## Regain RSS feeds for the University of Rostock

I’m consuming quite some input from the internet everyday. A substantial amount of information arrives through podcasts, but much more essential are the 300+ RSS feeds that I’m subscribed to. I love RSS, it’s one of the best inventions in the world wide web!

However, there are alarming rumors and activities trying to get rid of RSS… We probably should all get our news filtered by Facebook or something..!? The importance of RSS, which allows users to keep track of updates on many different websites, seems to get continuously ignored.. And so does the new website of our University, where official RSS feeds aren’t provided anymore :(

Apparently, many people were already asking for RSS feeds of the University’s webpage. At least that’s what they told me, when I asked… But the company who built the pages won’t integrate RSS anymore - probably wasn’t listed in the requirements.. And the University wouldn’t touch the expensive website.

“Fortunatelly,” they stayed with Typo3 as the CMS, which we’ve been using as well - before we decided to switch. And this Typo3 platform can output the page’s content as RSS feed out of the box, you just need to know how! ;-)

And… I’ll tell you: Just append ?type=9818 to the URL. That’s it! Really. It’s so easy.

Here are a few examples:

Sure, it doesn’t work everywhere. If the editors maintain news as static HTML pages, Typo3 fails to export a proper RSS feed. It’s still better than nothing. And maybe it helps a few people…

## Proper Search Engine for a Static Website powered by DuckDuckGo (and similar)

Static websites are great and popular, see for example Brunch, Hexo, Hugo, Jekyll, Octopress, Pelican, and …. They are easy to maintain and their performance is invincible. But… As they are static, they cannot dynamically handle user input, which is an obvious requirement for every search engine.

Lucky us, there are already other guys doing the search stuff pretty convincingly. So it’s just plausible to not reinvent the wheel, but instead make use of their services. There are a number of search engines, e.g. Baidu, Bing, Dogpile, Ecosia, Google, StartPage, Yahoo, Yippy, and more (list sorted alphabetically, see also Wikipedia::List of search engines). They all have pros and cons, but typically it boils down to a trade between coverage, up-to-dateness, monopoly, and privacy. You probably also have your favourite. However, it doesn’t really matter. While this guide focusses on DuckDuckGo, the proposed solution is basically applicable to all search engines.

## Theory

The idea is, that you add a search form to your website, but do not handle the request yourself and instead redirect to an endpoint of a public search engine. All the search engines have some way to provide the search phrase encoded in the URL. Typically, the search phrase is stored in the GET varialble q, for example example.org/?q=something would search for something at example.org. Thus, your form would redirect to example.org/?q=.... However, that would of course start a search for the given phrase on the whole internet! Instead, you probably want to restrict the search results to pages from your domain.

Fortunatelly, the search engines typically also provide means to limit search results to a domain, or similar. In case of DuckDuckGo it is for example the site: operator, see also DuckDuckGo’s syntax. That is, for my blog I’d prefix the search phrase with site:binfalse.de.

## Technical realisation

Implementing the workaround is no magic, even though you need to touch your webserver’s configuration.

First thing you need to do is adding a search form to your website. That form may look like this:

As you see, the form just consists of a text field and a submit-button. The data will be submitted to /search on your website.

Sure, /search doesn’t exist on your website (if it exists you need to use a different endpoint), but we’ll configure your web server to do the remaining work. The web server needs to do two things: (1) it needs to prefix the phrase with site:your.domain and (2) it needs to redirect the user to the search engine of your choice. Depending on the web server you’re using the configuration of course differs. My Nginx configuration, for example, looks like this:

