WURFL InFuze Module for Varnish: User Guide

This document is aimed at developers and system administrators who intend to install and configure the WURFL InFuze Module for Varnish-Cache on Unix, Linux, and other Unix-based systems such as FreeBSD. In the rest of the documentation, we will refer to the module as the WURFL VMOD (Varnish Module).

Installing libwurfl

In order for the Module to work it is ESSENTIAL that the libwurfl library is installed on your system. libwurfl is provided in your Customer Vault/FileX.

If you have not already installed libwurfl, instructions can be found here. Release notes for each API can be found here.

WURFL Varnish Module availability

The WURFL Varnish module is available for all major Varnish Cache versions.

Installing WURFL Varnish Module

You may already have an instance of Varnish Cache running on your system. In this case, we recommend that you stop any running Varnish Cache instance and check if you have the correct version of Varnish Cache installed.

__Warning:__ Be aware that some older linux distributions, such as Fedora 15, may install older versions of Varnish library which are NOT compatible with the WURFL C library release. Please make sure that you are running the correct version of Varnish software before installation of the WURFL VMOD.

Installing the WURFL Varnish Module on Ubuntu

You can get the Varnish Cache software from packagecloud.io, chosing the desired repo and then following the installation instructions related to DEB packages.

Once you have obtained the WURFL Varnish module DEB package from ScientiaMobile (be sure to get the module related to the Varnish Cache software installed), you can install it with:

sudo dpkg -r varnish-mod-wurfl
sudo dpkg -i varnish-mod-wurfl-x.y.z.0.varnish-5.2.1.x86_64.deb

Note: VARNISH MODULE INSTALLATION FOLDER: Please note that the WURFL Varnish module DEB package will install the module .so file in /usr/lib/varnish/vmods/
and will try to create symbolic links in /usr/lib/x86_64-linux-gnu/varnish/vmods and/or /usr/local/lib/varnish/vmods folders.
If your Varnish installation looks for vmods in different folders than /usr/lib/x86_64-linux-gnu/varnish/vmods and /usr/local/lib/varnish/vmods,
on Varnish startup you will see the following error : ..../vmods/libvmod_wurfl.so: open shared object file: No such file or directory.
In this case, please create a symbolic link to /usr/lib/varnish/vmods/libvmod_wurfl.so in your Varnish vmods folder.

Install WURFL Varnish Module on RedHat/Fedora/CentOS

You can get the Varnish Cache software from packagecloud.io, chosing the desired repo and then following the installation instructions related to RPM packages.

Once you have obtained the WURFL Varnish module RPM package from ScientiaMobile (be sure to get the module related to the Varnish Cache software installed), you can install it with:

sudo rpm -e varnish-mod-wurfl
sudo rpm -i varnish-mod-wurfl-1.9.4.0.varnish-5.2.1.x86_64.rpm

Note: VARNISH MODULE INSTALLATION FOLDER: Please note that the WURFL Varnish module RPM package will install the module .so file in /usr/lib/varnish/vmods/
and will try to create symbolic links in /usr/lib64/varnish/vmods and/or /usr/local/lib/varnish/vmods folders.
If your Varnish installation looks for vmods in different folders than /usr/lib64/varnish/vmods and /usr/local/lib/varnish/vmods,
on Varnish startup you will see the following error : ..../vmods/libvmod_wurfl.so: open shared object file: No such file or directory.
In this case, please create a symbolic link to /usr/lib/varnish/vmods/libvmod_wurfl.so in your Varnish vmods folder.

The installation process is now complete. Make sure to check the Configuration Guide and WURFL Varnish Module Examples sections to verify that everything was installed correctly.

Warning: VARNISH TUNING: Since libwurfl 1.8.3.1 the Varnish run time parameter thread_pool_stack needs to be tuned to meet WURFL requirements.
Its value should be changed to at least 96k executing varnishd daemon with the following command: varnishd -p thread_pool_stack=96k.
For Varnish versions prior to 4.0, the command is varnishd -p thread_pool_stack=163840

Configuration Guide

Varnish utilizes Varnish Configuration Language (VCL), a domain-specific language that can be used to define HTTP-request handling and media caching policies for the Varnish-Cache HTTP accelerator. For more information on VCL, please check the Varnish 5 VCL, Varnish 4.1 VCL, Varnish 4 VCL or the Varnish 3 VCL online documentation as well as other examples of VCL Usage.

Shown below is an example of a varnish.sample.vcl configuration file for WURFL setup in Varnish 5. Please refer to the directives guide which explains each element in detail (Table 1), their parameters, constraints, and default recommended settings. In order to test the correct installation of the WURFL Varnish module, you can use the VCL script located in /usr/share/wurfl/varnish.sample.vcl:

vcl 4.0;

import wurfl;
import std;

backend default {
    .host = "127.0.0.1";
    .port = "8080";
}

sub vcl_init {
    ### WURFL root definition. User MUST specify this path in order to make WURFL engine correctly start.
    wurfl.set_root("/usr/share/wurfl/wurfl.zip");

    ### WURFL Updater allows for seamless updates of the WURFL engine with new data downloaded from Scientiamobile.
    ### Updater configuration must be done after wurfl.set_root
    ### WURFL file should be either .zip or .xml.gz and match wurfl.set_root file type
    ### Put your personal updater URL taken from the Scientiamobile customer Vault.
    ### Valid values for the updater checking frequency (how often the updater checks for any new WURFL data file
    ### to be downloaded and used by the engine) are DAILY,WEEKLY
    ### Updater log file (wurfl-updater.log) may be found in "wurfl.set_root" folder. The folder and wurfl.zip file (which must already be present for the updater to work, should be writable by Varnish
    #wurfl.updater("https://data.scientiamobile.com/xxxxx/wurfl.zip","DAILY");
    #wurfl.updater("https://data.scientiamobile.com/xxxxx/wurfl.zip","WEEKLY");

