set_message('Varnish cache queued to be cleared. Please wait 1 minute before checking.');
  // no cache table should be cleared
  return array();
}

Now this piece of code simply adds the current domain to a ASCII text file on /var/www/varnishdomains2cleardir/varnishdomains2clear.

Preparing the file to the write

On CentOS you have to add /var/www/varnishdomains2cleardir to the httpd-writable directories list using:

mkdir /var/www/varnishdomains2cleardir;
chcon -v --type=httpd_sys_content_t /var/www/varnishdomains2cleardir;
chown myuser:mygroup /var/www/varnishdomains2cleardir;
chmod -R 777 /var/www/varnishdomains2cleardir;
touch /var/www/varnishdomains2cleardir/varnishdomains2clear;

Now the empty file is ready to be written by your hook_flush_caches() implementation. Now enable the clearvarnishcache module and clear the cache to write the current domain name to the file.

The clear varnish cache script

To clear the varnish cache you usually have to be logged as root using the command varnishadm. Here a script that will read the domains file written above, clear the varnish cache for that domain and then remove the domains lines.

#!/bin/bash
callinguser=`whoami`
if [ "root" != "$callinguser" ]
then
 echo "Only root can run this command."
 exit 1
fi
cd /path/to/clear/cache/command/

date=`date +%Y-%m-%d_%H:%M:%S`

# check lock
# prevent the script from being run more than once
if [ -f /tmp/clearcachevarnish-lock ]; then
echo "Script clearcachevarnish is already running. You can rm /tmp/clearcachevarnish-lock to break the lock manually."
exit 1
fi
touch /tmp/clearcachevarnish-lock
dominidapulire=`less /var/www/varnishdomains2cleardir/varnishdomains2clear`
while [[ ! -z $dominidapulire ]]
do
 dominio=$(echo "$dominidapulire" | sed -n '$p')
 echo $dominio
 dominidapulire=$(echo "$dominidapulire" | sed '$d')
 if [ "" != "$dominio" ]
 then
 varnishadm -T 127.0.0.1:6082 -S /etc/varnish/secret ban req.http.host == "$dominio"
 echo "varnish cleared on $dominio"
 fi
done
# remove all domains lines
truncate --size 0 /var/www/varnishdomains2cleardir/varnishdomains2clear

# remove lock
rm /tmp/clearcachevarnish-lock

Make¬†this script as executable .sh file using chmod a+x on it. If you run the bash script, varnish cache for files on the domains list will be cleared. It’s not so useful when using the Drupal UI so we should schedule this task periodically, e.g. every minute.

Scheduling the varnish clear cache

Here the crontab entry for execute the script every minute:


* * * * * root /path/to/clear/cache/command/clearcachevarnish.sh

The steps

  1. User clear Drupal cache
  2. hook_flush_caches() is invoked: the domains list file is written
  3. clear varnish cache script is launched by root every minute
  4. for each domain in the list, varnish cache is cleared

This is the end of this proof of concept. The code wasn’t tested against attacks so please comment if you have any suggestion to improve it. I’m not very fond of the idea of a php script writing something read by a bash script but this is the less problematic solution I found for this case.

Django and Drupal integration using drush via SSH

Some months ago I talked about how to achieve a unified login from Django to Drupal using drush. The basic assumption was that both Drupal and Django are on the same server. What if the two components are on different servers?

Paramiko is a SSH2 protocol library aimed to provide simple classes to make SSH connection. Let’s see how the code to call drush on command line changes.