So it sends the user to duckduckgo.com, with the query string site:binfalse.de concatenated to the submitted search phrase ($arg_q = the q variable of the original GET request). If you’re running an Apache web server, you probably know how to achieve the same over there. Otherwise it’s a good opportunity to look again into the manual ;-) Furthermore, the results pages of DuckDuckGo can be customised to look more closely like your site. You just need to send a few more URL parameters with the query, such as kj for the header color or k7 for the background color. The full list of available configuration options are available from DuckDuckGo settings via URL parameters. In conclusion, if you use my search form to search for docker, you’ll be guided to https://binfalse.de/search?q=docker. The Nginx delivering my website will then redirect you to https://duckduckgo.com/?q=site%3Abinfalse.de+docker, try it yourself: search for docker! This of course also works for dynamic websites with WordPress, Contao or similar… ## Run Baïkal through Docker Baïkal is a quite popular Calendar+Contacts server. It supports CalDAV as well as CardDAV. I’ve been using it for my calendars and adressbooks already for more than 4 years now. However, I initially installed it as plain PHP application with a MySQL database. The developers also announced quite early, that they are working on a Docker image, but there is nothing useful as of mid 2018. So far they just provide a quite inconvenient how-to and a list of issues that apparently prevent them from providing a proper Docker image. Thus, I just dockerised the application myself :) ## The Docker image Actually, creating a Docker image for Baïkal was super easy. In the end, it is “only” a PHP application ;-) The corresponding Dockerfile can be found in the root directory of Baïkal’s git repository (at least in my fork). The latest version at the time of writing is: So, it basically • installs some dependencies through apt-get, • installs the PDO-MySQL extension, • installs composer, • adds the Baikal sources into the image, • and finally installs remaining Baikal dependencies through composer. I distribute the image as binfalse/baikal. ## Using the Docker image Using the image is fairly simple. Basically, you only need to mount some persistent space to /var/www/Specific docker run -it --rm -p 80:80 -v /path/to/persistent:/var/www/Specific binfalse/baikal  Please make sure that the directory /path/to/persistent has proper permissions. In the container an Apache2 is serving the contents, so make sure the user www-data (UID 33) is allowed to rwx that directory. To start with, you can use the original Specific directory from the Baïkal repository. Then head to your Baikal instance (which will probably redirect to BASEURL/admin/install), and setup your server. Every configuration will be stored in the mounted volume at /path/to/persistent. ### SSL To support encrypted connections you would need to mount the certificates as well as a modified Apache configuration into the container. However, I recommend to run it behind a reverse proxy, such as binfalse/nginx-proxy, and let the proxy handle all SSL connections (as for all other containers). This way, you just need one proper SSL configuration. ### MySQL The default SQLite database is perfect for a first test, but is slow and just allows for a limited amount of SQL variables. If you for example have more than 999 contacts, the first sync of a clean WebDAV device will result in an exception such as: PDOException: SQLSTATE[HY000]: General error: 1 too many SQL variables  Thus, for production you may want to switch to a proper database, such as MariaDB. Lucky you, the Docker image supports MySQL! ;-) To reproducibly assemble both containers, I recommend Docker-Compose. Here is a sample config with two containers baikal and baikal-db: This assumes, that your Baikal configuration can be found in /srv/baikal/config. The database will be stored in /srv/baikal/database. Also note the database credentials for configuring Baikal. If you’re not running a reverse proxy in front of the application, you also need to add some port forwarding for the baikal container: ### Mail support I’m not sure why, but Baikal’s list of issues included support for mail. However, adding mail support should also be fairly easy if needed. I already wrote a How-To for PHP-mail in Docker. PLEASE NOTE: sSMTP is not maintained anymore! Please switch to msmtp, for example, as I explained in Migrating from sSMTP to msmtp. ## Logging with Docker In a typical Docker environment you’ll have plenty of containers (probably in multiple networks?) on the same machine. Let’s assume, you need to debug some problems of a container, eg. because it doesn’t send mails anymore.. What would you do? Correct, you’d go and check the logs. By default, Docker logs the messages of every container into a json file. On a Debian-based system you’ll probably find the file at /var/lib/docker/containers/CONTAINERID/CONTAINERID-json.log. However, to properly look into the logs you would use Docker’s logs tool. This will print the logs, just as you would expect cat to dump the logs in /var/log. docker-logs can also filter for time spans using --since and --until, and it is able to emulate a tail -f with --follow. However, the logs are only available for exsiting containers. That means, if you recreate the application (i.e. you recreate the container), you’ll typically loose the log history… If your workflow includes the --rm, you will immediately trash the log of a container when it’s stopped. Fortunatelly, Docker provides other logging drivers, to e.g. log to AWS, fluentd, GPC, and to good old syslog! :) Here I’ll show how to use the host’s syslog to manage the logs of your containers. ## Log to Syslog Telling Docker to log to the host’s syslog is really easy. You just need to use the built-in syslog driver: Voilà, the container will log to the syslog and you’ll probably find the messages in /var/log/syslog. Here