Add blog post about deprecating nodes

_posts/2016-12-07-deprecating-nodes.md

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+---
+title: Deprecating Nodes
+author: David Davis
+tags:
+  - release
+  - platform
+  - 3.0
+---
+
+Nodes were introduced in Pulp in 2.1.0 and provided a way to keep multiple Pulp
+servers synchronized. However, Nodes uses separate codepaths from the normal
+sync+publish codepaths which creates a few problems:
+
+* Nodes is less tested than sync+publish. This greatly reduces the user-to-user
+  usage and testing benefit.
+* Fixing bugs in sync+publish does not fix bugs in Nodes and vice-versa
+* Nodes has a good amount of bugs already reported that are still unfixed
+
+Given that much of the functionality of Nodes can be achieved by running Pulp
+with sync+publish workflow, the core team is removing Nodes in the next major
+release, Pulp 3.0. With Pulp 2.12, Nodes will be officially deprecated.
+
+In this blog post, I want to outline how users can sync content across Pulp
+servers without using Nodes and how tools like cron and systemd can be used to
+keep content updated across Pulp servers. I am going to illustrate a two-server
+example in which I'll call one Pulp server the parent and the other the child.
+However, this distinction is arbitrary as each server is a standard Pulp server
+installation without Nodes packages installed. The child Pulp server is called
+that because it is the one we want to mirror content to.
+
+Syncing Content to a Child Server
+---------------------------------
+
+Suppose I have an rpm repo called 'centos-base' on the parent Pulp server.
+First, I would want to publish that repository to make it available for the
+child Pulp server to sync:
+
+    pulp-admin rpm repo publish run --repo-id centos-base
+
+This repository should then be available via http or https. You can check its
+relative path via `pulp-admin rpm repo list --repo-id centos-base --details`.
+In my case, it's at "https://example.com/pulp/repos/centos-base". Now on the
+child node, I can create and sync the repository:
+
+    pulp-admin rpm repo create --repo-id centos-base --feed https://example.com/pulp/repos/centos-base
+    pulp-admin rpm repo sync run --repo-id centos-base
+
+Now the 'centos-base' repository from the parent Pulp server has been mirrored
+onto a child server.
+
+
+Automatically Updating Content
+------------------------------
+
+By using cron or a systemd timer, we can keep content on the child Pulp server
+up-to-date automatically. To make content available, you will need to call
+publish on the parent repository. This can be done automatically after each
+sync via the "auto-publish" feature, or periodically with a crontab entry such
+as:
+
+    @hourly pulp-admin rpm repo publish run --repo-id centos-base
+
+On on the child server, we could then sync our 'centos-base' repository hourly
+with:
+
+    @hourly pulp-admin rpm repo sync run --repo-id centos-base
+
+It's worth noting that you'll want to ensure that pulp-admin is pointing to
+the correct URL on each server. One option would be to edit the crontab for
+each server and have pulp-admin configured to point to Pulp via localhost.
+
+Also, by default, a pulp-admin certificate only lasts for 7 days before you
+must login again. To extend this period, configure `user_cert_expiration` in
+server.conf.