Prerequisites:

  • paramiko
  • on your app settings.py add:
  • DRUPAL_SERVER_SSH_HOST     = '0.0.0.0' # Your host here
    DRUPAL_SERVER_SSH_USERNAME = 'YourRemoteServerUserHere'
    DRUPAL_SERVER_SSH_PASSWORD = 'YourRemoteServerPasswordHere'

    And then:

    assert request.user.drupal_id > 0
    # user id to log in
    drupal_id = str(request.user.drupal_id)
    output = ""
    try:
     # a list with command as first element and arguments following
     get_password_recovery_url = ["drush", "-r", settings.DRUPAL_SITE_PATH, "-l", settings.DRUPAL_SITE_NAME, "user-login", drupal_id]
     # via ssh http://stackoverflow.com/a/3586168/892951
     ssh = paramiko.SSHClient()
     # add to known_host the remote server key if it's not already stored
     # @see http://jessenoller.com/blog/2009/02/05/ssh-programming-with-paramiko-completely-different
     ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
     ssh.connect(settings.DRUPAL_SERVER_SSH_HOST, username=settings.DRUPAL_SERVER_SSH_USERNAME, password=settings.DRUPAL_SERVER_SSH_PASSWORD)
     ssh_stdin, output, ssh_stderr = ssh.exec_command(" ".join(get_password_recovery_url))
     output_lines = output.read().splitlines()
     # taking only the first line of the output:
     # e.g. 'http://example.com.it/user/reset/16/1369986816/67k7ReHi97FdtRfdrrXGqqesyz6FXyy7T8jqHiXxsrY/login'
    except:
     # @todo additional statements here
     pass
    finally:
     if ssh:
      ssh.close()
    
    if output_lines:
    drupal_login_url = output_lines[0].replace("http://example.com/", "http://%s/" % settings.DRUPAL_SITE_URL).strip()
    
    destination = "%s?destination=%s" % (drupal_login_url, settings.DRUPAL_LOGIN_DESTINATION)
     return redirect(destination)
    else:
     return HttpResponse('
    <h1>Wrong request</h1>
    ')
    

    This is the same code of the previous howto, with the difference that drush now is running on a different server of django. You can use the same method to do anything you have to with drush, any time you call this piece of code an SSH connection is opened.

    See also:

Apache CentOS 6 cannot send email and Drupal get HTTP request status fails

I’m installing a Pressflow 6 on a new machine running CentOS 6. I’m using Apache MPM Worker with FastCGI. Then I get the classical e-mail error:

Unable to send e-mail. Please contact the site administrator if the problem persists.

Then I try to use sendmail:

sendmail -v yourmail@example.com < testmail

Where testmail is a file containing these lines:

Subject: test mail Ozu
Yasujiro Ozu
[blank line here]

And i get the message. PHP cannot send email through apache!

Trying a simple php script to send mail like drupal core do I got this error:

sendmail: fatal: chdir /var/spool/postfix: Permission denied

Then I check this variable following this awesome post:

# /usr/sbin/getsebool httpd_can_sendmail
httpd_can_sendmail --> off

Enable httpd_can_sendmail solve this issue:

setsebool -P httpd_can_sendmail 1

And wait. It will be a long wait using the -P option. And then PHP and Drupal can send mail.

Then check again the variable:

# /usr/sbin/getsebool httpd_can_sendmail
httpd_can_sendmail --> on

Now httpd can send mail. Try your script again.

The SMTP Authentication Support module is not working. This is another of these variables, the same that causes Drupal to show the “HTTP request status fails” message.

setsebool -P httpd_can_network_connect 1

And wait again. Both the SMTP module and the base Drupal networking are now working and Status report is all green.

Pair view fields content on a Drupal 7 view quick howto

Valid for: Drupal 7, Views 3.

I have two multiple text fields on a Drupal 7 content type.

multiple fields

I want to display those fields paired by delta in a view. Here the code I used in my module named mymodule.module.

function mymodule_views_pre_render(&$view) {
  // pair field contents
  if ($view->name == 'my_view_name' && $view->current_display == 'my_view_display') {
    foreach ($view->result as $key => $res) {
      if ($res->field_data_field_youtube_url_delta != $res->field_data_field_youtube_url_description_delta) {
        unset($view->result[$key]);
      }
    }
  }
}

Thanks to hook_views_pre_render().

I use this piece of code to pair Youtube URLs and plain text description  for a JSON output generated via Views Datasource.

Remember to disallow multiple values when adding these fields to your view or you’ll get incoherent results.