is an example of an Nginx, that I just started to serve my blog on my laptop: By default, the syslog driver uses the container’s ID as the syslog tag (here it is af6dcace59a9), but you can further configure the logging driver and, for example, set a proper syslog tag: This way, it is easier to distinguish between messages from different containers and to track the logs of an application even if the container gets recreated: If you’re using Docker Compose, you can use the logging keyword to configure logging: Here, I configured an nxinx that just serves the contents from /srv/web/default. The interesting part is, however, that the container uses the syslog driver and the syslog tag docker/website. I always prefix the tag with docker/, to distinguish between log entries of the host machine and entries from Docker containers.. ## Store Docker logs seperately The workaround so far will probably substantially spam your /var/log/syslog, which may become very annoying… ;-) Therefore, I recommend to write Docker’s logs to a seperate file. If you’re for example using Rsyslog, you may want to add the following configuration: Just dump the snippet to a new file /etc/rsyslog.d/docker.conf and restart Rsyslog. This rule tells Rsyslog to write messages that are tagged with docker/* to /var/log/docker, and not to the default syslog file anymore. Thus, your /var/log/syslog stays clean and it’s easier do monitor the Docker containers. ## Disentangle the Container logs Since version 8.25, Rsyslog can also be used to split the docker logs into individual files based on the tag. So you can create separate log files, one per container, which is even cleaner! The idea is to use the tag name of containers to implement the desired directory structure. That means, I would tag the webserver of a website with docker/website/webserver and the database with docker/website/database. We can then tell Rsyslog to allow slashes in program names (see the programname section at www.rsyslog.com/doc/master/configuration/properties.html) and create a template target path for Docker log messages, which is based on the programname: Using that configuration, our website will log to /var/log/docker/website/webserver.log and /var/log/docker/website/database.log. Neat, isn’t it? :) ## Inform Logrotate Even though all the individual logfiles will be smaller than a combined one, they will still grow in size. So we should tell logrotate of their existence! Fortunatelly, this is easy as well. Just create a new file /etc/logrotate.d/docker containing something like the following: This will rotate the files ending in *.log in /var/log/docker/ and its subdirectories everyday and keep compressed logs for 7 days. Here I’m using a maximum depth of 3 subdirectories – if you need to create a deeper hierarchy of directories just add another /var/log/docker/*/*/*/*.log etc to the beginning of the file. ## Dockerising a Contao website II This article is based on Contao 3. There is a new version, see Dockerising Contao 4 In a previous post I explained how to run a Contao website in a Docker infrastructure. That was a good opening. However, after running that setup for some time I discovered a few issues… A central idea of Docker is to install the application in an image and mount persistent files into a running container. Thus, you can just throw away an instance of the app and start a new one very quickly (e.g. with an updated version of the app). Unfortunately, using Contao it’s not that straight-forward – at least when using the image decribed earlier. Here I’m describing how I fought the issues: ## Issues with Cron The first issue was Contao’s Poor-Man-Cron. This cron works as follows: • The browser requests a file cron.txt, which is supposed to contain the timestamp of the last cron run. • If the timestamp is “too” old, the browser will also request a cron.php, which then runs overdue jobs. • If a job was run, the timestamp in cron.txt will be updated, so cron.php won’t be run every time. Good, but that means the cron.txt will only be written, if a cron job gets executed. But let’s assume the next job will only be run next week end!? The last cron-run-time is stored in the database, but the cron.txt won’t exist by default. That means, even if the cron.php is run, it will know that there is no cron job to execute and, therefore, exit without creating/updating the cron.txt. Especially when using Docker you will hit such a scenario every time when starting a new container.. Thus, every user creates a 404 error (as there is no cron.txt), which is of course ugly and spams the logs.. I fixed the issue by extending the Contao source code. The patch is already merged into the official release of Contao 3.5.33. In addition, I’m initialising the cron.txt in my Docker image with a time stamp of 0, see the Dockerfile. ## Issues with Proxies A typical Docker infrastructure (at least for me) consists of bunch containers orchestrated in various networks etc.. Usually, you’ll have at least one (reverse) proxy, which distributes HTTP request to the container in charge. However, I experienced a few issues with my proxy setup: ### HTTPS vs HTTP While the connection between client (user, web browser) and reverse proxy is SSL-encrypted, the proxy and the webserver talk plain HTTP. As it’s the same machine, there is no big need to waste time on encryption. But Contao has a problem with that setup. Even though, the reverse proxy properly sends the HTTP_X_FORWARDED_PROTO, Contao only sees incomming HTTP traffic and uses http://-URLs in all documents… Even if you ignore the mixed-content issue and/or implement a rewrite of HTTP to HTTPS at the web-server-layer, this will produce twice as much connections as necessary! The solution is however not that difficult. Contao does not understand HTTP_X_FORWARDED_PROTO, but it recognises the $_SERVER['HTTPS'] variable. Thus, to fix that issue you just need to add the following to your system/config/initconfig.php (see also Issue 7542):