    ### WURFL patches definition (as much as needed, patches will be applied in the same order as specified).
    #wurfl.add_patch("/path/to/patch1.xml");
    #wurfl.add_patch("/path/to/patch2.xml");

    ### WURFL cache: one of the following
    wurfl.set_cache_provider_lru(100000);
    #wurfl.set_cache_provider_none();

    ### WURFL user requested static capabilities (as an example, this is not a complete list)
    ### If you are upgrading from previous versions, remember that since module version 1.8.1.1
    ### you don't need to specify WURFL mandatory capabilities anymore.
    wurfl.add_requested_capability("is_console");

    wurfl.load();

    ### WURFL Updater startup. Must be done after wurfl.load
    ### With wurfl.updater_start the updater will execute an asynchronous check DAILY or WEEKLY (depending on wurfl.updater parameters)
    ### With wurfl.updater_runonce the updater will run only once executing a synchronous check
    # wurfl.updater_start();
    # wurfl.updater_runonce();

    if (wurfl.error()) {
            std.syslog(3, wurfl.error());
            return (fail);
    }
}

sub vcl_miss {
    ### Print requested static capabilities
    std.syslog(0, wurfl.get_capability("is_console"));

    ### Print useful WURFL setup information
    std.syslog(0, wurfl.get_api_version());
    std.syslog(0, wurfl.get_wurfl_info());
    std.syslog(0, wurfl.get_last_load_time());

    ### Print some virtual capabilities values
    std.syslog(0, wurfl.get_virtual_capability("advertised_browser"));
    std.syslog(0, wurfl.get_virtual_capability("advertised_browser_version"));
    std.syslog(0, wurfl.get_virtual_capability("advertised_device_os"));
    std.syslog(0, wurfl.get_virtual_capability("advertised_device_os_version"));
    std.syslog(0, wurfl.get_virtual_capability("is_largescreen"));
    std.syslog(0, wurfl.get_virtual_capability("is_app"));

    return(fetch);
}

sub vcl_pipe {
    return(pipe);
}

sub vcl_pass {
    return(pass);
}

Available Varnish Module functions list

Environment Info and Virtual Capabilities in WURFL Varnish Module

Since virtual capabilities are automatically calculated by WURFL, there are no explicit commands to request them.

There are some functions used to retrieve the virtual capabilities values and also some useful WURFL environment configuration information.

Please take a look at the VCL example and the functions table specified above.

WURFL Varnish Module Examples

If you try the following examples, you should restart Varnish each time a change is made.

Example 1:

In this example, we declare the vcl_recv subroutine, which is called when the complete request has been received and parsed. Its purpose is to decide whether an HTTP request should be served. Thus, certain conditions should be satisfied prior to serving the request itself. For example, the req object represents a single request and its parameters can be accessed via "dotted notation".

In our case, we test if the URL of the request is equal to / (root). Moreover we check if the browser runs on a device which has a resolution height equal to 960 pixels. If both of these conditions are true then we can use the directive set to assign a specific home page URL (/wide.html) to the request parameter URL.

The wurfl object is accessible after all the required variables have been initialized (see the varnish.sample.vcl script described before for more info). We can query WURFL for a static capability value simply by calling the function get_capability(cap_name).

The subroutine vcl_error is called every time we hit an error. At this point, the request has been cached by Varnish and as a result we have access to the obj object's variables in order to check if some error has occured.

For example, we can read the status variable, which contains the HTTP response status code returned by the server, and act accordingly by showing a message to the user which describes the problem or restarts the transaction to connect to the server.

Please note that, in the subroutine vcl_error, we return the error object to the client, which in turn can take some further actions.

#################################################################
########## Wurfl Static Capability switch example 1 ##############
##################################################################
sub vcl_recv {
    if ( req.url  == "/" && wurfl.get_capability("resolution_height") == "800") {
        set req.url = "/wide.html";
    }
}

sub vcl_error {
    if (obj.status == 750) {
        set obj.http.Location = "/wideversion/";
        set obj.status = 302;
           return(deliver);
    }
}

Example 2:

This example is similar to the previous one and shows how to throw an error explicitly to the client when both conditions are satisfied. Note that in this case, the request will be discarded by Varnish.

##################################################################
########### Wurfl Static Capability switch example 2 #############
##################################################################
sub vcl_recv {
    if ( req.url  == "/" && wurfl.get_capability("resolution_height")  == "800") {
        error 750 "Moved Temporarily";
    }
}

sub vcl_error {
    if (obj.status == 750) {
        set obj.http.Location = "/wideversion/";
        set obj.status = 302;
           return(deliver);
    }
}

Example 3:

In this example we call the hash_data() function, which will hash the data passed as parameter. Using the + operator, we can concatenate strings and then pass the result to the hash function. In this case, we consider concatenating the requested URL with the Device ID matched by WURFL.

##################################################################
############## Caching only URL + Device ID example 3 ############
#### Content is cached only if the URL+Device_ID is matching #####
##################################################################
sub vcl_hash {
    hash_data(req.url+req.http.host+wurfl.get_device_id());
    return (hash);
}

You should restart Varnish every time you make a change to the configuration in order to force a reload of the VCL configuration:

pkill varnishd
varnishd -f /usr/share/wurfl/varnish.sample.vcl

Note: In order to use service varnish start you should set properly all the required parameters in /etc/sysconfig/varnish.

Note: Due to a Varnish limitation, the only working log file is the syslog. If you want to check the error messages and other issues> that may have occurred, you should look into /var/log/messages.

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