01/02: website: Add post about 'guix deploy'.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix-artwork.

commit 117b9206b4b402a65233e79c84cbcc229655f322
Author: Jakob L. Kreuze <address@hidden>
Date:   Thu Jul 11 13:27:11 2019 -0400

    website: Add post about 'guix deploy'.
    
    Signed-off-by: Ludovic Courtès <address@hidden>
---
 website/posts/towards-guix-for-devops.md | 119 +++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)

diff --git a/website/posts/towards-guix-for-devops.md 
b/website/posts/towards-guix-for-devops.md
new file mode 100644
index 0000000..a302586
--- /dev/null
+++ b/website/posts/towards-guix-for-devops.md
@@ -0,0 +1,119 @@
+title: Towards Guix for DevOps
+date: 2019-07-11 13:14
+author: Jakob L. Kreuze
+tags: GSoC, Programming interfaces, Scheme API
+---
+
+Hey, there! I'm Jakob, a Google Summer of Code intern and new contributor to
+Guix. Since May, I've been working on a DevOps automation tool for the Guix
+System, which we've been calling 'guix deploy'.
+
+The idea for a Guix DevOps tool has been making rounds on the mailing lists for
+some time now. Years, in fact; Dave Thompson and Chris Webber put together a
+proof-of-concept for it way back in 2015. Thus, we've had plenty of time to 
gaze
+upon the existing tools for this sort of thing -- 
[Ansible](https://www.ansible.com/), [NixOps](https://nixos.org/nixops/) -- and
+fantasize about a similar tool, albeit with the expressive power of Guile 
scheme
+and the wonderful system configuration facilities of Guix. And now, those
+fantasies are becoming a reality.
+
+"DevOps" is a term that might be unfamiliar to a fair number of Guix users. 
I'll
+spare you the detour to Wikipedia and give a brief explanation of what 'guix
+deploy' does.
+
+Imagine that you've spent the afternoon playing around with Guile's `(web)`
+module, developing software for a web forum. Awesome! But a web forum with no
+users is pretty boring, so you decide to shell out a couple bucks for a virtual
+private server to run your web forum. You feel that Wildebeest admirers on the
+internet deserve a platform of their own for discussion, and decide to dedicate
+the forum to that.
+
+As it turns out, *C. gnou* is a more popular topic than you ever would have
+imagined. Your web forum soon grows in size -- attracting hundreds of thousands
+of simultaneous users. Despite Guile's impressive performance characteristics,
+one lowly virtual machine is too feeble to support such a large population of
+Wildebeest fanatics. So you decide to use Apache as a load-balancer, and shell
+out a couple more bucks for a couple more virtual private servers. Now you've
+got a problem on your hands; you're the proud owner of five or so virtual
+machines, and you need to make sure they're all running the most recent version
+of either your web forum software or Apache.
+
+This is where 'guix deploy' comes into play. Just as you'd use an
+`operating-system` declaration to configure services and user accounts on a
+computer running the Guix System, you can now use that same `operating-system`
+declaration to remotely manage any number of machines. A "deployment" managing
+your Wildebeest fan site setup might look something like this:
+
+```scheme
+...
+
+;; Service for our hypothetical guile web forum application.
+(define guile-forum-service-type
+  (service-type (name 'guile-forum)
+                (extensions
+                 (list (service-extension shepherd-root-service-type
+                                          guile-forum-shepherd-service)
+                       (service-extension account-service-type
+                                          (const %guile-forum-accounts))))
+                (default-value (guile-forum-configuration))
+                (description "A web forum written in GNU Guile.")))
+
+...
+
+(define %forum-server-count 4)
+
+(define (forum-server n)
+  (operating-system
+    (host-name (format #f "forum-server-~a" n))
+    ...
+    (services
+     (append (list (service guile-forum-service-type
+                            (guile-forum-configuration
+                             "GNU Fan Forum!")))
+             %base-services))))
+
+(define load-balancer-server
+  (operating-system
+    (host-name "load-balancer-server"
+    ...
+    (services
+     (append (list (service httpd-service-type
+                            (httpd-configuration
+                             ...)))
+             %base-services)))))
+
+;; One machine running our load balancer.
+(cons (machine
+       (system load-balancer-server)
+       (environment manged-host-environment-type)
+       (configuration (machine-ssh-configuration
+                       ...)))
+
+      ;; And a couple running our forum software!
+      (let loop ((n 1)
+                 (servers '()))
+        (if (> n %forum-server-count)
+            servers
+            (loop (1+ n)
+                  (cons (machine
+                         (system (forum-server n))
+                         (environment manged-host-environment-type)
+                         (configuration (machine-ssh-configuration
+                                         ...)))
+                        servers)))))
+```
+
+The take-away from that example is that there's a new `machine` type atop the
+good ol' `operating-system` type, specifying how the machine should be
+_provisioned_. The version of 'guix deploy' that's currently on the master
+branch only supports `managed-host-environment-type`, which is used for 
machines
+that are already up and running the Guix System. Provisioning, in that sense,
+only really involves opening an SSH connection to the host. But I'm sure you 
can
+imagine a `linode-environment-type` which automatically sets up a virtual
+private server through Linode, or a `libvirt-environment-type` that spins up a
+virtual machine for running your services. Those types are what I'll be working
+on in the coming months, in addition to cleaning up the code that's there now.
+
+And yes, you did read that right. 'guix deploy' is on the Guix master branch
+right now! In fact, we've already a successful deployment right here on
+[ci.guix.gnu.org](http://ci.guix.gnu.org/). So, if this sounds as though it'd 
be up your alley, run `guix
+pull`, crack open the 
[manual](http://guix.gnu.org/manual/en/html_node/Invoking-guix-deploy.html#Invoking-guix-deploy),
 and let us know how it goes!