In addition, this will generate URLs including the port number (e.g. https://example.com:443/etc), but they are perfectly valid. (Not like https://example.com:80/etc or something that I saw during my tests… ;-)

This workaround doesn’t work for Contao 4 anymore! To fix it see Dockerising Contao 4

### URL encodings in the Sitemap

The previous fix brought up just another issue: The URL encoding in the sitemap breaks when using the port component (:443).. Conato uses rawurlencode to encode all URLs before writing them to the sitemap. However, rawurlencode encodes quite a lot! Among others, it converts :s to %3A. Thus, all URLs in my sitemap looked like this: https://example.com%3A443/etc - which is obviously invalid.

I proposed using htmlspecialchars instead to encode the URLs, but it was finally fixed by splitting the URLs and should be working in release 3.5.34.

## Issues with Cache and Assets etc

A more delicate issue are cache and assets and sitemaps etc. Contao’s backend comes with convenient buttons to clear/regenerate these files and to create the search index. Yet, you don’t always want to login to the backend when recreating the Docker container.. Sometime you simply can’t - for example, if the container needs to be recreated over night.

Basically, that is not a big issue. Assets and cache will be regenerate once they are needed. But the sitemaps, for instance, will only be generated when interacting with the backend.

Thus, we need a solution to create these files as soon as possible, preferably in the background after a container is created. Most of the stuff can be done using the Automator tool, but I also have some personal scripts developed by a company, that require other mechanisms and are unfortunately not properly integrated into Contao’s hooks landscape. And if we need to touch code anyways, we can also generate all assets and rebuild the search index manually (precreating necessary assets will later on speed up things for users…). To generate all assets (images and scripts etc), we just need to access every single page at the frontend. This will then trigger Contao to create the assets and cache, and subsequent requests from real-life users will be much faster!

The best hack that I came up with so far looks like the following script, that I uploaded to /files/initialiser.php to Contao instance:

The first 3 lines initialise the Contao environment. Here I assume that ../system/initialize.php exists (i.e. the script is saved in the files directory). The next few lines purge existing cache using the Automator tool and subsequently regenerate the cache – just to be clean ;-)

Finally, the script (i) collects all “searchable pages” using the Backend::findSearchablePages() functionality, (ii) enriches this set of pages with additional pages that may be hooked-in by plugins etc through $GLOBALS['TL_HOOKS']['getSearchablePages'], and then (iii) uses cURL to iteratively request each page. ### But… The first part should be reasonably fast, so clients may be willing to wait until the cache stuff is recreated. Accessing every frontend page, however, may require a significant amount of time! Especially for larger web pages.. Thus, I embedded everything in the following skeleton, which advises the browser to close the connection before we start the time-consuming tasks: Here, the browser is told to close the connection after a certain content size arrived. I buffer the content that I want to transfer using ob_start and ob_end_flush, so I know how big it is (using ob_get_length). Everything after ob_get_length can safely be ignored by the client, and the connection can be closed. (You cannot be sure that the browser really closes the connection. I saw curl doing it, but also some versions of Firefox still waiting for the script to finish… Nevertheless, the important content will be transferred quick enough). In addition, I created some RewriteRules for mod_rewrite to automatically regenerate missing files. For example, for the sitemaps I added the following to the vhost config (or htaccess): That means, if for example /share/sitemap.xml not yet exists, the user gets automagically redirected to our initialiser.php script! In addition, I added some request parameters (?target=sitemap&sitemap=$1), so that the initialiser.php knows which file was requested. It can then regenerate everything and immediately output the new content! :)

For example, my snippet to regenerate and serve the sitemap looks similar to this:

Thus, the request to /share/somesitemap.xml will never fail. If the file does not exist, the client will be redirected to /files/initialiser.php?target=sitemap&sitemap=somesitemap, the file /share/somesitemap.xml will be regenerated, and the new contents will immediately be served. So the client will eventually get the desired content :)

Please be aware, that this script is easily DOS-able! Attackers may produce a lot of load by accessing the file. Thus, I added some simple DOS protection to the beginning of the script, which makes sure the whole script is not run more than once per hour (3600 seconds):

If $dryrun is true, it won’t regenerate cache etc, but still serve the sitemap and other files if requested.. However, if there is also no $_GET['target'] defined, we don’t know what to serve anyway and can die immediately…

You could include the script at the footer of your webpage, e.g. using

(you may want to make sure that the generated output, if any, is valid JavaScript. E.g. embed everything in /*...*/ or something…)

This way you would make sure, that every request produces a fully initialised system. However, this will probably also create unnecessary load every hour… You could increase the time span in the DOS-protection-hack, but I guess it should be sufficient to run the script only if a missing file is requested. Earlier requests then need to wait for pending assets etc, but to be honest, that should not be too long (or you have a different problem anyway…).

And if your website provides an RSS feed, you could subscribe to it using your default reader, which will regularly make sure that the RSS feed is generated if missing.. (and thus trigger all the other stuff in our initialiser.php) – A feed reader as the poorest-man-cron ;-)

### Share

As I said earlier, my version of the script contains plenty of personalised stuff. That’s why I cannot easily share it with you.. :(

However, if you have trouble implementing it yourself just let me know :)