Compile Xvfb for AWS Lamba

README.md

Compile Xvfb for lambda.

Referenes

Based on the following guide: https://ericdraken.com/running-xvfb-on-a-shared-host-without-x/

Using the following docker image: https://hub.docker.com/r/lambci/lambda/

Start up and attach to docker container to do the build on

It's an Amazon Linux image that matches the environment of Lambda tasks.

# On my Mac, from the directory where I'll be working on my lambda function.
$ docker run -v "$PWD":/var/task -it lambci/lambda:build bash
# bash-4.2#

Install Xvfb and some other dependencies

We'll need some utils that it comes with.

$ yum install xorg-x11-server-Xvfb.x86_64 wget

Download xorg-server source code and unpack

$ cd /tmp
$ wget https://www.x.org/releases/X11R7.7/src/xserver/xorg-server-1.12.2.tar.gz
$ tar -xvf xorg-server-1.12.2.tar.gz
$ cd xorg-server-1.12.2

Modify some files for keymap compiling.

Edit xkb/xkbInit.c at line 754 in XkbProcessArguments()

        return 2;
    }

    // ADDED - Change xkbcomp bin directory with an environment variable
    char *xkbBinDir = getenv("XKB_BINDIR");
    if (xkbBinDir) {
        XkbBinDirectory = Xstrdup(xkbBinDir);
    }

    // ADDED - Change base xkb directory with an environment variable
    char *xkbBaseDir = getenv("XKBDIR");
    if (xkbBaseDir) {
        XkbBaseDirectory = Xstrdup(xkbBaseDir);
    }

    return 0;
}

Edit xkb/ddxLoad.c at line 188 in XkbDDXCompileKeymapByNames()

    const char *emptystring = "";
    char *xkbbasedirflag = NULL;
    const char *xkbbindir = emptystring;
    const char *xkbbindirsep = emptystring;

#ifdef WIN32
    char tmpname[PATH_MAX];
    const char *xkmfile = tmpname;
#else
    // MODIFICATION - Now using 'default.xkm' file to satisfy xkbcomp
    // const char *xkmfile = "-";
    const char *xkmfile = "default.xkm";
#endif

Create default.xkb

Contents for default.xkb:

xkb_keymap "default" {
    xkb_keycodes             { include "evdev+aliases(qwerty)" };
    xkb_types                { include "complete" };
    xkb_compatibility        { include "complete" };
    xkb_symbols              { include "pc+us+inet(evdev)" };
    xkb_geometry             { include "pc(pc105)" };
};

Create and compile it:

$ cd /tmp
$ vim default.xkb
# Insert contents above and save
$ xkbcomp -xkm default.xkb

Copy it into your lambda function /lib

$ mkdir /var/task/lib
$ cp default.xkm /var/task/lib

Install devel dependencies

$ yum install pixman-devel.x86_64 \
    libdrm-devel.x86_64 \
    libX11-devel.x86_64 \
    mesa-libGL-devel.x86_64 \
    openssl-devel.x86_64 \
    xorg-x11-xtrans-devel.noarch \
    libxkbfile-devel.x86_64 \
    libXfont-devel.x86_64 \
    libpciaccess-devel.x86_64 \
    xcb-util-keysyms-devel.x86_64

Configure and Make

$ ./configure
$ make

Copy Xvfb to lambda lib

$ cp hw/vfb/Xvfb /var/task/lib

In a new terminal, boot up another docker mounted to our task dir

# cd (your task directory)
$ docker run -v "$PWD":/var/task -it lambci/lambda:build bash

Check that we have any linked libs

Looks ok?

$ ls -la /var/task/lib
total 10812
drwxr-xr-x 5 root root      170 Dec  2 23:55 .
drwxr-xr-x 4 root root      136 Dec  2 23:28 ..
-rw-r--r-- 1 root root      314 Dec  2 23:43 default.xkb
-rw-r--r-- 1 root root    11248 Dec  2 23:43 default.xkm
-rwxr-xr-x 1 root root 11054660 Dec  2 23:55 Xvfb

$ cd /var/task/lib

$ ldd ./Xvfb
  linux-vdso.so.1 =>  (0x00007ffdc6f1a000)
  libcrypto.so.10 => /lib64/libcrypto.so.10 (0x00007f10f11ca000)
  libdl.so.2 => /lib64/libdl.so.2 (0x00007f10f0fc5000)
  libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f10f0da9000)
  libpixman-1.so.0 => /usr/lib64/libpixman-1.so.0 (0x00007f10f0afe000)
  libXfont.so.1 => /usr/lib64/libXfont.so.1 (0x00007f10f08c9000)
  libXau.so.6 => /usr/lib64/libXau.so.6 (0x00007f10f06c6000)
  libm.so.6 => /lib64/libm.so.6 (0x00007f10f03c4000)
  libc.so.6 => /lib64/libc.so.6 (0x00007f10f0001000)
  libz.so.1 => /lib64/libz.so.1 (0x00007f10efdeb000)
  /lib64/ld-linux-x86-64.so.2 (0x000056118b113000)
  libfreetype.so.6 => /usr/lib64/libfreetype.so.6 (0x00007f10efb4f000)
  libfontenc.so.1 => /usr/lib64/libfontenc.so.1 (0x00007f10ef947000)

Try to start Xvfb

First, set the environment variables for keymap:

$ export XKB_BINDIR=/usr/bin
$ export XKBDIR=/var/task/lib

Fails with keymap error.

$ ./Xvfb :99
[dix] Could not init font path element /usr/share/fonts/X11/misc/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/TTF/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/OTF/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/Type1/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/100dpi/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/75dpi/, removing from list!
XKB: Failed to compile keymap
Keyboard initialization failed. This could be a missing or incorrect setup of xkeyboard-config.

Things I'm not sure about

1. I assume the target machine needs XKBDIR and XKB_BINDIR, but since the machine in question doesn't have X11, it doesn't have xkbcomp, so does that mean I need to compile that from source also?
2. Font errors above, not sure about that.

@san-kumar - While Xfvb indeed starts running on a lambda environment, I'm finding that windows are never produced (i.e. running xwininfo -root -tree lists no child windows). However, an identical docker image ran anywhere else works fine, I see all the different windows of the applications I open as expected. Very strange and frustrating, I guess it has something to do with the restrictions of the lambda environment. Have you found the same or does your Ubuntu 16 image there work fine?