Add classification documentation

To explain how the node groups created to support the extra large
architecture are laid out and work

Author: reidmv

Diff for: README.md

@@ -10,9 +10,13 @@ Note pending more detailed instructions:
 * This deployment assumes that at least for PE infrastructure nodes, Puppet certnames are correct, resolvable FQDNs.
 * This deployment assumes the control repository to manage PE is independent of the normal "customer" control-repo.
 
+## Documentation
+
+See this README file and any documents in the [docs](docs) directory.
+
 ## Architecture
 
-![architecture](architecture.png)
+![architecture](docs/images/architecture.png)
 
 ## Installation
 

Diff for: docs/classification.md

@@ -0,0 +1,75 @@
+# PE Extra Large architecture classification #
+
+## Overview
+
+This reference implementation uses four non-default node classification groups to implement the Extra Large HA architecture. Intentionally, classification of default, out-of-box node groups is not modified. This allows normal commands such as `puppet infrastructure enable replica` to behave more or less exactly as they would in Standard or Large architecture deployments.
+
+This image shows a fully expanded view of the PE Infrastructure node group, highlighting the new additions made to support the Extra Large archtecture.
+
+![PE Classification tree](images/pe-xl-classification.png)
+
+## Node Groups
+
+The new groups are:
+
+* PE Master A
+* PE Master B
+* PE Compile Master Group A
+* PE Compile Master Group B
+
+The configuration applied in each group looks as follows:
+
+### PE Master A
+
+![PE Master A group](images/pe-master-a.png)
+
+Notes for PE Master A:
+
+* The (initial) Primary Master is the only member of this node group
+* Sets as data two parameters
+    * `puppet_enterprise::profile::primary_master_replica::database_host_puppetdb`
+    * `puppet_enterprise::profile::puppetdb::database_host`
+* Sets both parameters to the name of the PuppetDB PostgreSQL node paired with this master
+* Uses a different PuppetDB PostgreSQL node than PE Master B
+
+### PE Master B
+![PE Master B group](images/pe-master-b.png)
+
+Notes for PE Master B:
+
+* The (initial) Primary Master Replica is the only member of this node group
+* Sets as data two parameters
+    * `puppet_enterprise::profile::primary_master_replica::database_host_puppetdb`
+    * `puppet_enterprise::profile::puppetdb::database_host`
+* Sets both parameters to the name of the PuppetDB PostgreSQL node paired with this master
+* Uses a different PuppetDB PostgreSQL node than PE Master A
+
+### PE Compile Master Group A
+![PE Compile Master Group A group](images/pe-compile-master-group-a.png)
+
+Notes for PE Compile Master Group A:
+
+* Half of the compile masters are members of this group
+* Applies the `puppet_enterprise::profile::puppetdb` class
+* Sets the `puppet_enterprise::profile::puppetdb::database_host` parameter
+    * Should be set to `"pdb-pg-a"`, where "pdb-pg-a" is the name of the PuppetDB PostgreSQL database host paired with the (initial) Primary Master
+* Modifies the `puppet_enterprise::profile::master::puppetdb_host` parameter
+    * Should be set to `[${clientcert}, "master-b"]`, where "master-b" is the name of the (initial) Primary Master Replica.
+    * If you have a load balancer for the compile masters in PE Compile Master Group B port 8081, you should use that load balancer address instead of "master-b"
+* Modifies the `puppet_enterprise::profile::master::puppetdb_port` parameter
+    * Should be set to `[8081]`
+
+### PE Compile Master Group B
+![PE Compile Master Group B group](images/pe-compile-master-group-b.png)
+
+Notes for PE Compile Master Group B:
+
+* The other half of the compile masters (those not in the PE Compile Master Group A node group) are members of this group
+* Applies the `puppet_enterprise::profile::puppetdb` class
+* Sets the `puppet_enterprise::profile::puppetdb::database_host` parameter
+    * Should be set to `"pdb-pg-b"`, where "pdb-pg-b" is the name of the PuppetDB PostgreSQL database host paired with the (initial) Primary Master Replica
+* Modifies the `puppet_enterprise::profile::master::puppetdb_host` parameter
+    * Should be set to `[${clientcert}, "master-a"]`, where "master-a" is the name of the PuppetDB PostgreSQL node paired with the (initial) Primary Master Replica.
+    * If you have a load balancer for the compile masters in PE Compile Master Group A port 8081, you should use that load balancer address instead of "master-a"
+* Modifies the `puppet_enterprise::profile::master::puppetdb_port` parameter
+    * Should be set to `[8081]`